Evaluating the mechanical performance of hot asphalt mixtures modified with metakaolin as filler

Abstract

Filler has an essential effect on the behavior of the hot asphalt pavement mixtures (HMA) through reducing the voids in the aggregate skeleton and reducing the temperature susceptibility of the asphalt binder layer. Recently the use of Metakaolin as a Pozzolanic admixture has been investigated to enhance the strength of cement concrete mixture. In this study, an experimental assessment of the mechanical properties of the HMA modified by Metakaolin as partial replacement of cement mineral filler was conducted. Five mixtures containing 0, 25, 50, 75, and 100 Metakaolin replacements percentages of ordinary cement were prepared at their optimum asphalt content. The Marshall properties, temperature susceptibility, and moisture damage are investigated for these mixtures. It was found that the addition of different proportions of Metakaolin filler as replacement of cement has a significant influence on the mechanical behavior of the HMA. The result illustrated that The Marshall's Stability, Flow and, density grow as the Metakaolin content grows until 50%, then the value starts to decrease at 75 and 100%. The air voids and voids in mineral aggregate decrease with increase the Metakaolin content to the lowest value at 50% of Metakaolin. The indirect tensile strength increases continuously as the Metakaolin content increases at 25, 40, and 60 oC, while temperature susceptibility decreases as Metakaolin content increases. The resistance to moisture damage has been improved by adding Metakaolin filler. It is concluded that the hot asphalt mixture can be modified by using Metakaolin as partial replacement mineral filler at 50% and optimum asphalt content of 5.2 %.