ENGINEERING RESEARCH INSTITUTE

I

r

CORRELATION OF LOCALLY-BASED PERFORMANCE OF ASPHALTS

WITH THEIR PHYSICOCHEMICAL PARAMETERS

TASK 1 REPORT JANUARY 1988

IOWA DOT PROJECT HR-298 ERI PROJECT 1942

Sponsored by the Highway Division of the Iowa Department of Transporatation and the

Iowa Highway Research Board.

ENGINEERING RESEARCH INSTITUTE

iowa state university eri 88-408

CORRELATION OF LOCALLY-BASED PERFORMANCE OF ASPHALTS .

WITH THEIR PHYSICQCHEMICAL PARAMETERS

TASK 1 REPORT JANUARY 1988

D. Y. LEE B.V.ENUSTUN

IOWA DOT PROJECT HR-298 ERi PROJECT 1942

Sponsored by the Highway Division of the Iowa Department of Transportation and the

Iowa Highway Research Board.

"The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the Highway Division of the Iowa Department of Transportation."

1.

2.

INTRODUCTION

1.1. Background 1.2. Objectives 1.3. Program of Study

EXPERIMENTAL

2.1. Materials 2.2. Procedures

iii

TABLE OF CONTENTS

2.2.1. Rheological properties 2.2.2. HPLC 2.2.3. Thermal analyses 2.2.4. X-ray diffraction

3. RESULTS

3.1. Rheological Properties 3.2. HPLC 3.3. Thermal Analyses 3.4. X-ray Analyses 3.5. Correlations

3.5.1. Rheological properties 3. 5 • 2 • . HP-GPC 3.5.3. Thermal analyses 3.5.4. X-ray diffraction

4. SUMMARY AND CONCLUSIONS

5. RESEARCH PLAN FOR TASK 2 (YEAR 2)

6. ACKNOWLEDGMENTS

7. REFERENCES

APPENDIX I

APPENDIX II

APPENDIX III

Page

1

1 2 3

3

3 5

5 11 16 21

22

22 43 43 48 48

53 53 57 57

58

59

60

61

iv

LIST OF TABLES

Table 1. Rheological properties.

Table 2. Temperature susceptibility.

Table 3. Low-temperature cracking properties.

Table 4. Thin film oven test hardening.

Table 5. Properties of recovered asphalts.

Table 6. Viscoelastic properties of thermal cycled samples at +5°C.

Table 7. Results of HP-GPC analyses.

Table 8. DSC test results.

Table 9. Shoulder height of x-ray diffraction spectrum at 28 = 4.83°C.

Page

23

29

36

38

42

46

47

49

50

v

LIST OF FIGURES

Figure 1. Summary of proposed research.

Figure 2. Modified cone and plate viscometer.

Figure 3. Mechanical model corresponding to asphalts at a low temperature.

Figure 4. Viscometer rotation plotted vs time (sample: JOS-01-0 at +S°C, after cooling from +2S°C for 6S hrs; L = 100 g;

Page

4

8

9

cone constant = 121S p. deg/g. sec. 10

Figure S. HP-GPC units. 13

Figure 6. (a) (b) (c)

DSC thermogram of B297S at 2 deg/min scanning rate. -18 DSC thermogram of B297S at S deg/min scanning rate. -19 DSC thermogram of B297S at 10 deg/min scanning rate.-20

Figure 7. Cross-section of x-ray analysis sample holder.

Figure 8. Penetration at 2S°C (77°F) and at S°C (41°F).

Figure 9. Viscosity at 60°C (140°F).

Figure 10. Viscosity at 13S°C (27S°F).

Figure 11. Ring and ball softening point.

Figure 12. BTDC of original (O} Jebro asphalts.

Figure 13. BTDC of original (0) Koch asphalts.

Figure 14. Penetration index.

Figure lS. PVN at 60°C (140°F).

Figure 16. PVN at 13S°C (27S°F).

Figure 17. Viscosity temperature susceptibility.

Figure 18. Retained penetration and viscosity ratio, thin film oven test.

Figure 19. PVN vs viscosity ratio.

22

24

2S

26

27

30

31

32

33

34

3S

39

40

vi

LIST OF FIGURES (Cont'd.)

Figure 20. Relationships between viscosity at 140°F (60°C) in poises, penetration at 77°F (25°C), and temperature susceptibility. 41

Figure 21. Viscoelastic properties of JOS-01-0, Jl0-01-0 and J20-01-0 at +s 0 c. 44

Figure 22. Viscoelastic properties of SC-SU and WR-SU at +S°C. 45

Figure 23. (LMS) 18 •125 plotted vs LMS. S6

1

I. INTRODUCTION

1.1. Background

Current specifications for asphalt cement contain limits on physical .·

properties based on correlations established in the past with field performance

of asphalt pavements. Recently, however, concerns have arisen that although

current asphalts in use meet these specifications, they are not consistently

providing the long service life once achieved.

There are a number of logically possible explanations of this situation:

[1] A considerable concern is associated with the recent world crude oil supply

and the economic climate after the 1973 oil embargo which may have affected the

properties of asphalt of certain origin (Hodgson, 1984). Blending several

crudes, as routinely practiced in refineries to produce asphalts meeting current

specifications, may have upset certain delicate balances of compatibility

between various asphaltic constitutents, which may manifest itself in their

long-term field performance bu~ not in original physical properties specified in

the specifications (Goodrich et al., 1985; and Petersen, 1984).

[2] The increased volume and loads of traffic on highways, which have occurred

over the decades, may have shortened the life span of pavements, indicating the

necessity of revising specification limits and/or imposing new provisions to

maintain desired durability.

[3] Inadequate mixture design, particularly poor gradation of aggregates,

changing construction practices and improper use of additives may also be

responsible for early deterioration of asphalt pavements (Anderson and Dukatz,

1985; and Hodgson, 1984).

[4] Specifications based only on physical properties of asphalts do not

guarantee adequate performance.

2

While the performance of the asphalt pavements could be improved by

judicious application of improved mix design techniques, more rational thickness

design procedures, better construction methods and quality control measures,

selection of asphalts based on performance-related properties, tests, and

specifications is the key to durable asphalt pavements.

Highway Research Project HR-298 was approved by the Iowa Highway Research

Board on December 2, 1986 to study the relationships between the performance of

locally available asphalts and_their physicochemical properties under Iowa

conditions with the ultimate objective of development of locally ·and

performance-based asphalt specifications for durable pavements; funding for Task

1 (year 1) of the three-year study was authorized in January 1987. This Task 1

report describes work performed and findings resulted during the first year of

the study •

..!..:!:_ Objectives

The objective of this study was to establish locally-based quality and

performance criteria for asphalts, and ultimately to develop performance-related

specifications ·based on simple physicochemical methods. Three of the most

promising chemical methods (high p~rformance liquid chromatography or HPLC,

thermal analysis or TA and X-ray diffraction or XRD) were selected to analyze

samples of:

a. Virgin asphalts from local suppliers.

b. Virgin asphalts subjected to thin film oven test.

c. Asphalts extracted from laboratory mixes prepared using the virgin

asphalts after they are artifically aged in chambers under

accelerated environmental conditions (exposures to ultraviolet

and infrared radiations, temperature and moisture extremes).

d. Asphalts extracted from pavements with known performance records.

;

.·•

3

The results obtained will be analyzed to find the fundamental asphalt

property variables (such as viscosity, molecular size, micelle size, transition

temperatures, temperature susceptibility, resistance to oxidative hardening,

reactivity with environment, etc.) which directly affect the field performance

in Iowa.

On the basis of the laboratory-field-property-performance correlations, we

expect to formulate specifications and establish testing procedures which can be

performed in the transportation materials laboratories of the Iowa DOT and ISU.

1.3. Program of Study

The ultimate objective of this study is to establish locally-based quality

and performance criteria as a basis for asphalt specifications, in other words,

the development of performance-based specifications for the state of Iowa.

This research will be carried out in six tasks completed in three years.

The specific tasks to be performed were presented in the research proposal and

are shown iri Figure 1.

2. EXPERIMENTAL

2.1 Materials

Asphalt cement samples representing those commonly used in Iowa were

obtained from Koch Asphalt Co., St. Paul and Jebro, Inc., Sioux City, Iowa. Two

sets of asphalt samples were supplied by each of the two suppliers: each set of

samples consisted of one AC-5, one AC-10 and one AC-20. The two sets of samples

from Jebro were received in February and September 1987; those obtained from

Koch were received in June and October 1987. A total of 12 virgin asphalt

cement samples were tested in Task 1. They were identified as J0501, J0502,

JlOOl, J1002, J2001, J2002, K0501, K0502, KlOOl, K1002, K2001 and K2002.

/

SELECT & .. .• OBTAIN ....,

r-. ASPHALT -CEMENTS .. THIN - FILM -- OVEN TESTS

TASK 1 TASK 1 ...

,, 1 • ,,,.

"' ...., .... -, SELECT & PREPARE MIXES

, ....,. TEST.

OBTAIN TEST MIXES EXTRACT ASPHALT ~ ~ - CEMENTS AGGREGATES - ASPH!!LTS --. .... .. .. - TASK 2 TASKS 2 & 3 TASKS 2 & 3

TASKS 1, 2, & 3 TASK 2 ...

+ j~ j~ .. ,

"' r ..... ARTIFICIALLY 1 ~

AGE MIXES , SELECT &

. .p.

SAMPLE -PAVEMENTS ... TASK 2 .. PERFORMANCE

CORRELATICN .

TASK 3· -j ~

... TASK 4

I • , .... .... / .... / .... , OBTAIN MATERIAL,

OBTAIN OBTAIN CONSTRUCTION, PREPARE PREDICT ORIGINAL ORIGINAL QUALITY CONTROL, ASPHALT PAVEMENT ' -

AGGREGATES ASPHALTS . MlUNTENANCE, SPECIFICATIONS - PERFORMANCE . PERFORMANCE & TRAFFIC DATA ' TASK 3 TASK 3 TASK 6 TASK 5 TASK 3

' -.

