Use of creep compliance interconverted from complex modulus for thermal cracking prediction using the M-E pavement design guide

The objective of this study is to evaluate the creep compliance (D(t)) of asphalt concrete (AC) mixtures for thermal cracking prediction of flexible pavements. Various AC overlay design factors influencing the thermal cracking resistance of flexible pavements, such as mixture properties and pavement structure, were included in the evaluation. Two sources of D(t) data were considered: (1) measurement from indirect tensile test and (2) numerical interconversion of complex modulus E*. Design input levels in the mechanistic-empirical design guide software do significantly impact the predicted thermal cracking distresses. For AC maintenance overlay design purposes, level 1 and 2 analyses yield very similar thermal cracking predictions, whereas level 3 analysis significantly underpredicts the extent of cracking when compared with to level 1 analysis. Some discrepancy exists in the thermal cracking predicted from measured and interconverted D(t) due to the inherent approximation nature of numerical interconversion methods. However, level 1 and 2 analyses using interconverted D(t) values provide results closer to the predictions from measured D(t) values than does level 3. Three mixtures are used in this study. The various analyses indicate that using a more ductile AC mixture for the surface layer significantly reduces the amount of thermal cracking at failure.