MOISTURE DAMAGE IN ASPHALT CONCRETE

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R E F E R E N C E COPy FOR LIBRARir USE O N L r

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM SYNTHESIS OF HIGHWAY PRACTICE

MOISTURE DAMAGE IN ASPHALT CONCRETE

TRANSPORTATION RESEARCH BOARD National Research Council

TRANSPORTATION RESEARCH BOARD EXECUTIVE COMMITTEE 1991

Officen

Chairman

C. M I C H A E L W A L T O N , Bess Harris Jones Centennial Professor of Natural Resource Policy Studies and Chairman, Civil Engineering Department, University of Texas at Austin

Vice Chairman

W I L L I A M W. M I L L A R , Executive Director, Port of Allegheny County

Executive Director

T H O M A S B. D E E N , Transportation Research Board

Members

J A M E S B. B U S E Y IV, Federal Aviation Administrator, U.S. Department of Transportation (ex officio)

G I L B E R T E . C A R M I C H A E L , Federal Railroad Administrator, U.S. Department of Transportation (ex officio)

B R I A N W. C L Y M E R , Urban Mass Transportation Administrator, U.S. Department of Transportation (ex officio)

J E R R Y R. C U R R Y , National Highway Traffic Safety Administrator, U.S. Department of Transportation (ex officio)

T R A V I S P. D U N G A N , Research <t Special Programs Administrator, U.S. Department of Transportation (ex officio)

F R A N C I S B. F R A N C O I S , Executive Director, American Association of State Highway and Transportation Officials (ex officio)

J O H N G R A Y , President, National Asphalt Pavement Association (ex officio)

T H O M A S H . H A N N A , President and Chief Executive Officer, Motor Vehicle Manufacturers Association of the United States, Inc. (ex officio)

H E N R Y J . H A T C H , Chief of Engineers and Commander, U.S. Army Corps of Engineers (ex officio)

T H O M A S D. L A R S O N , Federal Highway Administrator, U.S. Department of Transportation (ex officio)

W A R R E N G . L E B A C K , Maritime Administrator & Chairman, Maritime Subsidy Board, U.S. Department of Transportation (ex officio)

G E O R G E H . W A Y , JR., Vice President for Research and Test Department, Association of American Railroads (ex officio)

R O B E R T J . A A R O N S O N , President, Air Transport Association of America

J A M E S M. B E G O S , Chairman, Spacehab, Inc.

J . R O N B R I N S O N , President and Chief Executive Officer, Board of Commissioners of The Port of New Orleans

L . G A R Y B Y R D , Consulting Engineer, Alexandria, Virginia

A. R A Y C H A M B E R L A I N , Executive Director, Colorado Department of Highways

L . S T A N L E Y C R A N E , Retired Chairman of the Board & CEO, Conrail

J A M E S C . D e L O N G , Director of Aviation, Philadelphia International Airport

R A N D Y DOI, Director, IVHS Systems, Motorola Incorporated

E A R L D O V E , President, Earl Dove Company

L O U I S J . G A M B A C C I N I , General Manager, Southeastern Pennsylvania Transportation Authority (past chairman, 1989)

T H O M A S J. H A R R E L S O N , Secretary, North Carolina Department of Transportation

K E R M I T H. J U S T I C E , Secretary of Transportation, State of Delaware

L E S T E R P. L A M M , President, Highway Users Federation

D E N M A N K. M c N E A R , Vice Chairman, Rio Grande Industries

A D O L F D. M A Y , JR. , Professor and Vice-Chair, University of California Institute of Transportation Studies

W A Y N E M U R I , Chief Engineer, Missouri Highway i Transportation Department (past chairman, 1990)

A R N O L D W. O L I V E R , Engineer-Director, Texas State Department of Highways and Public Transportation

J O H N H . R I L E Y , Commissioner of Transportation, Minnesota Department of Transportation

D E L L A M. R O Y , Professor of Materials Science, Pennsylvania State University

J O S E P H M. SUSSMAN, Director, Center for Transportation Studies, Massachusetts Institute of Technology

J O H N R. T A B B , Director, Chief Administrative Officer, Mississippi State Highway Department

F R A N K L I N E . W H I T E , Commissioner, New York State Department of Transportation

J U L I A N W O L P E R T , Henry G. Bryant Professor of Geography, Public Affairs and Urban Planning, Woodrow Wilson School of Public and International Affairs, Princeton

University

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

Transportation Research Board Executive Committee Subcommittee for NCHRP

C. M I C H A E L W A L T O N , University of Texas at ûjri/i(Chairman)

F R A N C I S B. F R A N C O I S , American Association of State Highway and

Transportation Officials

T H O M A S D, L A R S O N , U.S. Department of Transportation

Field of Special Projects

Project Committee SP 20-5

V E R D I A D A M , Gulf Engineers & Consultants

R O B E R T N. B O T H M A N , Oregon Dept. of Transportation

J A C K F R E I D E N R I C H , New Jersey Dept. of Transportation

R O N A L D E . H E I N Z , Federal Highway Administration

J O H N J . H E N R Y , Pennsylvania Transportation Institute

B R Y A N T M A T H E R , USAE Waterways Experiment Station

T H O M A S H . M A Y , Pennsylvania Dept. of Transportation

E D W A R D A. M U E L L E R , Morales and Shumer Engineers, Inc.

E A R L S H I R L E Y , California Dept. of Transportation

J O N U N D E R W O O D , Texas Dept. of Highways and Public Transportation

T H O M A S W I L L E T T , Federal Highway Administration

R I C H A R D A. McCOMB, Federal Highway Administration (Liaison)

R O B E R T E . S P I C H E R , Transportation Research Board (Liaison)

W I L L I A M W . M I L L A R , Port Authority of Allegheny County

W A Y N E M U R I , Missouri Highway & Transportation Department

T H O M A S B . D E E N , Transportation Research Board

L . G A R Y B Y R D , Consulting Engineer, Alexandria. Va.

Program Staff

R O B E R T J . R E I L L Y , Director, Cooperative Research Programs

L O U I S M . M a c G R E G O R , Program Officer

D A N I E L W . D E A R A S A U G H , J R . , Senior Program Officer

I A N M . F R I E D L A N D , Senior Program Officer

C R A W F O R D F . J E N C K S , Senior Program Officer

K E N N E T H S. O P I E L A , Senior Program Officer

D A N A . R O S E N , Senior Program Officer

H E L E N M A C K , Editor

TRB Staff for NCHRP Project 20-5

R O B E R T E . S K I N N E R , J R . , Director for Special Projects

S A L L Y D . L I F E , Senior Program Officer

S C O T T A . S A B O L , Program Officer

L I N D A S. M A S O N , Editor

C H E R Y L C U R T I S , Secretary

REFERENCE copy FOR i m , - , , p - . ^ j ,

N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M S Y N T H E S I S O F H I G H W A Y P R A C T I C E


R. GARY HICKS Oregon State University, Corvallis, OR

Topic Panel

J O H N J . C A R R O L L , Federal Highway Administration, Washington, D.C. R O B E R T N. D O T Y , California Department of Transportation, Sacramento, CA R O B E R T P. L O T T M A N , University of Idaho. Moscow, ID G.W. M A U P I N , Virginia Transportation Research Council, Charlottesville, VA V Y T A U T A S P. P U Z I N A U S K A S , The Asphalt Institute. College Park, MD K E V I N D. S T U A R T , Federal Highway Administration, McLean, VA

p r o p e r t y o f

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R E S E A R C H S P O N S O R E D BY T H E AMERICAN A S S O C I A T I O N O F S T A T E H I G H W A Y A N D TRANSPORTATION OFFICIALS IN COOPERATION WITH THE FEDERAL HIGHWAY ADMINISTRATION f£627'92

T R A N S P O R T A T I O N R E S E A R C H B O A R D NATIONAL RESEARCH COUNCIL WASHINGTON, D.C. OCTOBER 1991

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP SYNTHESIS 175

Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research.

In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the fu l l cooperation and support of the Federal Highway Administration, United States Department of Transportation.

The Transportation Research Board of the National Research Council was requested by the Association to administer the research program because of the Board's recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as: it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state, and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them.

The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fu l f i l l these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board.

The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or duplicate other highway research programs.

Project 20-5 F Y 1987 (Topic 19-09)

ISSN 0547-5570

ISBN 0-309-04924-5

Library of Congress Catalog Card No. 91-66124

Price $10.00

Subject Areas

Materials and Construction

Mode Highway Transportation

NOTICE The project that is the subject of this report was a part of the National Cooperative Highway Research Program conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. Such approval reflects the Governing Board's judgment that the program concerned is of national importance and appropriate with respect to both the purposes and resources of the National Research Council.

The members of the technical committee selected to monitor this project and to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the project. The opinions and conclusions expressed or implied are those of the research agency that performed the research, and, while they have been accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National Research Council, the American Association of State Highway and Transportation Officials, or the Federal Highway Administration of the U.S. Department of Transportation.

Each report is reviewed and accepted for publication by the technical committee according to procedures established and monitored by the Transportation Research Board Executive Committee and the Governing Board of the National Research Council.

The National Research Council was established by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and of advising the Federal Government. The Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in the conduct of their services to the government, the public, and the scientific and engineering communities. It is administered jointly by both Academies and the Institute of Medicine. The National Academy of Engineering and the Institute of Medicine were established in 1964 and 1970, respectively, under the charter of the National Academy of Sciences.

The Transportation Research Board evolved in 1974 from the Highway Research Board, which was established in 1920. The T R B incorporates all former H R B activities and also performs additional functions under a broader scope involving all modes of transportation and the interactions of transportation with society.

NOTE: The Transportation Research Board, the National Research Council, the Federal Highway Administration, the American Association of State Highway and Transportation Officials, and the individual states participating in the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers' names appear herein solely because they are considered essential to the objective of this report.

Published reports of the

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

are available from:

Transportation Research Board National Research Council 2101 Constitution Avenue, N.W. Washington, D.C. 20418

Printed in the United States of America

PREFACE A vast storehouse of information exists on nearly every subject of concern to highway administrators and engineers. Much of this information has resulted from both research and the successful application of solutions to the problems faced by practitioners in their daily work. Because previously there has been no systematic means for compiling such useful information and making it available to the entire highway community, the American Association of State Highway and Transportation Officials has, through the mechanism of the National Cooperative Highway Research Program, authorized the Transportation Research Board to undertake a continuing project to search out and synthesize useful knowledge from all available sources and to prepare documented reports on current practices in the subject areas of concern.

This synthesis series reports on various practices, making specific recommendations where appropriate but without the detailed directions usually found in handbooks or design manuals. Nonetheless, these documents can serve similar purposes, for each is a compendium of the best knowledge available on those measures found to be the most successful in resolving specific problems. The extent to which these reports are useful will be tempered by the user's knowledge and experience in the particular problem area.

FOREWORD By Staff

Transportation Research Board

This synthesis will be of interest to pavement designers, construction engineers, maintenance engineers, and others interested in avoiding or limiting moisture damage in asphalt concrete. Information is provided on physical and chemical explanations for moisture damage in asphalt concrete, along with a discussion of current practices and test methods for determining or reducing the susceptibility of various asphalt concrete components and mixtures to such damage.

Administrators, engineers, and researchers are continually faced with highway problems on which much information exists, either in the form of reports or in terms of undocumented experience and practice. Unfortunately, this information often is scattered and unevaluated, and, as a consequence, in seeking solutions, full information on what has been learned about a problem frequently is not assembled. Costly research findings may go unused, valuable experience may be overlooked, and full consideration may not be given to available practices for solving or alleviating the problem. In an effort to correct this situation, a continuing NCHRP project, carried out by the Transportation Research Board as the research agency, has the objective of reporting on common highway problems and synthesizing available information. The synthesis reports from this endeavor constitute an NCHRP publication series in which various forms of relevant information are assembled into single, concise documents pertaining to specific highway problems or sets of closely related problems.

Moisture damage in asphalt concrete is a nationwide problem which often necessitates premature replacement of highway pavement surfaces. This report of the Transportation Research Board describes the underlying physical and chemical phenomena responsible for such damage. Current test methods used to determine the susceptibility

of asphalt concretes, or their constituents, to moisture damage are described and evaluated. Additionally, current practices for minimizing the potential for moisture damage are examined.

To develop this synthesis in a comprehensive manner and to ensure inclusion of significant knowledge, the Board analyzed available information assembled from numerous sources, including a large number of state highway and transportation departments. A topic panel of experts in the subject area was established to guide the researcher in organizing and evaluating the collected data, and to review the final synthesis report.

This synthesis is an immediately useful document that records practices that were acceptable within the limitations of the knowledge available at the time of its preparation. As the processes of advancement continue, new knowledge can be expected to be added to that now at hand.

CONTENTS 1 S U M M A R Y

3 C H A P T E R O N E I N T R O D U C T I O N

4 C H A P T E R T W O B A C K G R O U N D

Definition of the Problem, 4 Theories for Adhesion, 4 Factors Influencing Moisture Damage, 8 Corrective Treatments, 10 Additives, 10 Testing for Moisture Damage Potential, 15 Discussion, 19

20 C H A P T E R T H R E E S U R V E Y O F C U R R E N T P R A C T I C E S

Survey Questionnaire, 20 Extent of Moisture Damage Problems, 20 Effect of Aggregates, 22 Effect of Asphalt, 27 Asphalt-Aggregate Mixtures, 27 Field Procedures and Construction Factors, 29 Environmental Factors, 30 Methods of Correcting Pavements with Moisture Damage,

31 Related Research Activities, 32

35 C H A P T E R F O U R C O N C L U S I O N S A N D R E C O M M E N D A T I O N S Conclusions, 35 Recommendations for Implementation, 35 Recommendations for Further Study, 35

36 R E F E R E N C E S

39 B I B L I O G R A P H Y

42 A P P E N D I X A

51 A P P E N D I X B

79 A P P E N D I X C

ACKNOWLEDGMENTS This synthesis was completed by the Transportation Research Board

under the supervision of Robert E. Skinner, Jr., Director for Special Projects. The Principal Investigators responsible for the conduct of the synthesis were Herbert A. Pennock and Sally D. LifT, Senior Program Officers, and Scott A. Sabol, Program Officer. This synthesis was edited by Linda Mason.

Special appreciation is expressed to R. Gary Hicks, Director, Engineering Research, Oregon State University, who was responsible for the collection of the data and the preparation of the report.

Valuable assistance in the preparation of this synthesis was provided by the Topic Panel consisting of John J. Carroll, Federal Highway Administration; Robert N. Doty, California Department of Transportation; Robert P. Lottman, University of Idaho; G.W. Maupin, Virginia Transportation Research Council; Vytautas P. Puzinauskas, The Asphalt Institute, and Kevin D. Stuart, Federal Highway Administration.

Daniel W. Dearasaugh, Senior Program Officer, and Frederick D. Hejl, Engineer of Materials and Construction, Transportation Research Board, assisted the NCHRP Project 20-5 Staff and the Topic Panel.

Information on current practice was provided by many highway and transportation agencies. Their cooperation and assistance were most helpful.


SUMMARY Damage to hot-mixed asphalt concrete pavements caused by moisture is considered to be a widespread problem in the United States. This synthesis addresses the extent of the problem in both the United States and Canada. In particular, it addresses the factors affecting moisture damage, identifies ways of minimizing moisture damage (including the use of additives), and reviews the tests currently being used to identify moisture-sensitive mixtures.

The findings reported in this synthesis are the result of an extensive literature review together with a survey of current practices of state and provincial highway agencies in North America. The results of this synthesis clearly indicate that moisture damage is a widespread problem; however, the magnitude of the problem is being controlled through the use of improved mixture testing and the use of additives.

The study indicates moisture damage in asphalt concrete pavements may be associated with two mechanisms: (a) loss of adhesion and (b) loss of cohesion. The loss of adhesion is due to water getting between the asphalt and the aggregate and stripping away the asphalt film. The loss of cohesion is due to a softening of asphalt cement in the presence of water which weakens the bond between the asphalt concrete and the aggregate. The two mechanisms are interrelated. That is, a moisture-damaged pavement may be a combined result of both cohesion and adhesion losses.

Further, moisture damage is a function of several factors. These factors include asphalt concrete characteristics, environmental factors, and construction practices. Important characteristics of asphalt concrete include the nature of the aggregate, the nature of the asphalt cement, and the type of mixture. In general, clean aggregates with rough surface texture and low surface moisture, and asphalt cements with high viscosity are better in terms of resistance to moisture damage. Environmental factors that accelerate pavement moisture damage are climate and traffic loadings. The major damage occurs in extreme weather conditions, particularly freeze-thaw action, combined with heavy traffic volume. Construction factors affecting moisture damage include the quality of compaction and weather conditions during pavement construction. Control of air voids is generally considered the most important construction factor.

Methods of treatment to reduce moisture damage, particularly stripping, include use of good aggregate, pretreatment of aggregates, and use of additives. The survey results show that pretreatment of aggregate with lime is the most effective. The amount of lime typically used is in the range of 1 to 1.5 percent. Amines are used by many agencies as asphalt additives; however, their reported effectiveness is mixed.

A variety of test methods has been employed to assess the potential for moisture damage in asphalt concrete mixtures. Thus far, no test is "superior" or can correctly distinguish a moisture-susceptible mixture in all cases; however, the American Associa-

tion of State Highway and Transportation Officials (AASHTO) T 283 and the American Society for Testing and Materials (ASTM) D 4867 appear to have greatly improved the ability to detect moisture damage in paving mixtures.

Based on the study, implementation of the following procedures would minimize moisture damage in pavements: (a) incorporating tests such as AASHTO T 283 or ASTM D 4867 in normal mix design practice; (b) the use of lime-treated aggregate; and (c) use of good construction practices and improved pavement drainage.

C H A P T E R O N E

INTRODUCTION

PROBLEM STATEMENT

The durability of an asphalt concrete (AC) pavement depends to a degree on the adhesion between the asphalt cement and the aggregate. Although construction methods, traffic, environmental conditions, and mixture properties contribute to the deterioration of an A C pavement, the presence of water or water vapor (moisture) often is one of the factors affecting the durability of asphalt concrete mixtures.

Water or moisture damage in A C pavements may be associated with two common mechanisms, adhesion and/or cohesion. In the first mechanism, aggregates generally have a greater affinity for water than asphalt. Water can get between the asphalt and aggregate and "strip" the asphalt film away, leaving bare aggregate. This mechanism may be viewed in terms of debonding or a reduction in the contact angle between the asphalt and aggregate surface. The rate at which debonding takes place is a function of temperature, type of aggregate, viscosity and composition of the asphalt, and the asphalt film thickness. The second probable mechanism identified is the interaction of water with the asphalt cement which causes a reduction in cohesion within the asphalt cement, with a severe reduction in integrity and strength of the mixture. This type of moisture damage is not as visible to the human eye as the loss of adhesion. Graf (7) reports that the cohesive failure theory can further be divided into two distinctly different types of failure. The first involves a softening of the asphalt cement in the presence of water which wil l lead to a failure within the asphalt film of the aggregate matrix. The other involves the softening of the asphalt cement which weakens the bond between the asphalt cement and the aggregate, causing a separation of the film from the aggregate. Therefore, cohesion failure may be thought of as a combination of cohesion loss and adhesion loss.

OBJECTIVES

Damage to hot-mixed asphalt concrete pavement caused by moisture is a widespread problem. This synthesis:

• addresses the recognition and extent of the problem, • lists and reviews the tests currently being used to identify

the potential for the problem to occur and discusses the effectiveness of the tests,

• discusses procedures used to eliminate or reduce the extent of the problem in both overlays and new construction, and

• presents conclusions and recommendations regarding each of the above.

Most of the information used to satisfy these objectives comes from the results of a survey questionnaire together with a review of available literature.

SCOPE OF SYNTHESIS

This synthesis is organized into three major sections as follows:

• Chapter Two presents the results of a literature review to define the problem, identify mechanisms of moisture damage and the factors affecting it, identify corrective treatments, and review test methods currently used to detect potential moisture damage.

• Chapter Three presents the current state of the practice in North America. I t is the result of an extensive survey of all 50 states, 10 Canadian provinces, and Puerto Rico.

• Chapter Four presents the major conclusions and recommendations resulting from this synthesis.

Appendix A is the questionnaire, Appendix B is a summary of the responses, and Appendix C is selected test procedures for identifying moisture susceptibility.

C H A P T E R T W O

BACKGROUND

Research to date has provided a beginning for understanding the complex process of moisture damage in asphalt mixtures. This chapter discusses the damage process and several theories of how additives and other measures can reduce moisture susceptibility of asphalt mixtures.

DEFINITION OF THE PROBLEM

Water or water vapor (moisture) damage in AC pavements may be associated with two phenomena (2). First, water can interact with the asphalt cement to cause a reduction in cohesion with an associated reduction in stiffness and strength of the mixture. Second, water can get between the asphalt film and the aggregates, break the adhesive bond between the aggregate and asphalt, and "strip" the asphalt f rom the aggregate. Water typically gets between the asphalt cement film and the aggregate because the aggregate surface has a greater attraction for water than for asphalt. The mechanism associated with stripping may be viewed in terms of a reduction in the contact angle between the asphalt and aggregate surface, as shown in Figure 1.

Failure due to stripping occurs in two stages: the first stage is the stripping failure itself; the second stage is the failure of the pavement under traffic. Many asphalt pavements experience stripping failure within the mixture without structural failure of the pavement. I f stripping within the pavement becomes excessive, severe pavement deformation and failure may occur as a result of repeated loading (5). Stripping failures can take the form of potholes or cracking and surface raveling of the pavement (4). Wearing courses placed over stripped asphaltic bases are likely to exhibit adhesion failure by raveling and pothole formation (5).

The adhesion of asphalt cement to aggregate is related to the physical and chemical properties of both the asphalt and the aggregate and is reduced by the presence of water. In general, there have been some differences in opinion on the contribution of the chemical nature of the aggregate to adhesion of asphalt. Siliceous aggregates have been classified as hydrophilic and tend to strip more readily than limestone aggregates that have been classified as hydrophobic (6). Mertons and Wright (7) proposed another method of classifying aggregates. They state that both limestone and siliceous aggregates are readily wetted and indicate that both types are truly hydrophihc in character. The terms proposed by Mertons and Wright (7) are "electropositive" for the limestone aggregates and "electronegative" for siliceous aggregates. Electropositive refers to a positive surface charge on the aggregate. Electronegative denotes a negative surface charge. These two types of aggregates represent the extremes found in aggregate classifications; however, all aggregates carry some negative charges. A schematic classification system for aggregate, based on Mertons and Wright's system, is shown in

(a) The moment at which the aggregate, with the drop of bitumen. Is immersed in water. The contact angle is less than 90°.

(b) The water begins to remove the bitumen drop from the aggregate surface and the contact angle decreases.

Finally, the stage is reached where the contact angle is 0° and the bitumen loses contact with the aggregate surface.

FIGURE 1 (After 27).

Schematic of the stripping process

Figure 2. Selection of an asphalt and additives to prevent stripping is therefore highly dependent on the aggregate type. Experience to the contrary has been reported by Mathews (8). He indicates that relatively few aggregates are known to be completely resistant to the action of water under all conditions of

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FIGURE 2 Classification system for aggregates (After 7).

THEORIES FOR ADHESION

A n appreciation of the mechanism of moisture damage is strengthened by a review of theories of adhesion. Adhesion may be defined as "that physical property or molecular force by which one body sticks to another of another nature" (18). Several factors that affect the adhesion of the asphalt cement to the aggregate have been identified by Thelen (79). These factors include: (a) interfacial tension between the asphalt cement and aggregate, (b) chemical composition of the asphalt cement and aggregate, (c) asphalt viscosity, (d) surface texture of aggregate, (e) aggregate porosity, (0 aggregate cleanliness, and (g) aggregate moisture content and temperature at the time of mixing with asphalt cement.

Four broad theories have been presented to explain adhesion of asphah cements to aggregates. These include the Mechanical Theory, the Chemical Reaction Theory, the Surface Energy Theory, and the Molecular Orientation Theory. The actual mechanism by which adhesion works is not fully explained by any one theory. Adhesion is partially explained by each theory. Additives primarily address the chemical, surface energy, and molecular theories. These theories, together with the factors affecting adhesion, are discussed in the following sections.

practical use. He also asserts that the notion that "acidic" rocks have a higher potential for stripping than "basic" rocks is inaccurate.

Yoon and Tarrer (9) report that the chemical and electrochemical interaction between water and the aggregate surface plays a greater role in stripping than the physical characteristics of the aggregate. They state the zeta potential of the aggregate surface in water and/or the pH of the water imparted by the aggregate could be used to measure stripping potential. In general, the higher the zeta potential and/or the pH value, the higher the probability for stripping.

Development and evaluation of antistripping agents has been the subject of study by several researchers (2, 10-16). I n many cases, it is stated that moisture damage can be controlled or prevented by the use of an antistripping agent that is added to the binder in small quantities or by the use of lime added to the aggregate. Further, evidence suggests that the damage wil l be minimal i f stripping could be restricted to the coarse aggregate. I f the fine aggregate in the mixture strips, severe damage wil l result because the fine aggregate constitutes the basic matrix of the mixture (17). I t is apparent that moisture damage is influenced by many variables related to the materials involved, including: climate, loading conditions, construction practices, and roadway design techniques.

During the past decade, several major research studies have been conducted by the Federal Highway Administration (FHWA) and others to predict the extent of stripping damage in A C mixtures and to evaluate the effectiveness of antistripping additives. Indeed, no fewer than 18 states have conducted or participated in research projects focusing on stripping (i.e., Alabama, Arizona, Arkansas, Colorado, Georgia, Idaho, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, Montana, Oregon, South Carolina, Texas, Utah, and Virginia). To date (1991), however, no universally accepted laboratory test and specimen conditioning procedure, validated by field performance histories, has yet been developed to identify when and where moisture damage wi l l occur.

Mechanical Theory

Mechanical adhesion is affected by several properties of the aggregate, including (a) surface texture, (b) porosity (absorption), (c) surface coatings on the aggregate, (d) surface area, and (e) particle size {20, 21). Adhesion between the aggregate and asphalt cement takes place at the interface of the two materials (Figure 3). I t is often stated that the rougher the surface texture, the greater the total adhesion between the asphalt cement and aggregate. Further, Rice (21) indicates the stability and durabil-

Aggregate

Interface

Interstitial Asphalt

i l i l i i i i i S ^ ^ Asphalt

F I G U R E 3 bond.

Concept of the asphalt-aggregate

ity of the AC pavement is also related to surface roughness of the aggregate. The prevailing theory to explain the influence of surface roughness is that the asphalt cement is forced into the pores and irregularities of the aggregate surface to provide a stronger mechanical interlock. Asphalt retention has been noted to be better with rough, irregularly surfaced aggregates compared to smooth, glassy-surfaced aggregates (22). Following these arguments, Knight (23) and McBain and Hopkins (20) have attempted to relate the adhesion between the asphalt cement and the aggregate to the surface characteristics of the aggregate.

In some instances, however, surface roughness may work against adhesion. For rough-surfaced aggregates, it may be di f f i cult to maintain complete (uniform) coating of the aggregate. Consequently the thin films of asphalt cement at the edges of a rough feature may be susceptible to stripping (24). Knight ( 2 i ) noted that surface texture is influenced by mineralogical composition of the aggregate.

Porosity (the volume of the void space as a percentage of the total volume of the aggregate) and absorption (the volume of water held in the pore space of an aggregate) are believed by many to influence the stripping phenomenon. Although greater porosity and absorption capacity are generally associated with improved adhesion, the pore size may be more significant than the total volume of pores in the aggregate (9).

I t is generally held that the penetration of the asphalt into the pores of the aggregate enhances the mechanical interlock. Scott (5) states that the oily constituents of an asphalt enter the pores or capillaries of the aggregate and consequently are preferentially absorbed. The asphalt cement on the surface of the aggregate becomes harder and, therefore, has a higher viscosity owing to this preferential absorption of the oily constituents. Thelen (79) suggests that this interlock of the asphalt cement with the pores should cause the asphalt to adhere more strongly to the surface of the aggregate and, therefore, be less susceptible to stripping. Work presented by Ziesman (25) indicates that the asphalt cement physically interlocks with the aggregate as a result of the penetration of the asphalt cement into pores, crevices, and capillaries in the surface of the aggregate. Yoon and Tarrer (9) did not find a significant relationship between the physical characteristics of aggregate, pore volume and surface area, and stripping potential due to the overriding influence of chemical properties.

Dust and moisture very often coat aggregates that are used in road construction. Both dust and moisture prevent intimate contact between the aggregate and the asphalt cement and, as such, increase the tendency toward stripping. Dust on the aggregate surface is believed to reduce the degree of coating and often causes an increase in viscosity of the asphalt. To improve asphalt wetting in this case, a lower viscosity asphalt cement or an increased mixing temperature is generally used.

The greater the surface area of the aggregate, the greater the amount of asphalt cement required for stability (26). Results presented by Strauss and Anderson (2*) indicate that aggregates containing appreciable amounts of material finer than the No. 200 (75 /im) sieve require more asphalt cement to completely coat the aggregate than a comparable mixture with a lesser proportion of fines. Consequently, a mixture with substantial fines tends to strip more readily because complete particle coating requires more asphalt cement which is more difficult to achieve without creating a stability problem.

Chemical Reaction Theory

A number of investigators (22, 28, 29, 30) have noted that stripping is more serious in acidic aggregate mixtures compared to basic aggregate mixtures. This may be attributed to the fact that when the aggregate is wetted by the asphalt cement, adsorption occurs at the surface which is followed by the chemical reaction between the asphalt cement and the aggregate (31). Following this logic, it is argued that the chemical reaction between most asphalt cements and acidic aggregates is not as strong as the reaction between most asphalt cements and basic aggregates. They further state that additives that reduce the acidity of aggregates should improve the chemical reaction between the asphalt cement and the aggregate, thus reducing the tendency to strip.

Surface Energy Theory

The wetting ability of asphalt cement is defined as the ability of the asphalt cement to make intimate contact with the surface of the aggregate (32). The wetting ability of asphalt cement, as with other liquids, is related to its viscosity (i.e., the resistance to flow associated with molecular friction). For example, water is an excellent wetting agent compared to asphalt cement because it has a much lower viscosity. Wetting ability is also related to surface tension, which is the stress that tends to hold a drop of liquid in a spherical form.