FIGURE l . SUMMARY OF PROPOSED RESEARCH

5

In addition, two sets of asphalt samples recovered from pavement cores

taken in April 1987°were provided by the Materials Laboratory, Iowa DOT. These

samples were taken from seven-year old pavements of known performance with

respect to cracking (Marks and Huisman, 1985). They were identified as Sugar

Creek (surface, binder and base) and Wood River (surface, binder and base),

respectively.

Furthermore, 25 reference asphalt samples with extensive data from FHWA and

a reference asphalt from Montana State University were also obtained and will be

evaluated in Tasks 4 to 6.

2.2. Procedures

The 12 virgin asphalts (0 samples) were first aged following thin-film oven

test procedure (ASTM D 1754) and identified as R samples. The 12 original (0)

. and 12 aged (R) samples were then characterized by physical and chemical tests

as described in the following sections:

2.2.1. Rheological properties : Penetration at 41 and 77°F, viscosity at 77, 140

and 275°F, and ring-and-ball softening point tests were performed on both

original and TFOT aged residue asphalts. From these data penetration index

(PI), pen-vis number (PVN), viscosity temperature susceptibility, cracking

temperature, critical stiffness and critical stiffness temperature were

calculated.

In addition to the above mentioned standard tests, certain rheological

properties of a few samples were studied in greater depth at a moderately low

temperature, which might have some bearing on their low temperature performance

in the field. They were the samples JOS-01-0, Jl0-01-0, J20-0l-O, SC-S (Sugar

Creek surface) and WR-S (Wood River surface). The primary purpose of these

experiments was to see how the low temperature transformations revealed by

thermal analysis, to be described later, reflect on rheological properties.

6

The secondary purpose was to study the time dependence of these properties at a

low temperature.

A review of the relevant literature reveals that a considerable effort has

been made by the researchers sponsored by asphalt producers to establish a

universal relationship to describe rheological properties of all asphalts

(Brodnyan et al., 1960; Sisko and Brunstrun, 1968; Jongepiev and Kuilman, 1969;

and Dobson, 1969). However, ·the quest'ion of how fast an asphalt sample acquires

these properties when brought to a given temperature from a different

temperature, or whether these properties are indeed single valued functions of

temperature for practical purposes, seems to have received little attention.

The lower the temperature, the more valid become these questions due to sluggish

behavior of asphalts. The'contributions of many authors in this field were

confined to their in-passing remarks that rheological properties of asphalts

depend on their thermal history.

Hoping to get some discriminating information on asphalts possibly related

to thermal cracking of pavements, we studied viscoelastic properties of a few

samples at +S°C as a function of their thermal history and time. The reasons

for choosing this temperature were the following:

(1) It was the lowest temperature at which rheological tests were

manageable with the equipment on hand.

(2) It may reasonably be considered as an intermediate winter temperature

which prevails after a warm spell or after a severe cold.

(3) It is within a temperature range in which most·asphalts suffer a

thermal (endothermic) transformation upon heating (Noel and Corbett, 1970;

Albert et al., 198S; and Brule et al., 1986).

Experiments were designed to estimate the elastic shear modulus of the samples,

as well as their Newtonian viscosities at +S°C, using a cone and plate

viscometer.

7

To provide Newtonian conditions, the samples had to be sheared at extremely

low rates. This requirement coupled with shortening the testing time made it

necessary to increase the accuracy of displacement measurements by two orders of

magnitude. This was achieved by an optical method of measurement of the

rotation of the cone. For this purpose a replaceable reflecting mirror was

fastened on the cone axle as shown in Figure 2. A focusable beam of light from

a projection pointer was directed to the mirror, and its reflection on a

graduated screen was used to measure the rotation of the cone with an accuracy

of better than± 0.005 degree. With this modification of the cone and plate

-5 instrument, it was possible to work at an angular velocity of as low as 2 x 10

degree/sec.

An analysis of the experimental results has shown that the rheological

behavior of asphalts under Newtonian conditions at low temperatures can be

described reasonably well by the equation

x = Lt/8 + L(l - e-£1t/8l)/El + L(l - e-£2t/82)/£2

where x is the angle of rotation of the cone under an applied load L, t is

(1)

time; 8, 81 , 82 , £1 and Ez are constants. Equation (1) is known to describe the

motion of the viscoelastic system shown in Fig. 3 where the dashpots represent

Newtonian viscous elements and the springs represent Hookeian elastic elements

(Pagen, 1964). 8 characterizes the viscous behavior of the left-hand-side

dashpot, and is proportional to the true (steady) viscosity of the asphalt

sample. The proportionality constant is known as the "cone constant". 81 and 82

are similarly associated with the second and the third dashpots, respectively. £1

and £2 are the force constants of the first and the second springs,

respectively. They are proportional to the shear moduli of elasticity of the

sample. A typical plot of experimental x vs. t data is given in Fig. 4.

8

1·.

Figure 2. · Modified cone and plate vis.cometer.

9

/J,

,(J

L.

Figure 3. Mechanical model corresponding to asphalts at a low-temperature.

A detailed analysis of the experimental results shows, in general, that at

+5 °C , B ~ B1 > B2 and El < E2 •

The ref ore (2)

These make the third term in Eq. (1) negligible for most purposes.

An analytic examination of Eq. (1) in its exact form reveals that if

shearing continues long enough the experimental points on a x vs. t plot fall on

a straight line with a slope of L/ B, and an intercept of L ( l/q + l/E 2) as

indicated in Fig. 4. Therefore, it was possible to estimate the viscosity index B

and an equivalent shear modulus index £ defined by

1/ £' = l/E1 + l/Ez

from the slope and the intercept, respectively, of the experimental straight

line for a given set of data.

(3)

The viscoelastic properties of all five samples were investigated at +5°C

as a function of time by this method after mounting each sample on the cone and

plate assembly and keeping at 25°C for 24 hours.

I /.0 i-

0 500 /OOo

TIME

: j --~~-~.:__ __ :;---j

200()

Figure 4. Viscometer rotation plotted vs. time (Sample: JOS-01~0 at. +5°C, after cooling from +25°C for 65 hrs; L ~ lOQ g; cone constant= 1215 p. deg/g/sec).

11

Three of the samples (JOS-01-0, sc~s, and WR-S) were also investigated

0 similarly after quenching them from room temperature to -30 C for one hour and

rewarming to +5°C at a rate of 0.7 degrees/min. This conditioning was an

attempt to simulate the occasional severe winter conditions.

2.2.2. High performance liquid chromatography (HPLC): HPLC, specifically high

pressure gel permeation chromatography (HP-GPC) is a technique by which the

molecular size distribution of asphalt is determined by means of gels of

selected pore sizes as in sieve analysis. Recent reports from a Montana asphalt

quality study using this technique have shown considerable promise and have led

the Montana State Department of Highways to institute special provisions based

on requirements based on HP-GPC (Jennings et al., 1982, 1985, 1988). While

there were unresolved exceptions, it has been concluded that large molecular

size asphaltic constituents contribute to low temperature cracking of asphalt

pavements. Other studies (Zenewitz and Tran, 1987; and Button et al., 1983)

have related the amounts of small molecular size fractions to rutting and tender

mixtures~

Even though the purchase request for HPLC equipment was initiated in early

February 1987, shortly after the start of the research project, the equipment

was not complete and operational until late August 1987. While we were able to

complete the analyses of all the asphalt samples following the Montana protocol,

because of time limitations we were not able to explore other experimental

techniques and data analysis approaches. Recognizing the potential of the

HP-GPC technique and the weakness of the Montana procedure and interpretation,

it is planned that a more vigorous investigation for alternative procedures and

data interpretations of HP-GPC work will be pursued in Task 2.

A high performance gel permeation chromatography system (Waters) was used

during this study. This system consisted of a solvent reservoir; a high

pressure pump (Waters model 510); an injector (Waters model U6K); three

12

0 0 • .

"Ultrastyragel" columns (Waters),. one 1000 A.followed by two 500.A units;· a UV

absorbance. !fetec;tor set._ at ~40 nm. (Waters model 481); and .a data module (Waters

mqdel745) •. Th~ assembly of these units are seen in Fig. 5.

The solvent reservoir,-w~s. a one liter bott:le of tetrahydrofuran (THF) with

a stopper that had been modified so that three tubes entered the solvent "

reservoir.

HPLC grade THF is. packaged under nitrogen to preserve spectral integriq(

and is not inhibited for full .UV transparency. To preserve these co~d'itions and

isolate the THF from atmosphere, helium.gas was slowly bubbled into the solvent

via the tubing connected to the helium gas cylinder.

The second tube in the stopper contained desiccant chips to prevent

moisture from entering the solvent.

The third tube in the stopper was the draw-off line through which solvent

was drawn from the reservoir to the pump.

The dual head design~of the Waters Model 510 pump allowed one head to fill

with solvent while the other was delivering solvent at increased pressure to the

system and vice versa. This alternating action minimized flow fluctuations and

improved flow rate.

Asphalt samples of 0.02 to 0.05 grams were accurately weighed into a 20 ml.

glass Scintillation vial. THF (drawn from the solvent reservoir) was pipetted

into the vial to prepare a 0.5% (w/v) solution. The sample solution was then

transferred to a 15 ml. centrifuge tube, capped, and centrifuged.for 10 minutes

to remove foreign particles capable of plugging columns. Samples were weighed

ahead of time but dilution and centrifugation were done just before injection.

The delay time between sample dissolution and injection was kept constant from

sample to sample (approximately 30 minutes +5 minutes).·

Figure 5. HP-GPC units.

