Report No. COOT -DTD-R-94-3

Comparison of Test Results from Laboratory and Field Compacted Samples

JD.Stevenson FHWA Colorado Division 555 Zang Street. Room 250 Lakewood. Co. 80228

Tim Aschenbrener Colorado DOT 4340 East Louisiana Avenue Denver. Co. 80222

Final Report Febuary 1994

The contents of this report reflect the views of

authors who are responsible for the facts and t he

accuracy of the data presented herein. The

contents do not necessarily reflect the official

views of the Colorado Department of Transportation

or the Federal Highway Administration. This report

does not constitute a standard, specification, or

regulation.

i

Acknowledgements

The authors would li ke to express their gratitude to all of the project engineers who cooperated with our research study and allcwed us to obtain samples for this investigation: Van Pilaud (COOT-Region 3), Robert Birch (COOT-Region 6), Marv Bindel (COOT-Region 6), Gerry Padilla (COOT-Region 4), Kevin Albert (COOT-Region 2), and Bob Chaderton (COOT-Region 4). Oave Price (COOT-Research) obtained the field samples and assisted with laboratory testing.

The COOT research panel provided many excellent comments and suggestions for the study. It included: Byron Lord and Kevin StLart (FHWA - Turner Fairbank Highway Research Center); Ooyt Bolling (FHWA - Region 8), Jerry Cloud (FHWA - Colorado Oivision), Oenis Oonnelly and Steve Horton (COOT-Staff Materials), Ken Wood (COOT-Region 4 Materials), and Oonna Harmelink (COOT-Research).

Special thanks to the panel of Colorado asphalt paving experts who provided numerous ideas and suggestions which made this study more informational: Bud Brakey (Brakey Consulting Engineers), Jim Fife (Western Colorado Testing), Joe Proctor (Morton International), Scott Shuler (Colorado Asphalt Pavement Association) and Eric West (Western Mobile). Or. Jack Corlew (Process Consultant) provided a technical review.

ii

Technical Report Documentation Page

I. IleJ><'rt No, 2. Government Accession No. 3, Recipient's Catalog No,

CDOT-DTD-R-94-3

4, Titl< nnd Subtitle S, Report Date

Comparison of Test Results from Laboratory February 1994

and Field Compacted Samples 6. Performing Organization Code

7. Author(s) 8. Performing Organization Rpt.No.

Timothv Aschenbrener CDOT-DTD-R-94-3

9. PCI'fol'1ning Organization Name and Address 10. Work Unit No. (TRAIS)

Colorado Department of Transportation

4201 E. Arkansas Ave. 11. Contract or Grant No.

Denver Colorado 80222

12 . Spr.·llsOI'ing Agency Name And Address 13. Type or Rpt. And Period Covered

Colorado Department of Transportation F;n~1 'R .. nnrt

4201 E. Arkansas Ave. 14. Sponsoling Agency Code

Denver Colorado 80222

IS. Supplemcnhll'Y Notes

Prepared in Cooperation with the U.S. Department of Transportation Federal

H i ·~ hway. Adm inistration

Hi. Abl'=lrnct

Studies have been completed to verify the predictive capabilities of the testing equipment by performing tests on mixtures of known field performance. The Hamburg wheel-tracking device and the French rutting tester have the ability to model field performance very well.

The purpose of this report is to compare test results from the European testing equipment using laboratory and field compacted samples. The results from this study will be beneficial to 1) decide how close the laboratory compactors "simulate" field compaction, and 2) assist with the development of specifications for field acceptance testing.

When tested in the French rutting tester, samples compacted in the French plate compactor and linear kneading compactor produce samples that give very similar test results to field compacted samples. When tested in the Hamburg wheel-tracking device, results from the lab compacted samples indicated the mixes would be more resistant to moisture damage than the results from field compacted samples. The air voids in the field compacted samples were more uniformly distributed than in the lab compacted samples.

] mplcmcnla lion :

17. K,y Words 18. Distribution Statement

No Restrictions: This report is

available to the public through

the National Technical Info. Selvice. Springfield VA 22161

19.5eclIl'ity Clnssif. (report) 20.Seeurity Clnssir. (page) 21. No. or Pa~es 22. Price

Unclassified Unclassified 92 ...

Table of Contents

1.0 Introduction . . .. . ... . .... ... ... .. . . .. . . . .. . . .. ....... . . . . .. ...... .

2.0 Experimental Grid . . .. .. ... . . . ... . . . . : . . ........................... 2 2.1 Laboratory Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.1.1 French Rutting Tester ... .. . .. . .. .•.... ....... . • ... . .•.. 2 2.1.2 Hamburg Wheel-Tracking Device . . . . . . .... . ... .. . ... . .•... 4 2.1.3 Air Void Distribution ... . . . . . . . . . . . . . . . . . . . . . . • . . . • • . . . .. 7

2.2 Laboratory Compactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 2.2.1 Linear Kneading Compactor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2.2 French Plate Compactor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .• 9

2.3 Experimental Grid .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . .. 9

3.0 Site Information . . ... .... . .. . ............ . ... ..... .... ... ..... . .... 11 3.1 Site 1 .... .. . . . .• . .. . ... . . . . . . ... .. .. . ... .. . . . .... . . . .. . •.. 11 3.2 Site 2 . . . • . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . 11 3.3 Site 3 ... . .. . . . . .. . . . .... .. .. . ....• . . ..... . . . .. . .. . . . .. . .. . 12 3.4 Site 4 ... . ........................ _ . .... . __ ... _ ... .. .. _ . . . . 12 3.5 Site 5 ... .. . . .. .. . .... .. . . ..... . . . ..... .. . . ...• . .... . .• . .. . 12 3.6 Site 6 ... .... .. . . ..... .. .... . ........... .. .......... . ... ... 13 3.7 Site 7 ... . . .. . . ....... . . .. . . . . .. .. .. . . .. .. . .. . . . ... . . . .. . " 13

4.0 Test Results and Discussion . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . 14 4.1 Air Void Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14

4.1.1 Field Samples .. ... . . . . .. . . .. . . .. . .. . . . . . . .... • .. . .. . . 16 4.1.2 French Compactor . _ . _ . . _ ...... . _ . . . . . . . . . . . . . . . . . . . . .. 16 4.1.3 Linear Kneading Compactor ... .. .. .. . , . . . . . . . . . . . . . . . . . . . 18

4.2 French Rutting Tester ......... .. . . . .. . . .. . , ..... , ...... , ..... , 20 4.2.1 Comparison of Laboratory Compactors . .. , • . . .. , . .. . .... . .. . , 20 4.2.2 Comparison of Laboratory Compactors to Field Compaction. _ .. __ . 22

4.3 Hamburg Wheel-Tracking Device ... . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . 25 4.3.1 Comparison of Laboratory Compactors. . . . . . . . . . . . . . . . . . . . . .. 26 4.3.2 Comparison of Laboratory Compactors to Field Compaction . . . .• . . 28 4.3.3 Influence of Short-Term Aging .. .... .. .. .. ..... ... ... _ . . .. 28

5.0 Time for Field Compaction ...... . ... .... ...... . . ............ ... . ..... 30

6.0 Conclusions and Recommendations ... ......... ..... .... . ..... .. .. .. ... 33

8.0 References . .. . ... .. ........ .. . .. .... .. . .... ... .......... ... .. ... 34

iv

List of Tables

Table 1. The Experimental Grid Used for Each Site. . • . .. . .. . ...• . .. . . .. ....... 10 Table 2 . Air Void (%) Distribution - Average and Standard Deviation. .... .... ....... 14 Table 3 . Air Void (%) Distribution of Portions of Samples. ..... . . .. ... . . ....... . . 17 Table 4. The Rut Depths and Percent Rutting from Samples Tested in the French Rutting

Tester. .............. . . ... ..... . ...... ........... ... ... . . . .. . . 21 Table 5. Differences in Rutting Depths Between French and Kneading Compacted

Samples ..... ......... .... . .. .......................... . ... .... 22 Table 6. Differences in Rutting Depths Between Field and Lab Compacted Samples. . . . 23 Table 7. Stripping Inflection Points (Number of Passes). .. ... . . . . . ... . ......... . 26 Table 8. Differences in Stripping Inflection Points. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27 Table 9. Differences in Stripping Inflection Points Between the Kneading Compacted

Samples (Both with Additional Aging and with No Additional Aging) and Field Compacted Samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29

Table 10. Actual and Predicted Times Available to Achieve Field Compaction .. . . ..•.. 32

List of Figures

Figure 1. French Rutting Tester. .... .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Figure 2. Close-up of the French Rutting Tester. .. . . . . . .. . . . . . . .... . . . ...... , ' 3 Figure 3. Hamburg Wheel-Tracking Device .... , .... . . ... , ... , , . . , , , .• , , , . , , .' 5 Figure 4. Close-up of the Hamburg Wheel-Tracking Device. , . . ... , .. .. , . . , . , .. . " 5 Figure 5. Results from the Hamburg Wheel-Tracking Device. , , .. , . .. , , , , . , , , . , . .. 6 Figure 6, Linear Kneading Compactor. . ............ ... " .. , ' , '" . , " " " . . , 8 Figure 7, Schematic of the Linear Kneading Compactor, ." . .. .. , .. , . , .... , . . . .. 8 Figure 8. French Plate Compactor. . .. , , , , , , . . .. .. . .. . , . , . . . . . . . . . . . . . . . . . . 10 Figure 9. Layout of How 50·mm Thick French, 4O-mm Thick Linear Kneading, and Field

Compacted Samples Were Cut and Numbered ............ . ........... . . , 15 Figure 10. Layout of How 1 OO-mm Thick French Compacted Samples Were Cut and

Numbered. . . . .. . . .. . ... .. , ... .. . .. .. . ,. , .. .. . , ... .... ,... ... . . 15 Figure 11. Typical Distribution of Air Voids in a 1 OO-mm Thick French Compacted Sample

for Site 1. . .. .... ,', .. .. , .. . . . , . ..... ..... . .... .. ,. .. . . ... . .. . . 17

Appendices

Appendix A: Detailed Roller Pass Studies from Each Site Appendix B: Air Voids of Compacted Samples Appendix C: French Rutting Tester Results Appendix D: Hamburg Wheel-Tracking Results

v

Comparison of Test Results from

Laboratory and Field Compacted Samples

J.D. Stevenson and Tim Aschenbrener

1.0 Introduction In September 1990, a group of individuals representing AASHTO, FHWA, NAPA, SHRP, AI, and

TR3 participated in a 2-week tour of six European countries. Information on this tour has been

published in a "Report on the 1990 European Asphalt Study Tour" (1). Several areas for potential

improvement of hot mix asphalt (HMA) pavements were identified, including the use of

periormance-related testing equipment used in several European countries. The Colorado

Department of Transportation (CDOT) and the FHWA Turner-Fairbank Highway Research Center

(TFHRC) were selected to demonstrate this equipment.

Studies have been completed to verify the predictive capabilities of the testing equipment by

periorming tests on mixtures of known field performance. The Hamburg wheel-tracking device

and the French rutting tester have the ability to model field performance very well. Samples are

prepared for testing in the European equipment with laboratory compactors that are supposed to

"simulate" field compaction. It was desired to compare how well the laboratory compactors

modelled the actuallield compaction using roadway construction equipment.

