Experimental study on modeI fracture toughness of different asphalt mixtures

Low temperature cracking is one of the main distresses observed in pavements made of hot mix asphalt mixtures. As a material property, the fracture toughness of asphalt pavements is a fundamental parameter for estimating the load bearing capacity and resistance of cracked pavements against crack growth. In this paper, the fracture toughness (KIc) of different andvarious compositions of asphalt mixtures is obtained experimentally and the effects of asphalt characteristic specifications and its composition are investigated on the value of KIc. Several asphalt mixtures were prepared with three aggregate sizes, two aggregate types (limestone and siliceous), different air void percentages ranging from 3.5 to 8% and two binders (60/70 and 85/100). Other similar works have only studied the influence of limited characteristic parameters on the low temperature fracture resistance of asphalt mixtures. Several semi-circular bend (SCB) specimens subjected to three point bend loading were manufactured with different compositions and then were tested at -15oC. The experimental results showed the noticeable influence of characteristic specifications of asphalt mixtures on the value of KIc. Generally, the value of KIc decreases for those mixtures containing smaller size of aggregates made of siliceous with higher percentages of air voids and softer binder types.