Evaluation of brown coal fly ash for stabilising expansive clay subgrade: A sustainable solution for pavement construction

Brown coal fly ash (BCFA) is a lower-quality type of fly ash produced through brown coal combustion, and its disposal in landfills raises environmental concerns. This study, for the first time, evaluates the feasibility of using BCFA for stabilising expansive clay subgrade in pavement construction. Various engineering tests were conducted, including unconfined compressive strength (UCS), repeated load triaxial (RLT), soaked California bearing ratio (CBR), direct shear, and shrink-swell tests. The results indicated that adding BCFA increased UCS, resilient modulus, soaked CBR, and cohesion while reducing shrinkage-swell index and shrinkage/swell strain. The highest resilient modulus (82.52 MPa) and soaked CBR (3.41 %) were achieved with 3 % BCFA content. These findings recommend using 3 % BCFA as the optimum content for stabilising expansive clay subgrade. This research fills a gap by assessing the application of BCFA for stabilising expansive clay soil, providing insights for sustainable utilisation of this abundant waste material in construction.