Additionally, it is desired to improve the quality of HMA on projects by using results from these

tests as specifications. When accepting a laboratory mix design or a field produced material, it

is not clear how the laboratory compaction process models the field compaction. By comparing

field and laboratory compacted samples, information would be available to better prepare

acc~ptance specifications.

The purpose of this report is to compare test results from the European testing equipment using

labcratory and field compacted samples. The results from this study will be beneficial to 1)

decide how close the laboratory compactors "simulate" field compaction, and 2) assist with the

development of specifications for field acceptance testing.

1

2.0 Experimental Grid

2.1 Laboratory Tests

The tests used to compare field and laboratory compacted samples were the French rulling tester

and .the Hamburg wheel-tracking device.

2.1.1 French Rutting Tester

The French rulling tester is used to evaluate the resistance to permanent deformation. It is

manufactured by the Labarataire Central des Pants et Chaussees (LCPC) and is shown in Figure

1: a' close-up is shown in Figure 2. The samples tested are 500 x 180 mm (19.7 x 7.1 in.) and

can be 50 or 100 mm (2 or 4 in.) thick.

Two samples can be tested simultaneously. The samples are loaded with 5000 N (1 124 Ibs.) by

a pneumatic tire inflated to O.S MPa (87 psi). The tires load each sample at 1 cycle per second;

one cycle Is two passes. The chamber is heated to SO°C (140°F) but can be set to any

temperature between 350 and SO°C (950 and 140°F).

When a test is performed on a laboratory compacted sample, it is aged at room temperature for

as long as 7 days. It is then placed in the French rutting tester and loaded with 1000 cycles at

room temperature. The deformations recorded after the initial loading are the 'zero" readings.

The sample is then heated to the test temperature for 12 hours before the test begins. Rutting

depths are measured after 1 00, 300, 1000, 3000, 10,000, 30,000 and possibly 100,000 cycles.

The rutting depth is reported as a percentage of the sample thickness. After a given number of

cycles, the percentage is calculated as the average of 15 measurements (five locations along the

length and three along the width) divided by the original slab thickness. A pair of slabs can be

tested in about 9 hours.

A successful test will typically have a rutting depth that is less than or equal to 10% of the slab

thickness after 30,000 cycles. The results are plotted on a log-log graph paper. The slope and

intercept (at 1000 cycles) are calculated using linear regression. The equation Is:

2

Figure 1. French Rutting Tester.

Figure 2. Close-up of the French Rutting Tester.

3

where:

Y A ( X )B 1000

Y = rutting depth (%),

X = cycles,

A = intercept of the rutting depth at 1000 cycles, and

B = slope of the curve.

2.1.2 Hamburg WheeJ-Tracking Device

(Equation 1)

The Hamburg wheel-tracking device is used to determine the moisture susceptibility of HMA. It

is manufactured by Helmut-Wind Inc. of Hamburg, Germany and shown in Fig. 3: a close-up in

Fig. 4. A pair of samples are tested si~ultaneously. A sample is typically 26 cm (10.2 in.) wide,

32 em (12.6 in.) long, and 40 mm (1.6 in.) deep. Its mass is approximately 7.5 kg (16.5 Ibs.), and

the sample is compacted to 6 ± 1 % air voids. The samples are submerged under water at 500 e

(122°F), although the temperature can vary from 25°e to 700e (77°F to 158°F). A steel wheel,

47 mm (1.85 in.) wide, loads the samples with 705 N (158Ibs.) The wheel makes 50 passes per

minute over each sample. The maximum velocity of the wheel is 34 cm/sec (1.1 ft/sec) in the

center of the sample. Each sample is loaded for 20,000 passes or until 20 mm of deformation

occur. Approximately 6-1/2 hours are required for a test.

The results from the Hamburg wheel-tracking device include the creep slope, stripping slope and

stripping inflection point as shown in Fig. 5. The results have been defined by Hines (2). The

creep slope relates to rutting from plastic flow. It is the inverse of the rate of deformation in the

linear region of the deformation curve, after post compaction effects have ended and before the

onset of stripping. The stripping slope is the inverse of the rate of deformation in the linear region

of the deformation curve, after stripping begins and until the end of the test. It is the number of

passes required to create a 1 mm impression from stripping . The stripping slope is related to the

severity of moisture damage. The stripping inflection point is the number of passes at the

intersection of the creep slope and the stripping slope. It is related to the resistance of the HMA

to moisture damage.

4

Figure 3. Hamburg Wheel-Tracking Device.

Figure 4. Close-up of the Hamburg Wheel-Tracking Device.

5

.:- ... ~~ .. ~"".s_tlc·""'~;;;:~·"·:::::··~:::~f~::;:~~=n=_:_ F" :-~.-~. -~...,.~. -;~-;,,~c·~-~···-=·"=···="···I· ··1" r·~~···;~·;;~·~~~~·;~~"~!J·:·;~~~·~·t.~"·~~-;~i·~~"~0·· ~~···~~···i"~~~D··l· ·· JCreep --gj ope I. ........... .. ~.~._ ...... .. _. ........ . .................. ...................... . ·4· ...................... -.................. . .. "' "'.

, : ~=:= ==~-= = ____ ~ = t:s~~~~-=~= .~ . IStrlpping Slbpe-l a ·1 o· ...................... ................... - -. __ ... .. .. -.......... - ............... -.... ...................... ............... ..... . ...................................... ~; ...................... . E - . E ·1 2 .. .. :.................. . ..... - .... _ ... - ---. ~ .-..... -'-~ ..•. - .............. , .. -. ...................... ......... _ .................................................... .................... .. ::I E ~ :E

I .20l---~----~~-i6----~8~--~1tO---:1~2~~1~4--~1~6--~1t8--~20 o 2 4 No. of Passes

(Thousands)

Figure 5. Results from the Hamburg Wheel-Tracking Device.

6

2.1.3 Air Void Distribution

Since results of the tests are influenced by the air void contents of the samples tested, samples

. were compacted in the laboratory to an air void content as close to the field compacted sample

as possible. Just as differences in the actual air void content of a sample can influence the

results, the distribution of air voids throughout the compacted samples could influence the test

results. Therefore, samples from each of the compactors and a field compacted sample were

sliced into 12 to 24 pieces. The air voids of each piece were measured to determine the

distribution of air voids throughout each sample. The distribution of air voids were then compared

bel'Neen the various methods of compaction.

2.2 Laboratory Compactors

The laboratory compactors used to prepare samples for testing include the linear kneading

compactor and the French plate compactor.

2.2.1 Linear Kneading Compactor

The linear kneading compactor is shown in Figure 6 and is manufactured by RlH Specialty and

Machine in Terre Haute, Indiana. The compactor can produce samples for direct use with both

the Hamburg wheel-tracking device and the French rutting tester. Samples 320 x 260 mm (12.6

x 10.2 in.) and 40 mm (1.6 in.) or 80 mm (3.2 in.) thick can be produced on the Hamburg wheel'

tracking device. Samples that are 500 mm x 180 mm (19.7 x 7.1 in.) and 50 mm (2 in.) thick can

be produced for use on the French rutting tester. Additionally, two lifts of 50 mm can be used to

make a 100 mm (4 in.) thick sample for the French rutting tester.

Since samples are compacted to a known height, the targeted air voids of the compacted sample

are achieved easily. After determining the maximum specific gravity (AASHTO T 209) of the mix,

the mold Is filled with a pre-determined weight of material. The sample can then be compacted

within ± 1 % of the targeted air voids.

A series of 12-mm (0.5-in.) wide steel plates are placed on the loose mix in the mold. A

downward motion of the roller applies a force to the top of each plate while the mold moves back

and forth on a sliding table shown in Figure 7. A linear compression wave is produced in the mix

by the bottom edges of the plates as the roller pushes down on each plate. This kneading action

7

Figure 6. LInear Kneading Compactor.

o

Figure 7. Schematic of the LInear Kneading Compactor.

8

allcws the mix to be compacted without fracturing the aggregate. This compactive action is

probably very similar to a steel-wheel roller. The compaction lime is less than 10 minutes.

2.2.2 French Plate Compactor

The French plate compactor is shown in Figure 8 and is manufactured in France by the LCPC.

Samples compacted are 500 x 180 mm (19.7 x 7.1 in.) and 50 or 100 mm (2 or 4 in.) thick.

These samples can be used directly in the French rutting tester. When samples are prepared

for the Hamburg wheel-tracking device, the 50 mm thick sample is used and the length is

trimmed.

A pneumatic tire is inflated to 0.6 MPa (87 psi). The tire makes 2 passes on each outside edge

for every one pass in the center of the sample; for example, the entire sample width can be

covered in 5 passes (2 front, 2 back, 1 center) , 10 passes (4 front, 4 back, 2 center), 15 passes

(6 front, 6 back, 3 center), etc. The force applied by the wheel can vary from 0.2 to 0.6 MPa (29

to 87 psi). Therefore, the compactive effort can be controlled by varying either the number of

passes and/or the force applied by the wheel. This compactive effort is very similar to a

pneumatic-tired roller. The compaction time is approximately 30 minutes.

As with the linear kneading compactor, a pre-determined weight of material is used based on the

maximum specific gravity of the mix. The compaction is stopped when the sample is level with

the mold. Since this is a visual determination, it is difficult to precisely control the level of air

voids In the sample. Samples can usually be compacted to within ± 2% of the targeted air voids

with an experienced operator.

2.3 Experimental Grid

Seven sites were investigated in this study. The testing performed from each site is shown in the

experimental grid in Table 1.

9

Table 1. The Experimental Grid Used for Each Site.

Compaction Method (Sample Thickness)

Field French French Kneading Kneading Slab (100 mm) (50 mm) (100 mm) (40 mm) .

Hamburg X X X Device

French X X X X Rutter

Void X X X X Distribution

Figure 8. French Plate Compactor.

10

3.0 Site Information

Seven sftes were selected for this study. The following is a brief description of the site location,

laydown procedures, and field compaction procedures. A detailed roller pass study from each

site is in Appendix A. For the purpose of this study, a pass is defined as one compaction

machine rolling back and forth over a selected spot.

A specific location at each site was identified. Loose mix was sampled from this location, and

a roller pattern study was performed at this location. The percent relative compaction was

measured based on the maximum specific gravity (AASHTO T 209). Field slabs were later sawn

and cored at this same location.

3.1 Site 1

Site 1 was located on US-40 just north of Fraser. This project involved the placement of a 50-mm

thick overlay using a Grading CX mix. Bottom dump trucks placed the HMA in a windrow, and

an elevating loader was used to fill the paver hopper. The loose mix samples were taken from

the windrow in front of the paver in the shoulder area of the northbound lane.

The breakdown roller, a HYPAC C766B double-drum vibrating steel wheel roller, made 2.5 passes

on this section of pavement. The intermediate roller, a CAT PS-130 pneumatic roller, made 1

pass and the finish roller, a HYPAC C766B steel wheel roller with no vibration, made 2.5 passes

to finish the section. The final percent relative compaction achieved at the site was 92%.

3.2 Site 2

Site 2 was located on 120th Avenue between Lamar and Ponderosa Streets in Broomfield. This

project involved the placement of a 50-mm thick bottom course using a Grading C mix followed

by a 50-mm thick top course using a Grading CX mix. Rear dump trucks placed the HMA into

the hopper of a Material Transfer Vehicle (MTV). The MTV then filled the paver hopper. The

loose mix samples were taken at the auger of the paver in the outside shoulder area of the

eastbound lane during the placement of the bottom course.

