Potential of sugarcane bagasse ash for expansive subgrade stabilization for expanding Indian Road networks

The rapid expansion of India’s highway network under the Bharatmala Pariyojana, a national program intended at enhancing highway connectivity and freight efficiency, has increased the demand for durable and eco-friendly subgrade materials, in regions underlain by expansive soils. Traditional stabilizers such as lime and cement, though effective, are associated with high cost and carbon-intensive production. This study investigates sugarcane bagasse ash (SCBA), a waste by-product from sugar mill cogeneration plants, as an alternative stabilizing agent for expansive soils, addressing the limited integration of material characterization, geotechnical performance, and practical feasibility in existing studies. Physicochemical characterization using laser diffraction, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and X-ray fluorescence spectroscopy (XRF) confirmed the pozzolanic nature of SCBA in accordance with ASTM standards. Geotechnical evaluation included Atterberg limits, unconfined compressive strength (UCS), direct shear (DS), California Bearing Ratio (CBR), and swell pressure (SP) tests. Significant improvements were observed, with UCS increasing by 210.7% and SP reducing by 70.99% at an optimum SCBA content of 16%, satisfying IRC: 37 requirements for highway subgrade materials. Sustainability aspects were addressed through industrial waste utilization, reduced dependence on cementitious stabilizers, and a geospatial mapping showing that most national highways (NHs) lie within 100 km of sugar mills, indicating logistical feasibility. The results demonstrate that SCBA is a technically effective and contextually sustainable stabilizer for expansive soil subgrades, aligning with the sustainability and circular economy objectives promoted by the Ministry of Road Transport and Highways (MoRTH).