comparison of alternative asphalt concrete rut characterization

BERTHELOT, CROCKFORD & LYTTON 124.4.3 SHRP Simple Shear at Constant Height CharacterizationThe SHRP simple shear at constant height test employs the SHRP shear tester to characterize the elastic,viscoelastic, and plastic behavior of asphalt concrete mixes under states of mixed mode shear and uniaxialcreep loading. SHRP simple shear at constant height testing was performed on triplicate gyratorycompacted samples at seven percent air voids from each Radisson SPS-9A asphalt concrete mix at testtemperatures of 4°C, 20°C, and 40°C, and corresponding SHRP simple shear tractions of 345 kPa, 105kPa, and 35 kPa, respectively. Tables 11 and 12 summarize the total SHRP simple shear strainmeasurements across the Radisson SPS-9A asphalt concrete mixes and stress states-test temperaturesconsidered in this analysis respectively.A statistical analysis was performed at a 95 percent confidence level to evaluate the significance of thetotal SHRP simple shear strain measurements across the Radisson SPS-9A asphalt concrete mixes andtest temperatures-stress states employed in the analysis. A two-way analysis of variance concluded thatRadisson SPS-9A asphalt concrete mix type, test temperature-stress state, and the interaction effectsbetween Radisson SPS-9A asphalt concrete mix type and test temperature-stress state had a significanteffect on the mean total SHRP simple shear strain measurements. Duncan's pairwise comparison of themean total SHRP simple shear strain across the Radisson SPS-9A asphalt concrete mixes grouped by testtemperature-stress state determined that: mixes 900961 and 900962 were significantly different from allother mixes; however, mixes 900901, 900903, and 900960 were not significantly different; and mixes900901, 900959, 900960, and 900962 were not significantly different. Duncan's pairwise comparisonacross the test temperatures-stress states grouped by Radisson SPS-9A asphalt concrete mix determinedthat significant difference existed between the mean total SHRP simple shear strain measurements at 5°C(345 kPa), 20°C (105 kPa) and 40°C (35 kPa).Table 11 Total SHRP Simple Shear Strain Measurements and Duncan’s Pairwise Comparison(reference) of Radisson Specific Pavement Studies -9A Asphalt Concrete Mixes Grouped by TestTemperature-Stress StateSPS-9A TestSectionMean TotalSHRP SimpleShear Strain(mm/mm)Mean TotalSHRP SimpleShear StrainCoefficient ofVariation(Percent)Duncan's Grouping*900901 0.007145 6.21 B C900902 0.002038 55.49 D900903 0.008073 20.44 B900959 0.005119 31.53 C900960 0.006430 15.87 B C900961 0.011165 22.63 A900962 0.006000 31.96 CMean 0.006567 26.30* Asphalt concrete mixes with same letter are not significantly different.