11

The breakdown rolle r, a CAT double-dru.m vibrating steel wheel roller, made 1.5 passes on this

section of pavement. The intermediate roller, a Hyster C530Apneumatic roller, made 3 passes

and the finish roller, a HVPAC C766B double-drum vibrating steel wheel roller, made 5 passes

to finish the section. The final percent relative compaction achieved at the site was 93%.

3.3 Site 3

Site 3 was located on Navajo Street, north of Quincy Avenue in Englewood. This project involved.

the placement of a 50-mm thick overlay using a Grading C mix. Rear dump trucks placed the

HMA in the paver hopper. The loose mix samples were taken at the auger of the paver in the

southbound lane.

The breakdown roller, a Hyster C766A double-drum vibrating steel wheel roller, made 1.5 passes

on this section of pavement. The intermediate roller, a Ferguson FP 912 pneumatic roller, made

4.5 passes and the finish roller, an Ingersoll DA 40 steel wheel roller, made 2 passes to finish the

section. The final percent relative compaction achieved at the site was 93%.

3.4 Site 4

Site 4 was located on SH-119 in Boulder Canyon west of Boulder. This project involved the

placement of a 32-mm thick overlay using a Grading CX mix. Rear dump trucks placed the HMA

in the paver hopper. The loose mix samples were taken at the auger of the paver in the

westbound lane.

The breakdown roller, a bVNAPAC CC42 double-drum vibrating steel wheel roller, made 1 pass

on this section of pavement. The intermediate roller, a Hyster C530A pneumatic roller, made 6

passes and the finish roller, an Ingersoll DA 40 steel wheel roller, made 1.5 passes to finish the

section. The final percent relative compaction achieved at the site was 93%.

3.5 Site 5

Site 5 was located on SH-24, 0.6 miles west of Woodland Park. This project involved the

placement of a 50-mm thick overlay using a Grading CX mix. Rear dump trucks placed the HMA

in the paver hopper. The loose mix samples were taken at the auger of the paver in the

12

westbound lane.

The breakdown roller, a CAT CD534 double-drum vibrating steel wheel roller, made 1.5 passes

on ihis section of pavement. The intermediate roller, an Ingersoll PT125R pneumatic roller, made

2 passes and the finish roller, a Hyster C350C steel wheel roller, made 0.5 passes to finish the

section. The final percent relative compaction achieved at the site was 90%.

3.6 Site 6

Site 6 was located on US-40 near mile post 165 in Muddy Pass north of Kremmling. This project

involved the placement of a 50-mm thick overlay using a Grading CX mix. Bottom dump trucks

placed the HMA in a windrow, and an elevating loader was used to fill the paver hopper. The

loose mix samples were taken from the windrow in front of the paver in the southbound lane .

.The breakdown roller, a Hyster C766A double-drum vibrating steel wheel roller, made 1.5 passes

on this section of pavement. The intermediate roller, a Hyster C766A double-drum vibrating steel

wheel roller that alternated vibrating every 0.5 pass, made 1.5 passes. The finish roller, a Hyster

C350C steel wheel roller, made 2.5 passes to finish the section. The final percent relative

compaction achieved at the site was 96%.

3.7 Site 7

Site 7 was located on SH-287 in Broomfield. This project involved the placement of a 50-mm

thick overlay using a Grading C mix. Rear dump trucks placed the HMA in the paver hopper.

The loose mix samples were taken at the auger of the paver in the northbound lane.

The breakdown roller, a DYNAPAC CC42 double-drum vibrating steel wheel roller, made 2

passes on this section of pavement. The intermediate roller, a Hyster C530A pneumatic roller,

made 5 passes and the finish roller, a DYNAPAC CC42 double-drum vibrating steel wheel roller,

made 2 passes in the static mode to finish the section. The final percent relative compaction

achieved at the site was 93%.

13

4.0 Test Results and Discussion

4.1 Air Void Distribution

Air void distribution throughout the sample might effect the results from testing. The purpose of

this testing was to compare the distribution of air voids in laboratory compacted samples with that

in the field compacted samples.

To determine the air void distribution, samples from each compactor and from the field were cut

into small pieces. For each site a 50-mm thick French, a 40-mm thick linear kneading, and a field

compacted sample were cut into 12 pieces each. A 100-mm thick French compacted sample

from each site was cut into 24 pieces. Figures 9 and 10 show the actual layout of how the pieces

were cut and numbered. Each piece was then measured for air void content according to

AASHTO T 166 to determine the distribution. The results from this testing can be seen in Table

2 expressed in terms of the average (avg.) and standard deviation (S.D.)

Table 2. Air Void (%) Distribution - Average and Standard Deviation.

Compactor (Sample Thickness) Site

Field French French Kneading Sample (50-mm) (100-mm) (40-mm)

Avg. S.D. Avg. S.D. Avg. S.D. Avg. S.D.

1 7.6 0.25 7.1 0.47 7.6 1.39 6.8 1.47

2 5.6 0.47 5.6 0.64 6.2 1.22 6.2 1.09

3 7.7 0.15 6.6 0.67 6.8 1.16 5.7 1.01

4 8.4 0.67 7.6 0.68 7.3 1.99 5.9 1.64

5 9.2 0.55 11.4 0.46 7.6 1.17 7.7 1.55

6 5.1 0.54 6.4 0.95 6.3 1.46 3.1 1.30

7 10.7 0.27 9.3 0.98 9.3 1.57 7.3 1.10

I Avg. II I 0.41 I I 0.69 I I 1.42 I I 1.31 I

14

,/' ,l ,l 1 -.' 4 ,. 7 ,. 10

--------------T-----------------.J.:.-------------~:------_________ _ , , , 2 / S; / 8 ,.- 11

----------------:,,::-------------------.~~-------------------;1:-----------------, , . , 3/ S" 9 "';2 ,.' /' ,/

Figure 9. Layout of How 50-mm Thick French, 40-mm Thick Linear Kneading, and Field

Compacted Samples Were Cut and Numbered.

,,/ 18 ,./ 19 :/ , , , 13 22

-;72'~:7~~? i / i iii ,.. -------------------f----------------------i----------------------j--------------------- .

3 ! 6 1 9 .1 12

Figure 10. Layout of How 100-mm Thick French Compacted Samples Were Cut and

Numbered.

15

4. 1. 1 Field Samples

At each site, the air voids were more uniformly distributed in the field compacted samples than

in any of the laboratory compacted samples. The small variation of air voids found within the field

compacted samples was expected, since they were sawn from the center of the pavement, far

from its restrictive corners or edges. The variation in the laboratory compacted samples was due

to large deviations at the corners and edges of the sample.

4.1.2 French Compactor

As seen in Table 2, the 1 OO-mm thick French compacted samples have twice as much variation

in the distribution of air voids (S.D. of 1.42) as the 50-mm thick French compacted samples (S,o.

of 0.69). This differerice can be attributed to the thickness of the samples. Table 3 shows the

standard deviation of air voids in the top half of the 100-mm thick French compacted samples is

0.62, which is similar to the standard deviation for the complete 50-mm thick French compacted

samples (S.D. of 0.69, Table 2) and the 50-mm thick French compacted samples with the corners

removed (S.D. of 0.59, Table 3). For each case, the distribution is fairly uniform. The air voids

within the bottom half of the 100-mm thick French compacted samples are more variable (S.D.

of 1.25, Table 3). This is mainly due to high air voids in its corners (pieces 1, 3,10, and 12).

The distribution of air voids in a 100-mm thick French compacted sample can be further clarified

by observing Figure 11 . The entire graph shows a normal distribution skewed towards the higher

air voids. The air voids in the top half of the 100-mm thick French compacted sample (pieces 13

through 24) have a uniform and normal distribution. The air voids in the bottom half of the 100-

mm thick French compacted sample (pieces 1 through 12) skews the air voids to the high side.

The air voids in the bottom half of the 100-mm thick French compacted samples (S.D. of 1.25)

are more dispersed than in the top half (S.D. of 0.62). This is because the air voids in the

corners of the bottom half (pieces 1, 3, 10, and 12) are greater than 1 standard deviation from

the average percent air void content as shown in Figure 11. Also, for Site 1 the bottom half

centers around 8.7% air voids, which is about 2% higher than the average in the top half of 6.6%

air voids. The dispersion of air voids throughout the entire sample is increased since the top and

bottom halves center around two different values.

16

Table 3. Air Void (%) Distribution of Portions of Samples.

Site

1

2

3

4

5

6

7

I Avg. II

Top Half

Avg.

6.6

5.5

6.0

5.7

7.5

5.2

8.2

•

& • c

{J. C :;; '" . ~

J • "5

.I E ~ 1

I

100-mm French Compacted Samples

Bottom Bottom w/o Half Corners

S.D. Avg. S.D. Avg. S.D.

0.29 8.7 1.22 8.0 0.83

0.58 7.0 1.20 6.3 0.83

0.41 7.7 0.99 7.2 0.78

0.95 9.0 1.28 8.3 0.91

0.82 7.6 1.44 6.8 0.87

0.54 7.3 1.35 6.5 0.75

0.72 10.5 1.28 9.8 0.90

0.62 I I 1.25 I I 0.84 I

, ..: .. .... • 1 Standard Dellla1lon 1 Standar.:i Devle.llon Numbera Intlide srflph blllO Indlcah pi_that hM % air 'IOIde In tha.t IlII1g •.

1 ,. 1 ,. 1 ,.

20 V "_nIS_ - 7.6%

rs " • 8 7 •

21$ 24'" r,; ~ l' 1 10 a , , , , , , , , , , , , : o~ 5..9 6.3 6.7 1.1 1.5 1.9 8.3 8.7 9.1 9.5 9.9 19,5 10.7 11.1

~1 6..1 (1.$ 6.. 1.:3: 7.1 8.1 .IU U .. 3 9.1 10.110.$ 10.9

Percent Air Vol.

50-mm French

Without Corners

Avg. S.D.

7.0 0.39

5.4 0.58

6.3 0.58

7.3 0.67

11.3 0.42

6.0 0.79

8.8 0.72

I 0.59 I

Figure 11. Typical Distribution of Air Voids in a 100-iTlm Thick French Compacted Sample

for Site 1.

17

In France, the distribution of air voids is checked on each sample with a nuclear device. The air

voids are measured at 72 pOints on the sample, 24 points each on the top, middle, and bottom

layers. The standard deviation achieved for a 100-mm thick French compacted sample is

typically about 2.0 which is higher than any of the laboratory compacted samples in this study.

Thus, the samples in this study are well within the standard deviations obtained by the French.

Also, the percent air voids from top to bottom increased 2% in France's sample. As can be seen

in Table 3, the 100-mm thick French compacted samples had 2% higher air voids in the bottom

half for most sites.

Although there is a fairly uniform distribution in the 50-mm thick French compacted samples, the

variability of the distribution of air voids (S.D. of 0.69) is about 1.5 times that of the field

compacted samples (S.D. of 0.41) . The difference in variability is likely due to the corners and

edge pieces of the French compacted samples. The variability in the 100-mm thick French

compacted samples (S.D. of 1.42) is about 3 times that of the field samples. This can be

attributed to the high variability in the bottom . half and corners and edges of the top half as

discussed earlier. If the French compactor is used to simulate field compaction, it is

recommended that either 1) the 50-mm thick molds be used to compact the samples, or 2) 100-

mm thick samples should be compacted In 2 lifts.

