DESIGN AND CONSTRUCTION OF ROLLER COMPACTED CONCRETE

DESIGN AND CONSTRUCTION OF ROLLER COMPACTED CONCRETE PAVEMENTS

RAYMOND S. ROLLINGS, Research Civil Engineer, US Anny Engineer Waterway Experiment Station, Vicksburg, Mississippi, USA

ABSTRACf

Roller compacted concrete pavements are constructed of zero slump portland cement concrete placed with construction procedures similar to those used with asphalt concrete. These construction procedures can result in cost savings of 10 to 30 per cent compared to conventional concrete pavement construction. When properly proportioned and constructed, roller compacted concrete has strength equal to or greater than conventionally constructed concrete pavement with the same cement content. Roller compacted concrete pavement is not as smooth and has an open surface texture similar to asphalt concrete. Its major application has been for industrial pavements where these surface characteristics are acceptable, however as construction procedures improve, roller compacted concrete use is expanding to higher quality pavements. This paper reviews the procedures used to proportion, construct, and design roller compacted concrete pavements and discusses some areas needing further improvement and research.

INTRODUCTION

1. A roller compacted concrete pavement is a portland cement concrete pavement that is placed using construction procedures normally associated with asphalt concrete rather than the slipformed or formed construction techniques traditionally used with concrete pavement. Much of the current impetus for roller compacted concrete comes from its successful application in dam construction. Experience with soil-cement led to proposals by Raphael (1971) and others to construct embankments using cement enriched, unprocessed, natural granular materials. These proposals were followed by a number of successful roller compacted concrete gravity dams, and today it is an increasingly popular dam construction technique (e.g., Lowe 1988, Cannon 1985, American Concrete Institute 1980).

2. The USAE Waterways Experiment Station sought to extend the success of roller compacted concrete in dams to pavements (Burns 1978, Grau 1979, Hutchinson et al. 1987,

Pittman 1988). Initial emphasts was to provide an expedient portland cement concrete construction capability to military engineer units that did not have conventional slipform or form riding paving equipment. However, the potential economics of using roller compacted concrete for military facilities such as tank parking hardstands where many conventional pavement requirements could be relaxed soon became apparent. Today the US Army Corps of Engineers is actively pursuin~ this type of application. The economics of this construction method also led to its use for industrial pavements such as log sorting yards and port facilities (Hansen 1987). Roller compacted concrete is an increasingly popular construction method in the United States, and in March 1988 it was the topic of a specialty conference sponsored by the American Society of Civil Engineers in San Diego, California.

3. Roller compacted concrete is a construction method rather than a new material. Its economic savings are mainly in less costly construction techniques, not in material savings.

ACKNOWLEDGEMENT: The support of the USAE Waterways Experiment Station (WES) in collecting and preparing material for this paper is gratefully acknowledged. The review and comments of Dr. Paul Hadala, Mr Harry Ulery, Dr Walter Barker, Mr Don Ladd, and Mr David Pittman of WES on this work are greatly appreciated. The materi al presented here represents the views of the author only and does not reflect any official government view or policy. This paper is published with the permission of the Chief of Engineers.

PROCEEDINGS 14th ARRB CONFERENCE, PART 8 149

ROLLINGS - ROLLER COMPACTED CONCRETE PAVEMENTS

These savings come at the expense of the surface quality and smoothness. Consequently its primary applications have been for military and industrial pavements that can sacrifice some smoothness and texture quality for economics. However, construction techniques are improving so that applications for roller compacted pavements are steadily expanding. Recently it has been used for a street in Austin, Texas and an aircraft parking ramp in Portland, Oregon. Despite improvements, roller compacted concrete pavement does not have the same surface characteristics and appearance as conventional concrete pavement.

4. Roller compacted concrete has the potential to save on the order of 10 to 30 percent of the cost of a conventional concrete pavement. It is essentially a portland cement concrete that is proportioned to have zero slump and to be stable under the action of heavy vibratory rollers used for compaction. Additional rolling with pneumatic tired rollers and steel wheel rollers may be used to improve its surface texture. The zero slump characteristics of the material require special considerations in proportioning, mixing, construction, and design that will be discussed in the following sections. Roller compacted concrete described in this paper is a strong pavement surfacing with strength characteristics equal to or greater than conventional concrete. This construction technique could be used for base course construction as well as for the surfacing, but such applications are outside the scope of this paper.

PROPORTIONING

5. Roller compacted concrete for pavements is generally placed with a water-cement ratio between 0.3 and 0.4, and with a cement content

3 . 3 between 285 and 370 kg/m (470 and 612 lb/yd ). It usually contains sufficient paste to fill the aggregate voids and coat the aggregate particles. If it does not, Cannon (1985) suggests that the material will not develop any paste on the surface under the action of the vibratory roller and is more appropriately termed 'rollcrete.' This definition is convenient for separating zero slump, roller compacted concrete from other related products such as cement stabilized materials, cement modified materials, lean rolled concrete, econoctete, rollcrete, etc. There is often no clear differentiation between these terms, and depending on their engineering properties and the design requirements, they all have potential applications as subbases, bases, or surfacing for pavements.

6. There are two different approaches to proportioning roller compacted concrete: one uses modifications of stabilized soil concepts such as ASTM D 558, the other uses more conventional concrete proportioning philosophy as outlined in ACI 207.5R.

7. The modified stabilized soil approach determines the relation between moisture content and dry density for a specific cement and aggregate combination compacted at some laboratory compactive effort (usually modified AASHTO or the equivalent). This approach identifies

150

the optimum moisture content for achieving the maximum dry density of a specific material at the tested compactive effor t. Saucier (1984) and Anderson (1985) both observed that thi s laboratory approach tended to predict an optimum moisture content about 1 percent highe r than the actual optimum roller compacted concrete moisture content found in the field. Hess (1987) found that the standard AASHTO compaction procedure came the closest to predicting the field optimum compaction moisture content when compared with the modified AASHTO and vibratory table compaction method. Ragan (1988) observed that either more or less water could be needed in the field than was required by the laboratory compaction tests. Differences between laboratory and field determined optimum compaction moisture contents may be caused by variations in compactive effort, mixing, material proportions, or aggregate gradation. Increasing the compactive effort in the laboratory or increasing the size (hence compactive effort) of rollers in the field changes the relation between optimum moisture and density relationships for soils (e.g., Johnson and Sallberg 1960). Such relations probably also exist for roller compacted concrete although comprehensive testing on compactfve effort, moisture, and density relationships for roller compacted concrete has not been performed yet. The different levels of compaction generally used in the field and laboratory should be recognized when the modified stabilized soil approach to proportioning is used.