Rice (27 ) has noted that when asphalt spreads over and wets an aggregate surface, a change in energy takes place. This change of energy, referred to as adhesion tension, is a surface phenomenon that depends upon the closeness of contact and mutual affinity of the asphalt cement and aggregate (33). Rice (27) presents data indicating that adhesion tension for water to aggregate is higher than for asphalt to aggregate. Consequently, water wil l tend to displace asphalt cement at an aggregate-asphalt cement interface where there is contact between the water, asphalt, and aggregate. Mack (34) indicates that interfacial tension between the asphalt and aggregates varies with both the type of aggregate and the type of asphalt cement.

Molecular Orientation Theory

The molecular orientation theory states that when asphalt cement comes into contact with an aggregate surface, the molecules in the asphalt orient themselves so as to satisfy the energy demands of the aggregate (32). Work by Mack (34) and McBain and Hopkins (20) suggests that the alignment of asphalt molecules may be the result of the orientation of ions on the aggregate surface. More specifically, the asphalt cement molecules may orient themselves in the direction of polarization of the aggregate ions.

Water molecules are dipolar. Asphalt molecules are generally nonpolar although they contain some polar components. Consequently, water molecules, being more polar, may more readily satisfy the energy demands of an aggregate surface. Mack (34) further notes that the small proportion of asphalt cement molecules that are dipolar may have a greater energy demand for some aggregate surfaces than do water molecules. Thus, they would be able to displace water from the surface of the aggre-

W O R E MW AFTER MW ASPHALT FILM

! AGGREGATE I

(a) Effect from heating and melting asphalt

AGCEEGATE m

ASPHALT FILM

AGGREGATE AGGREGATE

(b) Molecular reorientation

ASPHALT FILM

•• 1 ^,AGGia;GATE

s

(c) Polarization effect ASPHALT FILM

WITH CATIONIC SUEFACTANT

i » AGGREGATE 1 ^ AGGREGATE | ^

(d) Increased polar additive migration

FIGURE 4 Mechanisms of asphalt adhesion improvement with microwave energy treatment.

gates. This effect may not be significant, however, because dipolar molecules are not predominant in asphalt cement.

Discussion

Recent work by Al-Ohaly and Terrel ( i 5 ) illustrates how adhesion is best described from an assimilation of the theories just discussed. They have completed some initial work on the effect of microwave heating on the adhesion of the asphalt and aggregate.

Improved adhesion from microwave heating of asphalt mixtures can reduce the moisture susceptibihty. They state that microwave radiation creates an alternating electromagnetic field when passing through a material. However, this only occurs i f the material is not electrically neutral. Water and aggregate respond to microwaves by heating, whereas asphalt does not. When an asphalt mixture is subjected to microwave radiation, the aggregates are heated and in turn heat the asphalt cement. This leads to one of the following:

• The heated asphalt becomes less viscous and wil l redeposit, thereby filling some permeable voids in the aggregate, as shown in Figure 4a, and improving the adhesion.

• A reduction of viscosity in the asphalt cement allows for the possibility of reorientation of the molecular polarity, illustrated in Figures 4b and 4c, which wil l strengthen adhesion.

• The lower viscosity allows for the migration of the positively charged cations in the antistripping agent to the asphalt/aggregate interface which is shown in Figure 4d. The increase in antistripping agent at the interface promotes a stronger bond.

A l l four theories are involved when the asphalt mixture is subjected to microwave heating. The redepositing of the asphalt in the aggregate pores not only increases the mechanical interlock, but is a function of a decrease in viscosity which increases the wetting ability of the asphalt. Decreasing the viscosity of the asphalt allows for molecular reorientation and chemical additive migration. A l l processes enhance the adhesion of the asphalt to the aggregate.

Strategic Highway Research Program (SHRP) project A-003B ( i d ) is currently developing an improved model for the chemistry of the asphalt-aggregate bond. The work effort is investigating all regions of the bond shown in Figure 3 (i.e., the aggregate surface, the interface region which comprises one or two layers of perhaps preferentially adsorbed asphalt constituents, the interstitial region where asphalt constituents may be structured according to the properties of the asphalt and aggregate, and the bulk asphalt whose properties may be affected by the preferential adsorption of asphalt constituents). The results of this effort should provide new insight into the theories of adhesion.

FACTORS INFLUENCING MOISTURE DAMAGE

The factors that influence moisture damage may be discussed under four broad headings: (1) asphalt concrete characteristics, including aggregate, asphalt cement, and type of mixture, (2) weather during construction, (3) environmental effects after construction, and (4) pavement subsurface drainage. A l l are summarized in Table 1 and each of these factors is discussed below.

Asphalt Concrete Characteristics

The asphalt concrete characteristics important to the mechanisms of moisture damage include the nature of the aggregate, the nature of the asphalt cement, and the type of mixture. The aggregate characteristics identified as being important to stripping include the surface texture, porosity, mineralogy, surface moisture, surface coatings, and surface chemical composition. For asphalt cement, viscosity is generally believed to be an important characteristic to consider; however, aggregate characteristics are more important.

Finally, moisture damage is believed to occur more easily in dense-graded mixtures compared to open-graded mixtures (57). Terrel feels that i f water or moisture is not permitted to stay in the mixture, the chance for either cohesive or adhesive type failures wi l l be minimized. This is true with free draining open-graded mixtures and may be true for very dense mixtures where water or moisture is prevented from entering the mixture.

Aggregate Characteristics

Aggregates are composed of minerals. Each mineral has a characteristic chemical composition and crystalline structure.

T A B L E 1 S U M M A R Y O F F A C T O R S I N F L U E N C I N G M O I S T U R E D A M A G E

Factor Desirable

Charactaristics

1) Aggregate

a) Surface Texture Rough

b) Porosity Depends on pore size

c) Mineralogy Basic aggregates are more resistant

d) Dust Coatings Clean

e) Surface Moisture Dry

f) Surface Chemical Composition Able to share electrons or form hydrogen bonds

g) Mineral Rller Increases viscosity of asphalt

2) Asphalt Cement

a) Viscosity High

b) Chemistry Nitrogen and phenols

c) Rim Thickness Thick

3) Type of Mixture

a) Voids Very low or very high

b) Gradation Very dense or very open

c) Asphalt Content High

4) Weather Conditions (During or Immediately Following Construction)

a) Temperature Warm

b) Rainfall During Construction None

c) Rainfall Following Construction Minimal

d) Freeze-Thaw Following Construction Minimal

5) Traffic Loading Low traffic

Rock types are identified based upon the mineralogical composition and the formation processes associated with the rock. Important to the stripping mechanism is the classification of an aggregate based upon its affinity for water. Although a complicated problem, aggregates that are hydrophilic generally have a greater affinity for water than asphalt cement. Aggregates that are hydrophobic generally have a greater attraction for asphalt cement than water. In general, it may be stated that hydrophilic aggregates are acidic and have a high siUca content; hydrophobic aggregates are generally basic and have low silica contents (24). Limestone and other carbonaceous rocks generally are categorized as hydrophobic aggregates. Hydrophobic aggregates, of course, are believed to provide greater resistance to stripping than hydrophilic aggregates. However, there are always exceptions to the rule. For example, an acidic quartzite has been found to be less susceptible to stripping than most basic aggregates (24), whereas a limestone aggregate mixture was observed to strip (38). Conglomerate-type aggregate containing minerals of clay compounds that cause degradation are more susceptible to stripping than aggregates of more uniform composition.

Limited data suggest that aggregate characteristics such as surface chemistry, surface area, pore size, or diameter make more difference than aggregate mineralogy to the water sensitivity of a mixture:

• Surface Chemistry. Some believe that the presence of iron, magnesium, calcium, and maybe even aluminum is beneficial on the surface of the aggregate while sodium and potassium are detrimental. Clay dust on the surface is also considered to be detrimental. The aggregate surface needs to be able to accept or

donate electrons or form hydrogen bonds, acid and base pairs, or insoluble salts.

• Porosity. Some porosity of an aggregate is desirable, but too much causes substantial amounts of absorption. The pore size makes a difference. I f the pores are too small for asphalt to move into, then porosity probably does not make much difference. I f the diameter of the pores is large and allows the asphalt to intrude, then the amount of porosity is important.

Stuart (J 9) has completed a study that identified the aggregates and minerals most prone to stripping. Table 2 summarizes the aggregates and minerals identified by the state highway agencies.

Asphalt Characteristics

Currently, it is not possible to make a general statement as to which asphalt characteristics are most important to stripping. However, most investigators have identified the fact that high-viscosity asphalt cements resist displacement by water to a greater degree than low-viscosity asphalt cements. This may be due to higher concentration of polar compounds in these materials that results in better wetting characteristics. Schmidt and Graf (10) note that i f asphalt cements have the same viscosity, the chemical composition of the asphalt appears to have a negU-gible effect on stripping. Others report that asphalt chemistry can be an important factor influencing stripping. Compounds contained in asphalts, such as certain forms of carboxylic acids and certain sulfoxide compounds, have been found to be susceptible to moisture damage (40, 41).

Asphalt does not really have a surface chemistry, unless one considers the interface between the asphalt and aggregate as the surface of the asphalt. Polar groups are more adsorptive than nonpolar groups. Sulfoxides and carboxylic acids are readily adsorbed but are also readily desorbed. Phenols and nitrogen bases are quite adsorptive but are retained more in the presence of moisture. Some polars must be present but the amount or percent in the total asphalt needed has not been defined. Basic nitrogens and phenols present in the asphalt are desirable (36).

Type of Mixture

Brown et al. (26) indicate that dense-graded hot mixtures should not strip unless there are excessive air voids, moisture, or insufficient asphalt cement, or unless the aggregates have absorbed coatings. A high percentage of voids in dense-graded mixtures generally is considered to be the most important factor contributing to stripping. Another important factor, however, may be the complete drying of the aggregates in the mixtures (19).

Good resistance to stripping in open-graded cold mix paving mixtures has been observed in the state of Oregon (42). This resistance may, however, be due to the antistripping agents that are contained in the emulsions used for these mixtures or to thicker asphalt coatings on the aggregate.

Weather During Construction

Weather conditions during construction of an asphalt concrete pavement have a pronounced influence on the susceptibility of

TABLE 2 SUMMARY OF AGGREGATES (AND MINERALS) ACCORDING TO THE D E G R E E OF STRIPPING ASSOCL\TED WITH THEM (39)

Slight Stripping Moderate Stripping Severe Stripping

a) Minerals

Biotite Biotite Biotite Hornblende Hornblende Hornblende Feldspars: Feldspars: Feldspars:

• Labradorite • Ollgoclase • Ollgoclase • Bytownite • Aibite • Aibite • Anorthite • Anorthite • Anorthoclase

Chlorite Garnet • Microcline Sericite Muscovite Quartz • Perthite Diopside Muscovite • Andesine Olivine Chalcedony Pyroxenes Quartz Auglte Calcite

b) Igneous Ftocks

Gabbro Biotite Granite Granite Basalt Basalt Biotite Granite Greenstone (Basalt) Olivine Dolerite w/Analcite Aplite Granite Quartz Dolerite Quartz Diorite Pegmatite Granite Diabase Andesite Soda Granite Scoria, Slag Diabase Granite Porphyry Peridotite Granodiorite

Obsidian Aibitised Olivine-Diorite Diorite Rhyolite Trachyte Pumice Dacite Syenite

c) Metamorphic Rocks

Siliceous River Sand Biotite Feldspar Gneiss Quartzlte Siliceous Sand w/lron Oxide Coat Feldpathic Quartz-Sercite Gneiss Granitic Gneiss Serpentine Granitic Quartz-Feldspar Gneiss Quartz-Sericite Schist Serpentine

Biotite-Muscovlte Schist Feldspathic-Quartzite Diabase-Hornfels Biotite Schist Hornblende-Gneiss Muscovite Schist Biotite Schist

d) Sedimentary Rocks

Limestone Limestone Iron Oxide-Rich Arkose Dolomite Dolomite Chert Graywacke Limerock Rint Limerock Reef Coral Breccia

Calcareous Sandstone Feldspathic Sandstone Sandstone Chalk Oolitic Limestone Argillaceous Sandstone

the pavement to moisture damage. If the weather is cool and wet during construction, moisture damage in the pavement is more Ukely to occur; generally speaking, these conditions are prevalent in the late fall. Insufficient or poor compaction can lead to stripping because the high air void content allows water penetration into the asphalt mixture.

Environmental Effects After Construction

Environmental considerations that affect stripping after con

struction include climate and traffic loadings. Temperature fluctuations, freeze-thaw cycles, and wet-dry cycles can all affect pavement stripping. Obviously, water is at the root of any moisture damage problem in an asphalt concrete mixture. At least two mechanisms (pore pressure buildup and hydraulic scouring) are associated with damage due to cyclic loading of the asphalt concrete by traffic. Consequently, it may be stated that, all other facts being equal, increased traffic loading (in terms of numbers of repetitions) would accelerate moisture damage.

10

Pavement Subsurface Drainage Chemical Additives

Pavement subsurface drainage (or the lack of it) has also been found to accelerate moisture damage in asphalt-aggregate mixtures. Kandhal et al. {43) presented results from three case histories in Pennsylvania that clearly show the moisture held within the pavement can lead to accelerated damage. Similarly, work by Forsyth et al. (44) in CaUfomia led to the same conclu-

C O R R E C T I V E TREATMENTS

While antistripping agents are the major topic here, other measures also can be employed to minimize moisture damage. These include the use of good aggregate, the use of pavement surface seals, and the pretreatment of aggregates. These three control measures are discussed briefly in the following paragraphs, followed by a detailed discussion of antistripping additives.

In general, to minimize stripping, aggregates should have low porosities of approximately 0.5 percent and a rough, clean surface (45). Initial rounded aggregates should be crushed to produce a rougher texture and coated aggregates should be cleaned through processing.

The entrance of water into a pavement structure can be substantially reduced by closing the pores or reducing the air voids. This can be done by using a dense-graded mixture or by applying a variety of pavement surface seals to the asphalt concrete surface. Perhaps the most common is "fog sealing" of a pavement surface. This technique consists of spraying a light application of liquid asphalt (typically an asphalt emulsion) without mineral aggregate filler to the pavement surface. Other commercially available seals are used also. If the source of moisture is from beneath the pavement, then sealing of the pavement surface could be detrimental. The seal could trap moisture vapor inside the asphalt concrete and promote stripping.

Pretreatment of aggregates involves modifying the surface properties of the aggregate prior to construction or prior to mixing with asphalt. In general, the pretreatment techniques seek to replace the aggregate surface ions that are likely to be removed by water or to cause weak bonding with the asphalt. Also, the pretreatment processes seek to promote a strong bond between the asphalt cement and the aggregate surface.

The chemical interaction at the surface of the aggregate plays an important role in moisture damage. The aggregate selectively absorbs some components of the asphalt. Acid-base interaction can occur; some salt formation may occur between carboxylic acids and monovalent and divalent alkali metals such as sodium, potassium, and calcium ions. Hydrogen bonding occurs between asphalt phenoUcs and the aggregate surface; some Van der Waals interactions also occur.

ADDITIVES

Two broad types of additives have been used to control moisture damage—chemicals and lime. Each of these is discussed in the following sections.

The majority of liquid antistripping additives are surface active agents which reduce the surface tension of the asphalt cement and, therefore, promote more uniform wetting on the aggregate. The adhesion between asphalt cement and aggregate also is improved. This improvement is associated with the fact that the antistripping agents give the asphalt cement an electrical charge that often is opposite to that of the aggregate surface.

The properties of asphalt cements containing antistripping agents can vary greatly. A number of antistripping agents used in the United States are indicated in Table 3. The chemical additives listed have been designed to be effective under certain mixture conditions as noted in the description part of the table. Some are designed for use in hot mixes while others are designed to be used with cutbacks or emulsions. Also, the concentration rates vary with the type of mixture being used. Although the materials cost between $0.50 and $1.00/lb in bulk, the actual increase in the cost of the mixture is about $0.50/ton.

Most chemical antistripping additives are classified as being "heat stable" by their manufacturers. This term implies that the chemical additive does not contain components that might react at elevated temperatures with some element of the asphalt and render the additive ineffective. The reaction is a function of temperature, increasing as the temperature of the asphalt increases (14). However, Yoon et al. (46) found that six of the chemical antistrip additives they tested decreased in concentration and effectiveness after being stored in asphalt at temperatures above 300°F. An illustration of four of these additives and the effect of exposure to 325°F is shown in Figure 5. This indicates a rather large variation in the heat stability of the different additives investigated.

The chemical composition of most commercially produced agents is proprietary information. Tunnicliff and Root (14), however, indicate that the majority of the surfactants currently in use are chemical compounds that contain amines. Amines are primarily basic compounds (R-NH2, where R represents a hydrocarbon chain) that are derived from ammonia. Amines that are produced from fatty acids (fatty amines) have a long hydrocarbon chain. They generally are believed to be the most suitable antistripping agents. When the fatty amines are added to asphalt cement, the asphalt cement is better able to wet the aggregate surface. Further, the fatty amines have the ability to improve the adhesion of the cement to the aggregate due to the chemical bond that they may make with silica (47).

The amines will form a positive ion (R-NH) when combined with water or an acid. In cationic surfactants, Held (48) states that the nonpolar end of the hydrocarbon attaches to the asphalt while the amine group forms ammonium salts with hydrogen ions in the aggregate. These cationic surfactants can destabilize the asphalt emulsions that form at the asphalt/aggregate interface.

There are two methods by which antistripping agents are added to asphalt concrete mixes. The simplest and most economical appUcation method is to introduce the additive to the asphalt cement in a liquid state and thoroughly mix the additive with the asphalt cement, prior to mixing the asphalt cement with the aggregate. Although this method is the most commonly used, it is inefficient in that much of the antistripping agent does not reach the aggregate/asphalt cement interface. The second method of application is to apply the antistripping agent directly

11

TABLE 3 TYPICAL ANTISTRIPPING AGENTS

Supplier Agent Description*

Tomah Products ACRA-500 100% active, soft paste, cationic adhesion agent, designed to bond asphalt to a variety of aggregate types. Rate: 0.4-1.0%

ACRA-2000 A liquid, cationic adhesion agent, designed to bond asphalt to a variety of aggregate types. Rate: 0.25-1.0%

SC-901 100% active, soft paste, cationic adhesion agent designed for use at low levels on very difficult aggregates. Useful In hot mix and cold mix. Rate: 0.15-0.50%

TAA-3000 100% active, low pour point, liquid adhesion agent. Useful In both hot mix and cold mix. Rate: 0.25-0.75%

101-25-B 100% active, low pour point, liquid anionic adhesion agent designed to compete with lime In difficult cases. Rate: 0.25^.50%

ScanRoad Inc. Perma-Tac» and Perma-Tac» Plus

Liquid, heat stable antlstrlpping additives for use In hot-mix asphalt. Can be used with wide variety of aggregates. Good general purpose additives. Usage level: 0.5-1.0%.

Kling* Beta LV(HM) High performance, heat stable antistripping additives for use in hot-mix asphalt. Usage level: 0.25-0.70%

Kling* Beta 2550(HM) Premium, liquid antlstrlpping agent for use in hot-mix asphalts for high performance. Gives normal TSR values near 1.0. Effective with wide range of aggregates. Usage levels: 0.25-0.70%.

Klinge Beta KY A high-performance additive used for cold-mixes and cutbacks. Especially effective with limestones. Usage levels: 0.5-1.0%.

Catimulse 101-AP and Catlmuls* 112-AP

Additives which Improve the coating characteristics of anionic emulsions. Best utilized in the soap phase prior to emul-sification but can be post-added. Typical usage rates: 0.25-0.50 by weight of asphalt.

Jetco Chemicals, Inc. Jetco AD-130 Heat stable, cationic, liquid adhesion agent. A versatile product for use with asphalt cement and cutback asphalt. Rate: 0.2-1.0%.

Jetco AD-150 Heat stable, 100% active cationic liquid adhesion agent for use with asphalt cement and cutback asphalt. Rate: 0.2-1.0%.

Jetco AD-164 Heat stable, 100% active, liquid adhesion agent for anionic emulsions. Rate: 0.1-0.3%.

AI<zo Chemicals, Inc. Redlcote 82-S Heat stable, cationic, liquid adhesion agent that produces a water-resistant film of asphalt even on Inferior grades of asphalt at use levels as low as 0.5%. Rate: 0.5-0.7%

Redicote 90-S Heat stable cationic, liquid adhesion agent. May be used In either hot mixes or with cutbacks. Rate: 0.5-1.0%

Redlcote 91-S A polar, heat stable, oil-soluble additive. Can be used with anionic and cationic emulsions. Rate: 0.5-1.0%

Morton International Pave Bond AP and Pave Bond AP Special

All purpose products that are effective with all types of aggregate. Both are heat-stable, liquid, alkaline additives. Rates: AP: 0.5-1.0%; AP Special: 0.25-0.5%

Pave Bond LP and Pave Bond Special

Free flowing, easy-to-handle liquids that are most effective with siliceous and mixed aggregates. Rates: LP: 0.5-1.0%; Special: 0.25-0.5%

Pave Bond A viscous liquid additive that Is effective with siliceous aggregates and offers excellent performance and cutback asphalts for winter stockpile. Rate: 0.5-1.0%

Sherex Chemical Co. Arosurf AA-88L Heat stable cationic asphalt adhesion aid. Useful In all asphalt applications, hot mix, cut-back, and emulsions. Rate: 0.25-0.75%

Arosulf AA-123 Heat stable cationic asphalt adhesion aid. Especially useful In hot mix applications. Rate: 0.25-0.5%

Westvaco Corp. Indulln AS-1 Heat stable, 100% active amine based adhesion agent. Can be used in asphalt cement, cutback, and cold mixes. Rate: 0.5-1.0%

Indulln AS-Speclal Heat stable, 100% active amine based adhesion agent. Can be used in asphalt cement, cutback, and cold mixes. Rate: 0.3-0.5%

AS-101 Heat stable, 100% active amine based high performance adhesion agent used in asphalt cement, cutback, and cold mixes. Rate: 0.3-0.5%

'Source: Manufacturers literature

12

z

• § •: m t < Q LU Z

a: CD z

i o I -z o DC HI Q-

80

60

40

20

1.0 wt% ADDITIVE NO. 2

- Q

1.0 wt% ADDITIVE NO. 2

- Q

0.5 wt% ~ —

. ADDITIVE NO. 3 \ ^

• \ ^ r n 0.5 wt%

- \ N. ADDITIVE NO. 1

. 0.5 wt%

1 I

^ ADDITIVE NO. 4

1 1

12 24 48

ADDITIVE HOLDING TIME IN ASPHALT AT 325°F, HOURS

F I G U R E 5 Heat stability of antistripping additive in AC-20 as determined by the boiling water test.

complete debonding could result from microwave treatment of mixtures in which the asphalt and aggregate are incompatible.

The amount of chemical additive used is important. When not enough is used, the amount of additive reaching the asphalt/ aggregate interface will be insufficient. However, if an excess amount of additive is used, a moisture-susceptible shear plane may form which would be detrimental to the mixture, as is shown in Figure 6 (49).

Lime Additives

Lime can be added to the aggregate in many ways; however, the improvement in adhesion provided by the hydrated lime only occurs after moisture has been introduced to activate the lime (11). It is generally believed that the lime produces a sharp decrease in the interfacial tension between the asphalt cement and water, thus resulting in good adhesion. Plancher et al. (13) suggest that hydrated lime improves stripping resistance as a result of its interaction with carboxyhc acids in the asphalt, forming insoluble products that are readily adsorbed onto the surface of an aggregate. Schmidt and Graf (10) note that the mechanism by which hydrated lime improves stripping resistance cannot be completely explained by the reaction of the as-phaltic acids with the lime. They note that lime, in general, provides calcium ions which can replace hydrogen, sodium, potassium, and other cations on the aggregate surface.

Acidic O H groups are found on the surface of siliceous aggregates. These groups (SiOH) form hydrogen bonds with the car-

to the aggregate surface. This method is undoubtedly the most efficient and possibly the most effective.

When the liquid antistrip additive is added to the asphalt cement, the chemicals reportedly migrate through the asphalt to the asphalt/aggregate interface (49). Upon reaching the surface interface, water (if present) is displaced and the surface interface becomes lipophilic (an affinity for oil). When the mixture is still hot and the viscosity of the asphalt cement low, chemicals are able to migrate to the asphalt/aggregate interface. However, when the mixture cools and the viscosity of the asphalt cement increases, the amount of chemical additive able to migrate decreases. The ineffectiveness of premixing the additives with the asphalt is a result of this slow migration. The normal time available for migration is approximately 3 hr, while 12 hr generally are needed to obtain the necessary amount of additive at the asphalt/aggregate interface (49). However, Yoon et al. (46) state that the additive concentration at the asphalt/aggregate interface rapidly attains an equiUbrium. Through evaluation of the diffusion rate it was estimated for one additive that 2 min would be required for 90 percent of the additive to pass through 1 mm of asphalt at a temperature of 300°F. This rate is dependent upon the additive in addition to the viscosity of the asphalt.

The use of microwave radiation or a cutback can help increase the amount of additive reaching the asphalt/aggregate interface. Application of microwaves to the mixture would speed up the migration of the chemical additive to the surface interface by forcing polarization (35). At a minimum, the application of microwave radiation would reduce the molecular orientation randomness that occurs at the interface and thereby improve adhesion. Al-Ohaly and Terrel caution that weak bonding or

CATIONIC SURFACTANTS

(a) Surface charge saturation

CATIONIC SURFACTANTS

PLANE

(b) Surface charge over-saturation

F I G U R E 6 Excessive Hquid antistrip agent.

13

boxylic groups from the asphalt and play a major role in the adhesion between the asphalt and aggregate. However, in the presence of water, the two groups dissociate and associate with the water molecules forming strong hydrogen bonds. The lime forms calcium salts with the carboxylic acid and the 2-quino-lenes, leaving the Si molecule to bond with the nitrogen groups in the asphalt (50). The bonds formed with the basic nitrogen are strong and promote adhesion.

Lime has been used in asphalt mixtures since about 1910 (2). Initially, it was used primarily to act as a mineral filler. Lime in its oxide (CaO) and hydroxide (Ca(OH)2) forms is active and will react with water quite readily. However, as a carbonate (CaCOj) lime will not provide the benefits desired for antistrip-ping purposes. Hydrated lime has a low specific gravity (~2.3), and about 85 percent passes the No. 325 sieve.

Lime is also available in two dolomitic forms. Type S is a compound of calcium hydroxide and magnesium carbonate, and Type N is a compound of calcium carbonate and magnesium oxide. Both types of dolomitic lime have been used as antistrip-ping additives. Generally, the resistance to stripping will increase with increased amounts of hydrated lime. However, if the aggregates are well coated, 1 to 1.5 percent of lime by weight of aggregate normally is adequate. Finer aggregates, however, have larger surface areas and may require higher percentages of hydrated lime to adequately protect the aggregate from stripping.

Methods of application include treatment of the aggregate with: (a) dry hydrated lime, (b) hydrated lime slurry, (c) dry hydrated lime with moist aggregate, and (d) hot (quicklime) slurry. All of the above have been shown to improve the resistance to stripping of asphalt mixtures. Each of the procedures is discussed below:

ture aids in the evaporation of the added moisture. However, use of this method can increase safety problems to workers.

In all cases the lime-treated aggregate has been used almost immediately after treatment. Some users, however, have stockpiled the lime-treated aggregate for up to 1 month prior to use.

TESTING FOR MOISTURE DAMAGE POTENTIAL

The development of tests to determine the potential of asphalt mixtures to experience moisture damage has beginnings as far back as the 1930s. Since that time numerous tests have been developed to help identify moisture-susceptible mixtures. The tests vary in how they test for moisture damage. In general, there are two categories into which the tests can be separated:

• Those tests that coat "standard" aggregate with an asphalt cement (with or without additive). The loose uncompacted mixture is then immersed in water (which is either held at room temperature or brought to a boil). A visual determination is then made of the separation of asphalt from the aggregate.

• The other group uses compacted specimens, either laboratory compacted or cores from existing pavement structures. These samples are then conditioned in some manner to simulate in-service conditions of the pavement structure. The results of these tests generally are evaluated by the ratios of conditioned to unconditioned results of either a diametral resilient modulus test, diametral tensile strength test, or both, and visual observation.

• Dry Lime. The primary problem with the addition of dry Ume is holding the lime on the surface of the aggregate until it is coated with asphalt. The loss of hme is greater in drum mixers, which will tend to pick up some of the lime in the gas flow and blow it out the stack. In addition, a portion of the dry lime combines with the asphalt acting as a filler. Aggregates can be treated by adding dry hydrated lime to the aggregates as shown in Table 4. The table lists additional advantages and disadvantages of each method; however, the addition of dry lime has not proven to be as consistently effective as the other methods described below.

• Hydrated Lime Slurry. The primary problem with the use of lime slurry is the additional water added to the aggregates. Since it must be removed by drying, it increases fuel costs and reduces production rates. Thus, application techniques should be directed toward minimizing the amount of water that must be removed when the aggregate enters the dryer of the drum mixer. Table 5 summarizes the commonly used techniques of introducing hme in this manner.

• Dry Hydrated Lime with Moist Aggregate. Possibly one of the most common ways to add lime is to increase the aggregate water content to 3 to 5 percent, followed by the addition of lime using a positive mixing pugmill or tumble mixer to obtain a homogeneous mix.

• Hot (Quicklime) Slurry. The use of quicklime (CaO) has some advantages. First, the cost is approximately the same as for hydrated lime. However, when the quicklime is slaked, the hydrated lime yield is about 25 percent greater (2). Also, the chemical reaction (exothermic) results in an elevated tempera-

Stuart (39) and Parker and Wilson ( J / ) , in evaluating test procedures, found that a single pass/fail criterion for any test could not be established that would result in 100 percent success. Therefore, terms such as "reasonable" and "good" are often used in conjunction with the description of how well the results of a test correlate with actual field performance, if there are sufficient data to make this determination.

