Fracture toughness of Gilsonite modified HMA mixtures under mixed mode I/II loading at different temperature conditions

Abstract

This study examines the fracture toughness of Gilosonite modified hot mix asphalt (HMA) mixtures. Pure mode I (i.e., Me = 1), two mixed I/II modes (i.e., Me = 0.79 and Me = 0.30), and pure mode II (i.e., Me = 0) by using semi-circular bend (SCB) at the temperatures of −18 °C, 0 °C and 25 °C are selected to perform the tests. Also, three different dosages of Gilsonite (i.e., 6 %, 12 %, and 18 % by weight of bitumen) are used to prepare HMA mixtures. The findings of this investigation demonstrate that the fracture toughness values of HMA mixtures increase with decreases in the temperature from 25 °C to −18 °C. Also, Gilsonite has a different and opposite influence on fracture toughness at different test temperatures. At the temperature of −18 °C, the incorporation of Gilsonite in HMA mixtures has a negative influence on the fracture toughness. Moreover, at this temperature, the fracture toughness decrease with increased Gilsonite dosages in HMA mixtures. Similarly to −18 °C, Gilsonite negatively affects fracture toughness at 0 °C, but less so than at −18 °C. On the opposite side, at the temperature of 25 °C, Gilsonite considerably improves the fracture toughness. which, in all loading modes adding Gilsonite increases the fracture toughness significantly. Maximum improvement at the temperature of 25 °C on the fracture toughness was 93 % and obtained in pure mode II when the Gilsonite dosage in the mixture was 12 %.