8. The second approach uses the mixture proportioning guidelines in ACI 207.5 'Roller Compacted Concrete.' ACI 211.3-75 'Standard Practice for Selecting Proportions for No-Slump Concrete' generally produces a mixture that is not stable under the action of vibratory rollers, so ACI 207.5R provides some adjustments to modify these procedures. However, this approach is more appropriate for mass concrete used in dams rather than pavements. An alternate procedure presented in ACI 207.5R determines the minimum paste volume required in the mixture and selects trial water contents on the basis of design strength and cement and fly ash content. Ragan (1988) has reported the ratios of air-free volume of paste to air-free volume of mortar used in this procedure have varied from 0.34 to 0.44 for nominal maximum size aggregates of 19 mm (3/4 in.) and 38 mm (1-1/2 in.) in past roller compacted concrete pavements. He reports that this ratio affects both the compactability and surface texture of the concrete.

9. At the present time there is no consensus on a single roller compacted concrete pavement mixture proportioning method. The modified stabilized soil approach provides information on compaction moisture and density and would be the most appropriate method for any roller compacted concrete that lacks sufficient paste to fill the aggregate voids and coat the particles (i.e. rollcrete by Cannon's definition). In other cases there is no demonstrated advantage of one approach over the other. Under these circumstances both approaches might be tried. All existing recommendations only provide

PROCEEDINGS 14th ARRB CONFERENCE, PART 8


initial estimates, and trial sections and field adjustments are normally necessary.

10. Pozzolans such as fly ash are often substituted for up to 30 percent by volume of the portland cement in roller compacted concrete pavements. These are valuable as fillers to reduce the requirement to fill voids in the aggregate with e i ther cement or water in addition to their potential cementitious value. Consequently, pozzolans that may not be as reactive as normally required may still have considerable benefit simply as a filler in roller compacted concrete.

11. Air-entraining admixtures have not been used with roller compacted concrete, and samples taken from roller compacted pavements have generally failed the laboratory freezing and thawing test (Ragan 1986). Without the entrained air bubbles roller compacted concrete is vulnerable if frozen while critically saturated. Damage could include scaling on the surface and spalling on the bottom of the slab and around joints and cracks where the concrete is most easily saturated. Roller compacted concrete has some inherent resistance to saturation from outside sources due to low permeability associated with its high density and low water-cement ratio. The low watercement ratio also leaves little fre ezable water in the concrete which makes saturation from outside sources more difficult t o achieve. Andersson (1987) has reported success in establishing a stable entrained air structure in roller compacted concrete by mixing the cement, water, air entraining admixture, and a high-range water-reducing admixture prior to adding the aggregate. Freezing and thawing damage to r oller compacted concrete has not been clearly identified in the fi eld although Hess (1987) feels that it may have been a contributing factor to raveling and spalling that occurred to roller compacted concrete pavement a t Toole Army Depot. Most roller compac ted concrete pavement installations are in mild climates and are relatively new. Also detailed damage s urveys with analysis of potential saturation and freezing and thawing cycles have not been performed for roller compacted concre te pavements. The concrete pore struc ture is potentially vulnerable, and ways to entrain air in roller compacted concrete are needed to overcome concerns over the freezing and thawing durability of roller compacted concrete.

12. The roller compacted concrete aggregate gradation strongly influences the construction difficulty and surface quality of the pavement. Figure 1 shows several aggregate gradations used in roller compacted concrete pavement projects . The first Army trial at Ft. Stewart used the conventional concrete aggregate gradation s hown in Figure 1 and encountered problems with segregation, pavement smoothness, and poor surface texture. The next project at Ft. Hood tried a we ll graded aggrega te, but continued problems resul t ed in switching to the fine r gradation shown in Figure 1 and reducing the maximum nominal size aggregate from 38 mm (1-1/2 in . ) to 19 mm (3/4 in.). Later projects


at Kitzingen, Ft. Lewis, and Toole Army Depot have continued the trend to smaller maximum size aggregates and well graded aggregates with improved pavement finishing characteristics, smoothness, and texture. Current practice is to use well graded aggregates similar to those in asphalt concrete with a maximum nominal aggregate size of 19 mm (3/4 in.) or 13 mm (1/2 in.) and with 5 to 10 percent nonplastic fines or inert filler. This practice is reflected in the current Corps of Engineers recommended gradation in Figure 1, but roller compacted concrete pavements have been successf ully built with a variety of aggregate gradations.

13. To date there is not an accepted method of preparing laboratory specimens. Hand rodded samples cannot be effectively prepared with this zero slump material, and the AASHTO compaction hammer does not always give good results (Cannon 1985). If there is sufficient paste to meet Cannon's definition of roller compacted concrete, then vibratory compaction seems to offer an effective method for sample preparation. Samples have been prepared using vibrating tables and a modified Vebe apparatus, but so far laboratory samples have not effectively predicted the strength of the in situ roller compacted concrete (Department of the Army 1987). Table I shows the variation between beams sawn from roller compacted concrete pavements and some fabricated beams. The variation between fabricated and actual pavement strength is probably due to failure to achieve equivalent level s of compaction in the field as were obtained in the laboratory, better curing in the laboratory , or both. More work on sample preparation is needed, and other pot ential methods of sample prepara tion such as gyratory compactors, kneading compactors, the Kango hammer (an instrument used to compact specimens of lean concrete in England) and a lternate vibratory methods should be investigated.

CONSTRUCTION

Mixing and Transporting

14. The plant used to mix roller compacted concrete must be capable of adequately and thoroughly mixing the stiff, zero slump concrete and must also produce the concrete at a rate to match the field placement and compaction operations . Consistent, uniform concrete delivered to the construction site at a rate so t hat the placement and compaction is continuous and without delays is a key contributor to the successful placement of a good quality roller compacted concrete pavement.

15 . Continuous mixers, batch mixers, and truck mixers have all been used successfully to mix roller compac ted concrete . In the United Sta tes continuous mixing plants such as produced by ARAN Equipment, Inc. of Queensland are the predominant method of producing roller compacted concrete for pavements. The vigorous action of the pugmill mixers used in such

151


U.S. STANDARD SI EVE OPENING IN INCHES U. S. STANDARD SIEVE NUMBERS HYDROMETER

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Figure 1. Aggregate gradations for roller compacted concrete pavements

plants is capable of thoroughly mixing the stiff concrete, and this type of plant can produce 225 to 550 metric tons per hour (250 to 600 tons/hour) to meet high pavement production rates .

16. Conventional concrete batch mixers have been the predominant method of mixing roller compacted concrete for dam construction in the United States and for pavements in Europe. Tilting drum mixers are widely used for producing large volumes of low slump (25 mm and less) concre te for slipformed airfield paving and have been used to produce zero slump concrete. Consequently, if properly selected and sized, they should be able t o meet the requirements for producing roller compacted concrete for pavements. Andersson (1987) reports that the vertical ~haft batch mixers used in Sweden usually have their production capacity reduced 1/3 when producing roller compacted concrete.

Pittman (1988) describes a spiral blade batch mixer used to produce concrete for a roller compacted pavement in Germany. The mixing time for all of these batch mixers may have t o be increased to ensure thorough mixing.

