COMPARISION OF THE FATIGUE LIFE OF ASPHALT MIXTURES CONTAINING 60-70 PEN AND 85-100 PEN ASPHALTS CEMENT

Fatigue resistance of asphalt mixture is the ability of the mix to withstand repeated bending without fracture. Fatigue is one of the common forms of distress in asphalt concrete pavement and manifests itself in the form of cracking resulting from repeated traffic loading. In the design of asphalt concrete pavements, it is important to have a measure of fatigue characteristics of specific mixtures over range of traffic and environmental conditions so that fatigue consideration can be incorporated into the designprocess. The fatigue characteristics of asphalt mixtures are usually expressed as relationship between the initial stress or strain and the number of load repetitions tofailure. Several methods have been developed for determining the fatigue life of asphalt mixtures, such as simple flexture, supported flexture, direct tension, indirect tension (diametral), triaxial and wheel-tracking test[1]. In this research the indirect tension test is used. Some of advantages of this test are: the test is simple in nature, the equipment is applicable for other tests (for example resilient modulus and tensile strength) and a biaxial state of stress exists possibly for a type better representing field conditions[1, 2] Fatigue life of an asphalt concrete mixture is influenced by several factors, such as asphalt type, asphalt content and air-void content. Other factors, such as temperature, frequency and rest periods of applied loads, as well as other properties, may also affect fatigue life[3]. In this study the influence of 60-70Pen and 85-100Pen asphalt cement (two types of asphalt cement that are used extensively in road construction in Iran) on fatigue life of asphalt mixture is investigated.