OPTIMIZATION OF AGGREGATE GRADATION BASED ON VOLUMETRIC PARAMETERS OF BITUMINOUS MIXTURES

Abstract

Choice of aggregate gradation, based on criterion of control points, is an empirical process when the asphalt mix design takes place. In this study, a method has been proposed for generation of alternate aggregate gradations based on asphalt film thickness index (FTI). This procedure relies on selecting aggregate gradation considering its closeness to the maximum density line (MDL) and target FTI. Five alternate gradations (A1, A2, A3, A4, and A5) were generated. For mix design, Marshall method is used and the bituminous mixes are prepared. The performance of the mix is assessed with the help of cyclic compression test (for rutting), indirect tensile strength (ITS) test (for moisture damage) and IDEAL-CT (for fatigue) and the comparison is carried out for the given control mixture (A1). It has been found that the asphalt mixtures with alternate aggregate gradations give comparable performance to the control mix. The results provide the requisite details for the proposed method, which can be successfully utilized to generate alternate aggregate gradations for production of asphalt mixtures. This will help in optimal utilization of the available aggregate stockpiles and will remove the conservative dependence on control points.