14

The Model U6K Universal Liquid Chromatograph Injector allowed samples to be

loaded at atmospheric pressure while THF was simultaneously being delivered to

the system at increased pressure. This was accomplished by isol?ting the sample

loading channel from the main stream while injecting a sample. The sample

channel, opened to atmosphere, made it possible to displace solvent with sample

as the sample was delivered from a syringe~ After sample injection, the channel

.was closed to atmosphere and pressurized. The solvent preferentially passed

through the sample channel (since it followed the path of least resistance) and

carried the sample to the columns. Flow rate was set at 0.9 ml./min. Sample

size was 100 ul.

The gel permeable columns separated the sample by molecular size. The

total solvent volume in the columns was distributed between interstitial volume

and pore volume. Each column contained six milliliters of interstitial and six

milliliters of pore volume for a total of twelve milliliters per column. Thus,

the system with three columns had a total of 36 milliliters of solvent volume.

Therefore, large molecules that didn't penetrate the pores (referred to as total

exclusion), passed directly through the columns and exited (or eluted) after 18

milliliters of interstitial solvent.

However, small molecules that penetrated all pores (total inclusion of both

interstitial and pore volumes) eluted after 36 milliliters of solvent.

Intermediate size molecules eluted between 18 and 36 milliliters. During the

method's development, columns of appropriate pore size were selected so that the

sample was neither totally excluded nor included, but distributed in the range

0 0

between 18 and 36 milliliters. A 1000 A and two 500 A columns in series

effectively separated the components in asphalt samples. To determine the

actual exclusion and inclusion pore sizes of the columns, prior to the present

studies a series of monodisperse polystyrene standards of known molecular

15

weight were analyzed using the uv detector at 254.nm. 'The following retention

times were determined from these standards:

Molecular Weight

470,000 240,000 110,000 35,000 8,500 1,800

Phenolphtalein (320) Xylene (106)

Retention Time (minutes)

17.20 17.34 17.58 18.32 20.61 23.79 28.50 34.98

These retention times will vary depending on the individual columns, the

precise flow rate, the amount of dead volume in the system and possible other

factors such as temperature and dilution time. Note that at molecular weights

greater than 110,000 there was little change in retention time, this indicated

total exclusion. The lower limit was not determined.

Gel particles within the columns are compressible and may be damaged at

high pressures so the maximum pump flow rate was set at 1.2 ml./min. (or 2000

psi backpressure). Additionally, column temperature fluctuations cause

particles to swell or shrink, thus changing pore size. To alleviate this

0 problem, a constant temperature water bath at 27 C isolated the columns from

room temperature fluctuations and maintained columns at a constant temperature.

The sample eluted from columns passed through the sample side of the flow

cell of the Lambda-Max Model 481 LC Spectrophotometer where a beam of UV light

passed through the sample. The amount of absorbed light is assumed to be

directly proportional to the concentration of asphaltic components. Absorption

units detected by spectrophotometer were converted to volts and transferred to

the Waters 745 Data Module where the signal was amplified and plotted versus

16

time. The resulting chromatograph depicted the molecular size distribution of

the sample. Chromatographs were automatically divided into slices of specified

time intervals and the area, molecular weight per slice, and cumulative percent

of area were calculated from dialog input and printed at the end of the

analysis. To standardize procedures, samples were analyzed using the same

dialog settings.

Twelve virgin asphalt (O) samples and their TFOT residues (R samples), as

well as six recovered core samples were analyzed by this method to determine

their large molecular size (LMS) ratings. This rating has been proposed by the

Montana State University research group as an index of low temperature

susceptibility of an asphalt sample (Jennings et al., 1980; 1982; and 1985). It

has been defined as the percent of the area under the chromatographic

(340 µm) UV absorbance vs. elution time curve as far as to a retention time (ca.

22 minutes) at which a standard asphalt sample exhibits its second inflexion

point, relative to the total surface area under the whole curve. Therefore,

prior or subsequent to each run, the standard asphalt supplied by the Montana

State University was also run to determine the correct cut-off time for that

sample. This way it was possible to make the estimations independent of

possible day-to-day drifts in the performance of the GPLC equipment. The

absorbance printouts of the data module were used for these computations.

Needless to add that between the runs, the "Ultrastyragel" columns were

routinely flushed with pure solvent for a sufficient length of time. The

columns were also flushed with pyridine once approximately in every two months.

2.2.3. Thermal analyses: Thermal analysis techniques have been used

extensively by chemists to identify and characterize polymers. Breen and

Stephens (1967) recommended the use of glass transition temperature from thermal

analysis data for predicting low temperature cracking of asphalt pavements and

also point out the possibility of using it for predicting cracks due to aging.

I

17

Following the methodologies initiated by Ferry et al. (Ferry, 1961) for

polymers, Schmidt et al. (1966) determined glass transition temperatures of

asphalts volumetrically and used them to predict their low temperature

viscosities. The predicted viscosities were not in good agreement with the

measured viscosities, in general. However, although based on a single

comparison, Schmidt (1966) correlates a high glass transition point, rather than

a high viscosity, to low temperature cracking of pavements.

The glass transition point is known to depend on the rate of temperature

change during scanning. Schmidt et al. recommend a rate of 2 degrees/min. to

obtain meaningful data. They tested 52 reference samples supplied by the Bureau

of Public Roads. In the present study we ran DSC tests in sealed aluminium

sample holders with one of these samples (B 2975, an AC-10 asphalt) at various

heating rates, using a DuPont 1090 instrument. The results are shown in Figs.

6a, b, and c. The glass transition point of this sample reported by Schmidt et

al. is tg = +S.4 c. Glass transitions. traceable on the curves by the method of

inflexion point (Wendlandt, 1984) in the vicinity of this value are indicated on

these figures. It appears from those values that the higher the heating rate,

the higher the estimated transition point, and that the tg estimated at a rate

of 5°C/min. is the closest to the reported value• We, therefore, used this rate

throughout the present work, scanning between -80 and +80°C. The precooling

0

rate was 10 C/min.

However, whether the apparent inflexion point in the vicinity of +5

observed with the sample B2975 indicates a glass transition or a transformation

of another kind is an open questi~n. Indeed these DSC thermograms are very

similar to those reported by Noel and Corbett (1970) and Albert et al. (1985).

The apparent inflexion point just mentioned happens to be in a region which is

interpreted by these authors as the region of an endothermic transformation such

as fusion or dissolution of crystallized asphaltic components, as will be

. Somplet B 2975 Sizes 11.4 MG I lB DEG/MIN CL Rale1 2 DEG/MIN W/ DEWAR Programs Inleraotive DSC V3.0

DSC Oat•• : 18-Deo-~7 T lm.. 121 321 49 Fil•· DATA.17 ee1 Operators AMENSON Plolted1 18-Deo-87 14127119

1.s~--------t-~-+-~t--+~-t-~+-__, __ .....,..~-+-~~--t~-+~-+-~t--+~-t-~+----1~---~--~t--T

1. 2

"· e

" ~ S.4 .... • ·o -LL S. S

;-g l

-s. 4

-e. e

-1. 2

-ae

------ .. 1 i··----

-se -40 -30 -2" -lS 0 12 20 ' DuPont 1090 Temperature (°C)

Figure 6(a). DSC thermogram of B2975 at 2 deg/min scanning rate.

,.,, • E " • 0 .....

LL

~ u • :c

Somplet ASPHALT 82975 Stz., 13. 4 MG Ra+.e1 5 DEG/MIN DSC

Dae•• 2-Apr-87 Time• 8135144 F1le1 ENUSTUN.19 EXT.07 Operalor1 AMENSON

ProgretN I n+.erao+. i ve DSC V3. 0 e -'-~t---+--+---1~....,~t---+~+-~~-+---1---+---+--+~-+---+

· Plol+.ech 2-Apr-87 .131 48a 19

-1

-2

-3 +5.5".

-4

-s

-8

-7

-SI -411 -· -28 -11 • 18 81 411 51 T Clll'lp•ra+.ure (°C) OuPon\ 1090

Figure 6(b). DSC thermogram of B2975 at 5 deg/min scanning rate.

...... \0

"" .. e "" • 0 -LL. ~ u :!

Samples ASPHALT 92975 Stzea 14.9 MG Ro~ea 11 DEG/MIN DSC

Da\e1 2-Apr-87 Time• 8116136 F&l .. ENUSTUN. 18 EXT. 07

Progr-a• In\•rao\lv• DSC V3. B Op•,..~OM AMENSON Plo~~eda 8-Apr-87 81 281 59

-18+--t---+---i---+--+-~~-+----t---+--+---t---+-~ ............ ~+--+~-+-~I---+-~+--+~+--+

-29

-22

-zs.s·

-24

-213 .15•

-28

--. ----38

-32

-sa -- -311 -28 -11 8 18 Temp.,..a~ur• C°C>

..a 5" DuPon~ 1''90

Figure 6(c). DSC therrnograrn of B2975 at 10 deg/min scanning rate.

N 0

21

discussed later. Also, there exists another inflexion point in the present

thermograms at a much lower temperature which corresponds to what these authors

consider as the glass transition point.

It appears that there is no correspondence between calorimetrically and

volumetrically determined transition points. It is possible that the transition

0

reported by Schmidt et al. (1966) as glass t,ransition in the vicinity of +5 C is

a volumetric manifestation of the above mentioned endothermic transformation.

Our previous experience is also such that glass transition points of an asphalt

sample determined by DSC do not correlate with thermomechanical results (*).

This state of affairs casts a shadow of doubt on the significance of the

glass transition points of asphalts, whether determined by calorimetric or by

volumetric measurements. Similar views were also expressed by Sisko et al.

(1968) and Jongepier et al. (1969) to the effect that the glass transition point

is an unsuitable parameter to describe the temperature dependence of rheological

properties of asphalts. In spite of this criticism, we consider that DSC of

asphalts may prove to be useful in indicating transformations of other kinds

related to their low-temperature susceptibility, as will be discussed later.

