comparison of alternative asphalt concrete rut characterization

BERTHELOT, CROCKFORD & LYTTON 24Table 22 Mean Triaxial Phase Angle and Duncan's Pairwise Comparison at Stress State Three andat 10 Hz Cyclic Frequency of Radisson Specific Pavement Studies -9A Asphalt Concrete MixesGrouped by Test TemperatureSPS-9A TestSectionMean TriaxialPhase Angle(Degrees)Mean TriaxialPhase AngleCoefficient ofVariation(Percent)Duncan's Grouping*900901 16.81 6.20 B900902 14.71 3.89 E900903 15.02 3.45 D E900959 14.06 3.17 F900960 16.05 4.32 C900961 17.76 1.87 A900962 15.39 5.60 DMean 15.69 4.07* Asphalt concrete mixes with same letter are not significantly different.Table 23 Mean Triaxial Phase Angle and Duncan's Pairwise Comparison at Stress State Three andat 10 Hz Cyclic Frequency across Test Temperatures Grouped by Radisson Specific PavementStudies -9A Asphalt Concrete MixTestTemperatureMean TriaxialPhase Angle(Degrees)Mean TriaxialPhase AngleCoefficient ofVariation(Percent)Duncan's Grouping *5°C 7.63 7.16 E20°C 14.73 3.46 D40°C 19.67 4.19 A70°C 18.48 2.35 B100°C 17.93 3.20 CMean 15.69 4.07* Test temperatures with same letter are not significantly different.In the past, triaxial testing of road materials has specified a 2:1 sample height to diameter dimensionalratio. One of the benefits to the rapid triaxial tester employed in this study is that it characterizes 150 mmtall by 150 mm diameter SHRP specified gyratory compacted samples without the need for sampletrimming, gluing end platens to the sample, or attaching membranes to the sample. This greatly decreasessample preparation and testing time. In addition, since end platens do not have to be glued to the samples,spatial stress/strain gradients and end shear effects are reduced. The ability to mechanisticallycharacterize 150 mm diameter by 150 mm tall gyratory compacted samples is beneficial given the roadindustry’s adoption of the SHRP gyratory compactor for laboratory compaction of asphalt concrete. Therapid triaxial tester could therefore, be employed as a complementary mechanistic characterization tool tothe SHRP gyratory compactor for asphalt concrete mix design and analysis such as the Superpave TM LevelI system. The rapid triaxial tester has also been demonstrated in the field for production testingapplications such as construction quality control/quality assurance [28].