Test Methods

From a review of the Uterature, the following tests have received the most attention and cover the variety of methods used to evaluate stripping potential and therefore were selected for review:

• Indirect Tension Test and/or Modulus Test with Lottman Conditioning—vacuum saturation with one freeze/thaw cycle (52, 53).

• A S T M D 4867—Indirect Tensile Test—moisture saturation only (54).

. Boiling Tests (ASTM D 3625),

. Immersion Compression Tests (ASTM D 1075, A A S H T O T 165),

• Freeze-Thaw Pedestal Test (not performed on complete mixture), and

. A A S H T O T 283 (indirect tensile test with a moisture saturation followed by one freeze/thaw cycle).

14

TABLE 4 METHODS OF INTRODUCING DRY LIME (2)

IMethods Advantages Disadvantages

a) Batch Mix Plants

On the Cold Feed - Scalping screen and belt changes can improve mixing

- Minimal equipment

- May produce dusting and some lime loss

- Mixing and coating of aggregates is minimized

Premixing Pugmill - Maximizes coating of the aggregate - Some lime loss due to dusting

- Minimizes losses due to dusting - Some lime may be lost in the asphalt cement

Pugmill Prior to Stockpiling

- Maximizes mixing and coating of the aggregate

- Minimizes losses due to dust

- Some lime may be lost in the asphalt cement

Prior to Stockpiling

- Lime may be added prior to stockpiling - Maximizes chance of carbonation occurring

- Some lime may be lost due to construction

b) Drum Mix Plants

On the Ckjid Feed - Scalping screen and belt changes can improve mixing

- May produce dusting and some lime loss

- Mixing and coating of aggregates is minimized

Premixing Pugmill - Maximizes coating of the aggregate - Some lime loss due to dusting

- Minimizes losses due to dusting - Some lime may be lost in the asphalt cement


- Allows aggregate drainage - Maximizes chance of carbonation occurring

- Only certain aggregates may be treated

Prior to Adding Asphalt

- Dust loss is minimized - Not recommended without special equipment

TABLE 5 METHODS OF INTRODUCING LIME SLURRY (AFTER 2)

Methods Advantages Disadvantages

a) Batch Mix Plants

On the Ctold Feed - Scalping screen and belt changes can improve mixing

- Requires more complex equipment


- Adding lime at each cold feed bin may be required

- Some dust loss may occur during drying

Premixing Pugmill - Better aggregate coverage and allows for drainage

- Minimizes losses due to dusting




b) Drum Mix Plants

On the Cold Feed - Scalping screen and belt changes can improve mixing


- Adding lime at each cold feed bin may be required

- Some dust loss may occur during drying

Premixing Pugmill - Better aggregate coverage and allows for drainage

- Minimizes losses due to dusting




On a Slinger Belt - Minimizes the amount of mixing - Maximizes the amount of moisture to be removed

15

An outline of each procedure is provided in Tables 6 to 11. The tables also summarize some of the advantages and disadvantages associated with each procedure.

It should be noted that other tests have been or are being used by highway agencies. Some of the other tests are mentioned in the next chapter. Survey of Current Practices.

Lottman Indirect Tension Test

In the Lottman procedure (52, 53), the specimens are 4 in. diameter by 2.5 in. height and are compacted to the air void content expected in the field (4 to 8 percent). Samples are tested unconditioned, after vacuum saturation, and after one freeze-thaw cycle. An index of retained strength (IRS) or modulus (IRM) is obtained by dividing the test values from the conditioned samples by the values obtained from the unconditioned samples. A ratio of 0.70 or greater is recommended by Lottman (55) and Maupin (38) who reported differentiating between stripping and nonstripping when values were between 0.70 and 0.75.

Some have argued that the Lottman procedure is too severe because of internal water pressures that develop during the transition from the vacuum freeze to warm water soak. However, Stuart (55) and Parker and Gharaybeh (56) generally found a good correlation between the laboratory and field results.

Tunnicliff and Root Test (ASTM D 4867)

This test also uses specimens 4 in. diameter by 2.5 in. high which are compacted to a void content of 7 ± 1 percent. The test focuses on controlling the degree of saturation in the test specimen. If the test specimen is not at 55 percent saturation after the initial vacuum soaking, then the specimen is returned for additional soaking until a saturation level between 55 percent and 80 percent is reached. After the initial vacuum soaking, if the sample is above 80 percent, it is discarded. The saturation level is important to ensure that enough moisture is present for stripping to occur.

A tensile strength ratio (TSR) is used to evaluate the test results. As with the IRS, the TSR is obtained by dividing the value for the tensile strength from the conditioned sample by the result for the unconditioned sample. Instead of a minimum ratio, a statistical student's t-test is performed to obtain the desired confidence level used to determine the effectiveness of an additive. Results from the test also appear to reflect the field performance results (55).

Boiling Tests (ASTM D 3625)

This test subjects a loose sample of coated mixture to boiling water for a period of 1 min. However, several agencies have used boiling periods up to 10 min. Some feel the test should be used

T A B L E 6 INDIRECT TENSION TEST AND/OR MODULUS TEST (52, 53f

Specimens 9 samples divided into 3 groups Size; 4-in. diameter by 2.5-in. height

Compaction ASTM Methods: D1559 or D1561 or 03387

Air Voids (%) Normally 3 to 5

Procedure Group 1: - Water bath for 5 hr - Test*" (unconditioned)

Group II & III: - Vacuum saturation @ 26 In. Hg for 30 min (conditioned) - Atmospheric pressure, submerged, for 30 min

Group II: - Test temperature water bath for 3 hr -• Test*" (conditioned)

Group III: - Freeze @ 0 ' F for 15 hr (conditioned) - Water bath @ 140*F for 24 hr

- Test temperature water bath for 3 hr -• Test*"

Damage Analysis Ratios: Diametral Resilient Modulus Test Diametral Tensile Strength Test

Group II Short Term ^ ^ ° " P Long Term Group 1 (saturation) Group 1 (accelerated)

Advantages - Conducted on lab mixes, field mixes, or core samples - Severe test - Can differentiate between additive levels - High correlation - Does not give biased results toward lime or liquid additive

Disadvantages - Time consuming (about 3 days for one freezo-thaw cycle) - Amount and type of equipment required is not always readily available

'There are a number of modifications to this test method. ''Test can be run @ 55° F or 73° F

16

T A B L E ? ASTM D 4867 INDIRECT TENSILE TEST

Specimens 6 samples - 2 groups of 3 Size: 4-in. diameter x 2.5 in. height

(for aggregate < 1 in.)

Compaction ASTM Methods: D1559 or D1561 or D3387

Air Voids (%) 6 to 8% or expected field level

Procedure Sort into groups so average air voids are approximately equal

Group 1: (unconditioned) store dry at room temperature

Group II: (conditioned) soak 20 min @ 77°F -> Test

- Obtain a 55% to 80% saturation level (20 in. Hg for about 5 min In distilled water)

- Reject if saturation is > 80% - Soak 24 hr @ 140° F - Soak 1 hr @ 77*F - Test

Damage Analysis - Diametral Tensile Strength (ASTM D 4123) - Visual

Advantages - Can use lab, plant, or field mixes; also cores from existing pavements - Mixtures with or without additives - Time required is moderate - Initial indications show good correlation (based on 80% retained strength)

Disadvantages - May require trial specimens to obtain air void level or degree of saturation - May not be severe enough

T A B L E S BOILING WATER TESTS (ASTM D 3625)

Specimens Field mixture representation @ design AC

( impact ion None

Air Voids (%) None

Procedure - Place about 950 ml of distilled water in 15002000 ml beaker - Heat to boll, then add mixture - Bring mix back to boil and hold for 1 min - Decant asphalt from vessel and refill with cold water

Damage Analysis - Visual assessment - < 95% retained Indicates moisture susceptibility problem

Advantages - Can be used for Initial screening - Minimum amount of equipment required • Can be used to test additive effectiveness - May be used for quality control - Can use lab mix, drum mix, or batch mix from field

Disadvantages - Subjective analysis - Uncompacted mix - Water purity can affect coating retention - Assessment of stripping In fines is difficult - Highly dependent on asphalt viscosity - Doesn't coincide with field experience

as an initial screening procedure because it provides reasonable results for differentiating between stripping and nonstripping mixtures, while others offer its benefits for use in quaUty control in field laboratories.

In Stuart's (55) evaluation of the procedure, boiUng times of 1 min and 10 min were used. He concluded that the 1 min test provided poor results compared with field experience as did the 10 min test. However, the 10 min test may prove useful for field

17

TABLE 9 FREEZE-THAW PEDESTAL TEST

Specimens 3 to 5 briquets 1-5/8-ln. diameter x 3/4-in. height AC @ 5% > optimum

Compaction In mold under 6200 lb for 20 min

Air Voids (%) None

Procedure - Cure briquets @ 75° F for 3 days - Place specimens on stress pedestal in water bottle - Freeze @ I C F for 15 hr - Place in warm water 75° F (room temperature) for 45 min - Place in 120°F oven for 9 hr - Repeat, beginning at freeze, if cracking is not present

Damage Analysis - Visual observation If crack develops in < 10 cycles, moisture susceptible

> 20-25 cycles, resists moisture damage

Advantages - None, research tool only

Disadvantages - Uses only a small portion of the mix; void content not known - Only fair correlation between field and lab results - Measures only cohesion - Requires special equipment - Takes time, 1 day for each cycle

TABLE 10 IMMERSION-COMPRESSION TESTS (ASTM D 1075, AASHTO T 165)

Specimens 6 samples - 2 groups of 3 4 in. diameter x 4 in. height

Compaction Double plunger - final pressure 3000 psi for 2 min (ASTM)

Air Voids (%) Varies

Procedure Group 1: Air cured @77'F- Test @ 77''F

Group II: Water cured @ 120° F for 4 days or 140° F for 1 day -» Test @ 77°F

Damage Analysis - Visual assessment - Unconfined compression @ 77°F and 0.2 in./min

Advantages - Uses actual mix

Disadvantages - Time required is 4 days plus • Poor reproducibility - Air void level plays significant role - Water quality (ions and salts) can affect moisture sensitivity - Equipment may not be readily available

determination for the presence of additives. Lee and Al-Jarallah (57) and Parker and Wilson (57) found that the test provided good correlations between the lab results and field performances. Also, the effectiveness of antistrip additives could be established, but the selection of aggregates that were likely to strip could not be determined (51). Parker and Gharaybeh (56) report that the boiling test did not evaluate the effects of lime correctly.

Parker and Wilson (51) found consistent correlations in their results between mixes, antistripping agents, and asphalt cements when using the Texas Boiling Test. They state that the results indicate the potential use of the boiling test as an indicator of an antistripping agent's effectiveness to prevent stripping. This conclusion is also supported in a separate study by Lee and Al-Jarallah (57).

TABLE 11 AASHTO T 283, INDIRECT TENSILE TEST

Specimens 6 samples/set of mix conditions Size: 4 In. diameter x 2.5 in. high

O^mpactlon ASTM Methods: D1559, D1561, or D3389

Air Voids (%) 6 to 8% or expected field level

Procedure Sort specimens Into two subsets of three specimens

Group 1: (unconditioned) store @ room temperature - Place in water bath @ 77° F for 2 hr prior to testing

Group 11: (conditioned) partial vacuum (20 In. Hg) for 5 min then soak for 30 min or until the degree of saturation Is 55-80% - Freeze @ 0°F for 16 hr followed by soaking In a 140° F bath for 24

hr - Place in water bath @ 77° F for 2 hr prior to testing

Damage Analysis Diametral Tensile Strength (ASTM D-4123) Visual

Advantages Conducted on lab mixes, field mixes, or core samples Severe test Can differentiate between additive levels High correlation Does not give biased results toward lime or liquid additive

Disadvantages Time consuming (about 3 days for one freeze-thaw cycle) Amount and type of equipment required Is not always readily available

Freeze-Thaw Pedestal Test

This test subjects small briquets (I'/g in. diameter by % in. high) to repeated freeze-thaw cycles. It is empirically based and attempts to simulate viscosity levels at 5 years of pavement life. Mechanical properties are minimized while the strength of the bond, both adhesion and cohesion, is evaluated. This is a result of the use of uniform sand size aggregate in the test.

Parker and Wilson (57) found that the test provided a poor correlation between the laboratory and field results. Based on the materials available in Alabama, the test showed little potential for identifying moisture-susceptible mixes or for isolating components that contribute to stripping. In contrast, Kennedy (5*) asserts the pedestal test does an excellent job separating known strippers and nonstrippers in Texas, but may be too time consuming.

Immersion Compression Tests (ASTM D 1075, AASHTO T 165)

This type of test is currently used by many agencies. In this test, cyUnders (4 in. X 4 in.) are compacted using a double plunger method with a pressure of 3(XX) psi. Specimens are conditioned by water soaking (120°F or 140°F water) and then tested for compressive strength. Unconditioned samples are also tested. A retained ratio equal to or above 0.70 is usually required for acceptability. This test has been criticized for producing retained ratios near 100 percent even when stripping is evident (55, 59). This has been attributed by Stuart to an increase in internal pressure and aggregate friction during testing resulting from

water replacing air in the voids and the insensitivity of compression tests to properly measure the effects of moisture damage. However, the Oregon Department of Transportation (based on results of a recent study) feels this test must be considered until proven ineffective (fiO).

AASHTO T 283

This test is a variation of the tests developed by Lottman described above (a modified Lottman). The basic difference is the conditioning procedure used. Samples are compacted to 7 ± 1 percent voids, conditioned using vacuum saturation to 55 to 80 percent degree of saturation, then tested using the indirect tensile test. These results are compared with tests on a companion set of unconditioned samples. Normally, a retained strength ratio of 70 percent is recommended.

Discussion

It is apparent from the literature review that a variety of test methods has been employed to assess (a) the potential for moisture damage in asphalt concrete mixtures or (b) the benefits offered by antistrip agents to minimize moisture damage in asphalt concrete mixtures. So far, no test has proven to be "superior." Nor can any test correctly distinguish a moisture-susceptible mixture in all cases.

In evaluating the results from conditioned and unconditioned samples, the determination of stripping versus nonstripping should not be made based solely on the modulus or tensile

19

strength ratios. Scherocman et al. (6/) and Busching et al. (62) report that the use of chemical additives can increase significantly the unconditioned strengths of test samples. The increase in strength for the conditioned sample is not proportionally the same; hence a lower retained strength ratio can occur even though the values for both the conditioned and unconditioned samples have increased.

In reviewing the conditioning procedures, three common methods stand out. One is the use of a static soak to wet the specimen, the second is to vacuum saturate to "force" moisture into the test specimen, and the third is the use of a freeze-thaw cycle to induce moisture damage to the specimen. All methods have an effect upon the retained strength and/or modulus. For example, in a report by Busching et al. (62), after saturation conditioning of the test specimens for 60 days, it was determined that high saturation levels that could occur in wet environments would significantly affect retained strengths even in the absence of freeze-thaw cycles. The use of freeze-thaw cycles accelerates the loss in strength. Generally, the results from the one cycle can be used to make initial determinations as to the effectiveness of a mixture with or without an additive. However, to obtain an improved indication of the long-term effectiveness of the mixture, multiple freeze-thaw cycles should be evaluated where numerous freeze-thaw cycles are expected. As the number of cycles increases, the damage per cycle decreases. Also, the order of retained ratios for a given group of additives would hkely not remain the same (61, 63). Additives that have the higher retained values after several freeze-thaw cycles (five to seven) would indicate a higher long-term performance.

The Tunnicliff and Root procedure (ASTM D 4867) is a recent development. Stuart (55) reported favorable results from the test data. The use of a freeze-thaw cycle is not incorporated into the test but can be an option. The focus is on vacuum saturation of the test specimen, which for a short duration (approximately one day in the Tunnicliff and Root procedure), has been reported as insufficient to induce moisture related damage. Hopefully, the use of A A S H T O T 283 will overcome some of these deficiencies.

In addition, it should be noted that SHRP has several contracts dealing with the development of improved test methods to evaluate moisture damage. SHRP project A-003A is developing improved methods for evaluating the effects of moisture, temperature, traffic, and aging on the moisture sensitivity of asphalt-aggregate mixtures (64). As part of SHRP Project A-(X)3B, several fundamental studies dealing with the asphalt-aggregate interface are underway to permit a better understanding of this complex problem. One such outcome is the development of the net adsorption test (36). It is designed to evaluate the compatibility and water sensitivity of asphalt-aggregate pairs. The test is composed of two steps: adsorption of asphalt from toluene followed by desorption of asphalt by water. The net result is a measure of the affinity and the water sensitivity of asphalt-aggregate pairs.

Finally, SHRP Project A-004 will use the same tests developed in A-003A to ensure that they will be apphcable for asphalt-aggregate mixtures containing additives. The additives will include polymers, fillers, and antistrip agents.

20

C H A P T E R T H R E E

SURVEY OF CURRENT PRACTICES

This chapter presents the results of an extensive survey regarding current practices of user agencies in North America on moisture damage of asphalt pavements. Appendix A presents the survey form used while Appendix B presents a detailed summary of the responses. The following sections describe the process and the significant findings.

S U R V E Y QUESTIONNAIRE

To aid in the preparation of this synthesis, a survey questionnaire was sent to 61 high way/transportation agencies which included the 50 U.S. states, 10 Canadian provinces, and Puerto Rico. Questionnaire recipients were asked a total of 32 questions regarding pavement distresses associated with moisture damage, aggregate and asphalt material properties associated with moisture damage, test methods used to identify or reduce the extent of moisture damage, construction factors that contributed to moisture damage, locations where moisture damage was most likely to occur, and type of treatments used to maintain or repair moisture-damaged pavements. Research activities relative to pavement moisture damage, either recently completed or currently underway, significant findings, and problems solved, as well as problems still unresolved, were also requested.

Fifty-three agencies responded, 46 from the United States (Figure 7) and the remainder from Puerto Rico and six Canadian provinces (Alberta, Manitoba, New Brunswick, Northwest Territories, Nova Scotia, and Ontario). Among the agencies responding, 37 reported moisture damage problems (34 from the U.S., two from Canada, and Puerto Rico). In order to evaluate responses from all agencies, respondents were asked to give their responses using a scale from 0 to 9. Typically, for questions related to moisture damage, the rating was 0 for no damage to 9 for severe damage. For questions with regard to the method of treatment of moisture problems or test procedures, the rating ranged from 0 for not effective to 9 for 100 percent effective. Recipients were also asked to provide copies of any specifications and/or test procedures currently being used by their agency to identify, reduce, or correct moisture-related problems.

E X T E N T O F MOISTURE DAMAGE P R O B L E M S

As indicated, Question 1 dealt with identifying the extent of moisture damage in the United States, Canada, and Puerto Rico. The results of the survey clearly indicated that moisture damage is a significant problem and covers the major part of the U.S. and

W A S H I N G T O N

M A I N E M O N T A N A N O R T H D A K O T A M I N N E S O T A

O R E G O N

W I S C O N S I N D A H O

B O U T H D A K O T A N E W Y O R K

C H G A

I O W A E N N S Y L V A N I N E V A D A O H I O

I L L I N O I S U T A H

C O L O R A D O K A N S A S R G I N I A M I S S O U R I

K E N T U C K Y C A L F O R N I A

O. C A R O L N A T E N N E S S E E

A R K A N S A S / ^ ^ - - r ^ ^ ^ ^ O O K L A H O M A A R I Z O N A N E W M E X I C O

G E O R G I A

A L A S K A

Did not respond

I I Moisture damage

[ [ No moisture damage

F I G U R E 7 States in the U.S. reporting moisture damage.

21

T A B L E 12 REASONS G I V E N FOR NO MOISTURE DAMAGE

Agency Good

Aggregate Antistrip

Agent Mid

Weather Good

Drainage kCx

Design Procedure

Construction Practices

a) United Stales

Alaska X

Rorida X X X

Indiana X X

Iowa X X

Maine X X

Massachusetts X X X X

New Hampshire X X

North Dakota No Reason Given

Ohio No Reason Given

Washington X X

b) Canada

Alberta X (lime)

X

Manitoba No Reason Given

Northwest Territories

Frost Heave and Other Cold Weather Problems are Far More Important

Ontario X (chemicals)

Canada (Figure 7). For the agencies not experiencing moisture damage, a number of reasons was given as to why they have not seen any problems. These reasons are summarized in Table 12.

Questions 2 to 7 of the survey were related to pavement problems resulting from moisture damage, including procedures for the determination of moisture damage and their effectiveness, types of pavement distresses due to moisture damage, and typical ages at which each pavement distress is first experienced. Figure 8 summarizes the survey results of procedures used to determine

Most E f fec t ive

Modera te ly g E f fec t ive

£ Slight ly

Not E f f e c t l v e n v i s u a l I n s p . S u r f a c e E x a m i n a t i o n of C o r e s C o r e T e s t i n g

• N u m b e r of r e s p o n s e s rating e f f e c t i v e n e s s

H = High; L = L o w ; X = M e a n ; S = S t a n d a r d Dev ia t ion

F I G U R E 8 Relative effectiveness of procedures for determining pavement distress due to moisture.

moisture problems. Thirty agencies reported that they identified moisture-related pavement distress through visual inspection of surface and examination of cores, with an average effectiveness of the method ranging from about 5 to 6, respectively. A rating of 6 is considered moderately effective. Note that a visual inspection of the surface is considered less effective than an inspection of cores. Twenty-one agencies used core testing procedures to identify the moisture damage problem. An average effectiveness of 6 for this procedure was noted. Both the core examination and core testing procedures seem to be very good at identifying the moisture damage problem with a score as high as 9 (100 percent effective) and a small standard deviation, indicating most agencies feel moisture damage is readily identified.

The percentage of asphalt pavements experiencing moisture distress ranged considerably among the states, as shown in Figure 9. From the data collected and summarized in the appendix, the following statistics were developed:

Percent of Pavements Experiencing

Moisture Distress Number of Agencies

Reporting

0-10 10-20 20-30 30-50

75

16 14 2 4 1

These data clearly indicate moisture-related distress to be a widespread problem.

22

W A S H N G T O N

M O N T A N A N O R T H D A K O T A M I N N E S O T A

O R E G O N

W I S C O N S I N S O U T H D A K O T A

N E W Y O R K I C H I G A

I O W A E N N S Y L V A N I N E V A D A N E B R A S K A

O H I O I L L I N O I S

C O L O R A D O

IRGINIA M I S S O U R I K E N T U C K Y C A L I F O R N I A

O . C A R O L NA

O K L A H O M A A R K A N S A S N E W M E X I C O

G E O R G I A

A L A S K A

HAWAII

• 0-10 • 10-20

Did not respond

I j No moisture damage

• 20-30 • 30-50

F I G U R E 9 Estimated percentage of pavements experiencing moisture-related distress.

When asked which types of distress result from moisture damage (see Question 4 in Appendix B), most agencies provided some type of response. Figure 10 summarizes these responses. Of the 37 agencies which indicated they experience moisture damage problems, 30 indicated that raveling was associated with moisture damage and the average level of severity was 3.4 (a slight problem). Only two agencies (Colorado Department of Transportation and New Brunswick Department of Transportation) reported that raveling due to moisture damage was a severe problem.

Twenty-five of the 37 agencies responding reported flushing problems to be associated with moisture, with an average severity rating of about 3 (or a slight problem). This was expected since

S e v e r e p rob lem 9

Modera te P r o b l e m

Sl ight , P r o b l e m

N o P r o b l e m " R a v e l F l u s h F a t i g u e T h e r m a l P o t h o l e s Rutt ing R e f C r

* N u m b e r of r e s p o n s e s

H = H igh ; L = L o w ; X = M e a n ; S = S t a n d a r d Dev ia t ion

F I G U R E 10 Relative severity rating for various pavement problems as affected by moisture.

flushing may be the direct result of the asphalt stripping from the aggregate and migrating upwards. For example, when polymer-modified chip seals have been used (sealing the surface), the moisture-vapor strips the asphalt from the aggregate and it accumulates at the surface.

It would also appear from the survey that fatigue cracking is not greatly affected by moisture in the asphalt-aggregate mixture (average severity rating of 2.9). However, both Georgia and Louisiana (states which have completed several research studies dealing with moisture damage) indicate moisture can affect the fatigue behavior of asphalt-aggregate mixtures. This confirms work by Kim et al. (65), in a study for the Oregon Department of Transportation, which definitely indicated moisture can affect the fatigue behavior of asphalt-aggregate mixtures. Also, stripping in the base layers can be expected to accelerate fatigue cracking in the surface layer. In SHRP Contract A-(X)3A, this problem is being evaluated and definitive information on the effect of moisture in fatigue behavior should be available in 1993.

The responses clearly indicate that thermal cracking (as expected) is not a major moisture-related distress. Of the 18 responses to this question, the average severity rating was about 1 (or no problem). Twelve agencies indicated that moisture has no effect on thermal cracking.

Of the 31 agencies responding to the effect of moisture on occurrence of potholes, the responses varied widely, with an average rating of about 4.3 (a slight problem). Both Missouri and Pennsylvania reported that moisture severely affects potholes.

The effect of moisture on rutting or permanent deformation problems was also rated to be a slight problem (average rating of about 4.3). Since moisture generally reduces the strength or stiffness of the asphalt-aggregate mixture, this should have been expected. However, only Nova Scotia reported that moisture severely affects rutting. This problem too is being studied by

23

M o d e r a t e g L

S l i g h t 3

N o n e 0 R a v e l F a t i g u e T h e r m a l P o t h o l e s R u t t i n g R e f C r k

* N u m b e r o f r e s p o n s e

H = H i g h ; L = L o w ; X = M e a n ; S = S t a n d a r d D e v i a t i o n

F I G U R E 11 Relative severity rating for various pavement problems as affected by freeze-thaw conditions.

SHRP Contract A-003A (36). Results on the effect of moisture on the occurrence of rutting should be available in 1992.

Very few states indicated that reflection cracking problems are directly related to moisture damage. The average was less than 2 (a slight problem). Only one agency (Delaware) indicated that reflection cracking was directly related to moisture.

Question 5 concerned the relative acceleration of the pavement distress due to repeated freeze-thaw conditions. As indicated in Figure 11, all of the distress modes appear to be accelerated by repeated freeze-thaw cycles, with the most severe being the effect on potholes. More than one-half of the 30 agencies reported a severity level of 7 or greater. The second most important distress type affected by freeze-thaw cycles was raveling, with an average score of about 4. Freeze-thaw cycles have a lesser effect on accelerating fatigue cracking, rutting, thermal, and reflection cracking, as shown in Figure 11. Flushing is reported to be the least severe in terms of how freeze-thaw cycles affect its occurrence.

Question 6 dealt with the typical age (years) when the various distress types occur due to moisture damage. It is obvious from the responses of the various agencies (Figure 12) that pavement distress resulting from moisture damage is first experienced from about 2 to 7 years (without additives) and 4 to 10 years (with additives). For raveling, the typical pavement age when distress is first noted ranges from about 4 to 6 years; for flushing, about 3 to 6 years; for fatigue cracking, about 7 to 8 years; for thermal cracking, about 8 years; for potholes, about 6 to 10 years; for rutting, about 4 to 5 years; and for reflective cracking, about 4 to 6 years. In all cases the use of an additive increases the life of the pavement. Even though these data are estimates, they do provide a relative indication of the effect of moisture on the pavement life for each of the distress types.

Question 7 was concerned with the relative severity of the pavement moisture problems since about 1965. Many engineers have hypothesized that, prior to the oil embargo of 1973, widespread moisture damage problems did not exist. After 1973, owing to the increased use of asphalt blends, they also hypothesized that moisture-related pavement damage increased. The results of the survey (Figure 13) indicate that without additives the average severity rating has increased gradually from a value

of 2 to a value of nearly 4. However, where additives have been employed the trend is not so clear. After 1973, there was a gradual increase in the severity rating followed by a drop-off since 1980. Currently, the pavement moisture problems with additives have a severity rating of 3 (slight problem).

E F F E C T O F A G G R E G A T E S

Questions 8 to 15 dealt with identifying the types of aggregates used in asphalt concrete pavements, the severity of pavement moisture problems for the type of aggregate, type of aggregate treatment used and its effectiveness, the effect of aggregate gradation, and the types of tests and specifications used for aggregates to preclude moisture damage. Certainly, the results of the literature review in Chapter Two indicate that the aggregate is a major contributor to moisture damage (stripping). The questions were written in such a way as to capture the state of the knowledge of the effect of aggregate type and treatment on moisture-related pavement damage.

The results from Question 8 clearly indicate that the most commonly used aggregates in asphalt mixtures are basalt, lime-

R a v e l i n g F l u s h i n g F a t i g u e C r k T h e r m a l P o t h o l e s R u t t i n g R e f l e c t C r k

a ) W i t h o u t A d d i t i v e s

R a v e l i n g F l u s h i n g F a t i g u e C r k T h e r m a l P o t h o l e s R u t t i n g R e f l e c t C r k

b) W i t h A d d i t i v e s

* Number of responses H = High; L = Low; X = Mean

F I G U R E 12 Typical pavement age when moisture damage is first experienced.

24

Severe Problem 9

I Slight a Problem

No Problem 0

16

11

16 15 14 H

12 11

1965-67 1968-70 1971-73 1974-76 1977-79 1980-82 1983-85 1986-88

a) Without Additives

Q u a r r y ^

C r u s h e d G r a v e l ^

B a s a l t G r a n i t e T r a p r o c k S a n d s t o n e D o l o m i t e G r e y w a c k e

L i m e s t o n e S l a g Q u a r t z l t e C h e r t R h y o l i t e O t h e r

* N u m b e r of r e s p o n s e s

F I G U R E 14 Types of aggregates most commonly used.

Severe Problem g

g kfoderate Problem

Slight

No Problem 0

20

18

10 17 16

1965-67 1968-70 1971-73 1974-76 1977-79 1980-82 1983-85 1986-88

b) With Additives H = High; L = Low; X = Mean

F I G U R E 13 Relative severity of pavement moisture problems over time.

stone, granite, quartzite, and sandstone, as shown in Figure 14. The effect of aggregate type in severity of moisture-related problems was also identified (see Figure 15). Those aggregates affecting moisture damage slightly (average rating < 3) included basalt, limestone, slag, traprock, sandstone, dolomite, and greywacke. Most of these were identified by Stuart (39) to be shght or moderate strippers. Aggregates with average ratings between 3 and 6 (slight to moderate problems) included granite, quartz-ites, cherts, and rhyolites. All of these were identified by Stuart to be severe strippers (39).

