INVESTIGATION OF AGGREGATE PARTICLES SHAPE ON CHARACTERISTICS OF HOT MIX ASPHALT

Abstract

This research represents a laboratory study of the effect of the aggregate shape in HMA. The shape ofaggregates particles is not the only factor of aggregate characteristics which effect on HMA. OtherParameters such as aggregate gradation and aggregate surface texture are also effect. The aggregateshapes considered for the study were cubical, disk and blade shapes. Two aggregate surface textures usedin the mix which were smooth and rough particles. The aggregate gradations used in the mixtures weremaximum, medium and minimum gradation .Shape of aggregate was determined through two methods.The first method was an image measurement of coarse aggregate while the second method was particleshape index. Marshal tests and indirect tensile test were performed to investigate the different inbehaviors of different samples with different parameters considered in this study taking into account thatthe control mix contains crushed gravel, rough aggregate particles with disk shape, medium gradation ofaggregate and 4% of limestone powder as mineral filler.The results showed that using of cubical aggregate shape increased each of Marshall Stability, bulkdensity, Marshall Stiffness, Marshall Quotient, Stiffness Modulus and the Indirect Tensile Strengthof the mix than disk and blade shapes while decreased each of flow and air voids. The results also,showed that medium gradation of aggregate had good results than other gradations. By using roughparticles the values of ITS and stiffness modulus were higher than using smooth particles