2.2.4. X-ray diffraction: X-ray diffraction spectra of asphalts have been used

for their structural characterization in relation to their quality (Williford,

1943; and Lee and Demirel, 1987).

All 12 original asphalt samples and their TFOT residues were subjected to

X-ray diffraction analysis by 8 - 28 scanning, using monochromatized CuKa. beam

with 1.54 A wavelength. The samples were molded in circular Plexiglas holders

exactly flush with their brim. The cross section of a sample holder is seen in

Fig. 7.

(*) Private communication with E. I. DePont de Nemours & Company, Wilmington, Delaware, 1971.

22 .

. c: I ~ --~3fl~~ ' I

Figure 7. Cross section of x-ray analysis sample holder.

3. RESULTS

3.1. Rheological Properties

Penetrations at 5 and 25°C (41 and 77°F), viscosities at 60 and 135°C and

softening points of the 12 original asphalt (O) samples as well as their thin

film oven test residues (R) are given in Table 1. While all 12 samples

generally met AASHTTO M226-2 specifications, variations between samples and

between suppliers within given viscosity grades existed. The variability in

penetrations are shown in Fig. 8; the variability in viscosities are shown in

Figs. 9 and 10. By far the most uniform results were observed in softening

points (Fig. 11).

23

Table 1. Rheological properties.

Sample I ·Sp.Gr. P25 P5 VIS 60 VIS 135 S.P ID I @ 25/25 poise c.s C

.. _ .. ____________ I __ . ______________________________________________ _ I

Jos-01-0 I 1.024 162 16 654.0 232.8 41.5 JOS-01-R I 1. 027 98 15 1369. 6 309. 3 48. 0

I J05-02-o I 1.019 160 1s 493.3 213.0 41.5 J05-02-R I 1.032 79 11 1528.1 336.7 50.0

' Kos-oi-o 1 1.023 193 22 556.o 225.o 40.5 KOS-01-R I 1.026 103 13 1272.7 334.7 49.0

I KOS-02-0 I 1.023 182 17 483.7 211.8 40.0 K05-02-R I 1.026 95 13 1159.5 321.5 48.0

-----------'--------------------------------------------------!

J10-01-o ! 1.031 91 11 1466.6 329.5 48.o Jl0-01-R I 1.034 60 8 2640.4 453.9 54.0

I J10-02-o I 1.019 92 11 1091.2 312.1 45.s Jl0-02-R I 1.031 59 10 2639.9 469.5 53.0

I Kl0-01-0 I 1.028 123 15 1024.3 307.1 45.5 Kl0-01-R I 1.030 72 9 2540.7 457.4 51.5

I Kl0-02-0 I 1.028 102 11 1078.9 311.2 46.0 • Kl0-02-R I 1.031 61 10 2734.9 461.9 53.5

---------·------·-- I ------------------------------------------------------!

J20-01-o I 1. 020 78 12 2444. 6 448. 1 so. o J20-01-R I 1. 029 57 10 5062. 5 660. 7 56. 0

I J20-02-o I 1.010 66 8 1020.0 450.8 49.5 J20-02-R I 1. 029 50 8 3929. 3 592. 8 54. 0

I K20-0l-O I 1.031 75 10 1893.3 430.3 49.0 K20-01-R I 1.034 49 8 4647.6 618.2 55.5

I K20-02-0 I 1.031 67 7 2010.0 428.3 so.o K20-02-R I 1.034 43 6 5000.9 581.4 55.5

P25 : penetration @ 25 C, 100 g, 5 sec. PS : penetration @ 5 C, 100 g, 5 sec. VIS 60 · : viscosity @ 60 C. VIS 135 : viscosity @ 135 c. S.P : R & B softening point. O original. R : thin film oven test residue.

E E 0

' ...

E E 0 ... ' ...

24

PENETRATION AT 41 F 22

20

18

16

14

12

10

e

6

4

2

0 J1-0 J2-0 K1-0 K2-0 J1-R J2-R K1-R K2-R

PENETRATION AT 77 F 200--~~-'-~~~~~~~~~~~~~~~--~~~~~~~~~~

190

180 170 160 150 140

130 120 110

100

90

80 :70 60

50 40

30 20 10 o_._....,.~~~"""'~o....-J"-..M~.c.;M.._.~~~,....~~""-.J,....;i""""'u;,},,'--~""""'.QI.--"~"""'~

J1-0 J2-0 K1-0

ISSI AC-5

K2-0 J1-R

~ IDENTif1CATION ~ AC-10

J2-R K1-R K2-R

IZZI AC-20

-·

Figure 8. Penetration at 25°C (77°F) and at 5°C (4.J, °F).

'f :J I .

11 :J J

t~I I

It ll

I

• II

4

:s

2

VISCOSllY AT 60 C, AC-5

"' "'


,,, .12 K1 ICI

~~"



25

26

lllllCOlllY Af ,. c, AC-I 7DO

eao

llOO

• 400

I 300

200

100

0 JI .II IC1 IC2

~~It

VISCOSllY AT 1llll C, ~10 7DO

eoo

500

i 400

I JOO

200

100

0 J1 .. .. IC2

~~It

• I


27

RING AND BALL SOFTENING POINT, AC-5 . --·------------------.

u

l I

RING AND BALL SOFTENING POINT, AC-10

u

1 I

RING AND BALL SOFTENING POINT, AC-20

u

l I

Figure 11. Ring and ball softening point.

28

Asphalt cements of high temperature-susceptibility may contribute to

rutting at high pavement temperatures and cracking at low pavement temperatures.

Temperature susceptibility of an asphalt can be evaluated by using the Shell

Bitumen Test Data Chart (BTDC), the Penetr.ation Index (PI), the Pen-Vis Number

0 0

(PVN) based on viscosity at 60 C or viscosity at 135 C, the

viscosity-temperature susceptibility (VTS), and the Asphalt Class Nuinber (CN).

The basic rheological data as plotted on BTDC are shown in Figs. 12 and 13; and

the derived PI, PVN, VTS and CN of the asphalt cement samples studied are given

in Table 2.

The CN shows the difference between measured and predicted penetration at

25°C. A small negative or positive CN value indicates a Class S (straight run

with a straight line, temperature-viscosity~penetration plot) asphalt. High

positive CN values indicate Class W (waxy) asphalts, and high negative CN values

indicate Class B (blown) asphalts. Either case reflects substantially high and

low· temperature-susceptibility. ·While a few of the samples showed somewhat

higher (e.g. J2 samples) or lower (e.g. Kl samples) temperature susceptibility,

the results on temperature susceptibility, especially measured by VTS and PVN,

were remarkably uniform. These are shown in Figs. 14-17.

Low-temperature asphalt stiffness has been correlated with pavement

cracking associated with nonload conditions. The low-temperature behavior of

asphalts can be evaluated either by estimating the temperature at which asphalt

reaches a certain critical or limiting stiffness or by comparing the stiffness

of asphalts at low temperatures (long loading times).

Table 3 presents the results of estimated low-temperature cracking

properties of the 12 asphalts. The properties include cracking temperature

(CT), temperature corresponding to asphalt thermal cracking stress of 72.5 psi

( 5 0 0 5 x 10 Pa), based on penetrations at 5 C and 25 C, temperature of equivalent

29

Table 2. Temperature susceptibility.

I Sample I CN Pim VTS PVN,60 PVN,135

ID I · ---------------- I -----------------------------------·-------------

! J05-01-0 I 5.17 -0.327 3.538 -0.432 -0.510 J05-01-R I 2.44 0.060 3.601 -0.462 -0.639

I J05-02-0 I 11.00 -0.378 3.497 -0.784 -0.675 J05-02-R 1 6.38 -o.b~6 3.569 -0.689 -o.742

! K05-01-0 I 5.09 0.028 3.497 -0.306 -0.344 K05-01-R I 4.76 0.510 3.503 -0.459 -0.462

I K05-02-0 I 8.73 -0.455 3.490 -0.580 -0.526 K05-02-R I 8.30 -0.038 3.498 -0.691 -0.614

-------------- I -----·--------"-----------------------------------! . J10-01-o I 3.67 -0.111 3.571 -0.509 -0.624. Jl0-01-R I 4.67 0.206 3.540 -0.552 -0.595

I J10-02-o I 9.98 -0.884 3.504 -0.001 -0.694 J10-02~R I 5.75 -0.072 3.515 -0.577 -0.565

I Klo-01-0 I 4.82 0.056 3.483 -0.400 -0.390 Kl0-01-R I 1.28 0.091 3.522 -0.309 -0.393

I Kl0-02-0 I 7.94 -0.414 3.494 ~0.654 -0.586 Kl0-02-R I 3.60 0.132 3.542 -0.492 -0.554

~----·---------- I -----------------------------------------------!

J20-01-o I -0.01 -0.012 3.524 -0.221 -0.333 J20-01-R I -3.67 0.526 3.499 0.016 -0.125

I J20-02-o I 11~15 -0.658 3.411 -0.110 -0.507 J20-02-R I 4.10 -0.247 3.487 -0.433 -0.411

I K20-01-0 I 6.84 -0.451 3.453 -0.548 -0.438 K20-01-R I 1.08 0.039 3.514 -0.300 -0.375

I K20-02-0 I 7.98 -0.488 3.481 -0.660 -0.564 K20-02-R ! 1.24 -0.264 3.589 -0.422 -0.586

CN : class number. Pim : measured penetration index. VTS : Viscosity-temperature susceptibility.· PVN,60 : Penetration-viscosity number @ 60 c. PVN,135 : Penetration-viscosity number@ 135 c. O original. R : thin film oven test residue.

tml\UOl.01""" tr-r-ir-r-.-r-r-r-"T"-rT r-,--,--~,-..-..-.--.--..-.-,

,, - - - r- - - r, '·-t-r- - - r--r-~ . ~-

•-r·

r- -r- . r-r- - r r-· - -,-r--r-,---r-,. +-+-!·-++ 1-1--i-t-+-+--+-

UIMTm.Olnm 1r-r-ir-r-,.-r-r-r"T"-rT-r-r-ri-r-r-r""T"""T"""T""l"""l ,, - - - r- - - - t-- - ,,

•1-+-iH--t-+-+-+-t--t--t- -

•Ill ·«I ·II ·211· ·8

- 1-t- 1--...-..-.-.-.... ·::-..