4.1.3 Linear Kneading Compactor

As shown in Table 2, the variability of the distribution of air voids in the 40-mm thick linear

kneading compacted samples (S.D. of 1.31) is approximately 3 times that of the field compacted

samples (S.D. of 0.41). With the linear kneading compactor, it is very important to get the loose

mix level in the mold before compacting. Also, extra material is needed in the corners, since they

tend to have a higher percentage of air voids. Great care was taken to follow these procedures

when compacting the samples for this test.

When the distribution was analyzed, no trend developed as to the cause. The poor distribution

was likely caused by not leveling the loose mix in the mold before compacting which is related

to operator experience. It was noticed that most of the deviation was from the middle-edge

pieces (pieces 4, 6, 7, and 9) of the sample. This was possibly caused by the scraping of

material from this area to the corners for extra material. It is recommended that extra material

18

be moved to the corners before leveling of the rest of the material to more evenly distribute the

air voids. Also, the development of some type of device to help level the loose material instead

of relying on the operators experience might prove to be beneficial.

As seen in Table 2, the variability of air voids in the 40-mm thick linear kneading compacted

samples (S.D. of 1.31) is about the same as that of the 100-mm thick French compacted samples

(S.D. of 1.42). This, once again, can be attributed to how level the material was before the

samples were compacted in the linear kneading compactor. Since the Hamburg wheel-tracking

device only passes over the center of the sample where the air void distribution is uniform, results

from testing will not be affected by the air voids in the corners or edges. It should be noted that

it is much easier to achieve the targeted air void content for the sample with the linear kneading

compactor than the French compactor.

19

4.2 French Rutting Tester

The French rutting tester is used to evaluate resistance to permanent deformation. The purpose

of this study is to compare results obtained on the French rutting tester from laboratory

compacted samples to those obtained from field compacted samples.

Loose mix was taken at the paver from each site. It was stored in closed containers in the

laboratory until time for compacting.

Before the loose mix could be compacted, it needed to be brought to the proper compaction

temperature. This compaction temperature varied with the grade of asphalt cement being used

at each site. The loose mix was placed in the oven in open containers for about 4 hours. The

use of open containers caused additional aging.

The loose mix was then ready to be compacted in the laboratory. For each site, a 50-mm thick

sample and a 1 OO-mm thick sample were compacted on the French compactor. Also, a 100-mm

thick sample was compacted on the linear kneading compactor. The air voids for samples tested

in the French rutting tester are summarized in Appendix B.

For the field compacted samples, a full-depth slab was sawn at each site. These full-depth slabs

were approximately 150-mm (6-in.) by 475-mm (19-in.) in size. Only the lift being placed when

the loose mix was taken in the field was to be tested. All other lifts were sawn from the samples

and discarded. All field compacted samples were plastered into a 50-mm thick mold.

4.2. 1 Comparison of Laboratory Compactors.

The samples were placed in the French rutting tester and loaded for 30,000 cycles. Plots of the

results are shown in Appendix C. A rutting percentage of greater than 10% of the total thickness

of the sample after 30,000 cycles was considered to be a failure. The actual rut depth (R.D.) in

millimeter and the rut depth expressed as a percentage of the sample thickness (%) are reported

in Table 4.

20

Table 4. The Rut Depths and Percent Rutting from Samples Tested in the French Rutting

Tester.

I

Compactor (Sample Thickness) Site

French (50-mm) French (100-mm) Knead. (100-mm)

R.D. % R.D. % R.D. %

1 9.96' 19.15 7.08 7.12 7.70 7.70

2 2.50 5.05 5.94 5.91 6.61 6.54

3" 3.20 6.70 3.75 3.75 4.00 4.00

4 3.28 6.52 4.51 4.56 4.04 4.01

5 7:77 16.55 8.78 9.73 6.95 6.93

6 1.84 2.74 2.59 2.45 2.30 2.24

7 1.78 3.34 2.22 2.49 2.19 2.18

. Avg. II 4.33 1 8.58 I 4.98 I 5.14 I 4.83 I 4.80 I R. D. - Rut depth in millimeters % - Percent rutting based on initial sample thickness • Test result at 30,000 cycles was extrapolated from 29,000 cycles. *. Test results are at 20,000 cycles.

Field Slab

R.D. %

4.23 8.08

3.61 7.00

19.00 35.70

3.82 7.23

6.07 11.71

0.89 1.76

2.35 4.58

5.71 I 10.87 I

As can be seen in Table 4, the actual rut depths of all the samples were fairly similar. The rut

depths expressed as a percentage of the sample thickness for the 50-mm thick French

compacted samples were 67% higher, on average, of those percentages from the 100-mm thick

compacted samples. This difference in percent rut depth would be expected since the 100.-mm

thick samples are twice the thickness of the 50-mm thick samples.

Table 5 shows that the actual rut depths (R.D.) of the 50-mm thick French compacted samples

averaged 0.49 mm less than those from the 1 OO-mm thick linear kneading compacted samples.

The actual rut depth of the 100-mm thick French compacted samples average 0.15 mm more

than the 1 OO-mm thick linear kneading compacted samples. These difference are very small.

21

Table 5 also shows that the rut depth expressed as a percentage of the sample thickness (%)

for the 50-mm thick French compacted samples averaged 3.94 percent higher than the 100-mm

thick linear kneading compacted samples. The percent rut depth for the 100-mm thick French

compacted samples averaged only 0.34 percent higher than those of the 100-mm thick linear

kneading compacted samples. The large difference between the 50-mm thick samples and the

100-mm thick samples can again be attributed to the 100-mm thick samples being twice the

thickness of the 50-mm thick samples.

Table 5. DIfferences in Rutting Depths Between French and Kneading Compacted

Samples.

Compactor (Sample Thickness) Site

French (50-mm) vs. French (100-mm) vs. Kneading (100-mm) Kneading (100-mm)

R.D. % R.D. %

1 2.26 12.61 -0.62 -0.58

2 -4.11 -1.49 -0.67 -0.63

3 -0.80 2.70 -0.25 -0.25

4 -0.76 2.51 0.47 0.55

5 0.82 9.62 1.83 2.80

6 -0.46 0.50 0.29 0.21

7 -0.41 1.16 0.03 0.31

BE -0.49 3.94 0.15 0.34

S.D. 1.939 5.165 0.855 1.173

R.D. - Rut depth in millimeters % - Percent rutting based on initial sample thickness Negative numbers indicate a rut measurement was higher in the second sample of the comparison.

4.2.2 Comparison of Laboratory Compactors to Field Compaction.

The field compacted sample at Site 3 failed dramatically while the laboratory compacted samples

did not. It is not clear why this happened.

22

Table 6 shows a comparison of the average difference in actual rut depths (A.D.) and percent rut

depths (%) between the laboratory compacted samples and the field compacted samples. The

actual rut depths generated by the 50-mm thick French compacted samples averaged 1.03 mm

more than those of the field compacted samples. The actual rut depth generated by the 100-mm

thick French compacted samples averaged 1.69 mm more than those of the field compacted

samples. The actual rut depth generated by the 100-mm thick linear kneading compacted

samples averaged 1.47 mm more than the field compacted samples. These average differences

are minimal and very similar.

Table 6. Differences in Rutting Depths Between Field and Lab Compacted Samples.

Compactor (Sample Thickness) Site

French (50-mm) French (100-mm) Kneading (100-mm) vs. Field Slab vs. Field Slab vs. Field Slab

A.D. % R.D. % A.D. %

1 5.73 11.07 2.85 -0.96 3.47 -0.38

2 -1.11 -1.95 2.33 -1.09 3.00 -0.46

3' -15.80 -29.00 -15.25 -31.95 -15.00 -31.70

4 -0.54 -0.53 0.69 -2.67 0.22 -3.22

5 1.70 4.84 2.71 -1.98 0.88 -4.78

6 0.95 0.98 1.70 0.69 1.41 0.48

7 -0.57 -1.24 -0.13 -1.68 -0.16 -2.40

EiB 1.03 2.20 1.69 -1.28 1.47 -1.79

S.D. 2.54 4.97 1.19 1.15 1.48 2.01

A.D. - Rut depth in millimeters % - Percent rutting based on initial sample thickness • - Not included in the averages or standard deviations Negative numbers indicate a rut measurement was higher in the second sample of the comparison.

Table 6 shows that the rut depth expressed as a percentage of the sample thickness for the 50-

mm thick French compacted samples averaged 2.20 percent more than those from the field

23

compacted samples. The percent rut depth from the 1 OO-mm thick compacted samples average

1.5 percent less than those from the field compacted samples. The larger differences from the

100-mm thick samples would again be attributed to them being double the original thickness of

the 50-mm thick field compacted samples.

There is very little difference in the actual rut depths from the 50-mm of 100-mm thick samples;

however, the percent rut depths in the 50-mm thick samples are different from those of the 100-

mm thick samples. Instead of using the percent rut depth, it is recommended to use the actual

rut depth for the acceptance criteria.

24

4.3 Hamburg Wheel-Tracking Device

The Hamburg wheel-tracking device is used to determine the moisture susceptibility of HMA. The

purpose of this study was to compare the results obtained from laboratory compacted samples

to those results obtained from field compacted samples.

Loose mix was taken at the paver from each site. It was stored in closed containers in the

laboratory until compaction time.

Before the loose mix could be compacted, it needed to be brought to the proper compaction

temperature. This compaction temperature varied with the grade of asphalt cement being used

at each site. The loose mix was placed in the oven in open containers for about 4 hours. The

use of open containers caused additional aging.

The'loose mix was then ready to be compacted in the laboratory. For each site, two 50-mm thick

samples were compacted on the French compactor. These samples were then cut to the proper

length to fit in the Hamburg wheel-tracking device molds. Two, 40-mm thick samples were

compacted on the linear kneading compactor for each site. The air voids for samples tested in

the Hamburg wheel-tracking device are summarized in Appendix B.

For the field compacted samples, two full-depth slabs were sawn at each site. These field

compacted samples were approximately 250-mm (1 O-in.) square. The material to be tested from

these field compacted samples was limited to the lift being placed when the loose mix was taken

in the field. All other lifts were sawn from the samples and discarded.

An earlier CDOT study (Reference 3) showed that aging affects the results. The difference

between field and laboratory aging might affect the comparison of test results from field and

laboratory compacted samples. Because of this, additional samples from each site were placed

in the oven in closed containers. This minimized the additional aging of the samples. Two 40-

mm thick samples from these closed containers were compacted on the linear kneading

compactor for each site.

25

Each pair of slabs was placed in the Hamburg wheel-tracking device and loaded for 20,000

passes of the wheel or until 20 mm of deformation occurred. Plots of the test results are shown

in Appendix O. For this study, the stripping inflection points were compared. The resulting

stripping inflection pOints for each pair of samples is shown in Table 7.

Table 7. Stripping Inflection Points (Number of Passes).

Compactor (Sample Thickness) Site

French Kneading Field Kneading (40-mm) (50-mm) (40-mm) Slab Closed Container

Aging

1 4600 6900 1000 5000

2 8100 >10,000 3700 9900

3 >10,000 >10,000 4600 7300

4 6900 9500 4300 >10,000

5 >10,000 >10,000 8500 >10,000

6 >10,000 >10,000 >10,000 >10,000

7 >10,000 >10,000 3200 >10,000

In an earlier COOT study (Reference 4), it was found that any sample with a stripping inflection

point greater than 10,000 passes performed well in the field . For this reason, the maximum

stripping inflection pOints recorded in Table 7 was 10,000 passes.

