Using two and three-parameter Weibull statistical model for predicting the loading rate effect on low-temperature fracture toughness of asphalt concrete with the ENDB specimen

Abstract

Loading rate can affect significantly the load bearing capacity and cracking resistance of asphalt mixtures that are basically visco-elastic materials. On the other hand, the scatter of mechanical test results obtained from the asphalt mixtures (as multi ingredients and randomly distributed heterogeneous materials) would be high. Therefore, in this research the effect of loading rate on mode I fracture toughness of a fixed hot mix asphalt (HMA) mixture is investigated experimentally using several test replicates and the obtained data are analyzed using two and three parameter Weibull statistical models. The Edge Notch Disc Bend (ENDB) specimen, (that is a circular disc containing an edge crack along the diameter and loaded by three point bending) is utilized for conducting the KIc experiments under three loading rates of 0.5, 5 and 10 mm/min. For each loading rate, twenty five ENDB specimens are tested at a fixed low temperature of −12 °C and the probability of failure and Weibull distribution curves are obtained. It is shown that both two and three parameter Weibull models can be utilized successfully for predicting the mode I fracture behavior of tested asphalt material in the considered range for the loading rate. By increasing the loading rate from 0.5 to 10 mm/min, the mean KIc values and other Weibull parameters are increased. The Weibull distribution parameters obtained experimentally from the loading rates of 5 and 10 mm/min, are also predicted in terms of the Weibull parameters of the ENDB specimen tested at loading rate of 0.5 mm/min considered as a reference case.