Performance Evaluation of Hot Mix Asphalt using Wheat Straw Ash as Bitumen Modifier

Abstract

In this research, the possibility of using Wheat Straw Ash (WSA) as an additive in Hot Mix Asphalt (HMA) was investigated. HMA is widely used as paving material and is subjected to different distresses due to environmental changes, temperature, traffic and increasing axle loads. To counter these permanent distresses, WSA was used as bitumen modifier in HMA. WSA contains 73% of SiO₂, which shows pozzolanic properties and increases the adhesion at the interface of Aggregate-Asphalt. The effect of various proportions of WSA by weight of binder on the performance based properties of binder HMA were investigated. Bitumen of PARCO refinery having penetration grade of 60/70 and aggregate of margalla quarry having maximum nominal size of 19mm (NHA-B Gradation) was used. Optimum percentage of WSA was determined from the conventional testing (Penetration, Softening point, Ductility and Viscosity) of bitumen that is 6%. The unmodified samples (containing 0% WSA) and modified samples containing 6% WSA were evaluated using Dynamic Shear Rheometer (DSR) to determine the performance Grade of bitumen. The results of DSR indicated the improvement in the Performance Grade of modified Bitumen. Marshall Mix Design method was adopted for preparation of unmodified (controlled with 0% WSA) and modified (controlled with 6% WSA) samples. These samples were then evaluated for HMA performance testing including Fatigue Failure and Moisture damage using UTM-25. The results showed significant increase against fatigue failure using 6% WSA by weight of bitumen as modifier but no effect was seen on the moisture damage. Thus based on research findings, mixtures prepared with WSA lead to better fatigue resistance and encourages the use of WSA in Asphalt modification through sustainable technology in an environment friendly way. Keywords: Wheat Straw Ash, Bitumen, Hot Mix Asphalt, Fatigue ix LIST OF ABBREVIATIONS AASHTO - American Association of State Highway & Transportation Official ASTM - American Standard Test Method CPEC - China Pakistan Economic Corridor DSR - Dynamic Shear Rheometer Gmb - Bulk Specific Gravity Gmm - Maximum Specific Gravity HMA - Hot Mix Asphalt ITFT - Indirect Tensile Fatigue Test ITS - Indirect Tensile Strength MS-2 - Manual Series (Asphalt Institute) NHA - National Highway Authority OBC - Optimum Binder Content SP-2 - Superpave mix design UTM - Universal Testing Machine Va - Air Voids VFA - Voids Filled with Asphalt VMA - Voids in Mineral Aggregates WS - Wheat Straw WSA - Wheat Straw Ash