17 . Tilting drum truck mixers were successfully used for some roller compacted concrete test fills using 38 mm (1-1/2 in . ) maximum sized aggregates (American Concrete Institute 1980). Truck mixers without tilting drums were used to mix roller compacted concrete with 38 mm (1-1/2 in.) maximum aggregate size for two tank roads at Ft. Stewart, Georgia . Discharge of the concrete was slow, but mixing appeared to be generally adequate although there were some segregation problems. Truck mixers have been used successfully with roller compac ted concrete, but their slow discharge and production rates make them poor candidates for pavement work.

TABLE I

COMPARATIVE FLEXURAL STRENGTH FOR FABRICATED AND SAWN BEAM SAMPLES

Flexural Stren~th (kPa) Fabricated Test Fabricated Sawn Sawn Source of Data

Ft. Hood 5,546 5, 781 0.96 Ft . Worth District 4,802 5,719 0 . 84 US Army Corps of Engineers

Ft. Lewis 4 , 444 3,328 1. 33 Seattle District 4 , 478 3,590 1. 25 US Army Corps of Engineers 3,913 3,962 0.99

Ft. Benning 5,512 4 , 899 1.12 Savannah Dis trict US Army Corps of Engineers

Kitzingen 7,613 5,395 1.41 Pittman 1988 7,793 6,428 1. 21

Toole Army 3,486 5,567 0 . 63 Hess 1987 Depot

152 PROCEEDINGS 14th ARRB CONFERENCE, PART 8


18. Attempts to produce roller compacted concrete with in situ mixing for a log sorting yard in Canada were unsuccessful (Piggott 1987). It proved impossible to obtain good dispersal of the cement in the aggregate, and this appr ~ ' ch is not recommended.

19. Nonagitating equipment such as dump trucks has been the primary method of transporting roller compacted concrete. If this stiff concrete is placed in mounds, as when a conveyor discharges into a truck or when concrete from a chute is allowed to build up in mounds, serious segregation will result. Surge hoppers, reduced free fall, and in general proper cuncrete discharge and placing procedures will avoid segregation problems.

Placement and Compaction

20. The construction procedures for roller compacted concrete are similar to those of asphalt concrete. The concrete is placed with an asphalt paver, preferably equipped with vibratory screeds, tamping bars, or both to ach ieve some initial compaction and surfa~e texture. Tamping bars cause closely spaced tears in the surface but achieve higher initial surface compaction than do vibratory screeds. The placed concrete thickness is usually 10 to 25 percent thicker than the design thickness to allow for compaction. The major compaction is provided by a vibratory roller such as those in Table II. Rollers typically are required to have a static load of not less than 2,060 and 2,700 kg per lineal metre of roller width (115 and 150 lb!in.) for lifts up to 150 mm and greater than 150 rom in thickness, regpectively

(WHhrow 1988 and Department of the Army 1987). Rollers should also operate with a frequency greater than 1,700 vpm, and an amplitude of at least 0.6 rom (0.025 in.). The pattern of compaction is similar to that used for asphalt concrete. Outside edges of the placement lane cannot be effectively compacted because the concrete tends to spread laterally under the roller. Therefore the placement should be planned to minimize the amount of unconfined edge that will have to be compacted. An unconfined edge should be rolled first to provide some confinement for the concrete in the interior of the placement lane. If another lane will be placed adjacent to the one being compacted while the concrete is still plastic enough to be compacted, approximately 250 to 500 mm (10 to 20 in .) of the edge should be left uncompacted so that the concrete on both sides of the joint is compacted at the same time. If on the other hand there will be an

. appreciable delay between lanes so that the concrete being placed would harden before the adjacent lane is placed, the outside edge of the lane should be rolled prior to the interior of the placement lane as for an unconfined edge. This outside concrete is poorly compacted and should be removed before placement of the adjacent lane. This can be done by simply scraping a vertical face on the edge with a motor grader, but the best solution is to saw and remove the outside 100 to 150 mm (4 to 6 in.). There is no specific time that can be specified at which the concrete can no longer be effectively compacted since this depends on characteristics of the concrete mix and the environmental conditions. This compaction time could be extended by using a retarder in the concrete.

TABLE II

SAMPLE VIBRATORY ROLLERS USED FOR ROLLER COMPACTED CONCRETE PAVEMENTS (DEPARTMENT OF THE ARMY 1987)

Drum Frequency Maximum Shipping Drum Drum Mass/ Range Lift

Construction Mass Mass Width m width Vibrations/ Thickness Project Date Type Roller kg kg m kg/m min mm

Ft. Stewart, GA July 1983 Tampo RS-28 8,520 4,890 2 .134 2,291 1,100 250 (Single drum) 1,500

Ft. Hood, TX July 1984 Tampo RS-188A 13,980 7,270 2. 134 3,407 2 ,200 262 (Double drum)

Ft. Lewis, WA Nov 1984 Tampo RS-28A 8,750 5,140 2.1 34 2,409 1,500 212 (Single drum) 1,700

Port of Tacoma, April 1985 Dynapac CC50A 14,270 7,130 2 .134 3,341 2,400 225 WA (Double drum)

Portland Aug 1985 ABG Puma 168A 16,755 3,300 1. 651 1,999 2,000 175 International (Single drum) 7,620 3,000 Airport, OR



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LEGEND OPERATING ROLLER STATIC DRUM MASSI FREQUENCY

NO, SYMBOL DRUM MASS DRUM WIDTH (VPM)

1, 0 1,432 KG 1,038 KG/ M 3,SOO

2 • 3,182 KG 2,094 KG /M 1,SOO

3 • 3,864 KG 1,807 KG /M 1,800

4 0 8,375 KG 4,11SKG/M 1,200

Figure 2. Variation in density of crushed limestone with depth for several vibrator y rollers

21. The strength and many other engineering properties of the roller compacted concrete depend on achieving adequate density. Therefore it is critical that the lift of concrete being placed does not exceed the thickness that can be compacted with the available compaction equipment. Figure 2 shows how rapidly compaction on a well graded, crushed limestone base course decreases with depth. This material is very stable and probably has stiffness and compaction characteristics similar to a well proportioned roller compacted concrete. These data suggest that maximum lift thickness for roller compacted concrete should be about 250 mm (10 in.) to obtain good density. If thicker pavements are needed, they will have to be placed in multiple lifts.

22. The significance of obtaining adequate density can be seen in Figure 3 where strength and density relationships for several roller compacted concretes are presented. The relationship from Andersson (1987) is based on the

154

most extensive data from two different mixtures., The other relations are least squares regression relationships from less extensive data reported by Burns (1975) and Pittman (1988). In all cases, small decreases in density result in large decreases in strength. It is also significant that, as illustrated in Figure 2, the lowest density and hence the lowest strength are at the bottom of the pavement where the load induced tensile stresses are the highest. The roller compacted concrete must also have a sound base to allow compaction. Roller compacted concrete plac ed directly on a resilient sub grade will be impossible to compact adequately.

