EXPERIMENTAL INVESTIGATION ON SUITABILITY OF SILTY CLAY MATERIAL AS A PARTIAL FILLER REPLACEMENT IN HOT MIX ASPHALT

Abstract

Hot mix asphalt (HMA) is crucial for road construction, requiring high-quality materials to withstand increasing traffic demands. Crushed stone dust is usually the preferred choice for filler material in daily construction activities. However, a challenge arises when trying to find enough filler material near the construction site. Silty clay materials samples were collected manually from borrow quarry site pits using hand tools. Four samples from different locations within a field were composited, mixed, and transported to the laboratory. Then, test specimens were made by varying the weight proportion of Silty clay material filler in the mixture. The optimum bitumen content was identified and various combination attributes were produced in compliance with the Marshal Mix design technique and requirements. Specifically, mixtures were prepared with 10%, 20%, 30%, 40%, 50% and 60% of the total weight of the control mix filler substituted by Silty clay and three Marshall Mix specimens were created. A total of Ninety specimens were prepared to determine the Optimum Bitumen Content (OBC) and the volumetric properties of the Hot Mix Asphalt (HMA). The NAPA (National Asphalt Pavement Association) procedure was used to ascertain the OBC for the mix. Out of the total specimens, ninety were prepared with Silty clay at various replacement percentages and tested. The thesis revealed that Silty clay material can be a suitable substitute for conventional filler materials in Hot Mix Asphalt (HMA). The Marshall Stability results for various percentages of Silty clay showed a consistent increase, rising from 13.2kN to 13.9kN and slightly decreases. This indicates that adding 40% of Silty clay enhances the Stability properties of the asphalt mix. The gradual rise in Stability can be beneficial, as it may improve the mix's workability during application. The study discovered that a 40% substitution of Silty clay achieved optimal Marshall Stability and improved flow characteristics, boosting the overall performance of the asphalt mixture. Furthermore, the research emphasized the cost benefits of utilizing locally sourced Silty clay over traditional fillers, addressing economic issues.