In an effort to eliminate or reduce the extent of moisture damage, many agencies use some form of aggregate treatment, including pretreatment with lime, washing out deleterious particles, and use of well-dried aggregates. Pretreatment with hme was generally reported to be most effective in eliminating and reducing moisture damage, as illustrated in Figure 16. Well-dried aggregates also seem to be effective in reducing moisture damage, with an average effectiveness second to pretreatment with lime. Prewashing aggregates was only shghtly effective.

The method of adding lime to aggregates seems to have a slight influence in its effectiveness. Dry lime has the lowest rating

Severe Problem

No Problem 0 Basalt GrsnKe Traprock Sandstone Dolomite G r e y w a c k e

Limestone S lag Quartzlte Chert Rhyolite Other

* Number of R e s p o n s e s

H = High; L = Low; X = Mean; S = Standard Deviation

F I G U R E 15 Relative effect of aggregate type on occurrence of moisture-related problems.

1 0 0 % E f fec t ive

^ M o d e r a t e 6

Sl ight 3

Not E f fec t ive 0 Pret reat w / L l m e W a s h out d e l e t e r i o u s

P a n i c l e s Wel l d r ied a g g r e g a t e

* N u m b e r of r e s p o n s e s rat ing e f f e c t i v e n e s s

H = H igh ; L = L o w ; X = M e a n ; S = S t a n d a r d Dev ia t ion

F I G U R E 16 Relative effectiveness of types of aggregate treatments used to reduce moisture damage.

25

lOOXEWectlve

% Moderate 6

Slight 3

Not Effective 0 Dry lime Moist Agg. Lime Slurry

• Number ot responses rating effectiveness H = High; L = Low; X = Mean; S = Standard Deviation

F I G U R E 17 Relative effectiveness of lime treatment of aggregate by method of lime addition.

with the most variable performance. Dry lime on moist aggregate and lime slurry appear to have similar high effectiveness levels. Two agencies use quicklime which appears to be very effective with a near perfect rating score, as shown in Figure 17. The amount of lime used in all agencies ranged f rom 1 to 2.5 percent, with 1 to 1.5 percent being the most common. Stockpiling the lime-coated aggregate is not necessary, as reported by most agencies.

Terrel and Shute (64) have hypothesized that aggregate gradation (and air voids) in the mixture can contribute greatly to the occurrence of moisture damage. Their theory on "pessimum voids" would indicate that moisture damage would be less for impermeable or free-draining mixes, as shown in Figure 18. This is not confirmed in the response to Question 13 where moisture damage appears to be more prevalent in open-graded mixtures than in dense-graded mixtures (see Figure 19). For example, 22 agencies reported moisture damage problems in dense-graded mixtures, ranging from a low of 1 to a high of 40 percent of all mixtures placed. Eleven states reported moisture damage problems with open-graded mixtures, ranging from 1 to a high of 50 percent of all mixtures. Nevada Department of Transportation, although they did not provide estimates, also indicated that voids have an important effect on moisture damage.

As discussed earlier, many agencies feel that aggregate type has a significant effect on moisture-related damage. Several standard tests have been used, including:

• AASHTO T 182 (Static Immersion Test). In this test the ^ - i n . X No. 4 sieve fraction of a coarse aggregate is coated with 5.5 percent of a standard binder and immersed in distilled water at 77°F for 16 to 18 hr. The percent coating is estimated after the soaking period and moisture damage is considered likely i f the coating is less than 95 percent.

. AASHTO T 210 (Wet Durability Test). Although not specifically designed for adhesion problems, this test indicates whether the aggregate wil l break down under traffic action in the presence of water. I f the aggregate fails this test, the asphalt-aggregate mixture could be susceptible to moisture damage.

• AASHTO T 84 and T 85 (Specific Gravity and Absorption). Highly absorptive aggregates often trap water in their voids which could lead to early moisture damage.

. Boiling Water Test ( A S T M D 3625). This test is similar to the static immersion test except the loose mixture is placed in boiling ivater. The amount of coating is generally estimated after 1 min (although some agencies used up to 10 min). The percent coating considered to be associated with moisture damage also varies, but is commonly 90 percent or less.

Other tests used, but not as extensively, include the California cleanness test and the zeta potential test.

100

LU O

2 O Q DC m uj i t UJ

IMPERMEABLE •PESSIMUM-VOIDS

F R E E DRAINING

10

AIR VOIDS, %

15 20

PESSIMUM VOIDS CONCEPT FIGURE 18 Relationship of air voids and relative strength of mixtures following water conditioning showing the region of pessimum voids (after 64).

11

11

22*

H

X+S

/ / / / / / ^ / / / / / /

^ » Dense-Graded Open-Graded All Mixes

* Number of responses H = High; L = Lov»; X = Mean; S = Standard Deviation

FIGURE 19 Percentage of various mixture types experiencing moisture damage.

26

100% Effective

o Moderate

Slight 3

Not Effective Q AASHTO

T-210 AASHTO

T-182 AASHTO T-e4 & 85

Boiling Water Test

* Number of responses rating effectiveness H = High; L = Lovi; X = fêan; S = Standard Deviation

FIGURE 20 Relative effectiveness of aggregate tests for determining aggregate propensity for moisture damage.

Question 14 addresses the relative effectiveness of each of these standard aggregate tests. As indicated in Figure 20, the relative effectiveness for AASHTO T 182 (two agencies reporting) was 6; for AASHTO T 210 (two agencies reporting) was 5.5; for AASHTO T 84 and T 85 (11 agencies reporting) was 3; and for the boil test (four agencies reporting) was 6. Clearly, there is no consensus as to what is an effective test on aggregates. For example, some agencies included tests such as immersion-compression or retained tensile strength as tests for aggregates. In this synthesis these are considered to be tests on mixtures and their relevance is discussed later in this chapter.

Although most agencies should have specific threshold values for the various aggregate tests, it did not come out from the survey. Most states indicated no specifications for aggregates to ensure good resistance to moisture damage. The Idaho Department of Transportation was the only agency that employed limits for the three AASHTO tests (T 182, T 210, and T 84 and T 85).

EFFECT OF ASPHALT

additive influences the interaction between the asphalt and aggregate.

Questions 16 to 19 deal with the observed effects of type or grade of asphalt on the occurrence of moisture damage in asphalt pavements. Utilization of asphalt additives and their effectiveness were also evaluated. Question 16 dealt with the source of asphalts used by the various agencies. Of the 31 agencies responding, one half responded they did not know the sources of asphalts being used within their agency. Of the agencies that identified the asphalt sources, several did attempt to rate whether one was more moisture susceptible than another. For example:

• The Arizona Department of Transportation indicated, of the various asphalt sources they use, all had about the same effect on moisture damage (rating of 5 or moderate effect).

• The California Department of Transportation and the Kentucky Department of Highways indicated that aggregates, not asphalt, are the most important factor affecting moisture damage in asphalt pavements.

• The Oregon Department of Transportation indicated that asphalt type has only a slight effect on moisture damage and that all asphalt types behave more or less the same.

• Nova Scotia indicates only a slight effect of asphalt source on moisture damage.

The general conclusion is that most agencies are not yet capable of identifying the effect of asphalt source on moisture-related damage, even though research studies indicate there is an effect. This is probably because aggregate type and void structure dominate the occurrence of moisture damage.

Nor did the survey results show any consensus that harder grades of asphalt performed better. However, the majority of the respondents indicated that the asphalt grade being used was moderately effective in its resistance to pavement moisture damage.

Finally, the survey also indicated that of the 37 respondents, 20 use amines to eliminate or reduce the extent of moisture problems, seven use polymers, three use portland cement, and seven use lime. The effectiveness of the additives is shown in Figure 21. I t is clear that the use of amines, portland cement, and lime generally are considered to be more effective than

As discussed in Chapter Two, it has long been conjectured that both the source and grade of the asphalt can have a significant effect on the occurrence of moisture damage. However, studies concerned with the effect of asphalt source (e.g., chemical composition) have been limited in scope and number. For example, Peterson et al. (40, 41) indicate that the asphalt chemical functional groups most easily displaced by water include carbox-ylic acids, anhydrides, and 2-quinolones. Most difficult to displace are ketones, phenolic OH, and pyrrolic N H . However, no completed study concerned with chemical composition has evaluated asphalt-aggregate interactions and moisture damage mechanisms over a broad range of asphalts and aggregates. This is being done as a part of SHRP Project A-003B (J(5). The viscosity of the asphalt has also been reported to influence stripping. High viscosity asphalts are generally harder to "peel" from an aggregate resulting in better resistance to moisture damage. Finally, where asphalts (in combination with a particular aggregate) are shown to be moisture susceptible, this condition is often treated using a variety of additives. The type and amount of

100% Effective

> Moderate 5

Slight 3

Not Effective o Portland Cement

* Number of responses rating effectiveness H = High; L = Low; X = Mean; S = Standard Deviation

FIGURE 21 Relative effectiveness of additives in eliminating or reducing moisture problems.

27

100% Effective

Slight 3

Not Effective 0 AASHTO AASHTO

T-182 AASHTO

T-283 Modulus

Ratio Boil TSR -T»st IjMlman or

Root-Tunnicllff * Number of responses rating effectiveness H = HIgti; L = Low; X = Mean; S = Standard Deviation

FIGURE 22 Relative effectiveness of mixture test procedures to identify moisture-related problems.

polymers in preventing moisture damage. However, it is not clear f rom the survey whether the agencies actually use lime and Portland cement as an asphalt additive or as a treatment for the aggregate. What is clear is that the effectiveness of the amines ranges widely from essentially not effective to highly effective. This should have been expected since the effectiveness of additives is highly dependent on the asphalt-aggregate combination used.

ASPHALT-AGGREGATE MIXTURES

The next set of questions dealt with the mixture test procedures used to identify moisture-related problems (Question 20), the criteria used with the test to determine whether moisture damage wil l occur (Question 21), whether the test method or the specification is inadequate (Question 22), and what the agency currently does i f the mixture fails the specification (Question 23).

In the survey, several standard tests were identified including:

• Immersion-compression (AASHTO T 165) . Static immersion (AASHTO T 182) . Retained tensile strength (AASHTO T 283) (modified

Lottman) • Modulus ratio (with Lottman conditioning) • Boiling water test (ASTM D 3625 or a variation) . Retained tensile strength (ASTM D 4867—Root-Tunnicliff

or original Lottman (53))

With the exception of the particle coating and boiUng water test, all of the other methods use the entire mixture and thus evaluate the effects of the coarse and fine aggregate, filler, asphalt cement, and additives. These tests indicate quantitatively a loss in a mechanical property due to a change in both the adhesion of the binder to the aggregate and the cohesive properties of the asphalt. Losses in mechanical properties are also a function of any losses in the strength of the aggregate due to conditioning processes such as freeze-thaw cycles.

The survey results, shown in Figure 22, indicated that 11 agencies employ an immersion compression test and it seems to

be moderately effective (rating of ~ 5). This is despite the concern of some agencies that the retained strength ratios are high compared with other tests such as A A S H T O T 283 or A S T M D 4867. Three agencies use AASHTO T 182 with an average effectiveness of 4 (slightly effective). Seven agencies use AASHTO T 283 (modified Lottman conditioning) with considerable success. The average rating was 7.5 (very effective). Only the Oregon Department of Transportation used the modulus ratio test (with Lottman conditioning) and they reported it to be a very effective test (a rating of 9). In fact, in a recent study for F H W A (60), they found that the modulus ratio test as well as AASHTO T 165 were better than A S T M D 4867 in detecting moisture damage. A boiling water test was used by eight agencies, with an average effectiveness rating of 5 (slight to moderately effective). The Root-Tunnicliff method (ASTM D 4867) is used by nine agencies; however, only four rated its effectiveness (range of 2 to 8 with an average value of 5). The Lottman procedure (53) was used by three agencies and it too was rated as being highly effective.

Other tests used included

• California Department of Transportation—Moisture-vapor susceptibility, swell test, a film stripping test, and surface abrasion test. A l l of these were indicated to be only slightly effective.

• Puerto Rico—Retained Marshall stability. The effectiveness of this test was not reported.

In summary, while several tests have been used, the most effective appears to be AASHTO T 283 (with modified Lottman conditioning).

The criteria used for each of the above mentioned tests to determine the existence of moisture damage include:

• Percent Retained Compressive Strength. Nine agencies reported the use of criteria for retained compressive strength with values ranging from 50 to 75 percent.

• Percent Retained Stability. Two agencies reported the use of retained Marshall stability with values from 75 to 80 percent.

• Percent Retained Tensile Strength. Nineteen agencies use this criterion. Threshold values range from 60 to 80 percent with most agencies using 70 to 75 percent.

• Percent Retained Modulus. Three agencies report the use of this criterion with only Oregon specifying a value of 70 percent.

• Minimum Wet Strength. Only two states reported the use of this criterion. No values were given, however.

• Percent Stripping (Visual). Seventeen agencies reported the use of this criterion with values ranging from 0 to 30 percent to indicate moisture damage. Most agencies, however, use values of 5 to 10 percent.

Only California employs other criteria for a moisture vapor susceptibility test (stability of 25 min and swell of 0.3 in. max).

The relative effectiveness of each of these criteria is summarized in Figure 23. As indicated, the agencies felt the criteria for retained compressive strength was moderately effective (average rating of 6); the retained Marshall stability was highly effective (average rating of 8); the retained tensile strength was highly effective (average rating of about 7); the retained modulus test was highly effective (average rating of 7); minimum wet strength was moderately effective (average rating of 6.5); and percent stripping was quite variable in effectiveness with values ranging

28

100% EHcctive

Not Eflective o Retained Retained Retained Retained Comp, Marstiall Tensile Modulus

Strength Stability Strength • Number o( responses rating effectiveness H = High; L = Low; X = Mean; S = Standard Deviation

MIn. Wet Strength

% Stripping Visual

FIGURE 23 Effectiveness of criteria used to determine that significant moisture damage exists.

from 2 to 8. Overall, most agencies feel their criteria to be moderately effective.

The next question asked " I f the test is not effective, is it the test procedure or the specifications (criteria) that need revising?" Nineteen of the agencies did not answer this question, apparently because they feel their test method and/or criteria are appropriate. However, six agencies felt the test procedures needed to be improved. Some of the responses are summarized below:

• Arizona—Need to improve reproducibility. • Arkansas—BeUeve the ideal test procedure should include

saturated specimens subjected to confining pressures, heat, and pulse loading.

• Kentucky—Feel that the test variables need to be tightened (e.g., percent saturation of 65 to 80 percent).

• Oregon—Uniformity is required for test procedures. • West Virginia—It is not possible to develop a test that

correlates to field behavior 100 percent of the time.

Question 23 dealt with the mixture design changes required i f moisture damage is detected using the various tests and mixture design criteria. Items considered and their effectiveness included (Figure 24):

• Change Asphalt (Grade or Source). Seven agencies indicated this to be an alternative. The effectiveness rating ranged from 0 to 6 with an average value of 3 (slightly effective).

• Lime Treat Aggregate. Thirteen agencies indicated this to be an alternative. The effectiveness rating ranged from 6 to 8 with an average value over 7 (highly effective).

• Change Aggregate. Fourteen agencies change the aggregate. This approach is also highly effective (average rating of 7).

• Treat Asphalt or Change Antistrip Agent. Fifteen agencies select this alternate which has an average effectiveness of about 6 (moderately effective).

Clearly, of the various alternates used, lime treating or changing the aggregate is the most effective.

FIELD PROCEDURES AND CONSTRUCTION FACTORS

The air void level (or permeability) of the mixture, which is influenced by compaction effort, asphalt content, aggregate gradation, and mixture temperature, can greatly influence moisture damage of pavements (5^, 59, 66). I n general, void levels between 8 and 15 percent are most susceptible to moisture damage (37). Void contents lower than 8 tend to produce impermeable mixtures while voids greater than 15 percent drain quickly and should be less moisture susceptible. Questions 24 to 26 were designed to identify whether field construction procedures could be changed to reduce their effect on pavement moisture problems. I t should be noted these questions are applicable to dense-graded mixtures only.

A l l of these concerns are legitimate. The industry needs to develop an improved, more reliable test that relates to field performance. This is one of the major research issues of SHRP A 003A which, it is hoped, wi l l address all of these concerns.

Only four agencies reported a need for improved criteria. Their responses are summarized below:

• Arizona—Need to test the field mixture and to increase minimum wet strength.

• Arkansas—Need to consider minimum strength values (wet and dry). Considering only percentages can be misleading.

• Georgia—Need criteria for minimum allowable tensile strength.

• Illinois—Need better correlation between laboratory and field performance.

Again, all of these concerns are being addressed by SHRP and, it is anticipated that improved guidelines for minimum strength and improved relationship between the laboratory and field wi l l be developed (36, 64).

100% Effective ^

Slight 3

Not Effective 0 Change Asph Lime Treat Agg Change Agg Treat Asph

• Number of responses rating effectiveness H = High; L = Low; X = Mean; S = Standard Deviation

FIGURE 24 Relative effectiveness of various mixture design guideUnes.

29

100% Effective

a> fifloderate 6

Slight 3

Not Effective 0

' Number of responses rating effectiveness H = High; L = Low; X = Mean; S = Standard Deviation

Control Temp @ Placement

FIGURE 25 Relative effectiveness of field control procedures to reduce moisture damage problems.

Figure 25 summarizes the relative effectiveness of controlling void level and/or mixture temperature. The results generally indicate that increased compaction (reduced voids) is highly effective in controlling moisture damage. Also, the results clearly indicate that control of mixture temperature (at placement) can have an important effect on reducing moisture damage, either through improved compaction or reduced mixture moisture. For open-graded mixtures ( > 15 percent voids), compactive effort is not as important. In these mixtures it is more important to ensure a thick asphalt film.

Questions 25 and 26 dealt with identifying the importance of various construction factors as to their contribution to moisture damage. These include:

• L i f t Thickness. Better compaction, hence lower voids, should result from thicker lifts (4 to 8 in.). Of the four factors assessed, clearly this appears to be the least important (average rating of 3), as shown in Figure 26; however, it was confirmed that most agencies have more problems when thin lifts were used.

Most important 9

Slight 3

Not important 0 Mix Temp Air Voids Base Drainage

• Number of responses rating importance H = High; L = Low; X = Mean; S = Standard Deviation

F I G U R E 26 Relative importance of selected construction factors on moisture damage.

• Mixture Temperature. Higher mixture temperatures should generally result in lower voids and/or less mixture moisture; hence, less moisture damage. The survey results show that mixture temperature has an important effect (average rating of 6) and all states concur that low mixture temperatures contribute more to moisture damage.

• A i r Voids. For dense-graded mixtures, voids (or permeability) are very important in relation to moisture damage. A l l states indicated higher voids (8 to 14 percent) contribute to greater moisture damage. However, void contents greater than this (such as in open-graded mixtures) have been reported to have good performance with respect to moisture.

• Base Drainage. Equally as important as air voids is base drainage (average rating of 7). A l l states indicated that poor base drainage greatly affects moisture damage.

Clearly, moisture damage can be minimized by good compaction and good drainage. I f all agencies recognize this, why are these end results so difficult to achieve? There appears to be a definite need for more intensive training efforts.

ENVIRONMENTAL FACTORS

There are several environmental factors that can influence the extent of moisture damage. Some of these include:

• High Rainfall. This affects the amount of water in the pavement.

• Freeze-Thaw Cycles. As indicated earlier, repeated freeze-thaw cycles accelerate moisture-related pavement distress due to the rupturing of the asphalt films.

• Cool-Warm Cycles. Thermal cycles may also affect bonding between the asphalt and aggregate and thus the potential for moisture damage.

• High Water Table. This condition often permits migration of moisture/moisture vapor into the pavement which can accelerate moisture damage.

Other environmental factors also can contribute to moisture damage. For example, in the Southeast part of the U.S., it has been reported that "bUsters" can form due to moisture vapor (heat after a rainstorm) or thermal expansion of entrapped water (67).

The results of the survey (Figure 27) indicated that moisture damage generally occurs more frequently in freeze-thaw areas (15 agencies); however, 14 agencies indicated moisture damage could be found in any environment within their jurisdiction. Areas of high rainfall and water table were also potential places for moisture damage (8 and 10 agencies, respectively). Cool-warm cycles were noted by only four agencies (Georgia, South Carolina, Kansas, and Oklahoma) as contributing to moisture damage. Other factors identified by the responses as contributing to moisture damage included:

• High traffic volume areas, • Overlays over portland cement concrete, • Shaded areas or mountain passes, and • Bad aggregates.

30

High Rainfall F"se2e-Thaw Cool-Warm High Water Table All Areas Moisture Damage

FIGURE 27 Number of responses indicating where moisture damage occurs by environmental areas.

below from escaping. The responses to Question 28, however, were quite mixed. Six agencies indicated that the moisture damage of the underlying layer is not affected by the addition of a chip seal/overlay; eight agencies indicate the damage is increased; eight indicate the damage is decreased; and 17 agencies did not know whether it was affected or not. Clearly, more work is needed to identify whether this is a problem and what conditions might contribute to acceleration of moisture damage in the underlying layers.

RELATED RESEARCH ACTIVITIES

The last three survey questions dealt with:

• Research completed or underway and significant findings, • Moisture damage problems solved, and • Pavement moisture problems which need to be solved.

From the responses, it is apparent that environment has a strong influence on the occurrence of moisture damage. I t is also apparent that test methods to evaluate moisture damage need to consider the environment in which the mixtures are to be placed. Certainly, i f freeze-thaw is not a problem in a given jurisdiction, it should not be considered in the test procedure.

METHODS OF CORRECTING PAVEMENTS WITH MOISTURE DAMAGE

Several methods have been employed over the years to correct (or repair) moisture-related distress in pavements. These include, but are not limited to:

• Conventional overlay, • Chip seal—conventional or polymer-modified, • Remove (mill) and replace, • Recycle—hot or cold, and • Patch—shallow or deep.

Table 13 summarizes the completed or ongoing research. Fifteen agencies have completed or are currently involved in studies dealing with moisture damage. These studies include evaluations of test methods, evaluation of antistrip agents, case histories, and effectiveness of repair treatments. I t clearly shows that considerable work is still needed to solve the pavement moisture problem. However, SHRP has several contracts dealing with moisture damage. SHRP project A-003A (titled "Performance Related Testing and Measuring of Asphalt-Aggregate Interactions and Mixtures") is concerned with developing an improved test method to evaluate moisture susceptibility. The effects of moisture, temperature, traffic, and aging are all being evaluated as a part of this effort (64). SHRP project A-003B (titled "Fundamental Properties of Asphalt-Aggregate Interactions Including Adhesion and Adsorption") is addressing several fundamental aspects including:

• The compatibihty of asphalts and aggregates in terms of their ability to form chemical bonds,

• The effects of aging on asphalt/aggregate chemistry and, in particular, on adhesion, and

Questions 28 and 29 addressed the effectiveness of each of these treatments.

Figure 28 summarizes the responses to Question 28 from the various agencies. Thirty-two agencies responded they remove and/or replace the moisture-damaged pavement. This method was also rated the most effective (average rating of 8). Recycling was also a widely used method to repair moisture-damaged pavements. Twenty-six agencies used this technique and the average effectiveness was 6. Conventional overlays were used by 27 agencies; however, the responses were mixed. Some agencies reported overlays were not effective while others reported that they were 100 percent effective. A n average rating of about 4 was noted for this type of treatment. Both chip seals and patches have been used by 24 agencies with an average effectiveness of 3 to 4.

Recently there have been increasing reports that placement of overlays and/or chip seals over a moisture-damaged pavement can accelerate the "stripping" of the asphalt off the aggregate in the underlying layer. This is in part due to the creation of an impermeable seal on the surface preventing moisture-vapor from

100% Effective

Slight 3

Not Effective 0 Overlay Chip Seal Recycle

* Number of responses rating effectiveness H = High; L = Low; X = Mean; S = Standard Deviation

FIGURE 28 Relative effectiveness of various methods of treatment to repair moisture-damaged pavements.

31

• The chemistry and influence of modifiers on additives in adhesion.

Preliminary results of this study have been presented in a paper by Curtis et al. (36).

In addition, F H W A also has a number of studies just completed or underway. They include

• "Evaluation of Asphalt Stripping Tests" with four state highway agencies (Indiana, Montana, New Mexico, and Oregon) to evaluate test methods AASHTO T 283 and A S T M D 4867.

• "Study of A C Stripping Problems and Corrective Treatments," to determine the most effective methods of introducing lime into asphalt mixtures and to improve the reliability of laboratory test methods used to evaluate moisture susceptibility.

NCHRP also has recently completed a major study (Project 10-17) titled "Use of Antistripping Additives in Asphaltic Concrete Mixtures—Field Evaluation," (68). The objectives of this study were to obtain information on long-term additive performance and determine how well laboratory tests evaluate long-term additive performance.

Nineteen full-scale pavement test sections were built in eight states. In each state, the test project included a control section without additive and a test section including an additive. In three cases, two test sections were used. Test projects were selected on the basis of the cooperating agency's preliminary tests and experience. Subsequent tests were performed on the actual materials used in the test projects.

The test method selected to evaluate long-term additive performance was the method developed in the laboratory phase, now A S T M Method D 4867. These tests revealed a range in potential for moisture damage among the control mixtures, and a range of improvement caused by the additives, resulting in less potential for moisture damage in the test mixtures.

In addition, an extensive program of tests on both aggregates and asphalt cements was included to evaluate thoroughly many factors which may affect moisture damage. The important find

ings f rom this program are that there is potential for moisture damage in the experimental mixtures, and that none of the additives increases the potential for moisture damage or converts otherwise satisfactory mixtures into mixtures likely to fail by some other mode.

Field evaluation includes core testing and condition surveys. A t this time, the experimental pavements range in age from approximately 2 to 4 years. There have been no premature, catastrophic failures. Pavement cores have revealed little moisture and little evidence of moisture damage. Condition surveys are in progress and are not included in this interim report.

Principal conclusions are: (a) the experimental pavements provide a satisfactory basis for a field experiment that can satisfy the objectives of the project, but (b) the experimental pavements have not yet been sufficiently wet and are not old enough for moisture damage of a severity to be conclusive to have occurred.

Table 14 summarizes the problems that the various agencies reportedly have solved. Clearly, the most important are:

• Lime treatment of aggregates has dramatically reduced moisture-related damage.

. Improved test methods (e.g., AASHTO T 283 or A S T M D 4867) allow one to better detect whether a problem exists.

Hopefully, the on-going efforts wil l continue to reduce the extent of the problems.

Table 15 summarizes the problems which agencies feel need to be solved. The consensus is that need exists for:

• Better test methods, particularly those that relate to field performance.

• Quantifying the effect of moisture on fatigue, rutting, raveling, etc.

• Identifying and quantifying clearly the fundamental causes of moisture damage.

• Development of better and more reliable antistrip agents.

Most of these problems are expected to be addressed by SHRP A-003A and A-003B.

32

TABLE 13 RESEARCH COMPLETED OR UNDERWAY AND SIGNIFICANT HNDINGS

StaU/Provlnca Rataarch Complatad Research Underway Significant FIndlnga

Arkansas •Contribution of roadway design and construction sequence to asphalt pavement moisture damage in Arkansas (no date)

Intone None reported

California •Effect of cleanness value on stripping of ATPB material"

•Mix design modifications for dense-graded mixes, OGAC, to improve asphalt concrete durability

No significant findings yet

Georgia •Evaluation of lime as an antistrip agent (no date)

•Evaluation of lime as an antistrip agent

None reported

Illinois •Cooperated in NCHRP Project 10-17, Moisture Damage Study (no date)

None No significant findings

Louisiana •Identification and quantification of the extent of asphalt stripping in asphalt pavements (August 1983)

•Boil test correlation of field stripping problems (July 1984)

•Study undenvay to evaluate a more objective test procedure (e.g., modified Lottman, etc.)

•Use boil test to approve materials for job mix formula

•Modified current boil test procedure

•Reduced const, air void content by lowering voids from 3-5% to 2-4% and increasing VFA 70-80% to 75-85%

•Increasing required roadway compaction to 96%

•Lower design void content of binder coarse from 4-6% to 3-5%

Minnesota •Evaluation of moisture sensitivity tests (e.g., Lottman, et al.)

None to date

Missouri •Identification and quantification of extent of asphalt stripping in flexible pavements (no date)

•Evaluation of laboratory test methods (ASTM D-4817 and immersion-compression)

None reported

Nevada •Moisture damage due to chip seals. Reports being prepared by UNR and is not available.

None reported

New Mexico •Evaluation of stripping tests and anti-stripping additives

None reported

New York •Stripping susceptibility of aggregate from New York state (April 1980)

•Evaluation of asphalt stripping associated with New York aggregates (July 1985)

None

Oregon •Evaluation of asphalt stripping test (March 1990) •Effectiveness of anti-stripping additives OSHD and OSU (April 1989)

None h4one reported

South Carolina •Investigation of stripping in asphalt concrete in South Carolina (July 1989)

•Re-use of moisture-damaged asphalt mixtures

None reported

Texas •Evaluation of pavement sections, NCHRP 10-17 •Treatment of asphalt mixes with lime and antistripping agents (no date)

•Study of field test sections with lime and antistripping agents

None reported

Virginia •Assessment of stripped asphalt pavements (January 1989)

•Effectiveness of anti-strip agents

•Uses strength measurements of cores to aid decisions regarding asphalt pavement rehabilitation

New Brunswick •Started research work with the Lottman procedure

*ATPB = asphalt treated permeable base

33

TABLE 14 MOISTURE DAMAGE PROBLEMS SOLVED

State/Province Problems Solved

Arkansas Moisture damage problems have not been solved In Arkansas, only reduced. We are requiring hydrated lime In our Type 1 (Interstate mixes) and are trying to control moisture wherever possible.

Califomia • Seldom overlay open-graded AC; It is first removed. • No longer cold recycle desert pavements which have been heavily crack sealed or have had

numerous seals placed.