Figure 12.

~ l'.l_l I i~ AC-10

30

•!lllllll. l'IJSJS ·r-r-.--r....-·r-r-r· u/

. t-t-- -

~ Penetration

• Viscosity

e - R & B softening· point

'

- --- 1

-- .. - I

·-·>-- • ... -->-I

~~.ioJ ·_ ~ s::· : . - - I

BTDC of original (0) Jebro asphalts.

31 QfaQI, Olrrm 1,-,.-,,-,_,.-,..""T"-r-r--,-T-..-,-,--r--,--,--,-.,-,.-..-.--. ,, . - ,, 1--~-- - - ----~-·- -

--~· -:. ·.~~- ti1t8~--!-!~~~~~~~1i!~~'~!~!!itr££~~~~~~j~.--tt::~t2t=-3· ~--} .. +±_;,,,=_±_~±:_=±±:r_0"t_clr - - .. ·-··r-· :.~~.-:..~..=.- ·i-- ~- -- -+-+--+--+-+-+ - ::: - ....... ~ .J .. -~ .: ::',:... ~:::: . ~- - . ==~- . ~-::.' . - r·- - '"°- --f-- -1-- - 1-- ......... ,__ - ->--+-+-+-,__,_, -+--..-+"'...,.-+-""°'~,-+-+--+-+-+-+-+-+-1-i

· - ·-++-+-1-•H-+ +-+-+-1--1'-l-t·-t·--t'~~+-<t-,·'"",-t- +-t--,f--IH-t-+-+--+-+-+- ~- ,.._,.... ~ - -·· - . ".. . +-·+->-<,-.-+-<>-<>·

.. _,_ .... t--.~--·-·-

··r- - - --~-- ·+-+-HH'-1-t-+-+- -~ ·- ·+-+-+-+-+-+-+-1--1

,.._,__ __ . -- ~- - ·-'- .

r-- ---~--•-<--+-+-..__,__.__.. Hl-+-+-+-t-+-+-· ·--- r-r- · ~H ": ;'>,_._,...__._..._._-1-·+-+-+-·t--t H~-;-t--+-+-+-t--+-+-+-+-H-1-+-+-++-+-+-+ +-+-+-+·-i"<*-~" ,Ac,-to I -1--+··+-+-~I>..... .. ·-

t-+-·+-1--t--HH-t-t-t-- -- -- 1 AC-10

AC-5 • ".-'"~~:-"""~~_._...__.__.._...__._._.._.~_,_,_..-L--'--f-'-_._'-'--'-.._,_,__._,_,_\~\~..__.11_..._..l_._..._..__.__._._._..__,_L..L_,_.._,_,__,_L-J.~I ·•·•·•··•·• 20••»• 11t0•noaollD•llll•ia•111111111lllD!JDlll1lO

1llff1Allll. •c

Qtat.ra,Olrrm 1.-.-.....,. ...... -,...,.,...,.....,--,--,-,.-<"""',....,....,.....,.....,. ...... ..,....,.....,......,

" -I

r--·1-- ··1--t - '-'""· - .

::. --= -

- " +-+-+-HI-+-+· -

.. -·--r-· . ·-·t--,

---l-- I

1-Hr~-t-+-+·-+++-+--~·I-- -- -+-+-+-+-+-HH-+-+-+-+++-+-+-+-+-'~!\..-+....-·~·+-+-+-+-+-"l~HH-t-t·-l-·l-+-+-+-+-1--IHH-t-t- I .. ·i'-1-W AC-20

Hl-t-+-+-+-+-+-c--t-+-+-t-+-H'-l-+-+-+-+-+-1--1-+-+-+-+-+-+-·+--11-+-+-+-t-~'r+,-'k--+41'-ll-+-l._,~~-+-lC-+~-t-+-l--1-t-+---r-

