Modelling Effect of Aggregate Gradation and Bitumen Content on Marshall Properties of Asphalt Concrete

Abstract

Current selection of aggregate gradation fails to explain completely the position of the aggregate gradation on a continuous scale. This study proposes a gradation index (GI) as a new parameter to determine the position ofthe aggregate gradation of the asphalt mixture on the continuous scale. The GI was used to develop a model of the Marshall properties. The aim of this study was todevelopa model between the GI and  bitumen content of the Marshall properties that includes density, voids in the mix (VIM), voids in mineral aggregate (VMA), voids filled with asphalt (VFA), stability, and flow. The materials used were unmodified Asphalt Cement 60/70 with bitumen content variation of 4.5% to 8.0% of the mix and five variations of the aggregate gradation. Curve fitting method is used to find partial correlation factor of the aggregate gradation and the bitumen content of the Marshall properties. Multiple Polynomial Regression (MPR) models were specified to find the relationship between the GI and bitumen content of the Marshall properties. The visualization of the relationship between the GI, bitumen content and Marshall properties used contour charts. The results showed that the MPR determines the model of the relationship between theGI and bitumen content of the density, VIM, VMA, VFA, stability, and flow that have a very strong relationship (R² > 0.9).Therefore, the model can be used to predict the Marshall properties.