Effect of gradation and waste plastic on performance of stone matrix asphalt (SMA)

Abstract

Stone Matrix Asphalt (SMA) is a gap-graded blend which possesses a high deliberation coarse aggregate framework with stone-to-stone contact along with a high binder content which adds flexibility and durability of the mix. The SMA is associate with the drain down of binder during mixing, transporting and laying of the mix. In sequence to prevent this and to improve the mix characteristics, it was proposed to study the properties of SMA by modifying it by adding waste plastics. Hence, stability, flow value, percentage drain down, and rutting characteristics of SMA mixes having different proportions of waste plastic were studied. Initially, it was decided on the basis of highest value of bulk density i.e., Chinese and Indian gradation of aggregates were selected. The Marshall Tests were conducted to find out Optimum Bitumen Content (OBC) with different proportions of bitumen and plastic content. Further, the drain down tests and rutting test using Immersion Wheel Tracking Device were also conducted on the SMA specimens at Optimum Plastic Content (OPC). From Marshall Test, for the SMA of Chinese gradation, OPC was found to be 8.0%, and that for Indian gradation it was 6.0% plastic content, respectively. Addition of waste plastic to the SMA leads to a decrease in the drain down value and satisfies the condition for both the gradations. Also, the rutting intensity was observed to be 42 per-cent greater for Indian gradation, when contrasted to that of Chinese gradation. Overall, Chinese gradation has shown the better results than the Indian gradation. IAEME Publication.