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6 TABLE 3 Summary of mix design results for Superpave mixes Aggregate NMAS, Gradation Optimum Pbe, VMA VFA % Gmm P0.075/Pbe mm Asphalt, % % % % at Nini 9.5 ARZ 6.7 6.2 18.4 76 89.0 0.8 9.5 BRZ 5.3 4.9 15.7 73 86.7 1.0 9.5 TRZ 5.4 5.0 15.6 75 88.9 1.0 19.0 ARZ 4.7 4.3 14.1 72 89.5* 1.2 Granite 19.0 BRZ 4.4 3.9 13.3 68 86.0 1.0 19.0 TRZ 4.0 3.6 12.5* 68 88.8 1.4* 37.5 ARZ 4.2 4.0 13.7 69 89.8* 0.8 37.5 BRZ 3.3 3.0 11.3 64 86.8 1.0 37.5 TRZ 3.6 3.3 12.0 65 88.1 0.9 9.5 ARZ 6.7 6.5 18.3 78* 88.4 0.8 9.5 BRZ 6.2 5.6 16.7 75 86.5 0.8 9.5 TRZ 6.0 5.4 16.3 75 87.7 0.9 19.0 ARZ 4.9 4.4 14.0 72 88.5 1.1 Gravel 19.0 BRZ 4.5 3.9 12.9* 69 86.3 1.3* 19.0 TRZ 4.4 3.8 12.8* 69 88.0 1.3* 37.5 ARZ 4.4 3.9 13.0 70 89.7* 0.8 37.5 BRZ 3.6 3.2 11.7 63 85.5 1.0 37.5 TRZ 3.9 3.5 12.0 66 85.6 0.9 9.5 ARZ 6.0 5.7 17.4 76 87.8 0.7 9.5 BRZ 5.0 4.6 15.3 72* 85.5 0.9 9.5 TRZ 4.4 4.2 14.4 70* 86 1.2 19.0 ARZ 4.1 3.5 12.6* 66 88.3 1.4* Limestone 19.0 BRZ 4.7 4.4 14.3 71 85.5 0.7 19.0 TRZ 3.3 2.8 11.0* 62* 85.7 1.8* 37.5 ARZ 3.2 3.1 11.8 64 88.8 1.0 37.5 BRZ 2.7 2.6 10.6* 60* 86.0 1.2 37.5 TRZ 2.8 2.6 10.6* 61* 87.7 1.1 * Did not meet Superpave Design Requirements the field where the stress is constant and the strain varies. 4.3 EVALUATION OF EFFECT OF t/NMAS ON Hence, the Superpave gyratory compactor likely does not pro- DENSITY USING VIBRATORY COMPACTOR vide a reasonable answer because the compaction provided by this device is different from the field. The big problem with After obtaining the results for the Superpave gyratory com- using this concept to establish a minimum t/NMAS is that pactor, it was concluded that more tests needed to be con- the voids continue to increase significantly as the t/NMAS ducted to better simulate compaction in the field. The air voids increases, making it impossible to select an optimum value. determined from the vacuum seal device were utilized in the The optimum t/NMASs established using the Superpave analysis. To further evaluate the relationship between density gyratory compactor vary from less than 2.5 up to approxi- and lift thickness, a similar study was conducted, but on a mately 8. This wide range of numbers did not allow specific smaller scale, using the vibratory compactor as the compaction criteria to be established. Hence, additional testing was per- mode. This was not part of the original proposed work, but formed using the laboratory vibratory compactor and field it was believed that the vibratory compactor might provide test section. compaction that has more typical of in-place compaction. TABLE 4 Summary of mix design results for SMA mixes Aggregate NMAS, Optimum Pbe, VMA, VFA, VCAmix,a VCAdrc,b mm Asphalt, % % % % % % 9.5 7.2 6.6 18.7 78 30.9 41.9 Granite 12.5 6.6 6.4 18.8 77 30.3 42.7 19.0 6.4 5.9 17.6 77 29.6 42.0 9.5 7.3 6.5 18.6 77 30.4 41.8 Gravel 12.5 6.8 6.1 17.7 77 31.1 42.1 19.0 6.7 6.2 17.8 76 29.3 42.0 9.5 6.2 5.8 17.4 76 30.7 38.4 Limestone 12.5 7.4 7.0 19.6 80 31.1 38.9 19.0 6.0 5.6 16.8c 77 29.8 40.3 a VCA = Voids in Compacted Aggregate b drc = dry-rodded compacted c Did not meet SMA Design Requirements

