Mixed Mode I/II Fracture Strength of Modified HMA Concretes Subjected to Different Temperature Conditions

Abstract In this article, the effects of fixed and variable temperature conditions on the fracture toughness of three different hot mix asphalt (HMA) concretes were investigated. The first HMA concrete contained a normal binder, the second one was modified with crumb rubber (CR), and the third mixture was modified with styrene-butadiene-styrene (SBS). The pure mode I, pure mode II, and three different mixed mode I/II fracture toughness values were calculated by performing fracture experiments on the semicircular bend specimens made of the aforementioned HMA concretes. The results displayed that the variable temperature condition reduced fracture strength of the HMA concretes. Moreover, the addition of SBS and CR improved the fracture strength of HMA concretes significantly, such that the CR enhanced the fracture strength between 2 and 22 % depending on the loading mode and environmental conditions. These values were between 6 and 34 % for the HMAs modified by SBS. Therefore, the fracture strength of HMA was more improved by the SBS than the CR. Furthermore, the HMA concretes were subjected to a critical condition under mixed mode I/II loading rather than pure mode I.