' AC-10 AC-S

~~~~~~~~.._..__.._,_..__._.,_...__.__._.....__._..._,,_.._f-' ....... '-'-<-<-'--'--'-...t......L....L....__,_.._.._.._.__...._.__. .............................................. _._.._.._..._.._.._~, ·:ID ·411 ·II ·ID ·9 20 II 4D IO II D II ., Ill Ill II) Ill !JD Ill 1lO

T!-llll.'t

Figure 13. BTDC of original (0) Koch asphalts.

PENETRATION INDEX, AC-5

IC .•

PENETRATION INDEX, AC-10

0.1

-0.1

-o.a

I: -u -oA

'

-0.S

-0.1

-0.7

-o.a

-0.t-'-~-.-~~-=====T-~~~~--,.--~~~~-.---'

.11 IC1

PENETRATION INDEX, AC-20 a.a~~~~~~~~~~~~~~~~~~~--.

0.5

0.4

0,3

G.2

0.1

-o.a

-G.l

-oA

-0.S

-0.1

-0.1--~..---~~~-.-~~~~~,~~~~~-.-__,

.It Kt ICl

Figure 14. Penetration index.

32

33 PVN AT 60 C, AC-5

PVN AT 60 C, AC-10

PVN AT 60 C, AC-20

Figure 15. PVN at 60°C (140°F).

PVN AT 135 C, AC-5 34

PVN AT 135 C, AC-10

-u~'~,,r--~~~----,,---~~~--.~~~~--.~__J J1 IC1 ICZ

PVN AT 135 C, AC-20

Figure 16. PVN at 135°C (275°F).

vrs. AC-5 35

• lLI

ll

I.I

e 2

l.S

o.a

0 JI J2 Kl ICZ

~~II

vrs. Ac-10 •

lLI

ll

I.I

~ 2

I.I

o.a

0 JI J2 ., ICI

~~II

vrs. Ac-20 •

lLI

ll

I.I

~ 2

t.I

Figure 17. Viscosity temperature susceptibility.

36

Table 3. Low-temperature cracking properties.

~--'-·---··- ·------'':'-.~T_··- --·----·-- ---.-:-;-----------------:,,....-.-··· ~.=--·--·--- -·-·- -·-- --··. ·····- ·--· ··--·· ··-·- ·-··----···-··· .. ·-· ---· ··-··· -···- ·-·

Sample I CT TES S,-23 S,-29 _. :~;- . _:ID ! .. ''h'c c ~si , .. . .. ksi

·--------·--_ --~----··---- I --·------""------=---------------------------·--·--------·-----c-----··--· I , • ',

J05-01..:o J05-01-R

J05-02-0 J05-02-R

I K05-0l-O I _K05-01-R !

I

-40.5 -45.0

-40.0 -40.0

-45.0 -42. 0.

-46.5 -47.0

-46.5 -40.0

-49.5 -43.0

0.406 1. 305

0.348 1.740

0.210· 1.015

1.160 2.610

1.595 4.350

0.725 1.740

ko5-02-o 1 -4o.o -45.o 0.290 0.125 K05-02-R ! -43.0 -42;0 · 1.015 3.625

·---'--------- I --------------~-----------------~-'-----------! -Jl0-01-0 ! -38.0 -40.5 1.450 J.10-01-R I -37. 5 -37. 0 2. 900

I J10-02-o I Jl0-02-R !

I Kl0-01-0 ! Kl0-01-R !

!

-38.5 -42.0

-42.5 -37.5

.:1

-34.5 -36.0

-44.5 -38.5

2.755 3.335

0.580 1.740

2.900 4.350

5.800 7.250

1.450 5.800

K10~02-0 ! -38.0 -42.0 1.305 3.045 K10-02~R ! -41.5 -36.5 2.030 5.800

-----------'-------------------------------------------. I J20-01-o I J20-01-R !

l J20-02-0 ! . J20-02-R I

! K20-01-0 I K20-0l-R !

I K20-02-0 I K20-02-R I

-42.5 -39.0 -42.5 -36.0

-36.5 -32.5 -39.0 -34.5

-39.5 -36.0 -39.0 -34.5

-34.0 -35.0 -35.0 -32.5

crack1ng temperature.

1.740 2.175

3.625 4.350

2.900 4.350

2.900 7.250

3.480 4.350

10.150 8.700

7.250 8.700

7.250 14.500

CT TES temperature of equivalent stiffness at 20 ksi,

10,000 sec. s,-23 s,-29 0 R

stiffness at -23 C, 10,000 sec. stiffness at -29 c, 20,000 sec. original sample. thin film oven test residue.

37

asphalt stiffness of 20,000 psi at 10,000 sec loading time (TES), estimated

stiffness at -23°C and 10,000 sec loading time, and stiffness at -29°C and

20,000 sec loading time. The following can be observed:

• Softer grade AC-5 had a lower cracking temperature and reached a

critical stiffness of 20,000 psi at a lower temperature than

harder asphalt AC-20.

e Within a given viscosity grade, cracking temperatures of asphalts

could vary by as much as 5°C.

• Low temperature stiffness values for asphalts of a given

viscosity grade could differ by a factor of 4.

The effect of heat, as determined by viscosity at 60°C (14cJF) and

0 0 penetration at 25 C (77 F), on the thin film oven test residues, are given in

Table 4 and shown in Fig. 18. Viscosity ratios were uniform at between 1.8 to

3.1 (all meeting AASHTO M226, Table 2, maximum ratio of 5); penetration ratios

varied between 0.49 and o.76.

The resistance of asphalts to hardening during hot-mixing and their

temperature susceptibilities are indirectly specified in AASHTO M226, Table 2.

These important properties are plotted in Fig. 19 in terms of PVN and viscosity

ratio at 60°C (140°F). Except for the second set of samples from Jebro,

asphalts supplied in Iowa appeared to be rather uniform. Relationships between

viscosity at 60°C (140°F), penetration at 25°C (77°F) and PVN of the 12 asphalts

are presented in Fig. 20 with reference to AASHTO M226.

The properties of recovered asphalt samples from Research Project HR-217,

80 months after construction, are given in Table 5. While aging has increased

the viscosities, the average PVN of -0.64 for Wood River asphalts and -0.97 for

Sugar Creek asphalts, changed little from those reported by Marks and Huisman

38

Table 4. Thin film oven test hardening.

I sample I Viscosity ratio Penetration ratio

ID I @ 60 c @ 25 c ____________ I __ ~-----------------------------------------------

1 J05-01 I 2. 09 o. 60

02 I 3.10 o.49 I

Jlo-01 I 1. 00 o. 66 02 I 2.42 o.64

I J20-01 I 2.01 o.73

02 I 2.15 o.76 ___ . _________ I ______ .1__. _________________________________________ _

I K05-01 I 2.29 o.53

02 I . 2.40 o.52 I

Kl0-01 I 2.48 0.59 o2 I 2.53 o.60

I K20-01 I 2.45 0.65

02 I 2.49 o.64

O·

I

I

39

Retained penetration @ 25 C

J1 J2 K1

lSSJ AC-05 m ldentlflcotlon

AC-10 ~ AC-20

Viscosity ratio @ 60 C 3.2""T'""~~~~~~~~~~~~--~--~~~~~---

3

2.8

2.1

2.4

2.2

2

1.1

1.1

1.4

1.2

o.a 0.1

0.-4

0.2

K2

o ...... ~~"""".....,..._~--~-..,~.._:u.. __ .-..~"'"'~1.A.ocw..~~..._~~1.A.AJ J1 J2

Sm!!1'J!I ldontlflcatlon ~ AC-10

1<1 K2

Figure 18. Retained penetration and viscosity ratio, thin film oven test.

0

-0.1 -

-0.2 -

-0.3 -

u.. -0.4 -0

"'" ... ~

-0.5 -

z 6: -0.6 -

-0.7 -

-0.6 -

-0.9 -

-1

0

0

-0.1 -

-0.2 -

-0.3 -

u.. -0.4 -Ill I' N

~ -0.5 -

z 6: -0.6 -

-0.7 -

-0.B -

-0.9 -

-1

0

PVN, 140 VS VISCOSITY RATIO

+ J20-1

+ KOS-1

+ + K10-1

JOS-1 +

J10-1 + K:i0-1

KOS-2 .p-

~t:P--22

+ + J20-2 + JOS-2

J10-2

I I I

2

VISCOSITY RATIO {R/O) AT 140 F

PVN,275 VS VISCOSITY RATIO

I

+ + J20ds-1+

K1.p-1 K20-1

+I- + J~5-+2

+ J10-1

I

2

~ffi=--~ +

J10-2

+ JOS-2

I

VISCOSllY RATIO (R/O) AT 140 F

I

4

I

4

Figure 19. PVN vs viscosity ratio.

40

..

(/) w (/)

0 a.. z -LL. 0 0 v -~ >-1--~ u CJ) ->

41

rooooo,.._ __ ~~l"'""-"~-r.-r-rn~~~~~~l'."T~-~-L·~ .. ~·~··=·i:::::::··::::I::::!::r:::W:w::t• r I »· '•••· '~» ... , .... ,,,., ......... ,o)~··•l .. •·l·"·i .. ·· ··1·····•'1• '·I

'\. • . • . . . :~~· ••. ;,. . ;,, ··-·, ·!-·~:(~ ..• , ... . 1.~~ ••• .... - ~I~~ -·· • •· ··I··•·• .. · · · ·t ··· ... :}"" · ·

Figure 20. Relationships Between Viscosity at 140°F in Poises, Penetration At 77°F, and Temperature Susceptibility;.

Table 5 .

. sample

WOOD RIVER

Surface Binder Base

SUGAR CREEK

Surf ace Binder Base

42

Properties of recovered asphalts

P25

43 71 56

24 35 26

VIS60 poise

4806.0 1701. 3 2471.2

8268.3 3624.3 4817.1

PVN60

-0.460 -0.742 -0.720

-0.763 -1.010 -1.137

P25 : penetration @ 25 C, 100 g, 5 sec. VIS60 viscosity @ 60 c. PVN60 : Penetration-viscosity number @ 60 C.

•

•

43

(1985). The significance of these data will be analyzed during Tasks 3 to 6 of

the study in relation to chemical changes and performance data.

The results of viscoelastic measurements at +5°C described in 2.2.1 are

given in Figs. 21 and 22, plotting viscosity and elasticity indices against

time. It will be clear from the description of these measurements that the

viscosity data presented pertain to Newtonian viscosity, i.e. viscosity at zero

shear rate.

Reviewing the viscoelastic data, one can observe that the rheological

properties of these samples exhibit strikingly different dependence on their

thermal history and time. Some properties do not stabilize even after seven

days. The estimated viscoelastic properties of these samples and their trends

are summarized in Table 6.

3.2. Gel Permeation Liquid Chromatrography (GPLC)

The results of GPLC runs with 12 virgin asphalt samples, their TFOT

residues and six recovered core samples as described in 2.2.2 are given in the

form of chromatograms in Appendix I. The estimated large molecular size .(LMS)

ratings of these samples as defined by the Montana State University research

group (Jennings. et al., 1980; 1982; and 1985) are tabulated in Table 7. In the

third column of this table tabulated are the fractional change of LMS upon TFOT,

except the last two values. The latter are the fractional change of LMS, going

from the base course to the surface course sample of the Sugar Creek and Wood

River projects, respectively.

3.3 Thermal Analysis

The results of DSC tests described in 2.2.3 are presented in Appendix II as

thermograms. The low temperature inflexion points on these thermograms, as

interpreted by Noel et al. (1970) and Albert et al. (1984) as glass transition

points, tg, are tabulated in Table 8. The rest of the thermograms, which have

44

r::::- ·1---.-::.. _ -~ - .-- ·+ _,,_.=

6

5

4

£

t

•

•

0.1--'--'---''---'~-'--'-~-'---'---'~-'--'--'--'-'-----'~-'--'--'--'-'-'~~-'-~~~

0 Hi-.s.

Figure 21. Viscoelastic properties of JOS-01-0, Jl0-01-0 and J20-01-0 at +5°C.

•

e

l

•

8.

6

5_

4

7

4 - -

3.

2

,9-• S ..

,] _

,3

,2

o.: ·-·--0

r- r·

····!·

. . . . . . .· . ~-- .:.....:..:....:..--.-~·~ --· .. -· .. : ....... , . .

. ----· ----------· -·---·

Figure 22.

45

·1--·

-- 1 :_i .. ;.

192

Tl~E Hrs.

Viscoelastic properties of SC-SU and WR-SU at +5°C.

46

Table 6. Viscoelastic properties of thermal cycled samples at +5 C. n : Viscosity, MP G : Elastic shear modulus, psi

I I I % variation I

3rd day valu~I in the first 3 days after I after cocilingl ____________________________ _ from +25 C I I

Sample cooling I warming I from +25 c I from -30 c l ·-----·-----··---------· _______ :.._: ______ I _____________ _ I I . I n G n G I n G

__ ... _ .. __ . ______ I --------·----------- _______________ I _____________ _ I I . I I

J05-01-0 I 225 12 31 0 I 29 -38 Jlo-01-0 I 1580 16 44 -18 I J20-01-o I 6990 13 93 -38 I

----------:-------------- ---------7---~:--------------sc-s I 29200 130 11 o I 160 650 WR-S I 9720 54 43 20 I 16 -14

* % change

n G

6 67

-72 -94 43 16

* % fractional change in initial value observed after warming from -30 C ~elative to that after cooling from +25 C.

Table 7.

J05-02-0 J05-02-R

K05-0l-O K05-01-R

. K05-02-0 K05-02-R

SC-Ba SC-Bi sc..:.s

WR-Ba WR-Bi WR-S

47

Results of HP-GPC analyses.

20.6 24.0

30.2 31.4

27.2 30.7

21. 8 24.9

24.9 27.4

30.8 32.8

+16

+4

+13

+14

+10

+7

2.26 2.42

2.12 3.25

0.64 1.06

0.64 1.02

2.26 2.78

1.46 2.02

0.36 0.74

1. 85 2.92

0.88 1. 50 1. 78

1. 68 3.34 1. 89

+71

+53

+66

+59

+23

+38

+105

+58

+102

+13

48

the same general appearance as reported by the latter-authors, consist of two

shallow endothermic peaks. The peak temperatures ti, tz and their mean tin are

also tabulated in Table 8. These regions were analyzed in the manner described

by Albert et al. to determine.the enthalpies of transformation fiH given in the

last column of this table.

3.4. X-ray Analyses

