Influence of flaky aggregate on stone mastic asphalt

Abstract

Stone Matrix Asphalt (SMA) is a gap-graded hot mix asphalt concrete that combines high quality coarse aggregate with a rich proportion of asphalt cement. The aim of this paper is to investigate and evaluate the characteristics of flakiness aggregate shapes towards stone mastic aggregate performance (SMA20). Flakiness aggregates are being avoided in bituminous aggregate because it has a significant influence towards gradation and interlocking characteristic of the aggregate which affect the bituminous concrete mix properties . Due to this significant influence of flakiness, it is recommended that the amount of flakiness should be limited. Therefore, based on the Jabatan Kerja Raya (JKR) and Malaysian Standards (MS), it specified that the maximum allowable flakiness should be less than 25% in asphalt cement mixture. This study will only focus on asphalt mixture that consists of 10%, 20% and 30% flakiness aggregate. The objective of this study is to determine the relationship between flaky aggregate index and the optimum bitumen content and stiffness modulus as well as resilient modulus. Hence, several tests like Marshall Tests, indirect tensile modulus test and dynamic creep test are conducted in order to find this type of relationships. Based on Marshall Tests, the optimum bitumen content obtained for 10%, 20% and, 30% was 6.3%, 6.4% and 6.5% respectively. Total number of 54 sample were prepared for this study The findings of this research are that the value resilient modulus and stiffness modulus decreases as the amount of flaky aggregate increases