Colorado Use of antistrip additive and requiring 70% Lottman greatly reduced stripping problems.

Georgia Moisture damage problems have not been solved yet; but they have been reduced significantly through use of lime.

Illinois Reld samples show higher split tensile test ratios than In design stage. Laboratory ratios less than 0.6 require an antistrip agent.

Kentucky Greater use of free draining bases and pipe collector to remove moisture.

Louisiana Improved antistrip agents; compatible material combinations; better asphalt coating of aggregates.

Missouri Use of lime has reduced damage to asphalt mixture used over waterproofing membranes on bridge decks.

Montana Use of lime has been Instrumental in preventing moisture damage.

Nevada • Significantly reduced moisture damage with the use of lime additive. • Better able to identify potentially moisture sensitive aggregates.

New Mexico Use of lime has decreased stripping problems.

New York Some problems have been solved by selecting aggregate not prone to asphalt stripping.

North Carolina Elimination of open-graded friction course and greater emphasis on obtaining required density.

Oregon • Solved severe stripping problems by required lime treatment of aggregate on interstate freeways, altitudes > 2500', and Central and Eastern Oregon.

• Minimized problems by testing for moisture susceptibility, and by requiring liquid anti-strip additives where necessary.

South Dakota No deep-strength pavements allowed (stripping associated w/transverse cracking in this design).

Texas • Elimination of or treatment with additives of high moisture susceptible combinations. • Requirement of in-place density to be 92%. • Elimination of low mix temperature have reduced potential for moisture damage.

Utah Use of lime has reduced moisture damage problems.

Virginia Less stripping through improved additives and increased use of lime rather than chemical additives. This is the direct result of the use of improved test methods (Root-Tunnicliff and modified Lottman).

Wyoming Reduced incidence of early moisture damage and stripping failure through use of lime.

New Brunswick Have reduced raveling of surface through use of lime.

34

TABLE 15 PAVEMENT MOISTURE PROBLEMS STILL NEEDING TO BE SOLVED

State/Province Problem

Arizona Evaluate the effect of long term stripping and the effect of moisture on fatigue life.

Arkansas • A test Is needed to identify moisture susceptible mixes using heat, pressure, and moisture. • The moisture levels that lead to stripping should be identified. We know a great deal about a mix at

high levels of saturation (60 to 100%) but what happens at lower limits is not known.

California Laboratory tests are needed that correlate well with field performance.

Colorado Antistrip additives are not always mixed thoroughly into the asphalt.

Georgia Effect of moisture on raveling, fatigue cracking, pot holes, and rutting.

Idaho Need an effective environmentally acceptable antistrip agent.

Illinois Need to correlate laboratory test methods and criteria to field performance.

Kansas Need an effective method to introduce lime into mixes when using drum dryer plants.

Kentucky What causes stripping? Is it a chemical or physical process?

Louisiana Need follow-up study to evaluate effectiveness of recent changes.

Maryland Clearly define the factors which cause the problem and recommend appropriate solutions.

Missouri Identify the causes of stripping.

Montana Does use of O G F C mixes accelerate moisture damage in underlying mats?

Nevada Identify the most economical way to extend the service life of a moisture damaged pavement.

New Mexico Minor stripping problems.

New York How to prevent potholes?

North Carolina Effect of moisture on rutting.

Oklahoma Information on long term effectiveness of chemical antistrip additions.

Oregon Development of a reliable moisture sensitivity test.

Pennsylvania Better laboratory stripping test and understanding of the relationship between base drainage to the problem.

Rhode Island Relation of asphalt content to susceptibility to moisture damage.

South Carolina Further investigation is needed to determine if our moisture damage problem has been solved.

South Dakota How to repair or stop the progress of stripping in existing pavements.

Texas Need a more effective antistrip agent and solution to moisture from base or pavement edge.

Virginia • Need a more effective additive. Lime and chemicals are not 100% effective. • Need to consider methods of preventing water from residing in mix (i.e., drainage, impermeability).

35

CHAPTER FOUR

CONCLUSIONS AND RECOMMENDATIONS

This synthesis has investigated moisture damage in asphalt concrete. A n extensive literature review on the mechanisms of moisture damage has been conducted. Factors affecting moisture damage have been examined. Corrective treatments to prevent asphalt concrete from moisture damage and test methods to determine moisture damage potential to the asphalt concrete material have also been investigated.

A n extensive survey questionnaire was conducted in North America on moisture damage of asphalt concrete. The survey looked into many possible aspects related to the moisture damage in the asphalt concrete. These aspects include extent of moisture damage on actual asphalt concrete pavements, effect of aggregate and asphalt, asphalt-aggregate mixture, field procedures and construction factors, areas where moisture damage is most likely to occur, and methods of test and treatment. Research activities, including research completed, research underway, and significant findings, also were covered in the survey.

voids is generally considered the most important construction factor.

• Methods of treatment to reduce moisture damage, particularly stripping, include use of good aggregate, pavement surface sealants, pretreatment of aggregates, and use of additives. The survey results show that pretreatment of aggregate with lime is the most effective. The amount of lime typically used is in the range of 1 to 1.5 percent. Amines are used by many agencies as asphalt additives; however their reported effectiveness is mixed.

• A variety of test methods has been employed to assess the potential for moisture damage in asphalt concrete mixtures. Thus far, no test is "superior" or can correctly distinguish a moisture susceptible mixture in all cases; however AASHTO T 283 and A S T M D 4867 appear to have greatly improved the ability to detect moisture damage in paving mixtures.

• For moisture-damaged pavement surface, removal of the damaged areas appears to be the most commonly used and the most effective method.

CONCLUSIONS

Based upon the material presented in this synthesis, the following conclusions appear warranted:

• Moisture damage in asphalt concrete pavements may be associated with two mechanisms: (a) loss of adhesion and (b) loss of cohesion. The loss of adhesion is due to water getting between the asphalt and aggregate and stripping the asphalt film away. The loss of cohesion is due to a softening of asphalt cement in the presence of water which weakens the bond between the asphalt concrete and the aggregate. The two mechanisms are interrelated. That is, a moisture-damaged pavement may be a combined result of both cohesion and adhesion losses.

• Four broad theories have been used to explain the adhesion of asphalt cement to aggregate. These are Mechanical Theory, Chemical Reaction Theory, Surface Energy Theory, and Molecular Orientation Theory. However, the actual mechanism by which adhesion works is not fully explained by any one theory.

• Moisture damage is a function of several factors. These factors include asphalt concrete characteristics, environmental factors, and construction practices. Important characteristics of asphalt concrete include the nature of the aggregate, the nature of the asphalt cement, and the type of mixture. In general, clean aggregates with rough surface texture and low surface moisture and asphalt cements with high viscosity are better in terms of resistance to moisture damage. Environmental factors that accelerate pavement moisture damage are climate and traffic loadings. The major damage occurs in extreme weather conditions, particularly freeze-thaw action, combined with heavy traffic volume. Construction factors include the quality of compaction and weather conditions during pavement construction. Control of air

RECOMMENDATIONS FOR IMPLEMENTATION

The following recommendations for implementation appear warranted:

. Agencies should use tests such as AASHTO T 283 or ASTM D 4867 to minimize moisture damage.

• The use of lime-treated aggregate appears to have greatly reduced moisture damage in asphalt-aggregate mixtures and should be continued.

• Good construction practices and improved pavement drainage have been shown to reduce moisture damage in asphalt-aggregate mixtures and should be continued.

RECOMMENDATIONS FOR FURTHER STUDY

The following recommendations appear to be warranted based on the results of this investigation:

• Develop a better fundamental understanding of the causes of moisture damage.

• Develop improved, more reliable laboratory test methods to assess the resistance of asphalt concrete mixes to moisture damage.

• Improve the relationships between laboratory test results and field performance so that the long-term effectiveness of the various treatment methods can be assessed.

• Improve mixture specifications for controlling moisture damage, particularly stripping, to control moisture damage due to the use of unqualified materials.

36

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Coplantz, J. S., J. A. Epps, and L. Quilici, "Antistrip Additives: Background for a Field Performance," in Transportation Research Record 1115, Transportation Research Board, National Research Council, Washington, D.C. (1987) pp. 1-11.

Craus, J., I . Ishai, and A . Sides, "Durability of Bituminous Paving Mixture as Related to Filler Type and Properties," Proceedings, Association of Asphalt Paving Technologists, Vol. 50 (1981) pp. 291-316.

Dalter, R. S. and D. W. Gilmore, " A Comparison of Effects of Water on Bonding Strengths of Compacted Mixtures of Treated versus Untreated Asphalt," Proceedings, Association of Asphah Paving Technologists, Vol. 51 (1982) pp. 317-326.

Douglas, J. F., "Adhesion Between Binders and Aggregates," Journal of Institution of Civil Engineers, England, Vol. 3 (1947) p. 292.

Dow, A . D., "Discussion of Application and Present Status of the Immersion-Compression Test by J. T. Pauls and J. F. Goode," Proceedings, Association of Asphalt Paving Technologists, Vol. 16 (1947) p. 392.

Endersby, V. A., R. L . Gri f f in , and H . J. Sommer, "Adhesion Between Asphalts and Aggregates in the Presence of Water," Proceedings, Association of Asphalt Paving Technologists, Vol. 16 (1947) pp. 411-451.

Field, F. and W. A. Phang, "Stripping in Asphaltic Concrete Mixes: Observations and Test Procedures," Proceedings, 12th Annual Conference of the Canadian Technical Asphalt Association, Halifax (1986).

Ford, M . C , P. G. Manke, and C. E. O'Bannon, "Quantitative Evaluation of Stripping by the Surface Reaction Test," in Transportation Research Record 515, Transportation Research Board, National Research Council, Washington, D.C. (1974) pp. 40-54.

Fromm, H . J., W. A. Phang, and M . Noga, "The Incidence of Stripping and Cracking of Bituminous Pavements in Ontario," presented at the 10th Annual Conference of the Canadian Technical Asphalt Association, Quebec City (1965).

Gilbert, P. and J. H . Keyser, " A Study of Currently Used Methods for Determining the Permeability of Bituminous Mixtures," Journal of Testing and Evaluation, Vol. 1, No. 6(1973).

Gilmore, D. W., J. B. Dariand, B. M . Dirdler, L. W. Wilson, and J. A. Scherocman, "Changes in Asphalt Concrete Durability Resulting from Exposure to Multiple Cycles of Freezing and Thawing," A S T M STP 899, American Society for Testing and Materials, Philadelphia, Pa. (1985) pp. 73-88.

Gilmore, D . W., R. P. Lottman, and J. A . Scherocman, "Use of Indirect Tension Measurements to Examine the Effects of Additives on Asphalt Concrete Durability," Proceedings, Association of Asphalt Paving Technologists, Vol. 53 (1984) pp. 495-524.

Graf, P. E., Discussion of "Factors Affecting Moisture Susceptibility of Asphalt Concrete Mixes", Proceedings, Association of Asphah Paving Technologists, Vol. 55 (1986) pp. 204-212.

Gzemski, F. C , "Factors Affecting Adhesion of Asphalt to Stone," Proceedings, Association of Asphalt Paving Technologists, Vol. 9 (1937) pp. 87-101.

40

Hazlett, D . G., "Evaluation of Moisture Susceptibility Tests for Asphaltic Concrete," Report 3-C-2-102, Materials and Test Division, Texas State Department of Highways and Public Transportation (1985).

Heinicke, J. J. and T. S. Vinson, "Effect of Test Condition Parameters on I R M r , " Journal of Transportation Engineering, Vol. 114, No. 2 (1988) pp. 153-172.

Hicks, R. G, J. E. Wilson, and G. E. Boyle, "Identification and Quantification of the Extent of Asphalt Stripping in Oregon— Phase I , " Report No. FHWA/RD-83-3, Federal Highway Administration, Washington, D.C. (1983).

Hicks, R. G., J. E. Wilson, M . D. Reaney, and J. G. Huddleston, "Identification and Quantification of the Extent of Asphalt Stripping in Oregon—Phase I I , " Report No. F H W A / O R -85-3, Federal Highway Administration, Washington, D.C. (1985) .

Highway Research Circular 78: "Thermodynamic Aspects of Stripping Problem," Highway Research Board, National Research Council, Washington, D.C. (1968).

Hudson, S. W. et al., " A C Stripping Problems and Correction Treatments," Report No. FHWA-RD-90-049 Federal Highway Administration, Washington, D.C. (1990) 181 pp.

Hughes, R. I . et al., "Adhesion in Bitumen Macadam," Journal of Applied Chemistry (1960) p. 10.

Ishai, I . , J. Craus, and M . Livneh, "Improvement of Stripping Resistance to Sensitive Aggregates in Bituminous Paving Mixtures," in Proceedings, 4th Conference on Asphalt Pavements for Southern Africa, Vol. 1 (1984) pp. 475-484.

Ishai, I . and S. Nesichi, "Laboratory Evaluation of Moisture Damage to Bituminous Paving Mixtures by Long-Term Hot Immersion," in Transportation Research Record 1171, Transportation Research Board, National Research Council, (1988) pp. 12-18.

James, J. M . , "Asphalt Mix Permeability," Final Report, Transportation Research Project No. TRC-82, Arkansas State Highway and Transportation Department (1988).

Jensen, H. , "Anti-Stripping Agents—Function, Apphcations and Methods," Technical Bulletin 1, Scan Road International, Singapore (1983).

Jimenez, R. A., " A Field Control Test for Debonding of Asphaltic Concrete," presented at the 68th Annual Meeting of the Transportation Research Board, Washington, D.C. (1989).

Jones, G. M . , "The Effect of Hydrated Lime on Asphalt in Bituminous Pavements," presented at National Lime Association Meeting, Colorado Springs, Colo. (1971).

Kelly, P. B., R. G. Hicks, A. M . Furber, and T. S. Vinson, "Test Method to Determine the Degree of Stripping from Aggregate," Phase I Report, Contract No. DTRS-57-85-C-00170, U.S. Department of Transportation, Washington, D.C. (1986) .

Kennedy, T. W., R. B. McGennis, and F. L . Roberts, "Investigation of Moisture Damage to Asphalt Concrete and the Effect on Field Performance—A Case Study," in Transportation Research Record 911, Transportation Research Board, National Research Council, Washington, D.C. (1983) pp. 158-164.

Kennedy, T. W., F. L. Roberts, and K . W. Lee, "Evaluating Moisture Susceptibility of Asphalt Mixtures Using the Texas Boiling Test," in Transportation Research Record 968, Transportation Research Board, National Research Council, Washington, D.C. (1984) pp. 45-54.

Kennedy, T. W., "Prevention of Water Damage in Asphalt Mixtures, Evaluation and Prevention of Water Damage to Asphalt Pavement Materials," A S T M STP 899, B. E. Ruth, Ed., American Society for Testing and Materials, Philadelphia, Pa. (1985) pp. 119-133.

Kennedy, T. W. and G. A. Huber, "Effect of Mixing Temperature and Stockpile Moisture on Asphalt Mixtures," in Transportation Research Record 1034, Transportation Research Board, National Research Council, Washington, D.C. (1985) pp. 35-46.

Kiggundu, B. M . and F. L . Roberts, "The Success/Failure of Methods Used to Predict Stripping Propensity in the Performance of Bituminous Pavement Mixtures," presented at the 68th Annual Meeting of the Transportation Research Board, Washington, D.C. (1989).

Kumar, A. and W. H . Goetz, "Asphalt Hardening as Affected by Film Thickness, Voids, and Permeability in Asphaltic Mixtures," Proceedings, Association of Asphalt Paving Technologists (1977).

Kumar, A. and W. H . Goetz, "Laboratory Measurement of Permeability of Compacted Asphalt Mixtures," in Transportation Research Record 659, Transportation Research Board, National Research Board, Washington, D.C. (1977).

Lottman, R. P., "The Moisture Mechanism that Causes Asphalt Stripping in Asphaltic Pavement Mixtures," Project Design UI45-302, IDHR-47, Idaho Department of Highways (1971).

Lottman, R. P., "Procedure for Predicting Laboratory Retained Strength Cut-off and Additive Benefit-Cost Ratios of Moisture Damaged Asphalt Concrete," in Transportation Research Record 911, Transportation Research Board, National Research Council, Washington, D.C. (1983) pp. 144-149.

Lottman, R.P., "Predicting Moisture-Induced Damage to Asphaltic Concrete: Ten Year Field Evaluation," Final Report, NCHRP Project 4-8(4), Transportation Research Board, National Research Council, Washington, D.C. (1986).

Lottman, R. P., "Asphalt Concrete Moisture Damage Analysis System C—Guide for Acmodas C," University of Idaho, Moscow, Idaho (1988).

Lottman, R. P. and D. L . Johnson, "Pressure-Induced Stripping in Asphaltic Concrete," in Highway Research Record No. 340, Highway Research Board, National Research Council, Washington, D.C. (1970) pp. 13-28.

Lottman, R. P., L. J. White, and D. J. Frith, "Methods to Predict and Control Moisture Damage in Asphalt Concrete," in Transportation Research Record 1171, Transportation Research Board, National Research Council, Washington, D.C. (1988) pp. 1-11.

McGlashan, D . W., "Asphalt DurabiUty and Its Relation to Pavement Performance—Adhesion," NCHRP Summary of Progress (1972) pp. 111-120.

McLaughlin, J.F. and W.H. Goetz, "Permeability, Void Content, and Durability of Bituminous Concrete," in Highway Research Board Proceedings, Vol. 34, Highway Research Board, National Research Council, Washington, D.C. (1955).

Majidzadeh, K . and R. R. Sanders, Jr., "Effect of Water on the Behavior of Sand Asphalt Mixtures Under Repeated Loading," in Highway Research Record No. 273, Highway Research Board, National Research Council, Washington, D.C. (1969) pp. 99-109.

Maupin, G. W., Jr., "Implementation of Stripping Test for Asphalt Concrete," in Transportation Research Record 712,

41

Transportation Research Board, National Research Council, Washington, D.C. (1979) pp. 8-11.

Maupin, G. W., Jr., "The Use of Antistripping Additives in Virginia," Proceedings, Association of Asphalt Paving Technologists, Vol. 51 (1982) pp. 342-362.

Maupin, G. W., Jr., "Assessment of Stripped Asphalt Pavement," presented at the 68th Annual Meeting of the Transportation Research Board, National Research Council, Washington, D .C. (1989).

Meissner, H. P. and G. H. Bauldauf, "Strength Behavior of Adhesive Bonds," Transactions, American Society of Mechanical Engineers, Vol. 73 (1951) p. 697.

Nesichi, S. and I. Ishai, "A Modified Method for Predicting Reduced Asphaltic Pavement Life from Moisture Damage," Proceedings, Association of Asphalt Paving Technologists, Vol. 55 (1986) pp. 149-174.

Nesichi, S., I. Ishai, M. Livneh, and J. Craus, "Investigation of Durability Properties of Bituminous Concrete for Highway and Airports," Research Report 85-68, Transportation Research Institute, Technion, Haifa, Israel (1985).

Parker, F . and F . Gharaybeh, "Evaluation of Tests to Assess Stripping Potential of Asphalt Concrete Mixtures," in Transportation Research Record 1171, Transportation Research Board, National Research Council, Washington D.C. (1988) pp. 18-26.

Payatakes, A. C , "Surface Chemistry Applied to Solid-Liquid Separations," in Theory and Practice of Solid-Liquid Separation (F.M. Tiller, ed.). University of Houston (1975).

Plancher, H., G. Miyake, R . L . Venable, and J.C. Peterson, "A Simple Laboratory Test to Indicate the Susceptibility of Asphalt Aggregate Mixtures to Moisture Damage During Repeated Freeze-Thaw Cycling," Proceedings, Canadian Technical Asphalt Association Meeting, Victoria, British Columbia (1980).

Puzinauskas, V. P., "Symposium on Antistripping Additives in Paving Mixtures," Proceedings, Association of Asphalt Pavijig Technologists, Vol. 51 (1982) pp. 263-264.

Rensel, P., "Simplified Quality Control of Asphalt Concrete," Proceedings, Northwest Roads and Streets Conference, University of Washington, Seattle (1965).

Sanderson, F . C , "Methylchlorosilanes as Antistripping Agents," in Highway Research Board Proceedings, Vol. 31,

Highway Research Board, National Research Council, Washington, D.C. (1952) pp. 288-300.

Shute, J . , "An Evaluation of Stripping in Asphalt Concrete Pavements," thesis presented to the Graduate College of Oregon State University, in partial fulfillment of the requirements for the degree of Master of Science (1989).

Stevens, D. E . , "Ravelling," Proceedings, Association of Asphalt Paving Technologists, Vol. 28 (1959) pp. 1-15.

Stroup-Gardiner, M. and J. A. Epps, "Four Variables that Affect Lime in Asphalt-Aggregate Mixtures," in Transportation Research Record 1115, Transportation Research Board, National Research Council, Washington, D.C. (1987) pp. 12-22.

Sulhvan, J . , J. E . Wilson, and T. George, "Mix Design Procedures and Guidelines for Asphalt Concretes, Cement Treated Base and Portland Cement Concrete," Oregon Department of Transportation (1981).

Takallou, H. T., "Stripping of Asphalt Pavements: State of the Art," thesis presented to the Department of Civil Engineering at Oregon State University, in partial fulfillment of the requirements for the degree of Master of Science (1984).

Tunnicliff, D. G. and R. E . Root, "Introduction of Lime into Asphalt Concrete," Report No. FHWA/RD-86/071, Federal Highway Administration, Washington, D.C. (1986) 97 pp.

Tunnicliff, D.H. and R . E . Root, "Testing Asphah Concrete for Effectiveness of Antistripping Additives," Proceedings, Association of Asphalt Paving Technologists, Vol. 52 (1983) pp. 535-560.

U.S. Army Corps of Engineers, "Engineering and Design—Flexible Airfield Pavements—Air Force," Em 1110-45-302 (1958).

Vallerga, B. A. and R. G. Hicks, "Water Permeability of Asphalt Concrete Specimens Using Back-Pressure Saturation," Journal of Materials, Vol. 3, No. 1 (1968).

Von Quintus, H. L . et a l , "Development of Asphalt-Aggregate Mixture Analysis Systems: AAMAS," Draft report to NCHRP, Project 9-6(1), Transportation Research Board, National Research Council, Washington, D.C. (1988).

White, T. D., "Stripping in HMA Pavements," Hot Mix Asphalt Technology, National Asphalt Paving Association (1987).

Winterkom, H. F . , G. W. Eckert, and E . B. Shipley, "Testing the Adhesion Between Bitumen and Mineral Surfaces with Alkaline Solutions," Proceedings, Association of Asphalt Paving Technologists, Vol. 9 (1937) pp. 63-85.

42

APPENDIX A

NCHRP Survey Questionnaire on l\/loisture Damage

NATIONAL R E S E A R C H C O U N C I L TRANSPORTATION R E S E A R C H BOARD

Constituhon Avenue Washington, D. 20418

c o M M i r r r r c o R R r s i ' o v n r v c r A D O K C S S R r rLV T O

March 14, 1989

State Materials Engineer Oregon Department of Transportation Salem, OR 97310

Subject: NCHRP Synthesis 19-09, "Moisture Damage in Asphalt Concrete"

Dear :

We are currently undertaking work on a synthesis dealing with "Moisture Damage in Asphalt Concrete". Moisture damage due to loss of adhesion is often referred to as stripping. Moisture damage, however, can also be associated with loss of cohesion (strength) of the binder or to deterioration of the aggregate. This moisture damage can lead to eariy pavement related distress. The purpose of this synthesis is therefore to identify the foltowing:

1. The extent and type of distress associated with moisture damage. 2. Test methods (asphalt, aggregate, mix) used to determine whether there will be a

moisture related problem. 3. Corrective treatments and the effectiveness of these treatments. 4. On-going (or recently completed) research whk:h deals with moisture related damage.

Your assistance in completing this survey and providing the requested information is greatly appreciated. Should you have^ny questions on the technical aspects of this survey, please do not hesitate to contact me or the project consultant. Dr. Gary Hicks (503\754-4273).

Very tnjiy yours,

Thomas L. Copas, P E Special Projects Engineer

TLC/nb end.

The National Rtsearch Council ;s the pnncipal operating agency of the National Academy of Sciences and the National Academy of Engineering to serve government and other organizations

43

Transportation Research Board

Moisture Damage in Asphalt Concrete for

Synthesis Topic. 19-09

Novemt}er 1988

Agency Reported by

Address . Title

Date Completed Telephone

Damage to hot-mixed asphalt concrete pavement caused by moisture is a national problem. Moisture damage can occur due to loss of adhesion (e.g., stripping), loss of cohesion (strength loss), or a combination thereof. This synthesis is to address the recognition and extent of the problem. The synthesis is also expected to review the tests used to identify moisture-sensitive asphalt concrete and should address the effectiveness of the tests. Rnally, the synthesis is expected to discuss procedures to eliminate or reduce the problem in both overtays and new constnjction. The purpose of this questionnaire is to obtain the various state practices on each of the issues.

Please answer the following questions with reference to your current practices and research regarding moisture damage in asphalt concrete pavements. Should there be additional infonnation (in the form of research reports, internal memos, specifications, cun-ent test procedures, proposed test methods, etc.) which would supplement your answers to the questions, we would appreciate copies of these.

In filling out the questionnaire, please indicate by a check mari< or, where requested, use the following scale to rate from no problem to severe, or for not effective to 100% effective.

No Problem Slight Problem Moderate Problem Severe Problem I I I I 0 3 6 9 I I I I

Not Effective Slightly Effective Moderately Effective 100% Effective

44

Transportation Research Board Moisture Damage in Asphalt Concrete

for

Synthesis Topic 19-09

March 1989

Do you experience premature asphalt pavement problems because of moisture damage?

Yes No

If yes, please complete the following questions. If no, please retum this questionnaire after indicating why moisture damage is not a problem in your pavements.

Pavement Distress

2. How do you determine whether nxsisture has contributed to the development of premature pavement distress and how effective do you find this procedure? (Rate 0 to 9 from Not Effective to 100% Effective)

a) Visual inspection of surface d) b) Examination of cores e) c) Core testing

What percentage of your asphalt pavements experience moisture-related distress?

a) 0-10% c) 30-50% b) 10-20% d) > 50% 'o

Which pavement problems in your agency do you feel are the result of moisture damage and what is their severity? (Rate 0 to 9 from None to Severe)

a) Raveling e) Pot holes b) Flushing f) Rutting c) Fatigue cracking g) Reflection cracking d) Themal cracking h) Don't know

5. Which of the moisture damage problems in your pavements do you feel are accelerated by repeated freeze-thaw conditions and what is the severity of the acceleration? (Rate 0 to 9 from None to Severe)

a) Raveling e) Pot holes b) Flushing f) Rutting c) Fatigue cracking g) Reflection cracking d) Thermal cracking h) Don't know

45

What is the typical age (years) for your pavements when each problem from moisture damage is first experienced? (L » Lime treated aggregate, C - Chemical treatment added to asphalt. Please use one of the folkjwing time periods: 0-1. 2-3, 4-5, 6-7. 8-10. 11-13, 14-16. >16 years.)

w/o with with Add. L C

a) Raveling b) Flushing c) Fatigue cracking d) Themnal cracking

w/o with with Add. L C

e) Pot holes f) Rutting g) Reflection cracking h) Don't know

What has been the severity of pavement moisture problems in your agency for each three-year period? Please indicate if additives were used to reduce moisture susceptibility. (Rate 0 to 9 from None to Severe)

a) b) c) d)

1965-67 1968-70 1971-73 1974-76

Severity Additives Used?

No No No No

Yes Yes Yes Yes

e) 0 g) h)

Severity

1977-79 1980-82 1983-85 1986-88

Additives Used?

No No No No

Yes Yes Yes Yes

Aaareaates

What is the type and approximate percentage of aggregates used in your asphalt concrete pavements?

a) Basalt b) Limestone c) Granite d) Slag e) Traprock f) Quartzite

gravel quarry % % % % % %

gravel guany g) Sandstone h) Chert i) Dotomite j) Rhyolite k) Greywacke I) Other

% % % % % %

What has been the severity of pavenrwnt moisture problems for each type of aggregate? (Rate 0 to 9 from None to Severe)

a) Basalt b) Limestone c) Granite d) Slag e) Traprock f) Quartzite

gravel guanv g) Sandstone h) Chert i) Dotomite i) Rhyolite k) Greywacke 1) Other

gravel guanv

46

10. What types of aggregate treatment, if any, have you used to eliminate or reduce the extent of moisture problems and how effective have these treatments been? (Rate 0 to 9 from Not Effective to 100% Effective)

a) Pretreat with lime c) Well dried aggr b) Wash out deleterious d)

particles e) None

Please enclose copy of lime treatment specifications if used.

11. If lime is used to treat aggregate, indicate the percentage of lime and effectiveness of the procedure. (Rate 0 to 9 from Not Effective to 100% Effective)

% Lime Effective

a) Dry lime b) Dry lime on nroist aggr c) Lime slurry d) Quicklime slaked

12. If lime is used, how long do you require the lime-treated aggregate to be stockpiled prior to use and what is the maximum time the aggregate may be stockpiled?

Min Max Comments

a) None

b) 1 day

c) 2-5 days

d) 6-10 days

e) 11-20 days,

f) > 20 days

13. Aggregate gradation is considered by some to influence asphalt stripping. For the types of mixes indicated, what is the extent of stripping experienced with each type (i.e., the percentage of dense-graded mixes that strip)?

a) Dense-graded % c) All mixes % b) Open-graded % d) Don't know

14. What specific tests on aggregates do you run to detect their propensity for asphalt stripping or pavement nrxjisture damage and how effective have you found this procedure? (Rate 0 to 9 from Not Effective to 100% Effective)

a) AASHTO T-182 d) b) AASHTO T-210 e) C) AASHTO T-84 & 85 f)

Note: By effective, is there a con-elation between the test and field pertonnance?

47

15. What specification do you use with the above aggregate tests to insure good resistance to moisture damage? (Rate 0 to 9 from Not Effective to 100% Effective)

a) AASHTO T-182 d) b) AASHTO T-210 e) C) AASHTO T-84 & 85 f) None

Please provide a copy of the specification and any referenced agency procedures.