The X-ray diffraction spectra obtained by 8 - 28 scanning of the original

samples and the TFOT residues, as described in 2.2.4, as well as of an empty

sample holder to represent the background, are presented in Appendix III.

According to Williford (1943) the height of the shoulder of the spectral

curve at low angles is a measure of the quality of the asphalt. This height

above the background (at 28 = 4.83 degrees) for various samples and their TFOT

residues are tabulated in Table 9.

Also indicated are the qualitative changes in the shoulder height and the

peak height upon TFOT for each sample.

3.5 Correlations

Poor field performance of asphalts under extreme climate conditions are

attributed mainly to low-temperature susceptibility of their rheological

properties (Schmidt, 1966; Breen et al., 1967; and Albert et al., 1985).

It has long been attempted to correlate some low temperature transitions in

asphalts, which are believed to effect their low-temperature rheology, such as

glass transition (Schmidt, 1966; Breen et al., 1967) and phase transformations

(Noel et al., 1970; and Albert et al., 1985) to their field performance.

One of the most fundamental, direct and conclusive approaches to correlate

rheological properties with another physicochemical property was made in the

Central Laboratory of Highways and Bridges in France .(Brule et al., 1987). The

researchers of this organization, starting from the experimental fact that

49

Table 8. DSC test results.

! Sample I t t 1 t 2 tm Enthalpy change

! g J/g ----------- I -----------·----------------------------------------------

! J05-01-0 ! J05-01-R I

I J05-02-o I J05-02-R I

! K05-01-0 ! K05-01-R I

!

-31 -29

-29 -30

-26 -26

17.0 16.0

17.0 17.0

17.5 17.0

47.5 48.0

41.0 39.5

53.0 47.0

32.0 32.0

29.0 28.0

35.0 32.0

12.0 10.1

10.3 15.0

8.2 a.a

K05-02-0 I -30 16.0 47.0 31.5 a.a K05-02-R I -29 17.0 53.0 35.0 8.4

--------~-'-------------------------~----------------------------!

Jlo-01-0 I Jl0-01-R !

I J10-02-o I Jl0-02-R I

l Kl0-01-0 I Kl0-01-R I

I

-30 -31

-32 -30

-31 -30

16.5 16.0

16.5 16.5

17.0 17.5

47.5 45.0

48.0 48.5

41.0 48.0

32.0 30.5

32.0 32.5

29.0 33.0

11. 2 13.9

9.3 10.5

6.9 7.5

Kl0-02-0 I -29 17.0 48.0 32.5 6.8 Kl0-02-R I -30 17.0 46.0 31.5 6.7

·---------·-·- --- I ---···-----------·-----·---------------------------------------!

J20-01-o I J20-01-R !

I J20-02-o I J20-02-R I

I K20-01-0 I K20-01-R I

I

-35 -35

-30 -29

-25 -22

16.0 17.0

16.5 16.0

17.5 19.5

44.5 47.5

47.5 53.0

47.5 47.5

30.0 32.0

32.0 34.5

32.5 33.5

11. 4 9.7

9.7 10.6

5.7 4.8

K20-02-0 I -26 22.0 50.5 36.0 6.0 K20-02-R I -30 29.5 53.0 41.0 7.8

-----·--·------- I -------------------------------------------------------------

SC-Ba SC-Bi sc-s

WR-Ba WR-Bi WR-S

! . ! -26 17.0 50.5 34.0 9.6 ! -31 16.o 44.o 30.-0 11.2 l -30 16.5 48.0 32.0 10.6 I I I !

-37 -35 -35

15.0 14.0 16.0

44.5 44.0 43.5

30.0 29.0 30.0

10.8 13.3 10.7

Table 9.

!

50

Shoulder height of x~ray diffraction spectrum at two theta = 4.83 degree.

Sample I Shoulder height change in change in I counts x 10 shoulder height peak height

---------------- '--------·---·--------------------------------------------~-·--·-------!

J05-01-o I 33 J05-01-R I 37 + 0

I J05-02-o I 26 J05-02-R I 40 + +

K05-01-0 K05-01-R

K05-02-0 K05-02-R

I . 26 37

36 36

Jl0-01-0 43 Jl0-01-R 37

Jlo-02-0 I 44

+

0 0

Jl0-02-R I 32 + I

Kl0-01-0 ! 34 Kl0-01-R ! 26 +

! Kl0-02-0 I 25 Kl0-02-R I 25 0 +

---------- ' ------------------~--------------------------------------!

J20-01-o I 25 J20-01-R I 41 +

I J20-02-o I 48 J20-02-R I 13

I K20-0l-O ! 36 K20-01-R I 18 +

! K20-02-0 I 25 K20-02-R I 39 +

51

non-Newtonian behavior of asphalts is enhanced at lower temperatures, and

considering the associative interactions between asphaltene micelles leading to

sizeable colloidal agglomerates, were able to correlate the GPLC profiles and

the asphaltene contents to rheological properties.

For this correlation they made use of the intensity of a sharp GPLC peak at

a molecular weight of greater than 100,000 obtained by a fast elution (3.5

0

ml/min.) using two 30 cm long Styragel columns of 1000 and 10,000 A pore sizes.

The purpose of this fast method was preventing the breaking up of asphaltene

agglomerates in the presence of the THF solvent. They also showed that TFOT

increases this agglomeration significantly.

+ The message in the results of the French research group is that the gel +

sol equilibrium in asphalts has an important bearing on their rheological

properties. Since agglomeration (gel formation) is exothermic, at low

temperatures the gel form, at higher temperatures the sol form is predominant at

equilibrium. The DTA studies of this group, as well as the DSC studies of Noel

et al. (1970) and Albert et al. (1985) in the absence of oxygen clearly shows

endothermic transformations as temperature is raised in the range of -S°C

through +80°C.

Although this transformation is referred to as melting of the crystallized

asphaltic components by Noel et al., as dissolution of these components in the

matrix by Albert et al., and vaguely as melting by Brule et al.; it may solely

or partly be gel to sol transformation following a sol to gel transformation

taken place at lower temperatures.

It appears, therefore, that the following factors may effect the asphalt

rheology at low temperatures:

(a) Predominance of agglomerates of asphaltene micelles,

(b) Presence of crystallizable components.

52

The LMS fraction defined and estimated by the Montana research group using

a GPLC method as described in 2.2.2 includes the agglomerated asphaltene

molecules in addition to other asphaltic components. If the concentration of

these agglomerates happens, for some reason, to be proportional to or be a

monotonic function of the LMS content in general, and further if they are

responsible for low temperature susceptibility of the asphalt (factor a), then

the LMS rating of a sample is expected to measure its poor low-temperature

performance. This is exactly what has been put forward by the Montana research

group on grounds of their experimental findings.

Whatever the nature of the endothermic transformation observed in thermal

analysis (factors a and/or b) is, it follows from the DTA results and the ideas ' . ,, . .

put forward by Brule et al. (1987) and the DSC results of Noel et al. (1970) and

Albert et al. (1985) that the location of the endothermic transformations on the

temperature scale described above may also characterize the low-temperature

susceptibility of the asphalt. For instance, the larger the endothermicity of

this transformation and higher the temperature range in which it occurs, the

more susceptible may be the sample.

As associative interaction between asphaltene molecules promotes a

structural order in the system, such an interaction is also expected to reflect

on x-ray diffraction spectra of the sample.

The experimental data presented in Section 3.1 through 3.4 will be reviewed

below, in relation to these expectations. Since no engineering service

information is available at this stage of the present project, except in the

case of samples labelled as SC and WR, this review will be confined to parallel

comparisons of various proper~ies between samples, and between artificially aged

and unaged samples.

53

3.5.1 Rheological properties: An inspection of viscoelastic data presented in

Figs. 21 and 22, and in Table 6 reveals that:

(a) All samples studied exhibit an increase in viscosity at +5°C after

cooling from +25°C in various extents. This trend appears to be more pronounced

in more viscous asphalts.

(b) With the virgin asphalts of high viscosity this increase is

accompanied by a decrease in elastic modulus. Some parallelism is observed

between this drift and their LMS rating,, as well as the peak-height of their

X-ray diffraction spectra.

(c) Among the samples conditioned at -30°C, the effect of low temperature

on viscoelastic properties of SC-SU is dramatic and in the opposite direction of

those of the other two samples. A drastic fall followed by a fast rise,

especially in its elastic modulus, deserves attention. Before low temperature

conditioning, the viscosity and elastic modulus of this sample are also

incomparably greater than those of the others. Comparing the two core samples

(SC-SU and WR-SU) one observes that the low-temperature (-30 C) susceptibility

of SC-SU is far greater. It is significant that the effect of natural aging in

the pavement as reflected on their LMS ratings (Table 7, column 3) is also much

greater in the case of the Sugar Creek sample.

(d) From the viewpoint of its time dependence after a cold shock, the

elastic modulus appears to be more characteristic and discriminating than

viscosity.

3.5.2 GPLC: The results on %LMS defined by MSU method as given in Table 7

showed the following:

1. The %LMS of original asphalts studied ranged from 20.6 to 30.9, all

higher than the maximum allowable %LMS of 16-17% for the Montana climate

(Jennings and Pribanic, 1988).

54

2. The %LMS of asphalts in a given viscosity grade varied up to 7.4%

between samples from the same supplier; this difference was as high as 9.6%

between samples of different suppliers.

3. While %LMS iricreased with viscosity at 140 F for asphalts from Jebro,

this was not the case for Koch asphalts which had relatively higher %LMS but in a

narrow range between 27.2 to 30.8.

4. Thin film oven treatment increased %LMS by an average of 2.87% (1.2

to 3.8%) to a low of 24% for J0502 and a high of 33% for J2001._

The last observation means that the GPLC technique can be used as a

reliable test to monitor aging, as concluded also by Brule et al. (1987) who

used a different and accelerated modification of the Montana method as described

earlier.

A comparative analysis of the GPLC size distribution curves shows that the

fractional increase in the largest detectable molecular size region (earliest

elution) as a result of TFOT, is the largest among the other regions of the LMS

fraction as defined by the Montana research group. Although this version of the

GPLC method differs from that used by Brule et al. in that the former is unable

to detect all asphaltene agglomerates in the 100,000 molecular weight range due

to their peptization during testing as mentioned earlier, we believe that the

early-eluted fraction is made up by the remnants of undissociated agglomerates,

and that the observation just mentioned is the result of formation of extra

agglomerates induced by TFOT.

Then, the early-eluted fraction content of a sample is expected to be

approximately proportional to the original agglomerate concentration, and thus

is a more sensitive index than LMS to characterize aging, as well as the low

temperature susceptibility of the sample.

With this consideration, in Table 7 we also tabulate (LMS) 18.125, the

