Impact of Aggregate Gradation and Type on Hot Mix Asphalt Rutting In Egypt

Rutting of flexible pavement is considered one of the major pavement distresses noted around the world and in Egypt. Many investigators showed at about 55 to 80% of rutting occurred in the surface layer. Rutting of asphalt surface layer may be due to many causes happened during construction phase and service phase. The main objectives of this research are to evaluate the impact of aggregate gradation and type on hot mix asphalt (HMA) rutting potential in Egypt, understand the effect of aggregate properties on Marshall mix properties and evaluate the relation between mix properties and rutting potential of HMA. Experimental program was designed and conducted on common asphalt paving mixtures of different aggregate sources and gradations. Samples prepared at optimum asphalt content, as defined by Marshall method, were tested using wheel track test and permanent deformation was measured. Study results showed that rutting resistance of asphalt paving mixes is affected by the mix gradation and type of aggregate. Coarser gradation (3A) had the highest resistance to rutting for all types of aggregate, while open graded mixes (2C) had the lowest resistance. Dolomite had the highest resistance for all types of gradations. Marshall flow had the highest linear correlation with rutting, with coefficient of determination (R 2 ) of 0.74.