4.3. 1 Comparison of Laboratory Compactors.

As can be seen in Table 7, the stripping inflection points were similar for both the 50-mm thick

French compacted samples and the 40-mm thick linear kneading compacted samples. There

were no stripping inflection points for samples compacted by either method for Sites 3, 5, 6, and

7. For Sites 1,2, and 4, the stripping inflection points from the samples compacted in the linear

kneading compactor were slightly higher than those compacted in the French compactor.

26

Table 8. Differences In Stripping Inflection Points.

Compactor (Sample Thickness) Site

French (50-mm) vs. French (50-mm) vs. Kneading (40-mm) Kneading (40-mm) Field Slab vs. Field Slab

1 -2300 3600 5900

2 -1900 4400 6300

3 0 5400 5400

4 -2600 2600 5200

5 0 1500 1500

6 0 0 0

7 0 6800 6800

EiEji -971

I 3471

I 4443

I 1228 2323 2615 S.D.

Negative numbers indicate a stripping inflection point was higher in the second sample of the comparison.

Table 8 shows the differences in stripping inflection pOints between the various samples, the

average difference, and the standard deviations. For example, the stripping inflection point for

the 50-mm thick French compacted samples from Site 1 (4600 passes) was 2300 passes less

than that of the 40-mm thick linear kneading compacted samples (6900 passes). The stripping

inflection point for the 50-mm thick French compacted samples from Site 4 (6900 passes) was

260D passes less than that of the 40-mm thick linear kneading compacted samples (9500

passes).

OVErall, the stripping inflection points for the 50-mm thick French compacted samples averaged

approximately 1000 passes less than those of the 40-mm thick linear kneading compacted

samples. This indicated that there is lillie influence in the stripping inflection points obtained from

samples compacted in the laboratory by either method.

As discussed in section 4.1, the air void distribution of the 50-mm thick French compacted

samples was more uniform than that of the 40-mm thick linear kneading compacted sample. This

27

would seem to indicate that the results obtained from the 50-mm thick French compacted samples

would differ from those obtained from the 40-mm thick linear kneading compacted samples. The

similarity in the stripping inflection points between the two types of laboratory compacted samples

shows that this difference in air void distribution between the two compactors is not sufficient to

affect the results. Either method of compaction would produce comparable results.

4.3.2 Comparison of Laboratory Compactors to Field Compaction.

Table 7 shows that all field compacted samples did strip and had lower stripping inflection pOints

than any of the laboratory compacted samples. This was likely caused by the laboratory

compacted samples having undergone additional aging.

As seen in Table 8, the stripping inflection points for the 50-mm thick French compacted samples

averaged 3471 passes more than those obtained from the field compacted samples. The

stripping inflection point for the 40-mm thick linear kneading compacted samples averaged 4443

passes (from Table 8) more than those obtained from the field compacted samples. The similarity

in these values would once again Indicate that both laboratory methods of compaction produce

similar results.

4.3.3 Influence of Short-Term Aging

Those laboratory compacted samples brought to compaction temperature in open containers

received additional aging. This additional aging might have caused the samples to perform better

than those aged in closed containers. For this reason, additional 40-mm thick samples from each

sighi were brought to compaction temperature in closed containers to minimize additional aging.

Table 9 shows the difference in stripping inflection points, the average difference, and the

standard deviations when comparing the 40-mm thick linear kneading compacted samples (for

both the samples with additional aging and without additional aging) to the field compacted

samples.

As can be seen in Table 9, the stripping inflection point for the 40-mm thick linear kneading

compacted samples with closed container aging averaged 3843 more than the field compacted

samples. The stripping inflection point for the 40-mm thick linear kneading compacted samples

with open container aging averaged 4443 passes more than the field compacted samples. The

28

stripping inflection pOints for the samples with closed container aging were very close to those

obtained from the samples with open container aging. Either method of heating the samples to

compaction temperature could be used. However, for consistency of results, it is recommended

to heat all field samples to compaction temperature in closed containers.

Table 9. Differences In Stripping Inflection Points Between the Kneading Compacted

Samples (Both with Additional Aging and with No Additional Aging) and Field Compacted

Samples.

Site Compactor (Sample Thickness)

Kneading (40-mm) with Kneading (40-mm) with Open Container Aging Closed Container Aging

vs. Field Slab vs. Field Slab

1 5900 4000

2 6300 6200

3 5400 2700

4 5200 5700

5 1500 1500

6 0 0

7 6800 6800

BE 4443 3843

S.D. 2615 2561

It is extremely interesting that laboratory compacted samples perform better than field compacted

samples. This should be investigated further. A first hypothesis is that the laboratory compacted

samples perform better because of the additional 4 hours of heating (aging) to bring the loose mix

to compaction temperature. A second hypothesis is that the laboratory compacted samples are

compacted at a much higher temperature (150°C or 300°F) than the field compacted samples

(93°C or 200°F) .

29

5.0 Time for Field Compaction

A detailed roller pass study was performed that included temperature measurements is shown

in Appendix A. It was decided to compare the actual time it took the mat to cool In the field to

the time predicted in the literature.

One of the most important phases of constructing a quality H MA pavement is the field compaction

phase. Steel wheel rollers and/or rubber tire rollers are used to reach a percent relative

compaction based on the maximum specific gravity (AASHTO T 209) . While reaching a specified

percent relative compaction is important, It is also important that the pavement Is sufficiently hot

while compacting. If the pavement is at too low of a temperature, no further compaction will occur

and stresses will be placed in the pavement which could potentially cause 1) micro-cracking, 2)

broken aggregate, and/or 3) interconnected air voids. For this reason, a minimum compaction

temperature is usually specified. There are many opinions on what this minimum temperature

should be. The COOT currently specifies that the percent relative compaction will be reached

before the mat surface temperature cools to 85°C (185°F).

It would be beneficial to be able to predict the amount of time it takes a mat to cool to this

minimum temperature. This would allow the contractor to know how much equipment is needed

at the site to be able to reach the specified percent relative compaction before the mat cools.

In the Hot Mix Asphalt Paving Handbook (5), an article by Dickson (6) is referenced. Reference

6 provides several graphs that can be used to predict the time for a mat to cool. These, graphs

are based on factors that can affect the rate of cooling. The factors Include ambient air

temperature, base surface temperature, laydown temperature, mat thickness, wind speed and

solar flux. The purpose of this study is to compare the time it takes the mat to cool in the field

to the times provided by these graphs.

There are a few problems with using the graphs. Accurately estimating the wind speed and solar

flux in the field is difficult. Also, there are an infinite number of combinations of all the factors

which affect the rate of cooling . For this reason, the report (6) only provided a few graphs of

30

some common combinations. The problem is that the actual site conditions seldom matched the

conditions that the graphs were based on. Also, the report did not remark on how much weight

should be given to each factor. This would allow estimating how factors different from the ones

that the graphs were based on would change the results obtained from the graphs.

For this study, a surface and an internal (at approximately the center) temperature of the mat in

the field were taken with every pass of the roller. The time was recorded when the pavement was

initially laid and each time a temperature was measured. From this, the actual time for the mat

to cool to a target- minimum temperature was obtained. Also, all field conditions that the graphs

wer~ based on were recorded. Then these conditions were used along with the graphs to predict

a time to cool.

As mentioned earlier, the field conditions were seldom the same as those conditions provided in

the graphs. For this reason, graphs with conditions similar but not exact to those conditions of

the field were used. In some cases, two graphs were used to get a range of time that the field

conditions fell between.

Table 10 shows the actual times for cooling measured in the field and the predicted times for

cooiing obtained from the graphs. It should be noted that the target minimum temperature for the

graphs represented an average temperature throughout the thickness of the mat. There was no

mention of where a temperature could be taken in the field to represent this. For this reason, a

surface and an internal temperature of the mat were recorded for this study. Later, it was found

that Reference 7 stated that a temperature reading of 85°C (185°F) taken 6 mm to 12 mm below

the surface of the mat would represent an average mat temperature of 79°C (175°F).

As can be seen in Table 10, the actual field time of cooling in each case was greater than that

predicted by the graphs. In most cases it was much greater than that predicted. This is partly

due to the differing conditions between the field and the graphs. As mentioned, these times could

be compared more accurately (see Appendix A for actual differences in conditions and possible

effect-s of the differences). For this reason, it is assumed that the graphs may underestimate the

actual time available for field compaction.

31

Table 10. Actual and Predicted Times Available to Achieve Field Compaction.

Amount of Time for Mat to Cool to Site Minimum Compaction Temperature

Actual Time Actual Time Predicted Time (Mat Surface) (Center of Mat)

1 N/A 50 min. 5-8 min.

2 36 min. N/A 18-20 min.

3 30 min. 30 min. 16-20 min.

4' 40 min. 10 min. 8-9 min.

5 53 min. 53 min. 9 min.

6 70 min. 70 min. 20 min.

7 40 min. 40 min. 20 min.

N/A - not available. • - 32-mm thick overlay.

32

6.0 Conclusions and Recommendations

1) The air void distributions in the field compacted samples were more uniform than those

obtained in the laboratory compacted samples. Generally, the results from the tests were not

influenced by the differences in distribution of air voids.

2) When using the actual rut depth measured in the French rutting tester, there was very little

difference in test results from samples compacted in the various laboratory compactors and field

compacted samples. When the percent rutting was measured, the 50-mm thick samples had

twice as much percent rutting as the 1 OO-mm thick samples. It is recommended that the actual

rut depth be used.

3) When using the Hamburg wheel-tracking device, there was little difference in the stripping

infl6ction point when different laboratory compactors were used. However, field compacted

samples typically had much lower stripping inflection points than the laboratory compacted

samples. This may be because of either 1) differences in the shorl-term aging created when the

loose field samples are heated to compaction temperature in the laboratory, or 2) the higher

compaction temperatures used in the laboratory than in the field.

4) The methods for predicting the available time to achieve field compaction may underestimate

the actual time available. The location the temperature is measured can influence the actual time

that is believed to be available. Therefore, when specifying the minimum temperatiJres to achieve

field compaction, the location the temperature is measured should also be specified.

33

7.0 Future Research

It is extremely interesting that laboratory compacted samples perform better than field compacted

samples in the Hamburg wheel-tracking device. This should be investigated further. A first

hypothesis is that the laboratory compacted samples perform better because of the additional 4

hours of heating (aging) to bring the loose mix to compaction temperature. A second hypothesis

is that the laboratory compacted samples are compacted at a much higher temperature (150°C

or 300°F) than the field compacted samples (93°C or 200°F). Cores from these sites could be

taken when they are one year old to help understand these differences.

8.0 References

1. Report on the 1990 European Asphalt Study Tour (June 1991), American Association of State Highway and Transportation Officials, Washington, D.C., 115+ pages.

2. Hines, Mickey (1991), "The Hamburg Wheel-Tracking Device," Proceedings of the Twenty­Eighth Paving and Transportation Conference, Civil Engineering Department, The University of New Mexico, Albuquerque, New Mexico.

3. Aschenbrener, T, and G. Currier (1993), "Influence of Testing Variables on the Results from the Hamburg Wheel-Tracking Device," Colorado Department of Transportation, CDOT­DTD-R-93-22, 116 pages.