23. The surface texture of the pavement can be improved by using a pneumatic tired roller behind the vibratory roller. This will work some fines to the surface to help close any voids, cracks, or tears in the surface. The pneumatic roller will usually leave roller



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LEGEND

- THEORETICAL MAXIMUM DENSITY

MO ., % MODIFIED PROCTOR DENSITY

C s COMPRESSIVE STRENGTH

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EXTRAPOLATED PAST ORIGINAL DATA

98 100

PERCENT DENSITY

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Figure 3. Effect of density on strength for roller compac ted concrete

marks in the surface tha t should be removed by a nonvibrating, steel wheel, finish roller .

24. Like any concrete, roller compacted concrete must be properly cured. A moist cure is desirable because of the l ow water cement ratio used in roller compacted concre t e. However, other curing mediums such as asphalt emulsion and curing membrane have been used successfully without an i nitial mo is t cure or af t er 24 hours of moist curing.

25. Concrete, regardless of placement method, is not inert, and throughout its life it undergoes volume change due to hydration, moisture changes, temperature fluctuations, and other related causes. To accommodate these volume changes in a pavement, either joints are placed where needed, or else the pavement will crack to form its own j oints. In mo~t roller compacted concrete pavement placed to date the contraction cracks are allowed to form naturally, and they become the pavement joints. The low water cement ratio results in low shrinkage and long spacing between contraction cracks (typically 12 to 18 m compared to 3.8 to 7.5 m for joints in conventional paving). On several past projects attempts to saw cut conventional contraction joints in the roller compacted concrete caused problems with raveling, and the saw cuts were abandoned . However, Pittman (1988) reports success saw cutting joints in a roller compacted concrete with a high cementitious material content. Random contraction cracks with associated minor raveling and spalling are not a concern for the industrial quality pavements where roller compacted concrete has been used so far. However, as roller compacted concrete use expands to higher quality pavements, the existence of random contraction cra'cks may be less acceptable to the user. Improved methods of obtaining saw cut contraction joints will be needed


in the future. Several future planned US Army Corps of Engineers projects plan to saw cut joints at 12 m (40 ft) spacing.

26. A commonly quoted surface smoothness criterion for roller compacted concrete js either 6 mm (1/4 in.) or 10 mm (3/8 in.) deviation from a 3 m (10 ft) long straightedge. Table III shows the results of surface smoothness tests on several recent roller compacted concrete pavements. Although the average smoothness measurement from these projects may meet the quoted criterion, the large coefficient of variation in the results show that large portions of the pavement fail to meet the smoothness criterion. Conventional pavements in the Corps of Engineers are generall y constructed to a smoothness tolerance of 6 mm (1/4 in.) in 3 m (10 ft) for roads and streets and 3 mm (1/8 in.) in 3.7 m (12 ft) for airfields. Improved construction techniques and use of smaller coarse aggregate sizes have caused a steady improvement in roller compacted concrete pavement smoothness, but it is still not equal to that of conventional paving.

27. If the surface smoothness of a pavement is not acc~ptable, an asphalt concrete overlay could be placed or the surface could be ground to tolerance. Both approaches have been used for roller compacted concrete as well as for conventional concrete pavements. Much of the smoothness problem originates in the thick lifts of concrete that vary in how much they compact under the roller resulting in an uneven surface. A similar problem exists when thick lifts of asphalt concrete are compacted.

28. The use of thin bonded concrete overlays to restore the surface of concrete pavements has become widespread in the United States and may offer another approach to solving roller compacted concrete smoothness problems. These overlays are typically only 50 to 100 mm (2 to 4 in.) thick, and the same concept could be applied to roller compacted concrete. Thin surface lifts of roller compacted concrete could be placed on a base slab of roller compacted concrete. These thin surface lifts would show less variability in compaction and a smoother pavement would result, but full bond must be achieved. Of course, the asphalt overlaying, surface grinding, or full bonding of a thin roller compacted surface lift to improve smoothness would decrease (or eliminate) the cost advantage of roller compacted concrete.

DESIGN

Conventional Rigid Pavements

29. In the United States rigid pavement design generally uses the AASHTO method (American Association of State Highway and Transportation Officials 1986), the Portland Cement Association method for airports (Packard 1973), the Portland Cement Association method for highways and streets (Portland Cement Association 1984), the Corps of Engineers design method (Rollings 1981, 1987), or some modification of these. The AASHTO method uses a performance algorithm based on the results of the AASHO Road Test

155


TABLE III

SURFACE SMOOTHNESS TEST RESULTS

Type of Test Mean Percent out Measurement Location n Deviation (mm) Cov (%) of Tolerance

Longitudinal Kitzingen 1 108 4.1 69 214 Toole Army 890 18

2 Depot 3

160 4.8 57 284 Ft. Lewis

Transverse Kitzingen 1 106 6.4 60 504

Toole Army 953 24 2

Depot 3 160 6.4 57 504 Ft. Lewis

1 2From Pittman 1988. 3From Hess 1987. 4Provided by Seattle District, US Army Corps of Engineers.

Assuming normal distribution of results and 6.4 mm acceptable deviation from straightedge.

n = number of measurements. Mean deviation measured from 4 m (Kitzingen), 3.7 m (Toole), and 3 m (Ft. Lewis) long straightedge placed on pavement surface. Cov = coefficient of variation = standard deviation + mean.

while the other three approaches are based on a structural fatigue analysis. A fatigue analysis requires calculating the load induced tensile stresses in a concrete pavement. The ratio of these calculated stresses to the flexural strength of the concrete is then related to the allowable number of cycles of load by a fatigue relationship.

30. The three fatigue design methods vary from one another in the analytical models used to calculate the stresses, the fatigue relationship used to relate stresses, flexural strength, and cycles of load to failure, and in What safety factors, adjustments due to observed field performance, etc. that the sources feel are appropriate.

31. The analytical models vary for each of the design methods. The Portland Cement Association airport design method uses the Westergaard solution for loads on the interior of a slab supported on springs while their highway design uses a finite element representation of the slab supported on springs. The Corps of Engineers uses the Westergaard solution for a load on a slab free edge supported by springs for their analytical model to calculate load stresses. When a load is placed adjacent to a conventional joint some portion of the load is transferred to the adjacent slab through aggregate interlock in contraction joints of properly sized slabs, dowel bars in construction joint s, keys in construction joints, or similar structural devices. Based on the results of field measurements the Corps of Engineers allows 25 percent of the applied load at the edge to be supported by the adjacent slab for design purposes. This lowers the design stress in the slab and significantly reduces the required pavement thickness . Successful use of

156

this concept for many years coupled with extensive field measurements support the validity of this approach. This load transfer only exists when there is an adjacent slab to carry the load as in most airfield facilities where outside pavement edges are not trafficked or in parking areas. The reduction for load transfer would not be made for a highway design where the traffic load travels next to a free edge where there is no adjacent slab. The Portland Cement Association design method for highways incorporates the concept of load transfer for highways with tied concrete shoulders, but the concept is not applicable or used for a conventional highway with an asphalt concrete shoulder.

