13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Effect of Characteristic Specifications on Fracture Toughness of Asphalt Concrete Materials Hamid Behbahani1, MohammadReza. M. Aliha2,*, Hassan. Fazaeli1, Mohammad.H. Rezaeifar1 1 School of Civil Engineering, Iran University of Science and Technology (IUST), Narmak, 16846-13114, Tehran, Iran 2 Welding and Joining Research Center, School of Industrial Engineering, Iran University of Science and Technology (IUST), Narmak, 16846-13114, Tehran, Iran * Corresponding author: mrm_aliha@iust.ac.ir Abstract In this research, the fracture toughness (KIc) of different compositions of asphalt mixtures is investigated experimentally and the effects of asphalt characteristic specifications including the aggregate size, aggregate type (i.e. limestone and siliceous), air void percentage and bitumen type on fracture toughness is studied. Several edge cracked specimens with the shape of semi-circular and subjected to symmetric three point bend loading were manufactured with different compositions and then tested at -15oc. The experimental results showed the noticeable influence of characteristic specifications of asphalt mixtures on the value of fracture toughness. Generally, the value of fracture toughness decreases for those mixtures containing smaller size of aggregates made of siliceous with higher percentages of air voids and softer binder types. Keywords Asphalt mixture, Low temperature, Fracture toughness, Characteristic specifications 1. Introduction Annually huge amount of money is spent for the design, construction and maintenance of asphalt pavements. Many types of cracks (e.g. top-down cracks in the surface of asphalt pavements) initiated due to daily or seasonal cyclic thermal loads or mechanical traffic loading are known as one of the main causes for the overall failure and a common mode of deterioration in asphalt pavement of roads and highways. Consequently, asphalt cracking may increase noticeably the maintenance and rehabilitation cost of pavements and hence the investigation of crack growth behavior in the asphalt pavements and overlays is an important issue for design, construction and maintenance of roads and highways in many countries. Under subzero and very low temperatures, asphalt pavements often behave as a brittle material and, hence, the risk of sudden fracture from pre-existing cracks in the pavement increases. Some experimental studies have been done in the past for investigating the crack growth behavior of asphalt pavements, using different test specimens. From the experimental view point, a suitable test specimen for asphalt mixtures should have simple geometry and loading setup. Accordingly, a few test specimens have been used in the past by researchers to obtain the value of fracture toughness for asphalt materials. The edge cracked rectangular beam subjected to three or four point bending [1, 2], the disc shape compact-tension specimen [3-5] and the semi circular bend (SCB) specimen subjected to three point bend loading [6-9] are some of the most frequently used configurations for fracture toughness testing of asphalt materials. For example, the fracture resistance of various asphalt mixtures has been investigated experimentally using SCB, the edge cracked rectangular beam specimen subjected to four-point loading, and the center crack plate under tension specimens by Molennar and coworkers [10,11]. Chen et al. [12] also employed the SCB specimen to study the effect of temperature on the fracture toughness of asphalt mixtures. Among
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