4. Aschenbrener, T., R.L. Terrel , and R.A. Zamora (1994), 'Comparison of the Hamburg Wheel­Tracking Device and the Environmental Conditioning System to Pavements of Known Field Performance," Colorado Department of Transportation, CDOT-DTD-R-94-1.

5. Scherocman, J.A. (1991), "Hot-Mix Asphalt Paving Handbook," AASHTO TRB, U.S. Army Corps of Engineers Publication UN-13 (CEMP-ET), 218 pages.

6. Dickson, P.F. and J.S. Corlew (1970), "Thermal Computations Related to the Study of Pavement Compaction Cessation Requirements," Proceedings, Association of Asphalt Paving Technologists, Vol. 39, pp. 377-403.

7. Principles of Constnuction of Hot-Mix Asphalt Pavements (1983), The Asphalt Institute Manual Series No. 22, Lexington, Kentucky, 291 pages.

34

Appendix A

Detailed Roiler Pass Studies from Each Site

A-l

App~ndj.x A·· Detailed Roller pass Studies from Each Site

Roller Pass <.Stud.yTanles

Note: NP in Number of passes. cdlumn· indicates that no pass was made by a roller at that time, but a mat temperature reading was taken to help monitor loss of heat. A -vib. suffix behind the roller type in the Roller column indicates the steel wheel roller was vibrating.

Site 1 - Fraser

HYPAC

CAT PS-130

HYPAC C766B

.. hr~

Rubber Tire 3044

Steel 8278

93

A-2

3.2

12.1

3.2

B-vib.

B-vib.

I

I

F

F

, AliIfd ... ...... thdi!f ..

15 C

50-mm

15 C

min.

16 C

16 C

5 min.

16 C

16 C

135 C

50-mm

8 min.

Our laydown temperature (127 C) .£alls between the graphs' 121 C and 135 C. with all other condition.s being similar, 'the time for cooling given by the graphs in this Ci;lSewP\1l!ibe~omew.her:e between 5 and 8 minutes. The actual time of 50 minutes shows·the graph being very conservative for this site. . .

Note: No surface temper~tures' ~~re tctkenat site 1 because heat spy gun was not available.

A-3

Roller Pass Study Tables

CAT

C530A

HYPAC C766B .

.... , au.

8618

At- ~;%'" ,. 10. _

cd I- e If : ;1 '& 'I ~

" ~.

~~t •. -,Ai: ;:. ~~9J ' ~. ' ..•• . ~: 29 'O*,$

. ' . " .. .~ ::4(}

'. ' .

1~ 9:41

l., 9:43

l i e f'" 121 9:44

2.i ~ . 9:45 .

.

wf\& 118 9!,4.Q, . ", .'

, ' );l.f llb 118 9:46' ".

Q 111 9:49

,W\, 110' 9:50'

Jj'!&,~ • . 10'4 9:51 .

1t~ 93 9:52 . ' .. t";l} ;'~; 82 19:,56

'.' . ' .. "

" i , . Ii.,.., ~. 77 .' 9 :57 ...

. 6~9 77 9:5,7 .. .

.

Ii"" 76 9:59

&1...Q 75 110':00 .

,~ 72 10':0'1

~~?O' 67 10..'0.7. .

f·~ • . 57 10':.2:). •. " .

,.0'1( 5.4 10,:24 . .. "

,.,$ 52 ' 10':25 ..

5.6

5.6

5.6

~" 'fuJ.m.JiS.

B~Vib.

B-Vib .

B-vib.

I

I

I

I

I

I

I

F-vib.

F-Vib.

F-vib.

F-vib.

F""'vib .

F-vib.

F-vib~

.' F-vib.

F-vib.

F-vib.

Note: No internal' telJlPera~iirel> ware taken' at site 2 because the thermometer malfuntioned. ".

A-4

llC

8

Time

50-rom

13 C

154 C

36 min.

16 C

16 C

149 C

20 min.

10 C

10 C

149 C

50-rom

19

18 min.

For this site,' the gr~phs ,sho,w the. mat cooling to 79 C in 18 to 20 minutes. Our actual time to <CQc}1:. to this temperature was 36 minutes. The wind speed at this site ' was*ess,t):ranhalf of the wind speed the graphs were based on, This.\'i"ould.Sl.lowthe rate of field cooling. Also, this was a night job •. The .. lackofsolarflux would decrease the rate of field cooling. When these differing conditions are taken into account, the graph might be close to the actual time.

A-5

Roller PassSfudy Tables

. ... '. ' . , '. " .

" I~ ;~;i NHidI ,;,. " '\ .:. .:i..'1ffi ~ }i''t@ "l~."" . "'!i!" llllifw .... < . . ~' !t,;

, ~fl" hff. ,. .; ~-.

• i+ 143·' 9; .' : ;13 . ".143.

M tQlf: 131 . 9:18 1'110

0.1 131 '9: I~ ,. '107 B-vib ..

1.0 119' .. . .<1 ,;; , '. .111 ..... ·B vib. tW .. . 116 ' .. '

9:25 .'. 106 .'

!Q>" I '.:1.08 '. 1"9:30 '96' .' 1

1., 91 I> 9:35 I 87 "·-vi h.

,i •.• @ 90 1·!f~3~. '-: .. ' 83" r

; .• .' ·9:3.9 ' .

89 82 . .r

3~. . . 89 '9:39-' . "S2

. .

. I' . '. r· ' .

j..,J . 89 9:40 r

, f!! <l-.. & 89 9:40 r . 4.$ 85 9:41 r

"t $, • . fI'= 85 9:41. .' r

-, J.' 82' .9:~~' . •••••• r ''';:'''''

.•• it 79 9:43 72 r

iff 75 9.:45 71,

~:t \i ill 73 9,50 70

i.~ 66 ',.

9 !;;7 . 66 F-Vib.

1.' . ·9:58 .... .

<63 . F-vib. 66

., .Jt' . 56 . 1Q: 61 . ·h···· I F-Vib. ' ....

ii . • $j>&:~' 52 '10:08 54· ,. F-vib.

Note: No internal temperatures : were taken for passes 3.5 through 5 . 5 at site 3 so that damage to the therinometerprobe could be prevented when roller passed over area.

A-6

. 3

16 C

8

· 50-1lUD

16 C

143 C

min.

30 min.

16 C

16 C

149 C

50-1lUD

20 min.

16 C

16 C

135

50-1lUD

19

16 min.

For this site,. the g:rapJ;l ' ~~OW$ - t!lle.liI~tCbQliJ:)g to 79C in 16 to 20 minutes. Our actual time to · cioer -to this temperature' was 30 minutes. The wind speed at this site· waS · ·les·s than half of the wind speed that the graph was based .. on. . Thi.s:w()~ld slow the rate of field cooling. When this differing condition is taken into account~ the graph might be close to the actual time.

A-7

Tire

Dresser

41

A-8

I

I

I

I

I

I

I

I

I

I

I

·F

F

F

12.1

3.2

~ n&.JJ 11 1_2 M'I

10 C

WiB I 'I'" Ct IIIIU\ hil. 32-mm

2 C

156 C

40 min.

10 min.

-1 C

-1 C

C

8 min.

4 C

4 C

149 C

.· 32-mm

" 19

9 min.

For this site, the graph ; shOw!> · .the : mat . _cooUngto 79 C in 8 to 9 minutes. Our actual time -to,::oool -bFtli,i.6 -.-temperature was 10 minutes. The windspeed at this site: _w~. riruch<lQwe:i:than: :_the graphs' wind speed. This would slaw th~ -ratlii _o'f.A:iel-d cooUng. -- Als_El, the ambient air temperatureatt,his site :wa-s - b.j.s:he!: t-~nthat \.{5jed in _ the gTaphs. This would slow ' the rate : of - fiEd_d --c_oo:U-li<J. -.' -. Our - laydown temperature was higher than the graphs' ; This would allow more time for compaction. When these differing conditionsJ;!,retaken iiltoaccount, the graph might be close to the actual time.- .

A-9

INIII d

Roller Pa§s studY-'l:'a,ples

. C530C

118

102

85

79

71

64

A-IO

4.8

8.0

4.8

B-vib.

B-vib.

B-vib.

I

I

I

I

F

- -:-. .

1'XZUII : : Til •

50-nun

-1 C

68 C

53 min.

53 min.

-1 C

-1 C

65 C

50-nun

9 min . .. -.: . -....

For this site, the graph shows the matc()oling to 79 C in 9 minutes. Our actual time to cool ' ,tethis: temperature was, 53 minutes. , The wind speed at this site was much lciwer ' thanth,e graphs' wind speed. This would slow the rate cif field cooling, <Al;so, -'thj;l ~ient air temperature at this site was _highertMri t::h4tu,sedirL tMgraph. This would also slow _the rate of field cooling. - OutlaydowIi ,b;mperature _was higher than the graphs' ,. " ,,!,,hiswo1;lld' increase the tiJtl9 available for compaction. When tliese differingconctitionlll are takeh irito -account, the graph might be conservative at this : ,site. '

A-ll

, ...... .....

. .. ; .

Roller PassStuaYTaoles

site 6 ....

c766A

C350C

·110 .

104

87

85

A-12

4.0

4.0

4 8·

. I-vib.

I

F

F

F

F

F

, 11 iaa1l

50-rom

16 C

185 C

70 min.

70 min.

16 C

16 C

49 C

50-rom

19

20 min.

For this site, the graph shows the"maf.c~)Qling to 79 C in 20 minutes. Our actual time .to Goolto .thistemperature. was 70 minutes. The wind speed at this site was much lowar than the'graph's wind speed. This would slow the rate of field cooling. Our laydown temperature was much higher than the graph's. This wo'uld increase,' the time available for compaction. When these differing ctmditioilsare taken into account, the graph might be slightly conservativ,e at this site.

A-13

Roller Pass Study Tables

CC42

ii: C530A

DYNAPAC CC42 10886 ..

. . ,

tiG' .. '. 141 - 10: OQ" :L38 - -

' ~ i ~, 103 I . iO;15 .• 103

• l· ~· ·· 9:L ;··10:25,91 •.•..

",, 4~.c'4 .., .....•. ,.. 10:35 , .... ;.. !

.$tfw 69 1();45 ',. .

67 ·10:46

67 10: 46 ,.

64 10 :48: •

, 59 , .

59 11:04 .

59 ...

55 11:05

A-14

4.0

11.3

4 0

B-vib.

·B-Vib.

B-vib.

B:-vib •

.I

I

I

I

I

F·.··

F .

F

'" 23 C

50-mm

27 C

,68 C

40 min.

40 min.

,. , ' . - , ' ,.

_ J<i' " .' ",« ;':7 ,~" '+, '"'' : . I"Il (I rill

.. to • • "' ... " ~, ,-,@ % ':1h 16 C , m: .... "'1! .. ~TII oK -:; "

~ \I • 16 C

, ,loll 'nltIUII _ ,%I 65 C ,

~

,"' !'ij '" IIA1I ~ ..... 50-mm

, 'Iliad ... ."" ,j, ';., :;-, ,,=,, ,"",.' -,~,~,-,,=,

Kph 'I' , ,," *" '1<' "

19

·1flli "tlhd Gmttt't~ , ',', IN ., 'q" Sunny

'",1. "hr .'1 .. CIIIIa4 .l':tra 1t~, d',:, ~ "", 'iii Ill ,", 20 min . , " .". -- ... :

For this site, the graph shows,the-rnatcooling to 79 C in 20 minutes. Our actual time ,to cool to.tl1iostemperatuI:'e,was 40 minutes. The wind speed at this site was lnuc:h ' lc>wer' than the' graphs' wind speed. This would slow the rate offield£ooJ.4nq. ,01i.,J::l.aydowntemperature was much higher thaIithe ,graph i S~ ,This wOuld, lncre'ase the time available for compaction. Also, ourbaseiindCilitPient air t~mperature are much higher than those of,thegraph. Thioswould increase the time available for compaction. When theS,e qifIerj.,llg, CS>Ii,ditio,.qs, aretiiken into account, the graph might be slightly conaerviitive at ,this site.