32. There are two basic methods to develop a rigid pavement fatigue design relationship. Flexural beams can be cast in the laboratory and tested under repeated loads to develop the required relationship . This is the approach used by the Portland Cement Association. The other alternative is to build full scale pavement test sections and traffic these with full size loads to develop a 'field' fatigue relationship. This is the approach used by the Corps of Engineers, and they have built and tested over sixty full size airfield pavement test sections in developing their relationship. Each approach to developing a fatigue relationship has its own advantages and disadvantages. These are discussed in detail in Rollings (1987) .

33. More extensive discussions on the requirements for these different design methods can be found in the references given for them earlier, and some comparisons of the different approaches can be found in Rollings (1985), Rollings (1987), or in standard texts such as Yoder and Witczak (1975).


ROLLINGS - ROLLER COMPACTED CONCRETE PAVEMENl S

Roller Compacted Concrete

34. Investigations have found that properly proportioned and compacted roller compacted concrete made with conventional materials have essentially the same engineering properties as conventional concrete (Tayabji and Okamota 1987). Roller compacted concrete has the potential to be used with substandard construction materials that have gradations, plasticity characteristics, or other properties not allowed in conventional concrete (Grau 1979, Hague and Ward 1986, Rollings 1988). These substandard materials often have high water demand and workability problems. Placing them with zero slump using roller compacted techniques minimizes the strength loss that occurs when additional water is needed to obtain workability for conventional concrete placement techniques. When these types of materials are being used, the resulting roller compacted concrete cannot be assumed to have the same engineering characteristics as conventional concrete.

35. The highest tensile stresses from loads on a concrete pavement are at the bottom of the slab which is also where roller compacted concrete is the weakest due to the reduction in density with depth. Table IV shows the strength of beams sawn from several roller compacted concrete pavements, and as expected, the Ft. Stewart pavement showed considerably less strength at the bottom than at the top. Ft. Hood showed the opposite trend, but this may have been due to curing problems encountered that may have contributed to the lower surface strength. The US Army Corps of Engi-

neers Seattle District found that the density of the roller compacted concrete at Ft . Lewis

3 3 was typically 48 kg/m (3 lb/ft ) less at the bottom of the pavement than at the top. This supports the Ft. Steward data. The structural performance of the roller compacted concrete is dependent on ' the density achieved at the bottom of the pavement, and therefore proper compaction procedures are a key to achieving a structurally adequate pavement.

36. The construction procedures used with roller compacted construction may lead to more variation in strength than normally encountered with conventional concrete paving. The strength of roller compacted concrete will be subject to the same causes of variation as conventional concrete plus the added variation due to its construction procedures. Also the stiffness of the material with resulting mixing difficulty and the tendency to use continuous mixing plants in place of weigh batching may cause additional variation in strength unless good construction practices are followed. The limited data in Table IV shows a large variation in the coefficient of variation of strength results. These coefficients range from 3.9 to 34.3 percent with an overall average of 13.5 percent. This average is higher than the 10 percent or less usually associated with conventional paving concrete strength. As roller compacted concrete pavement construction techniques improve, strength variability should decrease. More data of this type are needed to determine the appropriate amount of variation to consider in selecting design strengths.

TABLE IV

VARIATION IN ROLLER COMPACTED CONCRETE STRENGTH

Flexural Strength from Sawn Beams TOE of Pavement Bottom of Pavement

Mean Mean Location n (kPa) Cov (%) n (kPa) Cov (%)

Ft. Stewart (1) 4 8,308 7.2 4 5,653 34.3 (2) 4 8,929 17 .8 4 6,350 17.4 (3) 6 6,060 9.7 4 4,426 11.4 (4) 5 4,861 6.6 4 2,579 18.4

Ft. Hood 3 5,295 13.9 3 6,212 12.3

Ft. Lewis (1) 16 3,328 20.2 (2) 6 3,590 14.2 (3) 12 3,962 4.8 (4) 2 4,203

Ft. Benning 10 3,920 22.5

Toole Army Depot 16 5,,567 7.0

Kitzingen (1) 3 5,395 8.1 (2) 3 6,428 3 .9

n = number of beams in sample. Cov = coefficient of variation = standard deviation + mean. Strength determined at 28 days except at Ft. Stewart where beams were sawn several months after placement.


ROLLINGS -- ROLLER COMPACTED CONCRETE PAVEMENTS

1.0 .. AMERICAN CONCRETE INSTITUTE 1981 SMIN = 0.75

J: .... t:) O.B z w II: .... U)

-' « II: 0.6 :::> X w -' u.

~ ~ 0 .4 .... U)

::;; :::> ::;;

~ 0 .2 ::;;

100

-0_ ---TAYABJI AND OKAMOTA 1987 SMIN /SMAX = 0.10

CEMENT FLY ASH FLEX STR KG /M3 KG/ M3 kPa

0 169 0 4 ,720

• 144 29 5,305

C; 158 32 5 ,099 .. 156 27 4 ,03 1

SMIN /SMA X • MINIMUM STRESS/MAXIMUM STRESS

Pf '" PROBABILITY OF FAILURE

1,000 10,000

-SMAX Pf~50% __ ~ ____________ __

SMIN = 0. 15 SMAX -.--

100,000 1,000,000 10,000,000

CYC LES TO FAILU RE

Figure 4. Comparison of roller compacted concrete fatigue da ta with conventional concrete relationships

37. Figure 4 shows the available roller compacted flexural fatigue data from Tayabji and Okamota (1987) plotted with some typical laboratory flexural beam fatigue relationships (American Concrete Institute 1981) developed from conventional concrete test specimens. Concrete fatigue tests often show considerable scatter so they often are presented with a probability of failure as shown in Figure 4. Also as can be seen in Figure 4 the fatigue relation between the ratio of stress and flexural strength and the cycles of stress to failure is a function of the ratio of minimum stress applied to the beam and the maximum stress applied to the beam. The larger the variation between the minimum and maximum stress applied to the beam the less fatigue capacity the flexural beam has. Pavements in the field develop stresses when not under load due to factors such as moisture or temperature gradients. For instance, the ratio of minimum to maximum stress of the in-situ AASHO test pavement slabs varied from 0.16 to 0.60 considering just load and temperature stresses (Rollings 1987). The roller compacted concrete in Figure 3 has essentially the same fatigue characteristics as conventional concrete. Consequently, conventional concrete fatigue relationships in existing concrete pavement design methods can be used to design roller compacted concrete that uses conventional materials and that is adequately compacted.

