comparison of alternative asphalt concrete rut characterization

BERTHELOT, CROCKFORD & LYTTON 13Table 12 Total SHRP Simple Shear Strain Measurements and Duncan’s Pairwise Comparison ofTest Temperatures-Stress States Grouped by Radisson Specific Pavement Studies -9A AsphaltConcrete MixTestTemperature(Simple ShearTraction)Mean TotalSHRP SimpleShear Strain(mm/mm)Mean TotalSimple SHRPShear StrainCoefficient ofVariation(Percent)Duncan's Grouping*4°C (345 kPa) 0.004491 18.50 A20°C (105 Pa) 0.006959 29.68 B40°C (35 kPa) 0.008251 30.73 CMean 0.006567 26.30* Test temperatures-stress states with same letter are not significantly different.4.4.4 SHRP Frequency Sweep Shear at Constant Height CharacterizationThe SHRP frequency sweep shear at constant height test employs the SHRP shear tester to evaluate thecomplex shear behavior of asphalt concrete. SHRP frequency sweep shear testing was performed ontriplicate gyratory compacted samples at seven percent air voids from each Radisson SPS-9A asphaltconcrete mix at 4°C, 20°C, and 40°C, respectively. Since the Radisson SPS-9A test site is located onHighway 16 where the design traffic loading is a truck tire traveling at a posted speed limit of 100kilometers per hour, detailed analysis of the SHRP frequency sweep shear data was restricted to 10 Hzcyclic frequency. Tables 13 and 14 summarize the complex SHRP shear modulus measurements at 10Hz cyclic frequency across the Radisson SPS-9A asphalt concrete mixes and test temperaturesrespectively.A statistical analysis was performed at a 95 percent confidence level to evaluate the significance of thecomplex SHRP shear modulus measurements at 10 Hz cyclic frequency across the Radisson SPS-9Aasphalt concrete mixes and test temperatures employed in the analysis. A two-way analysis of varianceconcluded that Radisson SPS-9A asphalt concrete mix type and test temperature had a significant effecton the mean complex SHRP shear modulus at 10 Hz cyclic frequency. However, the interaction effectsbetween Radisson SPS-9A asphalt concrete mix type and test temperature was found not to have asignificant effect on the SHRP complex shear modulus measurements at 10 Hz cyclic frequency.Duncan's pairwise comparison of the mean complex SHRP shear modulus measurements at 10 Hz cyclicfrequency of the Radisson SPS-9A asphalt concrete mixes grouped by test temperature determined that:mix 900902 was significantly different from all other mixes; however, mixes 900901, 900903, 900959,900960, 900961, and 900962 were not significantly different. Duncan's pairwise comparison of the meancomplex SHRP shear modulus at 10 Hz cyclic frequency across the test temperatures grouped byRadisson SPS-9A asphalt concrete mix determined that significant difference existed between the meancomplex SHRP shear modulus measurements at 4°C, 20°C, and 40°C.