A-15

Appendix B

Air Voids of Compacted Samples

B-1

Appendix B Air Voids of Compacted Samples

French Rutter % Air Voids Table

" .... ~ §; toapuhft

~ !;!I:r.! " . '7 ,"' !ill

""""',." 'f' rti .,; dill pJ.,eM (SO '1lIIJ) (SOD ,11M) (JiOCh -i ~¥

l., l 8.0% 7.1% 7.7% 7.6% 8.2%

~ 7.0% 6.6% 7.5% 6.6% 8.0%

» 111 7.0% 6.7% 7.0% 7.4% 7.9%

JlW. ' 7.0% 6.4% 7.1% 6.9% 8.5%

"i 10.0% 11.5% 1:):.3% 9.8% 9.3%

" . I .. 4.0% 5 .• 7% .' . 6.2% 5.1% 4.2%

w '1 + 7.0% 9.5% 9.0% 7.6% 10.2% ..

Hamburg % Air Voids Table

htpt .0£ .. M

¥f

8.0% 7.4% 7.8%

.0% 7.3% 6.9% 7.0%

7.0% 7.0% 8.0% 6.4% 6.9%

7.0% 6.7% 8.2% 6.6%

10.0% 11.4% 9.0% 9.7% 9.2%

4.0% 5.2% 4.4% 4.5% 4.2% ., 7.0% 9.4% 9.0% 7.1% 7.2% 10.3% 10.5% 7.5%

B-2

Appendix C

French Rutting Tester Results

C-l

E E.. i= 0-W C

~

E E.. :I: .... IL

~ .... ~ II:

SITE 1, 5O-mm Thick French Sample Actual Rut Depth

1

: : ,

0.1 ! , , ! .. .. ! ,

! i i i i . ! : : 0.01 10

CYCLES

SITE 1, 100-mm Thick French Sample Actual Rut Depth

l00I~~~~~~~~~~~==~~~~~~~~~

10

1

0.1

~111~~11till~~J~~:i}lJ~fl~!~1!~1:~~1!:il~lt:rJI~11~~~~~1~J~~r~~~~[t~:llm~~~~~'~111:f~~~Jl~~11~~ ·······--f-·-/··tttnn··-·--·t···-t·il··j··nn----!···-·f--'-i-ttttf-------)···-ti-tlHi'

0.01 +--+-++i+H+i---,H-i-H+i+i--Hri-++iffi--+-+-+++fi.+j 10 100 1000 10000 100000

CYCLES

C-2

E E. l: .... IL

!!l !5 &I:

E E -t

w C

~

SITE 1, 100-mm Thick Linear Kneading Actual Rut Depth

l 003E~~:~-~~~:~~~!S~i~~~~~~~~~S~~~~f~~~SES~~~!~!~~=f~~~~~,~~~s~~§~,~~:~~~:"E:~~~~I~~~1E~~~:~E~tEi~i~:~~:~":~.~;:~~~!~~~E::~~~~§~~tE'~:~'i:~~!~~f=~=f~t~:~E~E§~~:~fE:::~~~S~~~~E:i~E=~~.~=fE~~~~~i: ·_·_·_ ./_···.)._·+··;··1-.... 4+··_····· ... ·· __ 1-··4·· ... ·.·1· .. '·,····· _ _ 4-_· ... ·_+··1_140+++-_· · __ ·<1-_·_1_·-1··+·.,.·1· .. 1_

10

1

::=:=:E:.~EiltfHI=~~=t:=r::Jffit+t::~:~:I:.~I=tI1J.fiE=~~:E~::r:r.J}!If 0.1 ;::::: ::::j:::::L:1::j;;i:JJi~:::::::::J::;;:j::::I::~:~ :!:j:j.:!::::::::::j::;:: k:::~::j::I:U!~:::::::::~:::::j::::~::~:~:!:j:i:

::~i!~:t.:~:f1~I~m~j~:·~F=r:1~~11:~:r~~:!~l!~!f~-fl:~11~ff.:~~-1~~:1:~n1~1:r 0.Q1 +--+-+-+++-i+fi--+-+-++++iifi--+-+++i++i+--+-++++++H

10 100 1000 10000 100000

10

1

0.1

CYCLES

SITE 1, 50-mm Thick Field Sample Actual Rut Depth

0.Q1 ;i:--+-+-+++-i+i±:--+-+-+i-+f+H--+-++++i-i1M--+-i-++.j..j..j.jj 10 100 1000 10000 100000

CYCLES

C-3

SITE 2, 50-mm Thick French Sample Actual Rut Depth

10

0.1

0.01 +---+-+-+++++-H---+-+-+++++i+--+-+-+++++i+--+-+-++H+H 10 100 1000

CYCLES 10000 100000

SITE 2, 100-mm Thick French Sample

1

0.1

100

Actual Rut Depth

1000 CYCLES

C-4

10000 100000

E !. :r .... ... l!l .... ii!

t w C .... ~

SITE 2, 100-mm Thick Linear Kneading Actual Rut Depth

10

1

0.1

0.01 10 100 1000

CYCLES 10000 100000

SITE 2, 50-mm Thick Field Sample Actual Rut Depth

. !

0.01{[1 0;--+-H-H-t7rl00~-+-+-+-H-~10~OOO+----lH-H1;l;iOO~0-+-+-+~f;l;i;Inyunun CYCLES

C-5

SITE 3, 50-mm Thick French Sample Actual Rut Depth

100====================================~==~

10

E !. :0: l-ll. UJ C I-:::> 0::

0.1

0.0114 0--+--+-++ffi~1 00i--+-+-+-t+++i1 000+----+---+-+++11+

000++-

0-+-+-+-+++

1 oooooi+!

E !. :0: I-Il. IU C I-:::> 0::

CYCLES

SITE 3, 100-mm Thick French Sample Actual Rut Depth

100'~====~~~"-=~================~~====~==== ::::::::::i::::::i::::~::~:~:i:.t.ti::::::::::r::::~:::~::l::i::i:i:i:i::::::::::l::::::i::::r::~:~:i:;.t!:::::::::::i:::::~:::.t::i::i::~:i:i:

10

1

0.1

!!!!!!~!!~hltt!!!!!!!!!!I!!!!lIl!!I!!fJf!!!!!!!:::::!::::::f::::t::umr!!!!!!!!!!I!!!!!!!l!I!!I!!!J!! ::::::::::l::::::j::::!:::;:::;::i:i:~:i:::::::::::t:::::~:::i=::;::;::j:j:j:i::::::::::j::::::;::::;:::;:::;:=i:t=:::;:::::::::::j:::::;:::;::;::;::j:j:j:

:::::::::f:::r:fnn~:::::::::r::~::n:fll:f:::::::::!:::::FI:ffi:m·::::::::l~lllllll ::::::::::l;:::;;I;::;I;;~;;;;:i:*$i::::;:;;:::i::::::~:::*::!::!::!:!:!:!:::::::;:;!;:;;;:I;;;;i:;*;*=j:~~;i:::::::::::i:::::~:::*::!::!::I:!:I: ::::::::::j::::::j::::1:::;::;:j:i=i=j::::,:::::::j::::::;:::i=::j::i::i:i:;:i::::::::::j::::::f::::f:::;::;:j:i=~:j:::::::::::f::::::j:::::j:::!::!::i:j:j: ·,········I······1··,·~,·+,+++·H"·""·",I,,,,,+"'+,+++I,I·I··········,.····,I,,-,I,,+·++++l',·,,·,"'+·,',+·,,+,+++1,1, "·"·····1······1····1··.,.·.,.·1·+<+1·,,,·,,,--,1-,,-,+-,,+,,1·+·1,1,1+,,,·,,,··I······I····I··.,.·.,.·I·.c-<+j·····_,,,,·I,·,,·+,,,+,·1,,1,,1,1,1, .... " .... i ...... i .... i···~··~·l·.&·;·l·"_,·,,··,;·,,·,+·,,.i-"l·-l"f,i,i,f"·"· .... i ...... i .... i ... ~ . .j..i·~·.i-i···,,,,,-,·i",,,+,,,.i-,,i,,i,,i,i,i, .......... i ...... i .... i-,J,J,i,~.~.i""".".,i,.".~ .. ,~ ... i .. i .. i.i.i.i .......... i, .. ,_,i."_i.,J,.L,j,~~j.,,."",,,i,,.,,,~,.,~ ... i .. i .. i.i.i,

"""""i,,,,,,i,,,,i,,J,J,i,~Ji,,,,,,,,,,,i,,,,,J,,,±,,i,,i,,i,i,I,I,,,,,,,,,,I,,,,,,i,,,,i,,J,J,i,&~i,,,,,,,,,,,i,,,,,J,,,±,,i,,I,,I,i,l, ::::::::::j::::::j::::j:::;::j::j:i=:j:i:::::::::::i::::::;::::j:::j::!::i:i:i:i::::::::::j::::::j::::j:::;::j::j:ttj:::::::::::i::::::;::::j:::j::j::1:j:i: ··········I······I····I"·~,·~,I,t-+I-",,,,,··,!·"·'-t·" I·"1·,l"!·!·I·I··········I·····,I"·,I,··~,+,I,I·+I,,,,,,,,·,·!",,,+,,,+,·,··,··t·!'!' ·"·······I······I····I"+·+,I,~,~,I·,,-,,,,··,I·,,·,+·,,<+,,I··1"1,1,1,1·,········I······I_"·I··ojo·+,I++I_,,·,,,,·,,I,,·,,+,·,~·"I"I"I.I,I,

.......... i······i··,·!"+,+,i,~-l-l,,,·,,,,,·,i,,,,·.j.,·,~··,i"i"i,i·f,i"········j···,·,j·"·j·,+,+,l_.i-.i-l",,·,·,,,,i"·".j.",~·"i,,j .. i.i,i,

.......... L-"l"-,i.,J,J,i,Hl,.".,.""i"",.~".L,.l,,l..i.i.i.i .......... l"."-i,."i,.J,J,i,Ul,."",.,.,i.".,J,,.j. .. j..j .. i.i.i.

A 01 +--i'-+' ...;1+1 i1"!HjhjHj--",;'-i'-·~' if...;; ';!';!';!';!--i'e.-+' ",;'",;'"'+1 ~!~! 1e.---+! __ !e.-j.! +! i!~[H!HjH . 10 100 1000

CYCLES

C-6

10000 100000

E !. :J:

t:: IU C I­::l 0::

E !. :J: I-0.. IU C I-::l 0::

SITE 3, 100-mm Thick Linear Kneading

1

1

Actual Rut Depth

SITE 3, SO-mm Thick Field Sample

.. : : "

Actual Rut Depth

1000 CYCLES

C- 7

: :

: !