38. Since material properties are similar, the major difference between roller compacted concrete and convent:f.onal concrete pavement design is caused by the differ.ences in ~oint structure . The low shrinkage in roller compacted concrete causes large spacings between contraction cracks. This spacing is usually greater than 12 m (40 ft) which exceeds the 3.8 to 7.6 m (12.5 to 25 ft) spacing between contraction joints in conventional concrete pavement. Consequently, the crack opening in roller compacted concrete pavement is larger than the joint opening in conventional concrete pavement, and aggregate interlock and load transfer across the crack for roller compacted

158

concrete will be smaller than for conventional concrete pavement contraction joints. Similarly, separation and poor l oad transfer is likely to occur at the longitudinal construction joints between placement lanes. Even in longitudinal construction j oints that were placed so that they could be compacted together, volume changes in the concrete are likely to cause separation at some joints in large paved areas. Some limited measurements for roller compacted concrete have found 17 to 19 percent load transfer at contraction cracks and 12 to 18 percent at construction joints (Hutchinson et al. 1987). This is below the 25 percent commonly assumed in design and well below the 30 to 37 percent for conventional doweled construction joints and saw cut contraction joints (Rollings 1987). The measured amount of initial load transfer for any joint will decrease with traffic repetitions, increases in joint opening due to temperature changes, etc. Therefore roller compacted concrete should not be designed with any allowance for load transfer, and design aids that use this assumption (e.g., Corps of Engineer design curves for airfields or parking areas) should not be used with roller compacted concrete unless they can be adjusted to remove the load transfer assumption. Some past projects have simply substituted the same thickness roller compacted concrete for conventional concrete without realizing that these are not necessarily structurally equivalent for facilities such as parking areas, storage yards, aprons, etc.

39. In the previous section four basic design procedures were mentioned that form the basis of most design procedures in the United States . Since the AASHTO approach is essentially empirically based on the performance of the spec ific pavements used in the AASHO test, there is little basis for extending the AASHTO lDethod to roller compacted concrete due to the different jointing practices . The portland Cement Association airport design method uses the interior slab analytical model which cannot effectively evaluate the differences in joint load transfer between conventional and roller compacted concrete. Therefore its use is not



recommended for roller compacted concrete. Both the Corps of Engineers rigid pavement design method and the Portland Cement Association method for highways use analytical models capable of evaluating load transfer at j oints (free edge model and finite element model). The published design aids for highways and streets without tied conc.rete shoulders from both groups should be usable without adjustment for roller compacted concrete since no load transfer is assumed for these cases. The published Corps of Engineers design aids for parking areas and airfields need to be adjusted to remove the 25 percent load transfer assumption or else the problem needs to be solved directly using stress analysis and fa tigue concepts. Because of the way the current Corps of Engineers design aids are structured, the load transfer assumption can be removed from any of these published after 1985 by reducing the concrete flexural strength used for design by 1/3. The calculation of a Corps of Engineers design will be illustrated with a sample problem in the next section.

40. When the design thickness of the roller compacted concrete exceeds the lift ·thi ckness that can be effectively compacted, the pavement must be built up in multiple lifts. The effect of multiple lift construction on design is best evaluated using overlay design concepts. The required lift thickness can be determined as

where

H b

required thickness of top lift

required monolithic thickness of pavement

thickness of bottom lift of concrete

n power to account for bond condition 1.0 if full bond, i.e., monolithic behavior 1.4 if partial bond, e.g., top lift cast on hardened bottom lift 2.0 if unbonded, e.g., positive bond breaker such as curing compound or asphalt emulsion is placed on bottom lift before top lift is placed

41. If a full bond is achieved between lifts, no increase in thickness is needed for the multiple lift construction. Felt (1956) concluded on the basis of a field survey that a

2 1,380 kPa (200 lb/in. ) bond shear strength was adequate to achieve full bond for fu lly bonded concrete overlays, and this criterion is still widely accepted. Figure 5 shows the bond strength in direct tension between lifts of roller compacted concrete from results reported by Hess (1987). For the mix and placement conditions encountered by Hess (1987) delays up to an hour between lift placements of roller compacted concrete still achieved significant tensile bond strengths. A cement grout placed between lifts may improve bonding and allow greater delays between lift placement. If the concrete of the bottom lift hardens or if


curing protection has to .be placed on the bottom lift before the top lift is placed then a partial bond or unbonded situation exists , and the total pavement thickness will increase. The actual effects of bond between lifts and particularly the requirements for full bond are poorly understood, and these are areas of planned research by several organizations.

TENSILE BONO STRENGT H, Ib/i n2

~ ~'-------'-I-----'-------'------~ ~

o

/ /

o

o

o g

L-____ L-____ ~ ____ _L ____ -L ____ ~ ____ _J o

~. ~. o

Itdll ' H.L!JN3~J.S ONOS 31 1SN3l.

Figure 5. Effect of delay between lifts on the bond strength of roller compacted concrete

Example Design Calculation

42. Comparative designs for a roller compacted concrete and a conventional concrete storage yard will be prepared to illustrate some of the design concepts discussed in the previous sections. The subgrade will be assumed to be a soft material with a CBR of about 2 or a modulus of sub grade reaction, k, of about

2 13.5 kPa/mrn (50 lb/in. /in.). The concrete will be assumed to have the same engineering properties regardless of construction method. The flexural strength will be 4,826 kPa

2 (700 lb/in. ); the modulus of elasticity will

be 27,600 MPa (4,000,000 lb/in. 2), and Poissons

ratio will be 0.15. The design vehicle will be a fork lift with a 67.8 t (149,160 lb) axle load. Each side of the axle has twin tyres spaced 508 mm (20 in.) center to center. Each tyre carries a load of 16.95 t (37.290 lbs)2 with a tyre pressure of 900 kPa (130 lb/in. )

2 2 and a contact area of 0.185 m (286.8 In. ). The design will select a thickness of concrete pavement to withstand 50,000 repetitions of this design vehicle at any single point.

43. .The low modulus of subgrade reaction is representative of wet, soft, cohesive subgrades. Regardless of construction method, a

159


granular base course must be placed on this material to protect against pumping and to serve as a construction platform. The roller compacted concrete must have a sound base to achieve compaction and the conventional concrete must have an adequate construction platform to allow setting of forms, operation of a paving equipment, traffic of concrete haul trucks, etc.

44. According to the criteria of the Corps of Engineers rigid airfield design m~nual (Department of the Army 1988), a 300 mm (12 in.) base on this subgrade would provide an effective modulus of sub grade reaction of 54 kPa/mm

(200lbs/in.2/in.). Major increases in base

thickness beyond this would result in only modest further improvements in the modulus of subgrade reaction. Regardless of concrete construction methods used, very soft soils of this nature are difficult to build on and stabilization of the sub grade may be needed to allow any kind of construction. More detailed discussion of the problems of building pavements on very soft soils can be found in Rollings, Poindexter, and Sharp (1988). For this problem a nominal 150 mm (6 in.) lime stabilization will be assumed to provide a construction platform for the placement and compaction of a 300 mm (12 in.) thick granular base course that provides an effective modulus of subgrade reaction of 54 kPa/mm

(200 lb/in.2/in.) at the surface of the base

course. Intern~l drainage must be provided for this base course to prevent water from being trapped above the lime stabilized subgrade.