Note: Do not inteude standard AASHTO or ASTM referenced procedures.

Asphalt

16. What is the source and percentage of cnjde or blend of asphalt cement produced for use in your asphalt conaete pavements?

Source % a) b) c) d) e) Don't know

17. Which of the asphaKs in Question 16 has been associated with moisture damage and what has been the severity? (Rate 0 to 9 from None to Severe)

Asphalt Source Severity

18. What grade of asphalt cement (AR, AC. Pen) for each cmde or blend in Question 17 provides the best resistance to pavement moisture? (Rate 0 to 9 from Poor to Best)

Asphalt Source Grade of Asphalt

19. What asphalt additive have you used to eliminate or reduce the extent of moisture problems and how effective have these additives been? (Rate 0 to 9 from Not Effective to 100% Effective)

a) Amines d) SiHcone b) Polymers e) c) Portland cement f) Don't know

48

Mix Design and Construction

20. What mix test procedures do you specify or use to identify moisture-related problems and how effective are these tests? (Rate 0 to 9 from Not Effective to 100% Effective)

a) AASHTO T-165 e) Boil Test b) AASHTO T-182 f) Lottman Test (NCHRP 246) c) AASHTO T-283 g) d) Resilient Modulus Ratio h)

Please provide a copy of your procedure if it is not a standard ASTM or AASHTO procedure. (This includes any modification made to standard procedures.)

21. What criteria do you use for the test in 20, above, to determine that significant moisture damage exists, and is the criteria effective? (Rate 0 to 9 from Not Effective to 100% Effective)

Rating a) % retained strength of compression b) % retained stability c) % retained strength tensile d) % retained modulus e) Minimum wet strength f) % Stripping (visual) g) Combination (specify)

(Also, please endose a copy of the part of your specifications which reference compliance with the test procedure indicated.)

22. If the test is not effective, is it the test procedure or the specifications that need revising?

a) Test procedure b) Specifications c) Don't know

Comments:

23. What specific mix design guidelines, if any, do you require if moisture damage is detected in 20, above and how effective are these guidelines? (Rate 0 to 9 from Not Effective to 100% Effective)

a) Select hard grade asphalt c) Change aggregate source b) Lime treat aggregate d) Add amines to asphalt

e)

Please provide a copy of your mix design guidelines.

49

24. What fiekJ procedures do you use to eliminate or reduce the extent of moisture problems and how effective are these? (Rate 0 to 9 from Not Effective to 100% Effective)

a) Compact to 7-8% voids c) Compact to < 5% voids b) Compact to 5-6% voids d) Control temp of placement

e)

25. In your opinion, which of the foltowing construction factors contribute to moisture damage. (Rate 0 to 9 from Not Important to Most Important)

a) Lift thickness d) Drainage of base layer b) Mix temperature f) c) Air voids g)

26. Moisture damage is most pronounced in:

a) Thick or thin lifts b) High or tow mix temperatures c) High or tow air voids d) With or without good base drainage

27. Moisture damage in your roadways generally occur in areas of (doni limit response to one if more than one occurs):

a) High rainfall areas b) Areas with freeze-thaw cycles c) Areas with cool-warm cycles d) High water table e) All areas g)

Corrective Treatments

28. What is the effectiveness of each method of treatment you use to maintain or repair moisture-damaged pavements? (Rate 0 to 9 from Not Effective to 100% Effective)

a) Overiay d) Recycle b) Chip seal e) Patch c) Remove f)

29. When using an overiay or chipseal on an existing asphalt pavement, how is moisture damage in the underlying pavement affected?

a) Not affected c) Decreased b) Increased d) Don't know

50

Research

30. What research relative to pavement moisture damage have you recerrtly completed or are currently involved with? Please indicate the significant findings.

If possible, please provide a copy of relevant reports.

31. Based on field evidence, what moisture damage problems have been solved in completed research or through past experience by your agency?

32. What pavement moisture problems still need to be solved?

Please retum by 1989 to: Thomas L Copas, P.E. Transportation Research Board 2101 Constitution Avenue Washington, D.C. 20418

51

APPENDIX B

Agencies Responding to NCHRP Questionnaire on IMoisture Damage

52

Agencies Responding to NCHRP Questionnaire on Moisture Damage

Agency Response Question #1

Alabama Hwv Dept. No

Alaska DOT&PF Yes No

Arizona DOT Yes Yes

Arkansas State Hwv Yes Yes

California (CALTRANS) Yes Yes

Colorado DOH Yes Yes

Connecticut DOT Yes No

Delaware DOT Yes Yes

Rorida DOT Yes No

Georaia DOT Yes Yes

Hawaii No

Idaho TransD. Dept. Yes Yes

Illinois DOT Yes Yes

Indiana DOH Yes No

Iowa DOT Yes No

Kansas DOT Yes Yes

Kentucky DOH Yes Yes

Louisiana DOT & Dev. Yes Yes

Maine DOT Yes No

Maryland State Hwv Admin Yes Yes

Massachusetts Dept. of Public Works Yes No

Michiaan DOT Yes No

Minnesota DOT Yes Yes

Mississippi Hwv Dept. Yes Yes

Missouri Hwv & Trans. Dept. Yes Yes

Montana Dept. of Hwvs Yes Yes

Nebraska Dept. of Roads Yes Yes

Nevada Yes Yes

New Hampshire DOT Yes No

New Jersev DOT No

New Mexico Hwv & Trans. Dept. Yes Yes

New York State DOT Yes Yes

North Carolina DOT Yes Yes

North Dakota State Hwv Dept. Yes No

Ohio DOT Yes No

Oklahoma DOT Yes Yes

Oreaon Hwv Division Yes Yes

Pennsylvania DOT Yes Yes

Rhode Island DOT Yes Yes

South Carolina Dept. of Hwys & Public Trans.

Yes Yes

South Dakota DOT Yes Yes

53

Agencies Responding to NCHRP Questionnaire on Moisture Damage (cont.)

Agency Response Question #1

Tennessee DOT Yes Yes

Texas State Dept. of Hwys & Public Trans.

Yes Yes

Utah DOT Yes Yes

Vermont Aaencv of Trans. No

Virqinia DOT Yes Yes

Washinaton State DOT No

West Virqinia Dept. of Hwys Yes Yes

Wisconsin DOT Yes Yes

Wyoming Hwy Dept. Yes Yes

Alberta Yes No

Manitoba Hwys & Transp. Yes No

Nova Scotia Dept. of Transo. Yes Yes

NW Territories Yes No

N.B. DOT Yes Yes

Ontario - Ministry Yes No

Puerto Rico Hwy Authority Yes Yes

54

Q2: How do you determine whether rrioisture has cbhtributed to the developrnerit o distress and how effective do you find this procedure? (Rate 0 to 9 from Not Effective to 100% Effective)

Agency Visual Inspection of Surface

Examination of Cores

Core Testing

Other/Comments

Arizona X x X

Arltansas 3 6 4 Examination of broken (8): Moisture testing of cores (4)

California 3 7 _

Colorado 7 6 5

Delaware 6 6 6

Georaia 0 3 7

Idaho _ 4 6

Illinois _ 5 5

Kansas X x .

Kentucky ' 6 6 3 Louisiana 8 6 6 Maryland 6 .

Minnesota 3 8

MississiDoi 7 7

Missouri 3 6

Montana 6 6 6 Nebraska _ _ . No response

Nevada 6 6 6 New Mexico 4 . prior to use of open-graded surface (8)

New York 6 9 North Carolina 3 5 6 Oklahoma 3 6 3 Oregon 5 7 6 Pennsylvania 3 9 9 Rhode Island 5 . .

South Carolina 3 4 8 South Dakota 2 7 7 Tennessee 5 7 4 Texas State 3 4 8 Deflection testing of pavement (4)

(Strength loss)

Uah 3 6 9 Virainia 5 5 7 West Virginia 5 8 Wisconsin 6 6 Wyoming _ 6 . Excavated samples (8)

Nova Scotia 7 8 New Brunswick 7 6 6

Puerto Rico X - -

X = no rating Rating scale: 0 = not effective

3 = slightly effective 6 = moderately effective 9 = 100% effective

55

Q3: What percentage of your asphalt pavements experience moistiire related distress? Q4: Which pavement problems (in your agency) do you feel are the result of moisture damage and wti at is their severity?

Agency

% of Pavements Experiencing

Moisture Related Distress

Pavement Problems Resulting from Moisture Damage:

Agency

% of Pavements Experiencing

Moisture Related Distress

Raveling Rushing Fatigue Cracking

Thermal Cracking

Pot Holes

Rutting Reflection Cracking

Arizona 30-50 3 6 6 0 3 6 0

Arkansas 20-30 0 3 3 0 4 6 0

California 0-10 1 . 1 . 2 2

Colorado 10-20 8 0 3 2 3 1 3

Delaware 10-20 3 0 0 0 0 6 9

Georgia 10-20 5 2 7 3 5 6 4

Idaho 30-50 5 . 4 4 6 . Illinois 0-10 _ 5 _ _ 5 5 _

Kansas 9 1 3 0 0 2 3 2

Kentucky 0-10 3 6 3 0 6 3 0

Louisiana 30-50 6 2 7 7 7

Maryland 0-10 6 _ 4 . Minnesota 10-20 2 1 0 0 6 2 0

Mississippi 10-20 5 . . 5 5 _

Missouri 0-10 6 0 0 0 9 3 0

Montana 0-10 _ _ 3 _ _ 3 _

Nebraska 0-10 3 _ 5 _ 6 _ _

Nevada 10-20 3 3 _ _ 6 7 _

New Mexico 0-10 2 . 1 . _

New York 0-10 1 0 3 3 1 3 3

North Carolina 10-20 3 2 4 0 3 3 0

Oklahoma 0-10 3 3 3 0 3 6 0

Oregon 10-20 3 7 5 3 7 5 4

Pennsylvania 0-10 2 5 _ _ 9 4

Rhode Island 10-20 6 _ _ _ 2 . _

South Carolina 30-50 2 6 _ _ _ 6

South Dakota 10-20 . _ _ _

Tennessee 0-10 7 _ _ 3 8 _

Texas 10-20 3* 3* 3* _ 6 3* _

Utah 20-30 . 5 _ _ . 5 _

Virginia 0-10 1 2 2 0 4 2 0

West Virqinia 0-10 3 1 0 0 7 1 0

Wisconsin 0-10 1 0 0 0 _ 0 0

Wyoming 10-20 . . _ - 3 6 .

Nova Scotia 30-50 4* 4* 4* 5* 9

New Brunswick 10-20 9 2 _ - 8 5

Puerto Rico Hwy Authority 0-10 X X

*Generally caused by mix or other problem, but moisture aggravates the problem.

56

05: Which of the moisture d^rhige problems in your pavemehts do you feel are accelerated by repeated freeze-thaw conditions and what is the severity 6f the acceleration^ (Ftete O to 9

Agency Raveling Rushing Fatigue

Cracking Thermal Cracking

Pot Holes Rutting

Reflection Cracking Comments

Arizona 3 3 3 3 6 3 0

Arl<ansas 0 0 0 0 4 3 0

California 6 _ 2 _ 7 0 _

Colorado 8 0 4 7 3 1 3

Delaware 6 _ . _ . 6 9

Georgia 5 2 3 6 8 7 4

Idaho _ _ _ 4 7 _ _

Illinois 2 1 _ _ 4 1 _

Kansas 3 3 0 0 4 2 4

Kentucky 3 1 2 0 7 1 4

Louisiana 3* _ _ _ .

Maryland 6 _ _ _ 8 _ _

Minnesota 3 0 0 5 9 0

Mississippi 3 _ _ _ 3 _ _

Missouri 6 0 0 0 9 3 0

Montana _ _ 3 . 3

Nebraska 1 4 7

Nevada 3 _ _ 8

New Mexico 2 1

New York _ 6 6 9 _ 6

North Carolina 5 2 5 5 6 3 5

Oklahoma 3 0 0 0 9 3 0

Oreaon 5 2 5 4 7 2 4

Pennsylvania 3 3 . . 9 4

Rhode Island 9 3 3 2 9 2 5

South Carolina _ . . Don't know

South Dakota _ Don't know

Tennessee 2 5 5 8

Texas 7** _ 5 . 9** . Utah 6 5 . 6 5

Virqinia 1 1 1 0 7 1 0

West Virqinia 5 1 1 1 5 1 1

Wisconsin 1 0 0 0 0 3

Wyoming . - . . 6 .

Nova Scotia 8 8 8 8 8

New Brunswick 9 0 9 2

Puerto Rico Hw y Authority - - - - - - - Not applicable

*ln open-graded mixes only **Much more severe with high void mixes Rating scale: 0 = none

3 = slight 6 = moderate 9 = severe

57

0 6 : What is the typical age (years) when each problem from moisture damage is first expertehc^d? (Without additives/WitK additiviBs)

Fatigue Thermal Pot Reflection Type of Agency Raveling Rushing Cracking Cracking Holes Rutting Cracking Additive

Arizona 0-1/0-1 2-3/2-3 11-13/11-13 11-13/11-13 6-7/6-7 Lime

Arkansas NR/0-1 NR/4-5 NR/8-10 NR/0-1 Chemical

California 0-1/NR . 5 /NR 1/NR 2 / N R None

Colorado 0-1/2-3 L i m e / C h .

Delaware NR/4-5 _ _ 4-5 /NR 4-5/NR Chemical

Georaia NR/11-13 NR/6-7 NR/8-10 N R / > 1 6 NR/8-10 NR/4-5 NR/4-5 Lime

Idaho 4-5/8-10 4-5/6-7 4-5/8-10 L i m e / C h .

Illinois 16/NR 2-3/NR _ 2-3/NR Chemical

Kansas 4-5/NR 2-3/NR 4-5/NR 2-3/NR 2-3/NR None

Kentucky 4-5 /NR 2-3/NR 8-10/NR >16 /NR 4-5/NR 6-7/NR > 16/NR None

Louisiana 2-3/NR * * / N R 4-5/NR 8-10/NR None

Maryland 4-5/NR _ 3-4/NR None

Minnesota 0-1/NR 4-5/NR 8-10/NR 8-10/NR None

MississiDOi 4-5 /NR 4-5/NR 4-5 /NR None

Missouri 2-3 /NR 4-5/NR None

Montana _ _ 2-3/2-3 2-3/2-3 Lime

Nebraska 2-3/NR 6-7/NR 6-7/NR Lime

Nevada 2-3/4-5 4-5/4-5 4-5 /NR 2-3/NR Lime

New Mexico DK DK DK DK DK DK DK Lime

New York 2-3/NR 0-1/NR 8-10/NR 2-3/NR 8-10/NR 8-10/NR 2-3/NR None

North Carolina DK DK DK DK DK DK DK None

Oklahoma 4-5/NR 2-3/NR 2-3/NR 4-5/NR 0-1/NR L i m e / C h .

Oreaon 4-5/6-7 2-3/4-5 6-7/8-10 2-3/2-3 4-5/6-7 6-7/6-7 2-3/2-3 L i m e / C h .

Pennsylvania 2-3/NR 2-3/NR 2-3/NR None

Rhode Island 4-5/NR 0-1/NR 8-10/NR 4-5/NR 14-16/NR 2-3/NR 2-3/NR None

South Carolina 4-5 /NR 4-5/NR 4-5/NR L i m e / C h .

South Dakota DK DK DK DK DK DK DK

Tennessee _ NR/2-3 NR/2-3 Chemical

Texas DK DK DK DK DK DK DK

Utah 0-1/14-16 0-1/14-16 Lime

Virainia DK DK DK DK DK DK DK L i m e / C h .

West Virainia 0-1/NR 0-1/NR None

Wisconsin 2-3/NR None

Wyominq _ _ 8-10/NR 6-7/NR None

Nova Scotia 4-5/NR 11-13/NR > 16/NR 6-7/NR 6-7/NR None

New Brunswick 0-1/NR 4-5/NR 4-5 /NR 0 / N R None

Puerto Rico 0-1/NR - - - 2-3/NR - - None

NR = No response DK = Dont know *Additive used with open-graded surface only

**AII ages

58

0 7 : What h a i been the severity of pavenrtent moisture problems in your agency for each three-year period? (Rate 0 to 9 from None to Severe) (Without additions/with additions)

Agency 1965-67 1968-70 1971-73 1974-76 1977-79 1980-82 1983-85 1986-88 Comments

Arizona - / 6 - /6 - / 6 -13 -13

Arl<ansas N/A N/A N/A N/A - / 3 - / a - / 6 -13

California 21- 21- 21- 4/ - 4 / - 4 / - 4 / - 4 / - Lime on a few croiects

Colorado - /2 - / I * AntistrlD req'd after 1986

Delaware 3 / - 3 / - 3 / - -13 - / 3 - / 3 - / 3 - / 3

Georaia - / 5 -n - /6 -16 - /6 - / 5 -13 - / 3

Idaho - / 3 - / 3 -13 -13 -13 - / 3 -13 - / 3

Illinois NA NA NA NA NA 2 / - 31- 31-

Kansas 1/- 1/- 1/- 1/- 1/- 21- 21- 21-

Kentucky 0 / - 0/ - 0/ - 01- 0/- 01- -/I -12

Louisiana NA NA 6 / - 6 / - - /6 - / 6 - /6 -13

Maryland NA NA NA NA NA NA NA NA Started chemicals in 79-80

Minnesota 21- 21- 21- 21- 5 / - 7 / - 71- 5 / -

MIssisslDOl 1/- 1/- 1/- 1/- -12 - /4 - /6 -/I

Missouri 3 / - 3 / - 3 / - 6/ - 9 / - 6/ - 6 / - -13

Montana - / 3 - / 3 - / 3 - / 3 -13 - / 3 - /4 - / 4

Nebraska NR NR NR NR NR NR NR NR

Nevada 4 / - 4 / - - /4 - /4 - / 5 - / 6 - /7 -17

New Mexico NR NR NR NR NR NR NR NR

New York 6 / - 6 / - 6 / - 3 / - -/I 1/- 1/- 1/-

North Carolina NR NR NR NR NR NR NR NR

Oklahoma 0 / - 0/ - 0 / - 0 / - 0/ - 3 / - 31- -/O

Oreaon -12 -12 - / 2 - /6 - /6 - /6 - /4 - / 3

Pennsylvania 01- 01- 0/- 0/ - 1/- 0/ - 0/ - 1/-

Rhode Island 21- 21- 21- 2 / - 2 / - 21- 2 / - 2 / -

South Carolina NA NA NA NA - / 5 -15 -12 - / 2

South Dakota NR NR NR NR NR NR NR NR

Tennessee -/O -/O -10 -/I - / 2 -13 -13 -13 AntlstriD req'd all mixes

Texas NA NA NA NA - / 5 - / 5 - /4 -13

Utah 3 / - 0 / - 0/ - 0/ - - /6 - /6 - /4 •13

Viroinla 3 / - 3 / - - /4 - / 5 - / 5 - /6 -n - / 6

West Virainia NR NR NR NR NR NR NR NR

Wisconsin 1/- 1/- 1/- 1/- 1/- 1/- 1/- 1/-

Wyominq NR NR -12 - / 2 - /4 - / 5 - / 3 - / 2 Beqan lime use in 1976

Nova Scotia 3 / - 3 / - 4 / - 4 / - 4 / - 4 / - 5 / - 5 / -

New Brunswick NR NR NR NR NR NR NR - /8

Puerto Rico NR NR NR NR 4 / - NR NR NR

NA = Not available; Rating scale:

NR = No response 0 = no problem 3 = slight problem

6 = moderate problem 9 = severe problem

59

08: What is the type and approximate percentage of aggregates used in your asphalt concrete pavements? (G=^ Gravel Q=Quarry)

Agency Basalt Limestone

Granite Slag Trap-rock

Ouartz-ite

Sandstone

Chert Dolomite

Rhyo-lite

Greyw-acke

Other

Arizona 25%0 5%G 20%G 40%G 5%G 5%Q

Arkansas 250 40%G 35%0

California XG XG XG XG

Colorado 90%G-1-0%Q

Delaware 50%0 40%0 10%O

Georaia 7%Q 85%0 1%0 2%Q 5%Q

Idaho 35%Q 5%G 58%G 2%0

Illinois 33%Q 5%Q 1%0 1%G 45%0 15%G

Kansas 50%Q 5%0 4%0 1%0 37% sand

Kentuckv 5G-720 3 0 3G 10 1G 150

Louisiana 22%Q 3%0 50%G 25%0

Maryland 1%Q 90%O 3%0 1%0 2%0 1%Q 2%0

Minnesota*

Mississippi 25%0 75%G

Missouri 75%Q 1%Q 3%0 3%G 17%Q 1%Q

Montana 5%G 10%G 25%G 5%G 10%G 15%G 5%G 5%G 10%G 10%G

Nebraska 65%G-3-O'ifcO

25%G-7-5%0

Nevada 45G 35G 5G 5G 5G 5G

New Mexico 10%G 10%G 80%G

New Y o r k " 20%G-7-0%O

2 % G -5%0

1%Q 5%0 1%G~ 1%Q

5%G 2%G 10%G-15%0

6 0 % G -3%0

North Carolina 15%0 70%O 5%G 10%0

Oklahoma 66%Q 5%0 1%0 20%G 5%Q 1%Q 2%0

Oregon 60%G-40%Q

5 % G -5%0

5%G~ 5%0

Pennsvlvania 40%O 3%Q 3%0 2%0 2%0 30%Q 5%0 15%G

Rhode Island 25%G 75%Q

South Carolina 5%Q 75%0 5%0 15%G

South Dakota** 5%G-

50%Q 50%G 5%G-5-

0%Q 5%G 5%G 5%G 25%G

Tennessee 75%0 250 250

Texas 50%0 20%O 5%0 2-5%Gt

Utah G G G G G G G

Virginia 10%Q 10%Q 50%Q 10%O 5%Q 5%Q 10%O

West Virginia 90%O 5%G 5%G

Wisconsin 10%G 10%G 10%G 5%G 35%G-30%Q

Wyoming 5%G-15%0

10%G~ 5%0

2%G 5%Q 55-60%G

Nova Scotia 10O 50O 40G

New Brunswick 30%G 20%G 10%G 15%0 25%Q

Puerto Rico 55%Q 25%0 20%Q

•Glacial sand and gravel "Total % = 200% (100%G and 100%O) tincludes Manufactured synthetic lightweight 5%

60

09: What has bean the severity of pavement moisture problems for each type of aggregate? (Rate 0 to 9 from None to Severe) (G = Gravel; Q = Quarry)

Agency Basalt Limestone

Granite Slag Trapr-ock

Ouartzite Sandstone

Chert Dolomite Rhyolite Greyw-acke

Other

Arizona 9 0 3G 6G 6G 3 0

Arltansas 2 0 7G 5 0

California Onlv a few sources in state are susceptible to severe strippinq

Colorado 2G-30

Delaware 3 0 9 0 6 0

Georgia 5 0 8 0 6 0 9 0 60

Idaho OQ OG 3G OO

Illinois 3 0 3 0 4 0 0 0 2 0 OO

Kansas 10 10 2G-2 0

10 3G

Kentucky 1G-20 OO 7G 9G 2 0

Louisiana 10 OO 7G 10

Maryland *

Minnesota NR

Mississippi 10 7G

Missouri OQ 30 OQ OO 6 0 OO OQ 9G 6 0 OO OQ 60

Montana OG 2G 4G 2G OG 6G 2G 6G 6G

Nebraska NR

Nevada 6G 6G 4G 6G

New Mexico 3G 6G 1G

New York 2G-2Q OG-OO 4 0 OO OG-OO 2G-20 OG-0 0

6G-60 OG-OO 4G-4Q

North Carolina OO 2 0 6G 2Q

Oklahoma OG-OO OG-30 0G-3Q OG-0 0

OG-OQ OG-OO OG-60 OG-6 0

OG-OO OG-OO OG-OO OG-O 0

Oreaon 6G-60 7 ?

Pennsylvania NR

Rhode Island 2G 20

South Carolina OO 5 0 8G

South Dakota NR

Tennessee 5 2 3

Texas 4 0 5 0 7 0 7 G / *

Utah NR

Virainia 4 0 4 0 9 0 6 0 9 0 5 0 4 0

West Virginia 10 10 3G

Wisconsin OG OG OG 3G OG-OO

Wvominq 1G-10 6G-30 6G 10 3G

Nova Scotia OG OG 2G

New Brunswick 8G 5G 7Q OO

Puerto Rico 0 0 9 0 0 0

•Moisture damage occurred on one job using limestone ••Includes manufactured - synthetic lightweight (4) NR = No Ratings Rating scale: 0 = no problem

3 = slight problem 6 = moderate problem 9 = severe problem

61

Q10: VVhat types of aggregate treatment f any, have you used to elinnmate 6r reciuc^ the extent of moisture problems and how effective have these treatments b e e n ? ( I^te 0 to 9 from Not Effective to 100% Effective)

Agency Pretreat W / U m e

Wash Out Deleterious

Particles Well-Dried

Aggregates None Other

Arizona 9 6 3 Pretreat w /cement -9

Arkansas 0

California 8

Colorado 8 5

Delaware X

Geora ia 8 1 7

Idaho 6 Antistrip-4

Illinois 4

K a n s a s X

Kentucky X

Louisiana X

Maryland X

Minnesota X X

MississioDi X

Missouri 6

Montana 7

Nebraska X

Nevada 7

New Mexico 7

New York X

North Carol ina 9 7 7

Ok lahoma 6 Chemica l Additive-6

Oregon 7 8

Pennsylvania X

Rhode Island 8

South Carolina 8

South Dakota X

Tennessee 2

Texas 8 *

Utah 9 Use manufactured f inesO)

Virqinia 8

West Virainia 5

Wisconsin X

Wyoming 8

Nova Scotia 5 X

New Brunswick

Puerto Rico X

•Standard specification for HMAC aggregates limits clay-like material by sand equivalent and decantation requirements Rating scale: 0 = not effective


62

O i l : if lime Is used to treat aggregate, Indicate the percentage of lime and effectiveness of the procedure(Rate 0 to 9 from Not Effective to 100% Effective).

Agency

Method of Addition

Agency %

Lime Dry

Lime

Dry Lime on Moist Aggregate

Lime Slurry

Quicklime Slaked

Arizona 1-2 6 9

California 1-2 X 8

Colorado 1 8

Georaia 1 8

Idaho 1 6

Missouri , 6 6

Montana 1.5 8

Nevada 1.5-2.5 X

New Mexico 1.5 7

North Carolina 1 9

Oregon 1-2 7 7

South Carolina 1 8

Texas 1-1.5 8 8 8

Utah 3 9 9 9

VirQinia 8

Wvomina 1 8 8

New Brunswick 1.5 8

Rating scale: 0 = not effective 3 = slightly effective 6 = moderately effective 9 = 100% effective

012: K lime Is used, how long do you require the lime-treated aggregate to be stockpiled?

Agency None 1

Day 2-5

Days 6-10 Days

11-20 Days

>20 Days

Arizona X

California X *

Colorado X

Georaia X

Idaho X

Missouri X

Montana X

Nevada** X

New Mexico X

North Carolina

Oreaon*** X

South Carolina X

Texas X

Utah X

Virginia X

Wvomina X

New Brunswick *

*Current in-house testing indicates no min. stockpile time needed, and max. of seven days would be appropriate. **(None) Does not require cure time when used as antistrip additive '••Minimum of 1 day. Maximum of days; however, a change is being considered

63

Q 1 3 : Aggregate gradation is <»hsidered by sorne to influ^ribe asphal t # i p ^ types of mixes indicated, what is the extent of stripping exper ienced with e a c h type J . e . the percentage of d e n s e - g r a d e d m i x e s that strip)?

A g e n c y Dense -Graded O p e n - G r a d e d All Mixes Don't Know

Arizona 3 0 %

Arkansas 2 5 % 1% 2 5 %

California 1% 1% 1%

Colorado 10% 15%

(Delaware 0-5% 0-5% 5%

Georg ia 6 0 %

Idaho 6 0 %

Illinois 5 % 0% 4 %

K a n s a s 5% 10%

Kentuckv 10% 5 %

Lou is iana 25-40%

Maryland X

Minnesota X

Mississippi 15%

Missouri X

Montana 1% 1%

Nebraska 2 %

Nevada (We believe that voids have more influence on stripping than gradation)

New Mexico 1%

New York 10% 50%

North Caro l ina 15% 15%

O k l a h o m a 2 % 0% 2 %

Oreqon 20% 10%

Pennsvlvania 1%

R h o d e Island 0% 5 0 %

South Caro l ina 3 0 % *

South Dakota X

T e n n e s s e e 5%

T e x a s X * *

Utah X * *

Virginia 5%

West Virainia X

Wiscons in X

W v o m i n a X

Nova Scot ia 2 %

New Brunswick 15%

Puerto Rico X * * *

*A lot of dense -g raded mixes underneath open-graded mixes have stripped * * H a v e exper ienced more prob lems with open-graded mixes , particularly in wet f reeze / thaw condit ions

***lf the improper aggregate is u s e d

64

0 1 4 : What specific tests on aggregates do you run to detect their propensity for asphalt stripping or pavement moisture damage and how effective have you found this procedure? (Rate 0 to 9 from Not Effective to 100% Effective)

Agency None AASHTO

T-182 AASHTO

T-210 AASHTO T - 8 4 & 8 5

Boil Test

Ftetalned Strength Others

Arizona Immersion-Compression (6) Root-Tunnlcliff (6)

Arkansas N/A N/A 1

California Surface abrasion (TM-360) (6)

Colorado 1

Delaware 3 6

Georqia 4 1 AASHTO-M29 (3)

Idaho 5 7 6

Illinois X

Kansas l i f t m a n (5) Root-Tunnicllff (3)

Kentucky

Louisiana 8

Maryland 3

Minnesota Modified Lottman

Mississippi X

Missouri 6

Montana 5

Nevada AASHTO T-283 (7)

New Mexico X

New York X

North Carolina X

Oklahoma X

Oreqon 3

Pennsylvania X

Rhode Island 5

South Carolina X Mix tests are used

South Dakota X

Tennessee 0

Texas X

Utah AASHTO T-283

VIrqinia 6 Root-Tunnicliff (8)

West Virqinia 7

Wisconsin 3

Wyominq 2

Nova Scotia X

New Brunswick X

Puerto Rico

N/A = Not applicable

65

Q15: What specification do you use with the above aggregate tests to insure good resistance to moisture damage? (Rate 0 to 9 from Not Effective to 100% Effective)

Agency None AASHTO

T-182 AASHTO

T-210 AASHTO T - 8 4 & 8 5

Boil Test

Retained Strength Others

Arizona Immersion-Compression (40-60%) (6)

Arkansas N/A N/A N/A

California Surface abrasion (15 grams max. loss)

Colorado X

Delaware 95%

Georqia AASHTO M-29 (3)

Idaho 5 7 6

Illinois X

Kansas X

Kentucky X

Louisiana 8

Maryland 3

Minnesota Lottman Guidelines

Mississippi X

Missouri 6 AASHTO T165 (6)

Montana 5

Nebraska X

Nevada NR

New Mexico X

New York X

North Carolina X

Oklahoma X

Oreaon X

Pennsylvania X

Rhode Island X

South Carolina X

South Dakota X

Tennessee X 0

Texas NR

Utah NR

Virainia 6 Root-Tunnicliff (8)

West Virqinia X

Wisconsin X

Wyoming NR

Nova Scotia X

New Brunswick NR

Puerto Rico NR

N/A = Not applicable NR = No response

66

Q16: W h i t is the source a n d perc^htag^ of c r i id^ br blend of asphalt cemeht produced for u s e in yoiir asphalt concrete p a v e m e n t s ?

