Evaluation the Using of Local Aggregate in High Modulus Asphalt Concrete Layers

Abstract

The performance of Hot Mix Asphalt (HMA) mixtures is greatly affected by the properties of the aggregate characteristics. The aggregate properties that significantly influence the performance of HMA mixtures are gradation, shape (angularity) and texture (roughness) .In 1990, the French Road Administration (LCPC) developed asphalt mixtures with a gradient "BBME", for the purpose of this new mixtures is to get a good resistance to rutting and good fatigue behavior. in Iraq, this type of the mixture is not used yet.The main purpose of this study is to evaluate the performance of asphalt mixtures with "BBME" gradient and compare them with the conventional mixture for binder course. To achieve this aim, one type of asphalt grade (40-50) from  Al-Nasiriyah refinery and two types of  local aggregates were used. First type of Al-nibaie area and the second from an area of ​​Badra and Jassan with two types of texture rounded and fully fracture. Physical tests on asphalt binder and aggregate, indirect tensile strength and wheel truck testing have been made in this work. Three asphalt contents (optimum asphalt content , optimum asphalt content ± 0.5) were used in indirect tensile strength test with one asphalt content (optimum asphalt content) in wheel truck testing under 60^° temperature. The results of experimental work showed that the Marshall stability for BBME mixture were more than that for conventional(SCRB) mixture by 3, 3, 4 percent for al-nibaie half fracture, Badra and Jassan fully fracture and Badra and Jassan fully rounded aggregate mixture, respectively. The Indirect Tensile Strength resistance of the BBME mixes were approximately equal with comparison to the conventional mixes for all aggregate types, and showed that the mixes contain optimum asphalt content have a resistance to indirect tensile strength more than that mixes contain (optimum asphalt content ± 0.5) for BBME and conventional mixtures. As result, the both conventional and BBME mixes were failed at the same number of passing but less at rutting depth for the mixtures with BBME gradation.The mixtures that contain al-nibaie aggregate have an excellent resistance to Indirect Tensile Strength and permanent deformation in comparison with other types of aggregate.Based on AFNOR specification with using K formula and values of rutting percent, it was found that the mixture used in this study, Class III, is the type used in the roads with higher traffic.

Keywords: BBME gradation, Marshall stability, Indirect Tensile Strength, Wheel Truck Testing, Optimum Asphalt Content.