| Popis: |
As stated in the House Bill 62 Transportation Budget in Brief, roughly 5 billion dollars isspent yearly on road pavement construction in the state of Ohio, with a significant chunkfor maintenance. Moreover, maintenance activities and their associated costs areincreased in the colder regions of the US where damages and distress on roadways areassociated to the Low Temperature Cracking (LTC) phenomena or at least incombination with other distress like rutting and fatigue cracking.Thermally induced internal cracking is a mechanism that occurs under low temperatureconditions. Akentuna et al. (2017) postulated that the differential in Coefficient ofThermal Contraction (CTC) values in asphalt binder and aggregate gives rise to thermallyinduced internal cracking at low temperatures. Owing to its potential significance andeffect on LTC modeling, this study investigated the thermally induced thermal crackingphenomena using the Indirect Tensile (IDT) test. The IDT test was selected since it is thetest procedure used in fracture property investigation in the AASHTOWare PavementMechanistic Empirical (ME) Design program for low temperature cracking modeling. Inaddition, a study on the effect of loading rate and temperature on asphalt mixtures duringthe ITS test was also investigated.Although thermally induced internal cracking was observed by Li et al. (2007) using theacoustic emissions test and Behnia et al. (2014) using the Disc-shaped Compact Test(DCT), its quantified effect has not been studied. The results garnered from this studyvalidated the occurrence of thermally induced internal cracking, evidenced by significantreduction in IDT peak strengths and energy at peak stress to averaged magnitudes of 4%and 12% respectively. The second objective of this study on varying loading rate andtemperature during the IDT strength tests proved that the standard test loading rate of12.5mm/min rate was too fast and not representative of field loading rate. In addition,knowing that LTC could occur even at lower stress compared to the IDT strengths,‘Creep to fail’ tests were performed to analyze the behavior of mixtures in suchcircumstances. Results showed that creep loads at extremely lower percentages of IDTstrengths still fractured asphalt samples with output parameters offering valuableinformation on crack behavior under low temperature conditions. Time to fracture andcrack speed parameters were shown to decrease 62% and increase 46% in thermallyinduced internal cracking samples. |