percentage of the fraction eluted within 18.125 minutes taken from the

55

printouts, and the fractional change of this fraction upon TFOT. It will be

noted that the fractional change of (LMS) 18.125 due to aging is much larger

than that of LMS defined by the Montana group.

In Fig. 23 (LMS) 18.125 is plotted against LMS for all the samples studied.

The trend shown in this plot is an evidence of approximately linear dependence

of the agglomerate concentration on the LMS rating, as hypothetically postulated

earlier in Section 3.5.

Repeated tests on a sample appear to yield (LMS) 18.125 values in close

agreement with each other. .However, to take care of day-to-day drifts in the

performance of the GPLC equipment, the adoption of a comparative procedure using

an external standard (such as the sample J05-0l-0) to determine the correct

cutoff time, is recommended for future work.

No correlation is observed between GPLC results and X-ray diffraction

results.

A quick search for correlations between the standard rheological indices

tabulated in Tables 1 through 5 and the LMS ratings shows that neither VTS nor

CT correlates with LMS, whereas there is a weak correlation between PVN and LMS

(r = -0.59) meaning that the samples of higher LMS content tend to behave less

temperature susceptible.

Glover et al. (1988) at Texas A&M University, using two columns and RI

detector, and defining LMS and SMS by retention times of 25 and 30 minutes (the

chromatograms were divided into three equal-time sections between 20 and 35

minutes), found relationships between viscosity temperature susceptibility (VTS)

and the molecular size distribution by HP-GPC: the lower the %LMS and the higher

the %SMS, the higher the temperature susceptibility. They also found

correlations between asphalt tenderness, percent asphaltenes and %LMS: high %LMS

was related to high asphaltene contents and non-tender asphalts. Based on this

56

.::: ::;. . ... I , ...... · I

! I

3 ...... . I . . . . . . . .

I , .

..l

' ~--' !

i i

._L~.--.'.--. _1_ '.. ' .i ·r ·········· r· ---! ...... ~

........ 1-

2Z 26 28 30

Figure 23. (LMS)lB.l2S plotted vs LMS.

57

study, there appeared to be desired lower limits of %LMS in asphalts to reduce

asphalt problems associated with tenderness. In view of the considerable data

by Jennings and his co-workers on the relationships between cracking, .. %LMS and

climate, it is likely that, for a given climatic zone, there is an optimum range

of %LMS (or %SMS) for the best pavement performance: too high LMS percentage

causes low-temperature cracking: too low %LMS causes high temperature rutting

and setting (tenderness) problems.

More extensive and systematic correlation tests will be conducted, during

the second phase of this project, between these indices and LMS ratings, as well

as the results of thermal and x-ray analyses.

3,5,3 Thermal analyses: A comparison of the DSC data summarized in Table 8

with each other and the results of other tests shows that the only correlation

that can be pointed out concerns 6H and the source of the sample: 6H values for

original J samples are on the average 24% higher than those for K samples.

The effect of aging on tg and other transformation points, as well as on 6H

appears to be in random directions. Considering that this effect on GPLC

results is unidirectional (see Section 3. 5. 2), it can be argued that the .thermal

effect of the gel to sol transition is overshadowed in thermal analysis by the

larger thermal effect .of dissolution of the crystallized components as treated

by Albert et al. (1985).

3.5.4 X-ray analyses: It appears from the X-ray diffraction spectra and the

Table 9 summarizing these spectra that no regular trend exists in these spectra

regarding the penetration grade or the sample source, nor regarding the effect

of aging. In contrast to what is observed in GPLC, the X-ray spectra are

effected by TFOT in quite a random fashion and direction. The significance and

implications of data in Table 9 will be investigated in Tasks 3-6 when

in-service pavement samples .of known performance information are studied.

58

4. SUMMARY AND CONCLUSIONS

Twelve samples from local asphalt suppliers and their TFOT residues, as

well as six core samples were studied by standard and some specific rheological

0 tests (at +5 C), GPLC, DSC.and X-ray diffraction analysis. The following

conclusions can be drawn from the results of these studies:

(1) Within each viscosity grade of asphalt cements available in Iowa and

meeting AASHTO Specification M226, there were differences in temperature

susceptibility between suppliers and between samples from the same supplier over

time.

(2) Distinctively different GPLC chromatograms were obtained among asphalts of

the same grades, same suppliers and samples supplied at different times.

(3) Distinctively different thermal analysis results and x-ray diffraction

patterns were obtained from asphalts of the same viscosity grades, same

suppliers and samples from the same suppliers but at different times.

(4) Whether and how these differences in physicochemical parameters among

asphalts available in Iowa reflect in mixture properties when they are mixed

with aggregates and in pavement performance under Iowa climatic conditions will

be investigated in Tasks 2 through 6 of this research.

(5) Large differences are observed between samples regarding the

time-dependence of their rheological properties at a low temperature when

brought from a higher or a lower temperature. Especially the strikingly

different and dramatic effect of a cold shock (-30°C) on the properties of the

sample SC-SU (core sample from the surface course of the Sugar Creek project)

might have an important bearing on its poor field performance.

(6) The said dependence appears to be proportionate to their viscosity and LMS

rating, in the case of virgin asphalts.

(7) The elastic modulus may be at least as important as the viscosity to

determine the performance-related low temperature rheology.

59

(8) No decisive correlation is observed between GPLC, DSC and X-ray results.

(9) In contrast to thermal analytic behavior and X-ray diffraction spectra, LMS

rating is found to be unidirectionally sensitive to aging. Hence, it can be

used to monitor or predict aging.

(10) The endothermic peaks on DSC thermograms indicate the presence of

crystallizable components, while the LMS rating measures the presence or

tendency of formation of gels. Therefore, the extent of these peaks (Lili) may be

used to evaluate the low temperature susceptibility of asphalts, together with

their LMS rating. These peaks are on the whole more pronounced in original J

samples than in K samples.

(11) The early-eluted fraction (e.g. (LMS)18.125) in GPLC is found to be a

better measure than the LMS defined by the Montana research group.

(12) Although it is based on a single comparison (Sugar Creek versus Wood

River), the "ageability", i.e. the increase in LMS rating by aging, rather than

the initial LMS rating, appears to be a performance predictor.

5. RESEARCH PLAN IN .TASK 2 (YEAR 2)

Research.in the second year will concentrate on changes in physicochemical

properties of asphalts tested in Task 1 when they are mixed with aggregates in

asphalt concrete mixtures. Asphalt concrete mixtures will be prepared in a

laboratory pugmill mixer using representative Iowa aggregates and asphalts

~ tested in Task 1. These mixes, both before and after artificially aged in

chambers under accelerated environmental conditions, will be tested for Marshall

properties (density, voids, stability and flow), resilient modulus, tensile

strength, stiffness, moisture susceptibility and fatigue life. Asphalts from

these mixes will be extracted and tested as in Task 1.

60

The number, type and sources of aggregates as well as the gradation of the

aggregates and levels of asphalt contents, will be selected in consultation with

the Iowa DOT and county engineers.

In addition, more vigorous investigation for alternative procedures and

data interpretation techniques for HP-GPC work will be undertaken for Task 1

asphalt samples.

6 • ACKNOWLEDGMENTS

This research was sponsored by the Highway Division of the Iowa Department

of Transportation (DOT) under Research Project HR-2.98. This study, under the

same title, was also supported by and designated as Project 1942 of the

Engineering Research Institute, Iowa State University.

The support of this research by the Iowa Highway Research Board and the

Iowa DOT is gratefully acknowledged. The authors wish to extend sincere

appreciation to the engineers of the Iowa DOT, especially Bernie Brown, Vernon

Marks, and Rod Monroe, for their support, cooperation, and counsel. The authors

would also like to thank Gerald Reinke, Koch Asphalt Co.; Alden Bailey, Jebro,

Inc.; Brian Chollar, FHWA; and Joan Pribanic, Montana State University, for

supplying the asphalt samples tested in the study.

The following individuals contributed, in various capacities, to this

investigation: Jerry Amenson, Barbara Hanson, Sang Soo Kim, and Shelley Melcher.

We are indebted to Turgut Demirel for the unselfish giving of his time and

consultation.

61

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2. Anderson, D. A. and E. L. Dukatz. 1985. Fingerprinting versus field performance of paving grade asphalts. Report No. FHWA/RD-84/095.

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4. Breen, J. J. and J.E. Stephens. 1967. and mechanical properties of asphalts. Association 12: 137-144.

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14.

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w. et al. · 1982. Use of high pressure liquid chromatography the effects of additives and fillers on the characteristics Research Report FHW~/MT-82/001.

62

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21. Pagen, Charles A. 1964. Rheological response 9f bituminous concrete. Highway Research Record, No. 67:1-26.

22. Petersen, J. c. 1984. Chemical composition of asphalt as related to asphalt durability: state of. the art. Transportation Research Record 999:13.

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25. Sisko, A. W. and L. c. Brunstrum. 1968. of asphalts in relation to durability and Proceedings of the As~ociation of Asphalt 37:448-473.

The rheological properties pavement performance. Paving Technologists,

26. Wendlandt, W. Wm. 1986. Thermal Analysis, Wiley., 439-440.

27. Williford, C. L. 1943. X-ray studies of paving asphalts. Texas Engr. Exp. Station Bulletin 73. A & M College of Texas, College Station, Texas.

28. Zakar, P. 1971. Asphalt. Chemical Publishing Co., Inc., New York.

29. Zenewitz, J. A. and Tran, K. T. 1987. A further statistical treatment of the expanded Montana asphalt quality study. Public Roads, 51(3):72-81.

APPENDIX I

HP-GP CROMATOGRAMS

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