0 1 7 : Which of the asphal ts in 0 1 6 has been associated with moisture d a m a g e and what h a s been the severity? (Rate 0 to 9 from None to Severe)

0 1 8 : Whtit grade of asphalt cement (AR, A C , Pen) for e a c h brude or blend in 0 1 7 provides the best resistance to pavement moisture? (Rate 0 to 9 from Poor to Best)

Agency Tvpe Severity Grade

Arizona California Bas in-70% 5 AC-40(4) Arizona

West Texas /Mex ico -20% 5 AC-20(4)

Arizona

California Coasta l -10% 5 AC-40(4)

Arkansas Smackover -20% AC-30 Arkansas

Unknown-80% AC-30

California California Vallev Aggregates the c a u s e of moisture d a m a g e

All sources:

AR-8000(no snowfall); AR-4000(others)

California

Los Angeles Basin

Aggregates the c a u s e of moisture d a m a g e

All sources:


California

Alaska N. S lope

Aggregates the c a u s e of moisture d a m a g e

All sources:


Colorado Conoco-50% Don't know A C - 5 Colorado

Sinclair-30% A C - 5

Colorado

Frontier-15% A C - 5

Colorado

Other-5% A C - 5

Delaware \ /enezuela-65% Delaware

Middle E a s t - 2 5 %

Delaware

Mexican-5%

Delaware

S o a n i s h - 5 %

Georgia AC-20&30 Georgia

AC-20&30

Idaho Don't know

Illinois

K a n s a s Coastal Ref.-6% K a n s a s

Diamond Shamrock-21%

K a n s a s

Farmland lnd.-21%

K a n s a s

Total Petrol.-21%

Kentucky ^ g r e g a t e s the c a u s e o f moisture d a m a g e

All: AR-8000 (no snowfall) AR-4000 (other)

Lou is iana* N. Louis iana-5% AC-30 Lou is iana*

Mississippi-5% AC-30

Lou is iana*

E. Texas -2 .5% AC-30

Lou is iana*

Venezuela-5% AC-30

Lou is iana*

Hawkins-22.5% AC-30

Lou is iana*

Mavan-40% AC-30

Lou is iana*

Arabian-17.5% AC-30

Lou is iana*

W. Texas -2 .5% AC-30

Maryland Don't know Don't know Don't know

Minnesota . Mississippi

Missouri

Montana

Nebraska

Nevada

67

0 1 6 : What Is the source and percentage of crude or blend of asphalt cement produced for use in your asphalt concrete pavements? (cont.)

017 : Which of the asphalts In 0 1 6 has been associated with moisture damage and what has been the severity? (Rate 0 to 9 from None to Severe) (cont.)

0 1 8 ; What grade of asphalt cement (AR, A C , Pen) for each crude or blend In Q l 7 provides the best resistance to oavement moisture? (Rate 0 to 9 from Poor to Best! (cont.)

Aqencv 1 Type Severity Grade

New Mexico Don't know Dont know Don't know

New York Venezuelan-50% New York

Mexican-20%

New York

Middle Eastern-10%

New York

Other-20%

North Carolina Amoco Use AC-20 in all mixes North Carolina

Chevron Use AC-20 in all mixes

North Carolina

Exxon Use AC-20 in all mixes

North Carolina

Shell Use AC-20 in all mixes

North Carolina

Trumbull Use AC-20 in all mixes

Oklahoma Don't know Don't know Don't know

Oregon Chevron-75% 2 Crude source & aggregate affects moisture damage not grade of asphalt

Oregon

McCall(Shein-20% 2

Crude source & aggregate affects moisture damage not grade of asphalt

Oregon

Witco-2% 2

Crude source & aggregate affects moisture damage not grade of asphalt

Pennsylvania Don't know Don't know Don't know

Rhode Island Atlantic Refininq-30% Rhode Island

Chevron Refininq-30%

Rhode Island

Seaview Refinerv-20%

Rhode Island

Others-20%

South Carolina Amoco-30% AC-20&30 South Carolina

Exxon-25% AC-20&30

South Carolina

Koch-20% AC-20&30

South Carolina

Seaview-15% AC-20

South Carolina

Shell-10% AC-20

South Dakota Don't know Don't know Don't know

Tennessee

Texas Harder asphalts better at strippina resistance

Utah AC-10 or AC-20

Virginia Don't know

West Virainia

Wisconsin /Vmoco-30% Wisconsin

Koch-50%

Wisconsin

Seneca-15%

Wisconsin

Murphv-5%

Wvomina Don't know

Nova Scotia Venezuela-75% 3 Nova Scotia

MidEast-25% 4 ••

New Brunswick Boscan-70% 85/100 New Brunswick

Arabian Liaht-30% 7

Puerto Rico Hw/y Authority

*AC-10 used only when reclaimed HMAC utilized at rates of 20-30% **No response

68

Q19: What asphalt additive have you used to eliminate or reduce the extent of moisture problems and how effective have these additives been? (Rate 0 to 9 from Not Effective to 100% Effective)

Agency Amines Polymers Cement Lime Others /Comments

Arizona 4 6 6

Arkansas 6 3

California None used

Colorado 7 6

Delaware 6

Georqia 5 3 8

Idaho 5

Illinois 6

Kansas None used

Kentucky

Louisiana 8

Maryland X

Minnesota Don't know

Mississippi 5

Missouri Don't know

Montana 5 8

Nebraska No response

Nevada 1 4

New Mexico 7-8* 7-8

New York 1

North Carolina 7

Oklahoma 6

Oreqon 6 0 7

Pennsylvania Don't know

Rhode Island None used

South Carolina 6 8

South Dakota Don't know

Tennessee 3 1**

Texas 4 2

Utah X

Virqinia 7 8

West Virqinia

Wisconsin None used

Wyoming No response

Nova Scotia None used

New Brunswick 5

Ontario 8

Puerto Rico None used

*w/amlnes **Polymers have not been in use long enough to evaluate Rating scale: 0 = not effective


69

020: What mix test procedures do you specify or use to identify moisture-related problems and how effective are these tests? (Rate 0 to 9 from Not Effective to 100% Effective)

Agency AASHTO

T-165 AASHTO

T-182 AASHTO

T-283 Modulus

Ratio Boll Test

Tensile Strength Ratio Others /Comments

Arizona 6*

Arkansas 6** 3

California Unknown (MVS)(3); Swell(2); R im strip(l)

Colorado 6* 8 * * *

Delaware 6

Georqia 6 Modified Lottman (8)

Idaho 5

Illinois Root-Tunnicliff (?)

Kansas Lottman (7)

Kentucky Root-Tunnicliff(5)

Louisiana 8

Maryland X

Minnesota None

Mississippi Root-Tunnicliff(8)

Missouri 6

Montana 7 6


Nevada 8 * * *

New Mexico 7

New York 3

North Carolina Root-Tunnicliff (?)

Oklahoma 6 * * *

Oregon 7 9

Pennsylvania 7

Rhode Island 5

South Carolina 6 Root-Tunnicliff(8)

South Dakota Root-Tunnicliff (?)

Tennessee 0 0 3 Root-Tunnicliff(2)

Texas 5

Utah 3 9

Virginia Root-Tunnicliff (?)

West Virginia 7 ?

Wisconsin Root-Tunnicliff (?)

Wyoming 6

Nova Scotia None

New Brunswick Lottman (7)

Puerto Rico Measurement of reduction in Marshall stability caused by immersion in water

• Immersion-compression, ATM 802G •• Immersion-compression, AHID TM

•••Modified version

70

021: What criteria do you use for the test in 20, above, to determine that significant moisture damage exists, and is the criteria effective? (Rate Oto 9 from Not Effective to 100% Effective)

Agency

% Retained Strength of

Compression % l^tained

Stability

% l^tained Strength Tensile

% Retained Modulus

Min. Wet Strength

Visual % Stripping Other /Comments

Arizona X ( 6 ) X ( 6 )

Arkansas 80(7) 30(2)

California 25 max. MVS 25 Min., Swell .03" max

Colorado 75(6) 70(8)

Delaware X ( 6 )

Georqia 60-80* 5(7) Need min. wet strenqth

Idaho X ( 7 ) X ( 7 )

Illinois X ( 3 ) X ( 3 )

Kansas X ( 6 ) X ( 6 )

Kentucky 70(7)

Louisiana 10(8)

Maryland X

Minnesota No response

Mlssisslool 75(8) 5(8)

Missouri X ( 6 )

Montana 70(7) 70(6)


Nevada X ( 8 ) X(8)

New Mexico X ( 7 ) X ( 8 )

New York X (3)

North Carolina X X Not a s p e c yet

Oklahoma X(61

Oreqon 75(6) 70(7)

Pennsylvania 80(7)

Rhode Island 50(5) Friction course only

South Carolina X ( 8 ) X (6)

South Dakota No response

Tennessee X ( 1 ) X (2)

Texas 70(7) (5)**

Utah 70

Virqinia 75(8) 0(6)

West Virainia X (7)

Wisconsin 70(?) Adopted In 1989

Wyominq 70(6) 70(?)

Nova Scotia No response

New Brunswick 80(8) 10 max. (5)

Puerto Rico 75(9)

*80% retained tensile strength when hydrated lime is * *Set for specific project. Normally is 10 to 20% max. Rating scale: 0 = not effective


specified; 60% retained tensile strength where chemical treatment Is allowed uncoated surface allowed by plan notes

71

0 2 2 : If the test is not effective, is it the test procedure or the spedfications that need revising?

Agency Test Procedure Specifications Don't Know Comments

Arizona Need to reduce lab to lab correlation problems

Test field mix and Increase wet strength

Arkansas (a)

California X

Colorado No response

Delaware

Georgia Need criteria for min. allowable tensile strength

Idaho No response

Illinois Need better correlation between lab and field performance

Kansas X

Kentuckv X ( b )

Louisiana Not applicable

Maryland X


Mississippi

Missouri X

Montana Not a problem


Nevada

New Mexico X ( c )

New York X

North Carolina X

Oklahoma Not applicable

Oreqon X ( d )

Pennsvlvania No response

Rhode Island

South Carolina No response

South Dakota

Tennessee X

Texas X

Utah No response

Virginia X ( e )

West Virginia No response

Wisconsin

Wyoming ..

Nova Scotia ..

New Brunswick ..

Puerto Rico

(a) Both-1 believe that an Ideal test procedure should include saturated specimens being subjected to confining pressure, heat and pulse loading Also the specification makes no exception for high dry strength in relation with wet strengths. Percentages are misleading.

b) Tighten variables, for example, % saturation can be 65-80% c) Currently involved in a research project evaluating stripping test methods d) Uniformity is required for test procedures e Its impossible to have an empirical test method which correlates to field behavior 100% of the time

72

0 2 3 : What s p ^ i f i c mix design guidelihes, if any, do you require if moisture d a m a g e is detected in 20, abdVa, and how effective are these guidel ines? (Rate 0 to 9 from Not Effective to 100% Effective)

Agency C h a n g e Asphalt Grade or Source

Lime Treat Aggregate

C h a n g e Aggregate

Treat Asphalt or Change Antistrip O t h e r / C o m m e n t s

Arizona P a s s / F a i l (6)

Arkansas 0 6 6 6

California 8 9

Colorado 7 9 6

Delaware 6

Georgia 8 4 Reduce pit f ines or natural sand (5)

Idaho 6 7 5

Illinois 4

Kansas None

Kentucky 2 4 7

Louisiana 8

Maryland X


MississipDi 8

Missouri X X

Montana 3 8


Nevada 7

New Mexico 7 8 Polymer w / a m i n e s (9)

New York X

North Carolina No response

Oklahoma 6 6 6

Oreaon 6 7

Pennsylvania Don't Know

Rhode Island 7

South Carolina Use additives in all mixes

South Dakota No response

Tennessee X 3 *

Texas X X

Utah 9

Virainia 8 7

West Virainia No response

Wisconsin X 9 3

Wvomina 8

Nova Scotia No response

New Brunswick e«*«

Puerto Rico 9

' increase additive dosage rate up to .7% based on the weight of the asphalt or change of asphalt. ••"Contractor has option of changing aggregate or asphalt sources or using a commercial antistrip agent

• • •Present ly researching procedures

73

Q24: What field procedures do you use to eliminate or reduce the extent of moisture problems and how effective are these? (Rate 0 to 9 from Not Effective to 100% Effective)

Agency Compact to Voids Control Temp

of Racement Others/Comments Agency 7-8% 5-6% < 5%

Control Temp of Racement Others/Comments

Arizona Comoact to 95% of Marshall (5)

Arl<ansas 4 3

California 7 Reouire 95% Rel. Compaction (8)

Colorado 6 8 5

Delaware 6 6

Georgia 3 4 2

Idaho 6

Illinois 5

Kansas 6 6

Kentucky 5 7

Louisiana X Require to 96% min. compaction

Maryland 8 8

Minnesota 7

Mississippi 8

Missouri 6 6

Montana 7


Nevada 7 7 Compact to 3-6% voids 7

New Mexico 7

New York X

North Carolina 8 8

Oklahoma 6 6

Oreaon 5

Pennsylvania Compact to < 8% voids (9)

Rhode Island 6 7 8 9

South Carolina X X Effectiveness not yet determined

South Dakota ?

Tennessee 5 6

Texas 7

Utah No response

Virainia . No response

West Virqinia 5

Wisconsin 9 9

Wyoming 6 6

Nova Scotia X

New Brunswick 8

Puerto Rico No response

74

025: In your opinion, which of the following constnjctidn factdt-s contribute to moisture damage? (Rate 0 to 9 from Not Important to Most Important)

Agency Uft

Thickness Mix Tern

P

Air Voids

Base Drainage Others

Arizona 4 4 7 4 Thorouahly dried aaareaate (4)

Arkansas 0 2 5 5 Season of placement (4) Construction Sequence (4)

California 5 8 9 9

Colorado 2 5 8 3

Delaware 3 6 9 6

Georaia 1 3 7 6 Use of hydroDhilic aqqr. (7)

Idaho 3 4 5 6

Illinois 7 8 7 Late season construction (8)

Kansas 7 4

Kentucky 3 1 7 9

Louisiana 6 6 Comoatibility of materials (8)

Maryland 9 9

Minnesota 4 6 9 3

MississiDPi 8

Missouri 0 6 6 9

Montana 6 7

Nebraska 2 4

Nevada 7 8

New Mexico 0 6 7 9

New York 3 6 9 6

North Carolina 5 8 8 8

Oklahoma 3 6 9 6

Oregon 6 6 9 Moisture in mix (8)

Pennsylvania 9 9

Rhode Island 6 7 8 9

South Carolina X

South Dakota 4 7 7 8

Tennessee 5 5

Texas 5- 9 8

Utah X

Virainia 7 8

West Virqinia 3 4 8 8

Wisconsin 3 9 9 3

Wyoming 0 3 6

Nova Scotia 7 5 9

New Brunswick 2 7 8 8

Puerto Rico X X

•Important only in that thin lifts are difficult to compact

75

026: Moisture damage is most pronounced in:

Agency Uft

Thickness Mix

Temp Air

Voids Base

Drainage Comments

Arizona Thin Low HiQh Without

Arkansas

California Thick Low Hiah Without

Colorado Thin Low Hiah Without

Delaware Hiah Without

Georaia Thick Low Hiah Without

Idaho Thick Low Hiah Without

Illinois Hiah

Kansas Thin Low Hiah Without

Kentucky Thin Low Hiah Without

Louisiana Hiah Without

Maryland Hiah Without

Minnesota Low Hiah Without

MississiDDl Hiah

Missouri Low Hiah Without

Montana Hiah Without

Nebraska Without

Nevada Hiah

New Mexico Low Hiah Without

New York Thin Low Hiah Without

North Carolina Thin Low Hiah Without

Oklahoma Low Hiah Without

Oreaon Thin Low Hiah Without

Pennsylvania Hiah Without

Rhode Island Thin Low Hiah Without

South Carolina Hiah

South Dakota Thick Low Hiah Without

Tennessee Hiah Without

Texas * Low Hiah Without

Utah No resoonse

Virainia Hiah Without

West Virainia Thick Hiah Without

Wisconsin Thin Low Hiah Without

Wyoming Thick Hiah

Nova Scotia Thin Low Hiah Without

New Brunswick Thin Low Hiah Without

Puerto Rico Thin Hiph W & W / 0

*Mlx at the interface of overlays on old concrete pavement.

76

Q27; Moisture darnage In u r rbiclways generally occur in areas of (dont limit response to one if rnore than one occurs):

Agency High

Rainfall Freeze-Thaw

Cycles Cool-Warm

Cycles High Water

Table All

Areas Others/Comments

Arizona X W/bad aooreaates

Arkansas X X Rainfall during cool period

California X

Colorado X X

Delaware X

Georoia X X X X X High traffic volumes

Idaho X

Illinois X X Over D-cracked pvt.

Kansas X X Overlays of PCCP

Kentucky X

Louisiana X

Maryland X

Minnesota X X Under Bridges

MississlDoi X

Missouri X

Montana Mt. pass/shaded areas

Nebraska X

Nevada X

New Mexico

New York W/hvdrophilic aoor.

North Carolina X

Oklahoma X X X X X

Oreaon X X X

Pennsylvania X

Rhode Island X X

South Carolina X X Traffic Loadings

South Dakota Deep-strength design

Tennessee X

Texas X

Utah X

Viroinia X

West Viroinia No response

Wisconsin X X

Wvomina X

Nova Scotia X X

New Brunswick X

Puerto Rico Hwy Authority X

77

Q28: What is the effectiveness of each method of treatment you use to maintain or repair moisture-damaged pavements? (Rate 0 to 9 from Not Effective to 100% Effective)

Agency Overlay Chip Seal

Remove & Replace Recycle Patch Other

Arizona 6 3 9 3

Arkansas 0 0 9 3 3

California 6 2 9 5 2

Colorado 6 2 9 4

Delaware 6 6 3

Georgia 6 4 5 7 4

Idaho 5 8 8 8 2

Illinois 3 3 9 6 2

Kansas 8 8 9 9 7

Kentucky 7

Louisiana 2 9

Maryland 9 9 8

Minnesota 4 4 8 5 1

Mississippi 7

Missouri 6 0 6 6 3

Montana 6 6 9 6 2

Nebraska 4 6

Nevada 9 7

New Mexico 4 4 9 7 1

New York 9 6 4

North Carolina 3 3 8 6 5

Oklahoma 3 0 9 3 3

Oreaon 3 2* 6 5

Pennsylvania 9 7

Rhode Island 0 0 9 8 2

South Carolina 8

South Dakota 3 1 9 2

Tennessee 4 9 2 3

Texas 3 4 8 7 4

Utah 3 3 8 9 2

Virainia 3 9 6

West Virqinia 3 3 3 9 5

Wisconsin 9 9 9

Wvomina 6 6

Nova Scotia 9 8 9 9 4

New Brunswick 6

Puerto Rico X X

•Sometimes causes stripping to accelerate, particularly polymer-modified chip seals

78

Q29: When using an ovisriay or chipseal on an existing asphalt pavement, how is moisture damage in th^ underlying pavernmt Effected?

Agency Not

Affected Increased Decreased Don't Know

Arizona (a)

Arkansas X

California Chip Seal Chip Seal Overlay

Colorado X

Delaware X

Georgia X

Idaho X

Illinois X

Kansas X

Kentucky X(b)

Louisiana X

Maryland X

Minnesota X

Mississippi X

Missouri X

Montana X

Nebraska X

Nevada X

New Mexico X

New York X

North Carolina X

Oklahoma X

Oregon X

Pennsylvania X

Rhode Island X

South Carolina X

South Dakota X

Tennessee X

Texas X(b)

Utah X

Virginia X(c)

West Virginia X

Wisconsin X Wyoming X

Nova Scotia X

New Brunswick X

Puerto Rico X

(a) Depends on drainage of underlying pavement (b) Depends on where moisture is coming from (c) Depends on drainage of base layer and porosity of surfacing

79

APPENDIX C

Selected Test Procedures

80

Standard Method of Test for

Resistance of Compacted Bituminous Mixture to Moisture Induced Damage

A A S H T O D E S I G N A T I O N : T 283-89

1. S C O P E

1.1 This method covers preparation of specimens and measurement of the change of diametral tensile strength resulting from the effects of saturation and accelerated water conditioning of compacted bituminous mixtures in the laboratory. The results may be used to predict long term stripping susceptability of the bituminous mixtures, and evaluating liquid anti-stripping additives which are added to the asphalt cement or pulverulent solids, such as hydrated lime, which are added to the mineral aggregate.

M 156 Requirements for Mixing Plants for Hot-Mixed, Hot-Laid Bituminous Paving Mixtures

2.2 ASTM Standards: D 3387 Test for Compaction and

Shear Properties of Bituminous Mixtures by Means of the U.S. Corps of Engineers Gyratory Testing Machine (GTM)

D 3549 Test for Thickness or Height of Compacted Bituminous Paving Mixture Specimens

for indirect tensile strength. The other subset is subjected to vacuum saturation followed by a freeze and warm-water soaking cycle and then tested for indirect tensile strength. Numerical indices of retained indirect tensile strength properties are computed from the test data obtained on the two subsets: dry and conditioned.

NOTE 1—It is recommended to prepare two additional specimens for the set. These specimens can then be used to establish the vacuum saturation technique as given in Section 9.3.

2. R E F E R E N C E D D O C U M E N T S

2.1 AASHTO Standards: T 166 Bulk Specific Gravity of

Compacted Bituminous Mixtures

T 167 Compressive Strength of Bituminous Mixtures

T 168 Sampling Bituminous Paving Mixtures

T 209 Maximum Specific Gravity of Bituminous Paving Mixtures

T 245 Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus

T 246 Resistance to Deformation and Cohesion of Bituminous Mixtures by Means of Hveem Apparatus

T 247 Preparation of Test Specimens of Bituminous Mixtures by Means of California Kneading Compactor

T 269 Percent Air Voids in Compacted Dense and Open Bituminous Paving Mixtures

3. S I G N I F I C A N C E AND U S E

3.1 As noted in the scope, this method is intended to evaluate the effects of saturation and accelerated water conditioning of compacted bituminous mixtures in the laboratory. This method can be used (a) to test bituminous mixtures in conjunction with mixture design testing, (b) to test bituminous mixtures produced at mixing plants, and (c) to test the bituminous concrete cores obtained from completed pavements of any age.

3.2 Numerical indices of retained indirect tensile properties are obtained by comparing the retained indirect properties of saturated, accelerated water-conditioned laboratory specimens with the similar properties of dry specimens.

4. S U M M A R Y O F M E T H O D

4.1 Test specimens for each set of mix conditions, such as, plain asphalt, asphalt with antistripping agent, and aggregate treated with lime, are tested (Note 1). Each set of specimens is divided into subsets. One subset is tested in dry condition

5. APPARATUS

5.1 Equipment for preparing and compacting specimens from one of the following AASHTO Methods: T 245 and T 247, or ASTM Method D 3387.

5.2 Vacuum Container, preferably Type D, from ASTM Method D 2041 and vacuum pump or water aspirator from ASTM D 2041 including manometer or vacuum gauge.

5.3 Balance and water bath from AASHTO T 166.

5.4 Water bath capable of maintaining a temperature of 140 ± 1.8 F (60 ± 1 C).

5.5 Freezer maintained at 0 ± 5 F ( -18 ± 3C).

5.6 A supply of plastic film for wrapping, heavy-duty leak proof plastic bags to enclose the saturated specimens and masking tape.

5.7 10 ml graduated cylinder. 5.8 Aluminum pans having a surface

area of 75-100 square inches in the bottom and a depth of approximately 1 inch.

5.9 Forced air draft oven capable of maintaining a temperature of 140 ± 1.8 F (60 ± 1 C).

5.10 Loading jack and ring dynamometer from AASHTO T 245, or a mechanical or hydraulic testing machine

81

T283 METHODS OF SAMPLING A N D TESTING 863

from AASHTO T 167 to provide a range of accurately controllable raies of vertical deformation including 2 in. per minute (50.8 mm per minute).

5.11 Loading Strips—If used, steel loading strips with a concave surface having a radius of curvature equal to the nominal radius of the test specimen. For specimens 4 inches (102 mm) in diameter the loading strips shall be 0.5 inches (12.7 mm) wide, and for specimens 6 inches (152.4 mm) in diameter the loading strips shall be 0.75 in. (19.05 mm) wide. The length of the loading strips shall exceed the thickness of the specimens. The edges of the loading strips shall be rounded by grinding.

6. P R E P A R A T I O N O F L A B O R A T O R Y T E S T S P E C I M E N S

6.1 Specimens 4 inches (102 mm) in diameter and 2.5 inches (63.5 mm) thick are usually used. Specimens of other dimensions may be used if desired and should be used if aggregate larger than 1 inch (25.4 mm) is present in the mixture and/or is not permitted to be scalped out.

6.2 After mixing, the mixture shall be placed in an aluminum pan having a surface area of 75-100 square inches in the bottom and a depth of approximately I inch (25.4 mm) and cooled at room temperature for 2 * 0.5 hours. Then the mixture shall be placed in a 140 F (60 C) oven for 16 hours for curing. The pans should be placed on spacers to allow air circulation under the pan if the shelves are not perforated.

6.3 After curing, place the mixture in an oven at 275 F (135 C) for 2 hours prior to compaction. The mixture shall be compacted to 7 ± 1.0 percent air voids or a void level expected in the field. This level of voids can be obtained by adjusting the number of blows in AASHTO T 245; adjusting foot pressure, number of tamps, levelling load, or some combination in AASHTO T 247; and adjusting the number of revolutions in ASTM D 3387. The exact procedure must be determined experimentally for each mixture before compacting the specimens for each set.

6.4 After extraction from the molds, the test specimens shall be stored for 72 to 96 hours at room temperature.

7. P R E P A R A T I O N O F C O R E T E S T S P E C I M E N S

7.1 Select locations on the completed pavement to be sampled, and obtain cores. The number of cores shall be at least 6 for each set of mix conditions.

7.2 Separate core layers as necessary by sawing or other suitable means, and store layers to be tested at room temperature.

8. EVALUATION O F T E S T S P E C I M E N S AND G R O U P I N G

8.1 Determine theoretical maximum specific gravity of mixture by AASHTO T209.

8.2 Determine specimen thickness by ASTM D 3549.

8.3 Determine bulk specific gravity by AASHTO T 166. Express volume of specimens in cubic centimeters.

8.4 Calculate air voids by AASHTO T269.

8.5 Sort specimens into two subsets of three specimens each so that average air voids of the two subsets are approximately equal.

9. P R E C O N D I T I O N I N G O F T E S T S P E C I M E N S

9.1 One subset will be tested dry and the other will be preconditioned before testing.

9.2 The dry subset will be stored at room temperature until testing. The specimens shall be wrapped with plastic or placed in a heavy duty leak proof plastic bag. The specimens shall then be placed in a 77 F (25 C) water bath for a minimum of 2 hours and then tested as described in Section 10.

9.3 The other subset shall be conditioned as follows:

9.3.1 Place the specimen in the vacuum container supported above the container bottom by a spacer. Fill the container with distilled water at room temperature so that the specimens have at least one inch of water above their surface. Apply partial vacuum (10 to 26 inches Hg) for a short time (5 to 10 minutes). Remove the vacuum and leave the speci

men submerged in water for a short time (5 to 10 minutes).

9.3.2 Determine bulk specific gravity by AASHTO T 166. Compare saturated surface-dry weight with saturated surface dry weight determined in Section 8.3. Calculate volume of absorbed water.

9.3.3 Determine degree of saturation by comparing volume of absorbed water with volume of air voids ftom Section 8.4. If the volume of water is between 55% and 80% of the volume of air, proceed to Section 9.3.4. I f volume of water is less than 55%, repeat the procedure beginning with Section 9.3.1 using more vacuum and/or time. I f volume of water is more than 80%, specimen has been damaged and is discarded. Repeat the procedure beginning with Section 9.3.1 using less vacuum and/or time.

9.3.4 Cover the vacuum saturated specimens tightly with a plastic f i lm (saran wrap or equivalent). Place each wrapped specimen in a plastic bag containing 10 ml of water and seal the bag.

9.3.5 Place the plastic bag containing specimen in a freezer atO ± 5 F ( - 1 8 ± 3 C) for a minimum of 16 hours.

9.3.6 After removal from the freezer, place the specimens into a 140 ± 1.8 F (60 ± 1 C) water bath for 24 ± 1 hours. As soon as possible after placement in the water bath, remove the plastic bag and film from the specimens.