E !. :J: .... ... w C .... :J I<:

E !. :J: .... ... w C .... :J I<:

SITE 4, 50-mm Thick French Sample Actual Rut Depth

10

.1

0.1

Site 4, 100-mm Thick French Sample Actual Rut Depth

lOO~========================~~~======~

10

1

0.1

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::::::::::l:::::J:::~::I::l:J:~J~::::;::::~:::::I::::l::~:~:l:j:l:l::::::::::I:::::4:::~::I::!:~J~~:::::::::~:::::l::::~::~:~:I:I:I: ··········l·····+···~··l··/·+·t+i··········+·····,····1··-l-·o)·~·t·!·I··········l·····+···~··l··I·t-+t-t-·········t-·····I····/··t-·t-·'·I·'· ::::::::::;:::::::;:::::j:;::j::j:+::;:++:::::::::+:::::;::::i:::;:::;::j:j:;:j::::::::::j::::::;::::+::j::j:+:;:++:::::::::+:::::l::::;:::r-::r-:i:;:;: ::::::::::i:::::t::t::i:ttitt::::::::::t:::::i::::1::i:i:i:i:it:::::::::i:::::i:::t::i::t:titt:::::::::t:::::i::::i::t:t:i:i:i: ··········j·····t···~···H·tHt·········t···+···'·-t-Htj·t··········j·····t···t··l··~·Htl··········t·····I··--j--t-l--j-It

0.01 +--+-i-+++*H---+-+++++H+--+-+++i++f+--+-+++i++H 10 100 1000 10000 100000

CYCLES

SITE 7, 50-mm Thick Field Sample Actual Rut Depth

100~========~======~~~==============~

~.~!l!1~lli'!~111 10

0.1

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::::::::::i:::::i:::t::i::i:tiit:::::::::i::::t:::i::i:i:t:i:i:t::::::::::i:::::i:::t::l::t:titt:::::::::t:::::i::::i::t:t:ti:j: ··········l·····t···t··jtttH········t····!····!··ttttj-t··········j·····t···t··j··t·i"ttt·········~·····l····f·fH-!-j'

0.01 I J I III I I I I III I I I I

10 100 1000 10000 100000 CYCLES

C-15

Appendix D

Hamburg Wheel-Tracking Results

D-l

E !. " .11 " " !! Q. ,I; E ::I E .~

::Ii

E !. " .11 " co !! Q. ,I; E ::I

.Ii ~

::Ii

0

-2

-4

-6

-8

-10

-12

-14

-18

-18

-20 o

0

~ ~

2

-2 1"-----4

-8

-8

-10

-12

-14

-18

-18

-20 o 2

Site 1, 50-mm Thick French Samples Temperatura = 50 C

"\.

\ 1\ '\

\

4 8 8

\ \

10 12

No. of Pa •••• (Thou~.nd.)

14

Site 1, 40-mm Thick Linear Kneading Temperatura = 50 C

--~ ~

4 8

'" '\ \ \

\

8 10 12

No. of Pus.s (Thou •• nd_)

D-2

\ \

14

16 18 20

18 18 20

0

·2 ~

E !. c

.S! .. .. I! a. 1: E :J

.~ " :;

E

·4

·6

·8

·10

·12

·14

·16

·18

·20 o

o

·2

·4

!. ·6 c

.11 .8 .. .. a. ·10 1: E ·12 :J J ·14

·16

·18 .

1\

·20 o

\ \

SITE 1, 40·mm Thick Linear Kneading No AddHional Aging

'::::::

2

~ '\

2

......

'\ \

1\

4 6

4 6

~

8

.

10 12

No.ofP ...... (Thousand.)

Site 1, Field Sample Temperature = 50 C

8 10 12

No. of P ...... (Thou •• nd.)

D-3

14

14

16 18 20

16 18 20

0

·2

·4 ~ I---

E E. c

.11 .. .. ! a. .§ E " E

j

·8

·8

·10

·12

·14

·15

·18

·20 o

0

·2

·4

E E. ·8

c .11 .. ·8 .. I!

·10 a. .§ E ·12 " ·S ·14

::Ii ·18

·18

·20

2

I'-.

0 2

Site 2, 5D-mm Thick French Sample hmparalure = 50 C

---r--. ~ ~

r--,

"" ~ I~

4 8 10 12 14 18

No. of PUBe. (Tbou.anda)

Site 2, 40·mm Thick Linear Kneading Temperalure = 50 C

4 6 B 10 12

No. of Puae. (Thou.ends)

0-4

14 15

"" 18 20

18 20

E E.. c

.11 " " ! D. .§ E ::I E ·x " ~

E E.. c

.S! .. " ! D. .§ E ::I

.~ ~

::!

0

1"--

Site 2, 40·mm Thick linear Kneading No Additional Aging

-2 -----..... --....... -4

-8

-8

-10

-12

-14

-16

-18

-20 o

0

-2 I" -4

-6

-8

-10

-12

-14

-16

-18

-20 o

2 4

...., ~

'\

\

2 4

~

'" \ "J

\

6 8 10 12

No. of PasseB (Thou.and.)

Site 2, Field Sample Temperature = 50 C

\.

\

6

"-'\

8

\ \. q

\ 10 12

No. of Passes (Thouaanda)

D-5

\ \ \ 14

14

16 18 20

16 18 20

Site 3, 50-mm Thick French Sample Temperalure = 50 C .

Site 3, 40-mm Thick Linear Kneading Temperalure = 50 C

4 6 8 10 12

No. of Passes (ThouaandB)

D-6

14 16 18 20

0

~

Site 3, 40-mm Thick Linear Kneading No Additional Aging

-2 -......-..... ~ -4

E E- -6

c .Q .. -8 .. !

-10 Do ..§ E -12 " .§

-14 ; ::;

E E-c

.51 .. .. ! Do

..§ E

" E .~

::I!

-18

-18

-20 o

0

2

-2

-----~ -4

-8

-8

-10

-12

-14

-16

-18

-20 o 2

4

""

4

~ \ \

\

\ \

\ \

8 8 10 12 14

\

No. of Passes (Thou.and.)

Site 3, Field Sample Temperature = 50 C

\ \

\

8

\ \

8 10 12

No. of Paaa •• (Thou.llnd_)

D-7

14

18

16

18 20

18 20

E !. c .g m m ! a. .!ii E ~

E 'x • ::Ii

E

0

~ -2

-4

-8

-8

-10

-12

-14

-18

-18

-20 o

o "--

-2

-4

!. -8 c

.11 -8

~ a. -10 .!ii E -12 ~

E ~ -14

-16

-18

-20 o

2

2

Site 4, 50-mm Thick French Sample Temperature = 45 C

----..... ~ h.

......... I----

4 6 8 10 12

No. of Passes (Thou •• nd.)

14

Site 4, 40-mm Thick Linear Kneading Temperature = 45 C

r-- t----....

18

........ ~

18 20

"'------r----

4 6 8 10 12

No. of P ••••• (Thousands)

D-8

14 18 18 20

E E-c

.11 m • ~ ,I; E ~

~ " :!

E E-c

.11 :I I! '" ,I; E " E .~

::;

0

-2

-4

-8

-8

-10

-12

-14

-16

-18

-20 o

0

'---

-2 1,\

-4

-6

-8

-10

-12

-14

-18

-18

-20 o

""'--

2

2

"-

Slie 4, 4O-mm Thick Linear Kneading No Addhlonal Aging

~ "'-

""" ""-

4

" \ \

\

4

8 10 12

No. of Passes (Thou.anda)

Site 4, Field Sample Temperalure = 45 C

\ \

\

B 10 12

No. of Passes (Thou.and.)

D-9

"'-

14 18

.

14 18

"'-~

18 20

18 20

Site 5, 50-mm Thick French sample Temperature = 35 C

4 8 10 12

No. of PSSSBS

(Thou •• nds)

14

Site 5, 40-mm Thick Linear Kneading Temperature = 35 C

4 6 8 10 12 No. of Puses

(Thou •• nds)

D-IO

14 16

16 18 20

18 20

0

"---2

-4

E ..s -8

c .2 -8 " " G ~

-10 Q.

1: E -12

" .~ -14 " ~ -18

-18

-20 0 2

0

-2 1\

E ..s c .2

! Q.

1: E " .~

:i

-4

-8

-8

-10

-12

-14

-16

-18

-20 o

""-'"

2

"-

Site 5,40-mm Thick Uriear Kneading No Additional Aging

4 8 10 12

No. of Passes (Thou •• nd.)

Site 5, Field Samples Tomporatll18 = 35 C

14

.

I'--...

'"

4

'\ 1\

8

\ \

1\ '\ \

10 12

No. of Pas ••• (Thousands)

D-ll

14

18 18 20

16 18 20

E S c .2 m m I! Il.

E E " .Ii " :!

E S c

.11 " .. I!! Il. E E

" .~ :::Ii

0 "-..

-2

-4

-6

·8

-10

·12

·14

·16

·18

·20 o

0

·2

-4

·6

·8

·10

-12

-14

·16

·18

·20

.

0

2

2

Site 6, 50-mm Thick French Sample Temperature = 40 C

4 8 10 12

No. of Pas.e. (Thou.and.)

14

Site 6, 40-mm Thick Linear Kneading Temperature = 40 C

4 8 8 10 12 14

No. of Paso •• (Thousand_r

D-12

18 18 20

16 18 20

E !. c

.51 • • I! ... E E " E ~ ~

E !. c

.51

i ... E E " .Ii

I

0

·2

·4

·6

-8

-'0 -'2

-'4 -'6 -'8 -20

0

0

-2 1\

-4

-8

-8

-'0 -'2

-'4 -'6 -'8 -20

o

2

"" ---..........

2

Site 6, 40·mm Thick Linear Kneading No Addilioral Aging

4 8 8 '0 12 No. of Passes

(Thou •• nda)

Bite 8, Field Sample T.mperalUre = 40 C

14

~

16

" k

4 8 8 10 12 No. of P ......

(Thou .. nda)

D-13

14 18

18 20

N~

18 20

E E-c .Il .. .. !! Il. .§ E ::I E .~

:::;

E E-c .Il .. .. ! Il. .§ E ::I

.Ii 111 ::;

0

-2

-4

-6

-8

-10

-12

-14

-16

-18

-20 o

0

-2

-4

-8

-8

-10

-12

-14

-16

-18

-20

"---....

I--..

0

2

2

Site 7, 50·mm Thick French Sample Temperature = 50 C

4 6 8 10 12

No. of P .... e. (Thousand_)

14

Site 7, 40·mm Thick Linear Knead Ing Temperature = 50 C

4 8 8 10 12

No. of P ...... (Thousands)

D-14

14

.

16 18 20

16 18 20

0 , ·2

·4

E !. ·8

I: .11 -8 .. .. l ·10 S E :J

.Ii :I :z

E !. I: .11 .. " l S E :J

.Ii

:i

·12

·14

·18

·18

·20 o

0

·2 1\

·4

·8 .. ·10

·12

·14

·18

·18

·20 o

~

2

2

'\ \

4

Site 7, 4o-mm Thick Linear Kneading No Additional Aging

4

\ \ \ \

8

.

10 12

No. of Pu.es. (Thou .. nd.)

Site 7, Field Sample Temperature = 60 C

\ 8 10 12

No. of P ...... (Thou.llndl)

D-15

--~

16

14 18

~ --

18 20

18 20