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7 16.0 14.0 Air Voids, % - Vacuum Seal Method y = 1.0576x + 0.0992 12.0 2 R = 0.9887 10.0 8.0 6.0 4.0 2.0 0.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 Air Voids, % - AASHTO T166 Figure 1. Relationship between air voids for ARZ mixes. The vibratory compactor used compacted beam samples for of the vibratory specimen that could be obtained was 75.0 mm, the wheel-tracking device. which would only be 2.0 t/NMAS. For the SMA mixes, three Of the 36 mix designs analyzed for Part 1, 14 mixes were NMASs were selected (9.5 mm, 12.5 mm, and 19 mm). The selected for further study. Two types of aggregates, granite t/NMAS ratios utilized were 2.0, 3.0, and 4.0. The compactive and limestone were used. For Superpave designed mixes, effort for each t/NMAS was varied over a range including two gradations were utilized (ARZ and BRZ) along with two 30 sec, 60 sec, and 90 sec of compaction. The range of com- NMASs (9.5 mm and 19.0 mm). The 37.5-mm NMAS mix pactive efforts was selected for two reasons: (1) there is no was excluded from the study because the maximum thickness standard compactive effort for the vibratory compactor and 20.0 18.0 Air Voids, % - Vacuum Seal Method 16.0 y = 1.1074x + 0.3893 2 R = 0.978 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 Air Voids, % - AASHTO T166 Figure 2. Relationship between air voids for TRZ mixes.

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8 20.0 18.0 Air Voids, % - Vacuum Seal Method 16.0 y = 1.201x + 0.4379 2 14.0 R = 0.9264 12.0 10.0 8.0 6.0 4.0 2.0 0.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 Air Voids, % - AASHTO T166 Figure 3. Relationship between air voids for BRZ Mixes. (2) the effects of compactive effort on density at different ferent t/NMAS values. However, in a few cases there was a thicknesses could be evaluated. After compaction, the bulk difference. Also, in many cases the best t/NMAS was 2.0, specific gravity was measured and the data were analyzed to which is significantly lower than that observed on field proj- provide recommendations concerning the minimum t/NMAS. ects. Typically, it was assumed that coarse graded mixes To determine the minimum t/NMAS, relationships between would have a desired t/NMAS greater than fine-graded average air voids for the two types of aggregates and t/NMAS mixes. The results did not always follow that trend. It was were plotted for each NMAS, compaction time, and grada- judged that some fieldwork was necessary to validate the tion, as shown in Figures 11 through 17. In many cases there results with the Superpave gyratory compactor and with the was very little difference between the densities for the dif- vibratory compactor. 22.0 20.0 18.0 Air Voids, % - Vacuum Seal Method y = 1.6583x - 0.9272 16.0 2 R = 0.7185 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Air Voids, % - AASHTO T166 Figure 4. Relationship between air voids for SMA mixes.

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9 18.0 TRZ ARZ 16.0 BRZ y = 32.71x -0.9062 y = 31.16x -0.8913 R 2 = 0.9998 BRZ 14.0 R2 = 0.9807 Average Air Voids, % TRZ 12.0 10.0 8.0 6.0 ARZ 4.0 y = 22.729x -0.8484 R 2 = 0.9771 2.0 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 t/NMAS Figure 5. Relationships between air voids and t/NMAS for 9.5-mm Superpave mixes. 12.0 ARZ TRZ y = 24.593x -1.2151 BRZ y = 17.879x -1.0631 -1.187 10.0 2 R = 0.9772 R 2 = 0.9963 y = 26.047x 2 R = 0.9954 Average Air Voids, % 8.0 6.0 ARZ BRZ 4.0 TRZ 2.0 0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 t/NMAS Figure 6. Relationships between air voids and t/NMAS for 19.0-mm Superpave mixes. 9.0 TRZ BRZ -0.7561 -0.841 8.0 y = 10.185x y = 14.404x 2 2 R = 0.9053 R = 0.9874 7.0 Average Air Voids, % 6.0 ARZ 5.0 BRZ 4.0 TRZ 3.0 ARZ -0.2991 y = 6.2838x 2 2.0 R = 0.8546 1.0 0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 t/NMAS Figure 7. Relationships between air voids and t/NMAS for 37.5-mm Superpave mixes.