9.3.7 After 24 ± 1 hours in the 140 F (60 C) water bath, remove the specimens and place them in a water bath already at 77 ± 1 F (25 * 0.5 C) for 2 ± 1 hours. It may be necessary to add ice to the water bath to prevent the water temperature from rising above 77 F (25 C). Not more than 15 minutes should be required for the water bath to reach 77 F (25 C). Test the specimens as described in Section 10.

N O T E 2 — A n alternate method is to eliminate 9.3.4, 9.3.5 and the words "after 16 hours" in 9.3.6. This will eliminate the freeze thaw conditioning.

10. T E S T I N G

10.1 Determine the indirect tensile strength of dry and conditioned specimens at 77 F (25 C).

10.2 Remove the specimen from 77 F (25 C) water bath and place between the two bearing plates in the testing machine.

82

864 METHODS OF SAMPLING AND TESTING T283

Care must be taken so that the load will be applied along the diameter of the specimen as illustrated in Table 1. Apply the load to the specimen by means of the constant rate of movement of the testing machine head of 2 inches (50.8 mm) per minute.

NOTE 3—When reviewing a failure or stripped pavement, the temperature of ttie conditioned specimens in 10.1 and 10.2 of 77 F (25 C ) should be changed to 55 F (13 C ) .

10.3 If steel loading strips are used, record the maximum compressive strength noted on the testing machine, and continue loading until a vertical crack appears. Remove the specimen from the machine and pull apart at the crack. Inspect the interior surface for stripping and record the observations.

10.4 If steel loading strips are not used, stop loading as soon as the maximum compressive load is reached. Record the maximum compressive load. Remove the specimen, measure and record the side (edge) flattening to the nearest 0.1 inch. The flattening may be easier to measure i f the flattened edge is rubbed with the lengthwise edge of a piece of chalk. After recording the flattening, replace the specimen in the compression machine and compress until a vertical crack appears. Remove the specimen from the machine and pull apart at the crack. Inspect the interior surface for stripping and record the observations.

11, C A L C U L A T I O N S

11.1 I f steel loading strips are used, calculate the tensile strength as follows:

TABLE 1 Maximum Ibisilc Stress (S„) for a Base Index of a 10,000 lb Load, 4" Diameter Spcdmen, 1 Inch in Length

S, 2P

where:

S, = tensile strength, psi, P = maximum load, pounds, I = specimen thickness, inches, and D = specimen diameter, inches.

Width of Flanened Area,

in Inches

Maximum Tensile Stress, S,o. PSI

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

1,640 1,629 1,619 1,606 1,595 1,571 1,540 1,508 1,470 1,438 1.405

P „ M a x

LLL

End View of Specimen At Start of Test End View of Specimen at />„ Max

11.2 I f steel loading strips are not used, calculate the tensile strength of a 4-inch (102 mm) diameter specimen as follows:

S, = S,oP 10,000 r

where:

S,

P t

= tensile strength, psi, = maximum tensile stress corre

sponding to the width of flattened area from Table I ,

= maximum load, pounds, and -- specimen thickness, inches.

11.3 Express the numerical index or resistance of asphalt mixtures to the detrimental effect of water as the ratio of the original strength that is retained after the freeze-warm water conditioning. Calculate as follows:

S2

Tensile Strength Ratio (TSR) = —

where: S\ = average tensile strength of dry sub

set, and S2 = average tensile strength of condi

tioned subset.

83

Standard Method of Test for

Effect of Water on Cohesion of Compacted Bituminous Mixtures

A A S H T O D E S I G N A T I O N : T 165-86' (1990) TASIM D E S I G N A T I O N : D 1075-81)

1. S C O P E

1.1 This method covers measurement of the loss of cohesion resulting from the action of water on compacted bituminous mixtures containing penetration grade asphalts. A numerical index of reduced cohesion is obtained by comparing the compressive strength of freshly molded and cured specimens with the compressive strength of duplicate specimens that have been immersed in water under prescribed conditions.

2. R E F E R E N C E D D O C U M E N T S

2.1 AASHTO Standards: T 166 Bulk Specific Gravity of

Compacted Bituminous Mixtures

T 167 Compressive Strength of Bituminous Mixtures

2.2 ASTM Standard: C 670 Practice for Preparing

Precision Statements for Test Method for Construction Materials

3. S I G N I F I C A N C E AND USE

3.1 This method is useful as an indicator of the susceptibility to moisture of compacted bitumen-aggregate mixtures.

4. APPARATUS

4.1 One or more automatically controlled water baths shall be provided for immersing the specimens. The baths shall

' Except for SI units this method agrees with A S T M D 1075-81.

be of sufficient size to permit total immersion of the test specimens. They shall be so designed and equipped as to permit accurate and uniform control of the immersion temperature within plus or minus 1 C (2 F), they shall be constructed of or lined with copper, stainless steel, or other nonreactive material. The water used for the wet storage of the specimens shall be either distilled or otherwise treated to eliminate electrolytes and the bath shall be emptied, cleaned, and refilled with fresh water for each series of tests.

4.2 A manually or automatically controlled water bath also shall be provided for bringing the immersed specimens to the temperature of 25 ± 1 C (77 -)- 2 F) for the compression test. Any convenient pan or tank may be used provided it is of sufficient size to permit total immersion of the specimens.

4.3 A balance and a water bath with suitable accessory equipment will be required for weighing the test specimens in air and in water in order to determine their densities, the amount of absorption, and any changes in specimen volume resulting from the immersion test.

4.4 A supply of flat transfer plates of glass or metal will be required. One of these plates shall be kept under each of the specimens during the immersion period and during subsequent handling, except when weighing and testing, in order to prevent breakage or distortion of the specimens.

5. T E S T S P E C I M E N S

S.l At least six 102 by 102 mm (4 by 4 in.) cylindrical specimens shall be made for each test. The procedures described in the Standard Method of Test for Compressive Strength of Bituminous Mixtures

(AASHTO T 167) shall be followed in preparing the loose mixtures and in molding and curing the test specimens.

6. D E T E R M I N A T I O N O F B U L K S P E C I F I C G R A V I T Y O F T E S T S P E C I M E N S

6.1 Allow each set of test specimens to cool for at least two hours after removal from the curing oven described in AASHTO T 167. Determine the Bulk Specific Gravity of each specimen in accordance with the procedures and calculation of Method A of T 166, Bulk Specific Gravity of Compacted Bituminous Mixture.

7. P R O C E D U R E

7.1 Sort each set of six test specimens into two groups of three specimens each so that the average bulk specific gravity of the specimens in group 1 is essentially the same as for group 2. Test the specimens in group 1 as described in 7.1.1. Test the specimens in group 2 as described in 7.1.2 unless the alternate procedure described in 7.1.3 is specified.

7.1.1 Group/—Bring the test specimens to the test temperature. 25 ± 1 C (77 ± 2 F), by storing them in an air bath maintained at the test temperature for not less than 4 h and determine their compressive strengths in accordance with AASHTO T 167.

7.1.2 Group 2—Immerse the test specimens in water for four days at 49 ± 1 C (120 ± 2 F). Transfer them to the second water bath maintained at 25 ± 1 C (77 ± 2 F) and store them there for 2 h. Determine the compressive strength of the specimens in accordance with AASHTO T 167.

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T165 METHODS OF SAMPLING AND TESTING 423

7.1.3 Group 2, Alternate Procedure— Immerse the test specimens in water for 24 h at 60 ± 1 C (140 ± 2 F). Transfer them to the second water bath maintained at 25 ± 1 C (77 ± 2 F) and store them there for 2 h. Determine the compressive strength of the specimens in accordance with AASHTO T 167.

8. C A L C U L A T I O N

8.1 Calculate the numerical index of resistance of bituminous mixtures to the detrimental effect of water as the percentage of the original strength that is retained

after the immersion period. It shall be calculated as follows:

Index of retained strength, % = ^ } ^

where:

S] = compressive strength of dry specimens (group 1), and

$2 = compressive strength of immersed specimens (group 2).

9. P R E C I S I O N

9.1 Single-Operator Precision—The single-operator standard deviation has been found to be 6 percent (see Note).

Therefore, results of two properly conducted tests by the same operator on the same material should not differ by more than 18 percent (see NoteX

NOTE—These numbers represent, respec-dvely, the (IS) and (D2S) limits as described in AASHTO Recommended Practice R4 , for preparing Preciskn Statements for Ifcst Methods for Construction Materials.

9.2 MuUilaboratory Precision—Tht multilaboratory standard deviation has been found to be 18 percent (see Note). Therefore, results of two properly conducted tests from two different laboratories on identical samples of the same material should not differ by more than 50 percent (see Note).

85

Designation: D 3625 - 83

Standard Test Method for Effect of Water on Bituminous-Coated Aggregate—Quick Field Test'

This sundard is issued under the fixed designation D 3625; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last leapproval. A superscript epsilon (<) indicates an editorial change since the last revision or tcapproval.

1. Scope 1.1 This method covers a rapid field test for visually deter

mining the loss of adhesion in uncompacted bituminous-coated aggregate mixtures due to the action of boiling water.

2. Referenced Document 2.1 ASTM Standard: E 1 Specification for ASTM Thermometers^

3. Significance and Use 3.1 The conditions of test are designed to rapidly deter

mine, in the field, the resistance of bituminous-coated aggregate mixtures to the accelerated action of boiling water. The loss of adhesion of the bitumen to the aggregate is visually estimated.

3.2 This test method is useful as an indicator of the relative susceptibility of bituminous-coated aggregate to water but should not be used as a measure of field performance because such correlation has not been established.

4. Apparatus 4.1 Scoop, shovel, or other implement capable of removing

a representative sample from a larger mass of bituminous-coated aggregate.

4.2 Glass Beakers. Heat-Resistani, two, 1500 to 2000 mL in size, or suitable metal containers of similar dimensions and capacity.

4.3 Source of Water (at least 1 qt (950 mL) for each test). 4.4 Device for heating water (hot plate, camp stove, torch,

etc.). 4.5 Thermometers—ASTM Low-Distillation Thermome

ters, graduated either in Fahrenheit or Celsius as specified, having a range from 30 to 580T or - 2 to -(-300*C, respec-

' This method is under the jurisdiction of ASTM Committee D-4 on Road and Paving Materials, and is the direct responsibility of Subcommittee D04.22 on EfTect of Water and Other Elements on Bituminous Coated Aggregates.

Current edition approved March 25. 1983. Published October 1983. Originally published as D 3625 - 77. Last previous ediuon D 3625 - 77.

Annual Book of ASTM Standards, Vol 14.01.

lively, and conforming to the requirements for Thermometer 7F or 7C as prescribed in Specification E 1.

5. Procedure 5.1 Pour approximately 1 qt (950 mL) of water into a

suitable container (see 4.2) and heat to boiling. 5.2 With a suitable implement (see 4.1), place approxi

mately '/2 lb (225 g) of the bituminous-coated aggregate in the boiling water while the container is exposed to the heat source. Bring the water back to boiling and hold for 1 min. (Avoid excessive manipulation of the bituminous-coated aggregate.) The temperature of hot mixtures should be below boiling temperature (212*F or lOO'C) before placing in boiling water.

5.3 At the end of 1 min, remove the container and its contents from the heat source. Carefully decant at least one half of the hot water without disturbing the coated aggregate and refill with cold water. (For comparison, place a similar amount of fresh bituminous-coated aggregate (approximately 'A lb or 225 g) into a second container and cover with unhealed water.)

5.4 By observation through the water from above, estimate the percentage of the total visible area of the aggregate that retains its original coating as above or below 95 %. Any thin, brownish, translucent areas are to be considered fully coated.

NOTE—Only top portion of coated aggregate should be evaluated by visual estimation for percent of retained coating.

6. Report 6.1 Report the estimated retained original coated area as

"above 95 %" or "below 95 %."

7. Precision and Bias 7.1 This test method, which requires subjective evaluation

of test results and reporting of only two possible conditions, does not lend itself readily to a conventional statistical round-robin exercise. At present, there is no precision and bias statement for this test method, and no work is planned to develop one.

Tlw American Society tor Testing and Materials lakes no position respecting the validity of any patent rights asserted in connection with any Hem mentioned In this standard. Users ol this standard are expressly advised that determination ol the validity ot any such patent rights, and the ris/t of infringement of such rights, are entirely their own fosponsiWWy.

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every live years and if not revised, either reapproved or withdrawn. Your comments are invited either lor revision ol this standard or lor additional standards and should be addressed to ASTM Headquarters. Your comments will receive carelul consideration at a meeting ol the responsible technical committee, which you may attend. H you leel that your comments have not received a lair hearing you should make your views known to the ASTM Committee on Standards. 1916 Race St.. Philadelphia. PA 19103.

441

86

Designation: D 4867 - 88

Standard Test Method for Effect of Moisture on Asphalt Concrete Paving Mixtures^

This standard is issued under Ihe fined designation D 4867; the number immediately following Ihe designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last leapproval. A superscript epsilon (<) indicates an editorial change since the last revision or rcapproval.

1. Scope

1.1 This test method covers procedures for preparing and testing asphalt concrete specimens for the purpose of measuring the efTect of water on the tensile strength of the paving mixture. This test method is applicable to dense mixtures such as those appearing in the Table for Composition o f Bituminous Paving Mixtures in Specification D3515. This test method can be used to evaluate the effect o f moisture with or without antistripping additives including liquids and pulverulent solids such as hydrated lime or portland cement.

1.2 The values slated in inch-pound units are to be regarded as the standard. The values in parentheses are for information purposes only.

1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is tlie responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1. Referenced Documents

2.1 ASTM Standards: D979 Method for Sampling Bituminous Paving Mixtures^ D 1074 Test Method for Compressive Strength of Bitumi

nous Mixtures^ D1559 Test Method for Resistance to Plastic Flow of

Bituminous Mixtures Using Marshall Apparatus'* D1561 Method for Preparation of Bituminous Mixture

Test Specimens by Means of California Kneading Compactor^

D2041 Test Method for Theoretical Maximum Specific Gravity o f Bituminous Paving Mixtures'

D 2726 Test Method for Bulk Specific Gravity and Density of Compacted Bituminous Mixtures Using Saturated Surface-Dry Specimens'

D 3203 Test Method for Percent Air Voids in Compacted Dense and Open Bituminous Paving Mixture Specimens'

D 3387 Test Method for Compaction and Shear Properties of Bituminous Mixtures by Means of the U.S. Corps of Engineers Gyratory Testing Machine ( G T M ) '

D 3496 Method for Preparation of Bituminous Mixture Specimens for Dynamic Modulus Testing'

' This lest method is under the jurisdiction of A S T M Commi l l ec D-4 on R o a d Paving Materials and is the direct rcsponsibihty of Subcommittee D04.22 on

•'eci of Water and Other Elements on Bituminous Coated Aggregates. Curroni edition approved Nov. 25, 1988. Pubhshcd January 1989. •J •!'»/»«/ nmik of.-iSTM Siandtints. Vols 04.03 and 04.08.

imuKil ISoiik III . ISr.U Slaiulurds. Vol 04.0.1.

D3515 Specification for Hot-Mixed, Hot-Laid Bituminous Paving Mixtures'

D3549 Test Method for Thickness or Height of Compacted Bituminous Paving Mixture Specimens'

D3665 Practice for Random Sampling of Construction Materials'

D4123 Method of Indirect Tensile Test for Resilient Modulus o f Bituminous Mixtures'

3. Summary of Test Method 3.1 Potential for Moisture Damage—The degree of sus

ceptibility to moisture damage is determined by preparing a set of laboratory-compacted specimens conforming to the

' job-mix formula without an additive. The specimens are compacted to a void content corresponding to void levels expected in the field, usually in the 6 to 8 % range. The set is divided into two subsets of approximately equal void content. One subset is maintained dry while the other subset is partially saturated with water and moisture conditioned. The tensile strength o f each subset is determined by the tensile splitting test. The'potential for moisture damage is indicated by the ratio of the tensile strength of the wet subset'to that of the dry subset.

3.2 Additive Eêct—The efTect of an antistripping additive is deterntined on a' set of specimens containing an additive prepared and tested as described in 3.1. The effect of an additive <ioS3ge may be estimated by repeating the tests on sets with difTerent additive dosages.

3.3 Plant-Produced Mixtures—The potential for moisture damage or the efTectiveness of an additive in a plant-produced mixture is determined on specitnens that are laboratory compacted to expected field-level void content, divided into wet and dry subsets, and evaluated as described in 3.2.

4. Significance and Use 4.1 This test method can be used to test asphalt concrete

mixtures in conjunction with mixture design testing to determine the potential for moisture damage, to determine whether or not an antistripping additive is effective, and to determine what dosage of an additive is needed to maximize the effectiveness. This test method can also be used to test mixtures produced in plants to determine the effectiveness of additives under the conditions imposed in the field.

5. Apparatus

5.1 To prepare and compact the specimens use apparatus from any one of the following: Test Methods D 1074, D 1559, D 3387, D 3496, or Method D 1561.

5.2 Vacuum Pump or Water Aspirator in accordance with Test Method D2G41.

569

87

D4867

5.3 Manometer or Vacuum Gage in accordance with Test Method D2041.

5.4 Container, preferably Type D, of Test Method D 2041.

5.5 Balance in accordance with Test Method D 2726. 5.6 Water Baths J\\xtt: 5.6.1 One waterbath in accordance with Test Method

D2726. 5.6.2 One bath capable of maintaining a temperature of

140 ± 1.8T(60 ± I.O°C) for 24 h, and 5.6.3 One bath capable of maintaining a temperature of

77 ± i . 8 T ( 2 5 ± l.O'C). 5.7 Loading Jack and Ring Dynamometer in accordance

with Test Method D 1559, or a Mechanical or Hydraulic Testing Machine capable of maintaining the required strain rate and measuring load with equal or better precision.

5.8 Loading Strips in accordance with Test Method D4123.

6. Preparation of Laboratory Test Specimens

6.1 Make at least six specimens for each test, three to be tested dry and three to be tested after partial saturation and moisture conditioning.

6.2 Use specimens 4 in. (101.6 mm) in diameter and 2.5 in. (63.6 mm) high, in general, but specimeii^- 6f other dimensions may be used i f desired. When using aggregate larger than 1 in. (25.4 mm), use specimens at least 6 in. (152.4 mm) in diameter.

6.3 Prepare mixtures in batches large enough to make at least 3 speciniens or, as an alternative, prepare a batch just large enough for 1 specimen. I f theoretical maximum specific gravity is to be determined, use a batch large enough or prepare a separate batch to provide a specimen for this purpose.

6.4 When a liquid antistripping additive is used, heat a sufficient quantity of asphalt cement for one batch to 300 ± 1 0 T ( 148.9 ± 5.6°C) in a closed 1-qt can in an oven. Add the required quantity of additive and immediately, mix, for approximately 2 min, with a mechanical stirrer approximately 1 in. (25.4 mm) from the bottom of the container. Maintain the treated asphalt cement at 300 ± l O T (148.9 ± 5.6°C) in the closed can until it is used. Discard the treated asphalt cement i f not used the same day it is prepared, or i f allowed to cool so that it requires reheating.

6.5 When using a pulverulent solid antistripping additive , use the addition procedure simulating the procedure expected in the field. Follow the procedure specified in either 6.5.1,6.5.2, or 6.5.3.

6.5.1 When dry powder is added to dry aggregate, dry, batch, and heat the mineral aggregate to 300 ± 1 0 T ( 148.9 ± 5.6°C). Add the required quantity of additive to the aggregate, and thoroughly mix the entire mass until a uniform distribution of additive is achieved. Take care to minimize the loss of additive to the atmosphere in the form of dust. After mixing, maintain the treated aggregate at the required mixing temperature until it is used.

6.5.2 When dry powder is added to damp aggregate, batch the damp mineral aggregate, and adjust the moisture content of the combined aggregate to the expected field moisture level. Add the required quantity of additive to the damp aggregate, and iliorouglilx iiii.x the entire mass until a

uniform distribution of additive is achieved. Take care to minimize the loss of additive to the atmosphere in the form of dust. After mixing, dry the treated aggregate, heat to the required mixing temperature, and maintain at that tempera-ture until it is used.

6.5.3 When powder slurry is used, add the required quantity of additive to water using the powder to water ratio expected in the field. Take care to minimize the loss of additive to the atmosphere in the form of dust. To prevent settling, continuously mix the resulting slurry until it is used. Batch the damp mineral aggregate, adjust the moisture content as required in 6.5.2, add the required quantity of slurry, and thoroughly mix the entire mass until a uniform distribution of slurry is achieved. After mixing, dry the treated aggregate, heat to the required mixing temperature, and maintain at that temperature until used.

6.6 Proportion, mix, and compact specimens in accordance with one of the following: Test Methods D 1074, D 1559, D3387, D 3496, or Method D 1561 and 6.6.1 and 6.6.2. I f Test Method D 1559 is used, either a manual or mechanical hammer may be used.

6.6.1 After mixing, stabilize the mixture temperature of each specimen at the required compaction temperature, in a closed container, in an oven for 1 to 2 h. I f preparing a multi-specimen batch, split the batch into single-specimen quantities before placing into the oven.

6.6.2 Compact the specimens to 7 ± 1 % air voids, or a void level expected in the field at the time of construction. This void level can be obtained by adjusting the following: the static load in double-plunger compaction; the number of blows in a marshall hammer compaction; the foot pressure, number of tamps, leveling load, or some combination in kneading compaction; or the number of revolutions in gyratory compaction. Determine the exact procedure by trial for each mixture.

6.6.3 Cool specimens in the mold to room temperature as rapidly as possible in a stream of moving air, extract from molds, then follow the procedure outlined in Section 8 within 24 h.

7. Preparation of Field Specimens

7.1 Select a truck to be sampled in accordance with Practice D 3665.

7.2 Secure a sample from the truck at the plant in accordance with Method D 979.

7.3 Stabilize the mixture temperature to approximately the temperature found in the field when rolling begins. Maintain this temperature in a closed container, in an oven i f necessary, for approximately the time lapse between mixing and the start of actual rolling.

7.4 Compact the specimens in accordance with 6.6.2, and cool and extract from the molds in accordance with 6.6.3.

7.5 I f specimens are not to be compacted in the field laboratory, place the samples in a sealed container, transport to the laboratory, and reheat to the temperature required in 7.3. Proceed with the steps in 7.4.

NoTi: 1—Specimens made from plant-produced mixtures in accordance with Section 7 may yield dilTerent results from specimens made from laboratopi-produced mixtures of the same job mix made i" accordance wiih Section 6.

570

88

D4867

8. Procedure

N o n . 2—A Jata sheet thai is convcnicni for use wiili this procedure apix:ars in Appendix X I .

8.1 Determine the theoretical maximum specific gravity in accordance with Test Method D 2041.

8.2 Determine the specimen height in accordance with Test Method D 3549.

8.3 Determine the bulk specific gravity in accordance with Test Method D 2726, and express the volume of the specimen in cubic centimeters. The term {B-C) in Test Method D 2726 is the volume of the specimen in cubic centimetres.

8.4 Calculate the percent air voids in accordance with Test Method D 3203, and express the volume of air in cubic centimeters. The volume of air is the volume of the specimen in 8.3 multiplied by the percent air voids.

8.5 Sort the specimens into two subsets so that the average air voids o f the two subsets are approximately equal. Store the subset to be tested dry at room temperature.

8.6 Partially saturate the subset to be moisture conditioned with distilled water at room temperature using a vacuum chamber. I f it is difficult to reach the minimum degree of saturation required in 8.6.3, the water used to saturate may be heated up to I40*F (60°C).

8.6.1 Partially saturate, to the degree specified in 8.6.3, by applying a partial vacuum such as 20-in. (508-mm) Hg for a short time such as five min.

N O I L 3—Experiments with partial vacuum at room temperature indicate that the degree of saturation is very sensitive to the magnitude of the vacuum and practically independent of the duration. The level of vacuum needed appears to be different for different mixtures.

8.6.2 Determine the volume of the partially saturated specimen in accordance with Test Method D 2726. Determine the volume of the absorbed water by subtracting the air-dry mass of the specimen in 8.3 from the saturated surface-dry mass of the partially saturated specimen.

8.6.3 Determine the degree of saturation by dividing the volume of the absorbed water in 8.6.2 by the volume of air voids in 8.4 and express the result as a percentage. I f the volume of water is between 55 and 80 % of the volume of air, proceed to 8.7. I f the volume of water is less than 55 %, repeat the procedure beginning with 8.6.1 using a slightly higher partial vacuum. I f the volume of water is more than 80 %, the specimen has been damaged and is discarded.

NOTE 4 — I f the average air voids of the saturated subset is less than 6.5 %. a degree of saturation of at least 70 % is recommended.

8.7 Moisture condition the partially saturated specimens bv soaking in distilled water at 140 ± 1.8T (60 ± 1.0°C) for 24 h.

NOTE 5—If a freeze-thaw conditioning cycle is desired, the following procedure is suggested instead of the procedure in 8.7. Wrap each of the partially saturated specimens tightly with two layers of plastic film using masking tape to hold the wrapping if necessary. Place each wrapped specimen into a leak-proof plastic bag containing approximately 3 m L of distilled water, and seal the bag with a tie or tape. Place the wrapped and bagged specimens into an air bath freezer at - 0 . 4 ± 3 . 6 T ( - 1 8 ± 2.0'C). After at least 15 h in the freezer, remove the specimens and immerse ihcni in a water bath at I 4 0 ± l . 8 ' F ( 6 0 ± 1.0'C) for 24 h. After 3 min of immersion, after specimen surface thaw occurs, remove the bag and wrapping from the specimens.

8.8 Adjust the temperature of the moisture-conditioned subset bv soalcing in a water bath for 1 h at 77 ± i 8*F (75 -t-rc). • ~

8.9 Measure the height of the moisture-conditioned subset by Method D 3549, and determine volume by Test Method D 2726.

8.9.1 Determine the water absorption and the degree of saturation in accordance with 8.6.2 and 8.6.3. A degree of saturation exceeding 80 % is acceptable.

8.9.2 Determine the swell of the partially saturated specimens by dividing the change in specimen volumes in 8.6.2 and 8.3 by the specimen volume in 8.3. Determine the swell of moisture-conditioned specimens by dividing the change in the specimen volume in 8.9 and 8.3 by the specimen volume in 8.3.

8.10 Adjust the temperature of the dry subset by soaking in a water bath for 20 min at 77 ± 1.8'F (25 ± 1.0°C).

8.11 Determine the tensile strength at 77 ± 1.8T (25 ± l.O'C) of both subsets.

8.11.1 Place a specimen into the loading apparatus and position the loading strips so that they are parallel and centered on the vertical diametral plane. Apply a diametral load at 2 in./min (50.8 mm/min) until the maximum load is reached, and record the maximum load.

8.11.2 Continue loading until the specimen fractures. Break the specimen open and visually estimate and record the approximate degree of moisture damage, i f any.

8.11.3 Inspect all surfaces, including the failed faces, for evidence o f cracked or broken aggregate, that may influence test results, and record observations.

9. Calculations 9.1 Calculate the tensile strength as follows:

5 , = 2PMD

where: 5, = tensile strength, psi (kPa) P = masimum load, lbs (kg) I = specimen height immediately before tensile test, in.

(mm), and D = specimen diameter, in. (mm).

9.2 Calculate the tensile strength ratio as follows: TSR = {S,JSjm

where: TSR = tensile strength ratio, % S,^ = average tensile strength of the moisture-conditioned

subset, psi (kPa), and 5,d = average tensile strength of the dry subset, psi (kPa).

10. Report 10.1 The report shall include the following information: 10.1.1 Number of specimens in each subset, 10.1.2 Average air voids of each subset, 10.1.3 Average degree of saturation after partial saturation

and after moisture conditioning, 10.1.4 Average swell after partial saturation and after

moisture conditioning, 10.1.5 Tensile strength of each specimen in each subset, 10.1.6 Tensile strength ratio, 10.1.7 Results of visually-estimated moisture damage ob

served when the specimen fractures, and.

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89

# D 4 8 6 7

10.1.8 Results of observations of fractured or crushed aggregate.

11. Precision and Bias

11.1 Precision—The standard deviations for use with this test method have been determined using laboratory-mixed specimens conditioned in accordance with 8.7. Neither plant-mixed material nor the conditioning in Note 5 has been studied. Nineteen laboratories participated in the precision study by testing five asphalt concrete mixtures, two of which contained a liquid antistripping additive.

11.1.1 Within-Laboratory Precision—The single-operator standard deviation of tensile strength for either dry or moisture-conditioned specimens has been found to be 8 psi

(55 kPa). The D2S limit for the maximum allowable difference in tensile strength between duplicate specimens of the same mixture tested by the same operator is 23 psi (159 kPa).

I I . 1.2 Between-Laboratory Precision—The multilabora-tory standard deviation of the tensile-strength ratio has been found to be 8 %. The D2S limit for the maximum allowable difference in tensile-strength ratio between results of tests performed on samples of the same mixture by two different laboratories is 23 %.

11.2 Bias—This test method has an undetermined bias because the value of a tensile-strength ratio can be defined only in terms of the test method.

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D 4 8 6 7

A P P E N D I X

(Non-Mandatory Information)

X I . M O I S T U R E D A M A G E L A B O R A T O R Y DATA S H E E T

Project

Additive Dosage

Compaction Method Etion

Date Tested Sample I.D.

Date Tested

Diameter 0

TNckness t

Dry mass In air A

SSO mass B

Mass in water C

Volume (a-C) E

Bulk Sp. Gr. {AIE) F

Max Sp. Gr. G

»AirVoid(100(G-F)/G) H

Volume AirVoid, HE/100 /

Load (lbs) P

Saturated min. @ ••Hg

SSD Mass B-

Mass in water C

Volume ( 8 ' - C ) £ '

VolAtw. water(B'- /A) J'

» Saturation (lOOJ'//)

XSwell(100(£'-£)/£)

Conditioned 2 4 h in 140°F water

Thicl ness t"

SSO Mass S "

Miss in water C "

Volume ( B " - C " ) £ "

VolAbs. Water ( e ' M ) J "

X Saturation. (100J"/0

X Swell, 100<£"-£)/£

(lbs (kg)) p..

fry Strength. 2 P / ( D T

Wet Strength, 2 P " / ( " D T

JSR, 100S^S„

Viiual Moisture Damage

5[«ck/Break Aggregate

573

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