45. The Corps of Engineers fatigue criterion for concrete pavements is

where

DF = 0.50 + 0.25 Log C

DF Design factor R/(ao)

R Flexural s trength of concrete

a = Load transfer factor 0.75 for conventional concrete pavement joints achieving 25 percent load transfer 1.00 for no load transfer

a = maximum stress calculated using the Westergaard free edge model

C Coverages of traffic or maximum number of stress repetitions at a point

For the 50,000 coverages or stress repetitions of this design problem, a design factor of 1.6747 is needed. This is a large storage area where conventional concrete paving would have load transfer so the difference between the pavement designs is only the load transfer factor a. Since the required design factor, the concrete flexural strength, and the appropriate load transfer are known, an allowable stress can be calculated for the roller com-

160

pac ted concrete and the conventional concrete. The allowable conventional concrete stress with

2 a equal to 0.75 is 3,842 kPa (567 lb/in. ), and the allowable roller compacted concrete stress with a equal to 1.0 is 2,882 kPa

2 (425 lb/in . ).

46. Selection of a design thickness for this problem is an iterative process of trying different thicknesses until these allowable stresses are met. The Westergaard free edge stress can be found using influence charts such as published in Yoder and Witczak (1975) or, as was done for this example, using one of the computerized solutions such as the H-51 program (Kreger 1967). The maximum Westergaard stress for this problem occurs when the forklift axle is perpendicular to a joint with the outside t yre immediately adjacent to the joint. The allowable stresses a.re met for this problem when the conventional concrete is 383 mm (15.3 in.) thick, and the roller compacted concrete is 463 mm (18.5 in.) thick. The difference between these two thickness requirements is due only to the different assumptions about load transfer across joints since all other material properties are assumed to be the same. If this had been a road, both designs would assume the free edges are trafficked, and the thicknesses would both be 463 mm (18.5 in.). The stabiliza tion of the subgrade and the addition of the granular base course is primarily a benefit for construction. Increasing the design modulus of subgrade reaction from

13.5 kPa/mm (50 lb/in . 2/in.) to 54 kPa/mm

(200 Ib/in.Z/in.) only decreased the required pavement thickness by 11.6 and 10.7 percent for the conventional and roller compacted concrete pavements respectively.

47. The required 463 rum (18. 5 in.) thick roller compacted concrete must be placed in two lifts to ensure that compact ion is achieved. If complete bond is achieved between lifts no change in total thickness is required. If, however, there is a delay between placement of lifts a partial bond design must be made. If a 300 mm (12 in.) first lift is placed (note this is stretching the recommended maximum lift thickness and will require the best possible compaction effort) then the required final lift thickness (HI) is determined from the equation

given earlier as

H 1.4 = H1 . 4 _ H 1.4 1 b

H 1.4 1

(463 mm)1.4 _ (300 mm)1.4

HI = 264 nun

With a partial bond between lifts the t otal thickness becomes 564 mm (22.5 in.). The requirements to achieve full bond and monolithic behavior between lifts is an important question requiring further study.

48. The variability in the flexural strength of concrete must be recognized in proportioning the concrete mixture to ensure that the



strength used for design is met or exceeded. In this example, if the designer wishes for 90 percent of the concrete to exceed the design

2 strength of 4,826 kPa (700 lbs/in. ), the mean flexural s t~ength of the concrete must increase as the coe ff i cient of variation of the flexural strength increases. Assuming a normal distribution of test results , a coefficient of variation of 10 percent would require a concrete proportioned to provide a mean strength of

5,444 kPa (790 lbs/in.2) if the 4,826 kPa 2 (700 lbs/in. ) design strength is to be equaled

or exceeded 90 percent of the time. For coefficients of variation of 15 and 20 percent this mean concrete strength increases to 5,753 kPa

(834 lbs/in. 2) and 6,061 kPa (879 lb/in.2).

49. This example illustrates several points about roller compacted concrete pavement design. First, a sound base must be provided to allow compaction of the roller compacted concrete. Although roller compacted concrete has properties similar to conventional concrete, the lack of load transfer at joints and contraction cracks requires thicker roller compacted concrete pavements than conventional concrete pavements for some types of pavement. If the pavement is too thick to be compacted in a single lift, multiple lift construction will be needed. If full bond is not achieved between lifts the overall pavement thickness must be increased to account for the bond condition. And finally, the amount of variation in the concrete flexural strength must be considered in proportioning a mix to ensure the design strength is equalled or exceeded.

CONCLUSIONS

50. Roller compacted concrete is an innovative construction procedure capable of reducing the cost of portland cement concrete pavements by 10 to 30 percent. This savings results in an open surface texture and less smooth pavement than normally associated with concrete pavements. However, better selection of concrete proportions and improved construction procedures are improving the quality of roller compacted concrete. Also , many roller compacted concrete pavements have problems with raveling and spalling of joints and contraction cracks. The smoothness and raveling problems are not a concern on the industrial type pavements where roller compacted concrete has had its major applications to date, but improvements in these ~reas will be needed as roller compacted concrete pavements are tried for higher quality pavements. Skid resistance data are lacking and will be needed for evaluating roller compacted concrete's potential fo r higher speed pavements.

51. Roller compacted concrete is a high strength product when properly compacted. With its low water-cement ratio it can achieve hi ghe r strength than conventional concrete · at the same cement contents, or it can ach ieve higher strength than conventional concrete at a lower cement concrete. However, the inability to prepare representative samples hinders mix proportioning and quality control and makes selecting a realistic design strength diffi-


cult. Consequently, some of the potential strength advantages of roller compacted concrete cannot be exploited yet. Despite its strength, roller compacted concrete has a potential durability problem if it is exposed to freezing and thawing while critically saturated. Concepts for incorporating entrained air into roller compacted concrete to solve this durability problem need to be pursued.

52. Present data indicate that roller compacted concrete made of conventional materials has the same engineering characteristics as conventional concrete. Therefore normal concrete pavement analytical and design methods can be used with roller compacted concrete as long as corrections for the lack of load transfer and adjustments for multiple lift construction are made when they are needed.

REFERENCES

American Association of State Highway and Transportation Officials. 1986. 'AASHTO Guide for Design of Pavement Structures,' Washington DC.

American Concrete Institute. 1981. 'Considerations for the Design of Structures Subjected to Fatigue Loading,' ACI 215R-74, revised 1981, Detroit, Michigan.

American Concrete Institute. 1980. 'Roller Compacted Concrete,' ACI 207.5R-80, Detroit, Michigan.

