Comparison of Test Results from Laboratory and Field Compacted Samples · Report No. COOT...
Transcript of Comparison of Test Results from Laboratory and Field Compacted Samples · Report No. COOT...
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.
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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.
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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
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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
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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.
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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:
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Figure 1. French Rutting Tester.
Figure 2. Close-up of the French Rutting Tester.
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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.
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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.
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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.
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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.
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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.
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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
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SITE 6, 100-mm Thick French Sample Actual Rut Depth
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C-12
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SITE 7, 50-mm Thick French Sample Actual Rut Depth
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SITE 7, 100-mm Thick French Sample Actual Rut Depth
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C-14
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;;;;;;;,;;I;;:;;~:;;t;;i;;i;1~~:;;;;;:;:;;;;~;;;i;;t;t;!;!;!~;,,;;,;;,I:,,;:f,,;~,;i;;i;~~~t;:::::::~::l;;i;;~;~;r;1;1; . __ ... -- .. I .•••• .j. ••• .j. •• j •• ' •• I.j..H .••.••.•• ·+.-_··!-_··1·_+·++H·I_· __ · ___ ·_I· __ ·_+···.;.··j··,·.c.+oI-+·········f-·····I····I··f-·+·I·/·/· .•••••••.• 1 .•••• .j.·.-+·++++++·········+·····/···+·+·.j.4·/·/·I··········/·····.j.···+··!··I·!·+f-+·········+·····/· ... ~ .. .;.++/./. ··········~·····t···t··i··r·tt·ri··········t·····j····t··t·"!"·t·~·~·t··········~·····"!"···t··i··r-i·tti"·········t·····!····!··'!··t·t·!·j· ·········"j"····t···t-"i"·[·tttt·········t·····j····t··t·t·t·jtt·········"j"····t···i···j··j·tttt·········i······j····t··i··t·t·j·j· ••••••. ··+····.j.···+··/··/·.j.+~+·········+·····I····I··.J.··~·I·/·/·I··········I·····+··-+··/··;++++········+·····/····,··+·.;.·H·/·
::::::::::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
··········t······~···t-··!··I··~+·~~··········~·····I····/··-I"··'·/·I·I·/··········,······'···I···j··I·i·+t-i··········t-·····I····/··+·t-·/·l·l·
::::::::::I:::::!!]J:I:!iff:::::::::!:::::l::I~fJI~j~j~!::::::::::!:::::!::!f!!!!!!!f~r~~~~~~~~~:~::j:::I::f:f:!:I:J: ··········l·····+···t-··!··,·+++t-·········-I"·· ···/··+·-I"·/·'·I·/··········I·····+···~··I··I·t-+t-t-·········t-·····,····/··t-·t-·/·'·I·
!~!!!!~~!!!~~~11IIli!i:!!::::!I:~~!I!!!!!!!!1!!I!I!I!!!!!!!!!!I!!!!!!!lIIfifr:::::::::[::r!!IJll!I!I! ··········I·····+···t-··I··/·+·,-I"+·········-I"·····I····'··-I"·o)·,·,·,·,··········I·····+···t-··I··/·t--I"++·········-1······1····/··'\"·'\"·,·,·,· ::::::::::j::::::;::::+::;::i:+:f++:::::::::+:::::;::::j::+:+:j:j:;:j::::::::::;::::::;::::+::j::j:+=i"++:::::::::~::::::i::::i::+:l::i:j:;:
::::::::::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