American Concrete Institute. 1975. 'Standard Practice for Selecting Proportions for No Slump Concrete,' ACI 211.3-75, Detroit, Michigan.

~erican Society for Testing and Materials. 1982. 'Moisture Density Relations of SoilCement Mixtures,' ASTM D558-82, Philadelphia, Pennsylvania.

Andersson, Ronny . 1987. 'Swedish Experience with RCC,' Concrete International, Design and International, Vol 9, No 2, American Concrete Institute, Detroit, Michigan.

Anderson, Fred. 1985. Roller Compacted Concrete I nteragency Forum, Department of the Interior, Bureau of Reclamation, Lakewood, Colorado.

Burns, Cecil D. 1978. 'Compaction Study of Zero-slump Concrete,' Miscellaneous Paper S-76-16, USAE Waterways Experiment Station, Vicksburg, Mississippi.

Cannon, Robert W. 1985. 'Design Considerations for Roller Compacted Concrete and Rollcrete in Dams,' Concrete International, Design and Construction, Vol 7, No 12, American Concrete Institute, Detroit, Michigan.

Department of the Army. 1988. 'Rigid Pavements for Airfields,' Technica l Manual 5-8 25-3, Washington, DC.

Department of the Army . 1987. 'Standard Practice for Concrete Pavements,' Technical Manual 5-82 2-7, Washington DC.

161

ROLLlNGS.- ROLLER COMPACTED CONCRETE PAVEMENTS

Felt, E. J. 1956. 'Resurfacing and Patching Concrete Pavement lJith Bonded Concrete,' Proceedings, Vol 35, Highway Research Board, Washington, DC.

Grau, Robert W. 1979. 'Utilization of Marginal Construction Materials for LOC,' Technical Report GL-79-21, USAE Waterways Experiment Station, Vicksburg, Mississippi.

Hansen, Kenneth D. 1987. 'A Pavement for Today and Tomorrow,' Concrete International, Design and Construction, Vol 7, No 2, American Concrete Institute, Detroit, Michigan.

Hague, M. N. and Ward, M. A. 1986. 'Marginal Materials in Roller Compacted Concrete for Pavement Construction,' Journal of the American Concrete Institute, No 4, Proceedings Vol 83, Detroit, Michigan.

Hess, John R. 1987. 'Roller Compacted Concrete Pavement for Toole Army Depot, Utah,' MS Thesis, California State University, Sacremento, California.

Hutchinson, Ronald L., Ragan, Steven A., and Pittman, David W. 1987. 'Heavy-Duty Pavements,' Concrete International, Design and Construction, Vol 9, No 2, American Concrete Institute, Detroit, Michigan .

Johnson, A. W. and Sallberg, J. R. 1960. 'Factors that Influence Compaction of Soils,' Highway Research Board Bulletin 272, Washington DC.

Kreger, W. C. 1967. 'Computerized Aircraft Ground Flotation Analysis-Edge Loaded Rigid Pavement,' EER-FW-572, General Dynamics, Fort Worth, Texas.

Lowe, John. 1988. 'Roller Compacted Concrete Dams--An Overview,' Roller Compacted Concrete II, Kenneth Hansen and Leslie Guice, editors, American Society of Civil Engineers, New York.

Packard, Robert G. 1973 . 'Design of Concrete Airport Pavements,' Engineering Bulle-tin 050.03P, Portland Cement Association, Skokie, Illinois.

Piggott, Robert W. 1987 . 'Ten Years of HeavyDuty Pavement in Western Canada,' Concrete International, Design and Construction, Vol 9, No 2, American Concrete Institute, Detroit, Michigan.

Portland Cement Association . 1984. 'Thickne s s Design for Concrete Highway and Street Pavement,' Engineering Bulletin 109.01P, Skokie, Illinois.

Pittman, David W. 1988. 'Construction of a Roller Compacted Concrete Pavement Hardstand at Kitzingen, West Germany ,' 14th Australian Road Research Board Conference, Canberra, Australia.

162

Ragan, Steven A. 1988. 'Proportioning RollerCompacted Concrete in Pavement Mixtures,' Roller Compacted Concrete II, Kenneth Hansen and Leslie Guice, editors, American Society of Civil Engineers, New York.

Ragan, Steven A. 1986. 'Evaluation of the Frost Resistance of Roller-Compacted Concrete Pavements,' Transportation Research Record 1062, Transportation Research Hoard, Washington DC.

Raphael, Jerome M. 1971. 'The Optimum Gravi ty Dam ,' Rapid Construction of Concrete Dams, American Society of Civil Engineers, New York.

Rollings, Raymond S. 1988. 'Substandard Materials for Pavement Construction,' 14th Australian Road Research Board Conference, Canberra, Australia.

Rollings, Raymond S., Poindexter, Marian E., and Sharp, Kieran G. 1988. 'Heavy Load Pavements on Soft Soils,' 14th Australian Road Research Board Conference, Canberra, Australia.

Rollings, Raymond S. Overlays for Airfield sertation, University Park, Maryland.

1987. 'Design of Rigid Pavements,' Ph.D . Disof Maryland, College

Rollings, Raymond S. 1985. 'Review of Rigid Airfield Pavement Design , ' Pavement Design Seminar, Duntroon, Australia.

Rollings, Raymond S. 1981. 'Corps of Engineers Design Procedures for Rigid Airfield Pavements,' 2nd International Conference on Concrete Pavement Design, Purdue University, West Lafayette, Indiana.

Saucier, Kenneth L. 1984. 'No-Slump RollerCompacted Concrete (RCC) for use in Mass Concrete Construction, ' Technical Report SL- 84-17, USAE Waterways Experiment Station, Vicksburg, Mississippi.

Tayabji, Shiraz D. and Okamoto, Paul A. 1987. 'Engineering Properties of Roller-Compacted Concrete,' Presented at 1987 Annual Heeting of the Transportation Research Board, Washington DC.

Withrow, Howard. 1988. 'Compaction Parameters of Roller Compacted Concrete, ' Roller Compacted Concrete II , Kenneth Hansen and Leslie Guice, editors, American Society of Civil Engineers, New York .

Yoder, E. J. and Witczak, M. W. 1975. Princjples of Pavement Design, John Wiley and Sons, Inc., New York.


R .S . Rollings


Raymond S. Rollings earned a B.S. degree from the US Military Academy, a M .S.C.E.from the University of Illinois, and a PhD.from the University of Maryland. He has been a research civil engineer with the USAE Waterways Experiment Station Geotechnical Laboratory's Pavement Systems Divisionfor 10 years and previously served as a civil engineering officer with the US Air Force. He is a member of the American Concrete Institute Technical Committees for Fatigue of Concrete and Concrete Pavements and the American Society of Civil Engineer's Construction Division Committee on Inspection.


Documents

DESIGN AND CONSTRUCTION OF ROLLER COMPACTED CONCRETE