Experimental investigation of semi-flexible pavement performance using optimized nano-silica and sugarcane bagasse ash modified grouts

Abstract Semi-flexible pavement (SFP) combines the flexible properties of asphalt with the rigidity of a cementitious slurry, providing improved structural and durability performance. However, the reliance on ordinary Portland cement in SFP contributes notably to global CO₂ emissions. In particular, the sugarcane and ethanol industries generate substantial amounts of sugarcane bagasse ash (SBA), which is often disposed of despite its potential as a pozzolan. Therefore, this study explores the potential use of SBA, along with nano-silica (NS), as a partial cement replacement to develop a more sustainable and higher‑performing grout for SFP applications. Control grouts were formulated with water-to-cement (w/c) ratios ranging from 0.30 to 0.45 and superplasticizer (SP) dosages of 0% to 1.5%, while modified grouts incorporated 0–20% SBA (in 5% increments) and 1% NS. The optimal control grout was achieved at a w/c ratio of 0.35 and 1% SP, satisfying flow criteria and achieving a maximum 28‑day compressive strength of 48.50 MPa. The optimal sustainable grout contained 10% SBA and 1% NS, providing a 21.7% increase in compressive strength compared to the control grout. Microstructural observations confirmed a denser matrix with enhanced C–S–H formation and reduced voids, contributing to improved early strength and superior grout‑asphalt interaction. SFP specimens prepared with the optimized grout were evaluated for Marshall stability, resilient modulus (MR), indirect tensile strength (ITS), tensile strength ratio Hamburg wheel tracking, and fuel resistance. Compared to hot mix asphalt (HMA), SFP exhibited significantly enhanced performance, including approximately 88.5% higher Marshall stability, MR values exceeding 5000 MPa, 70% lower rut depth, 92% moisture‑induced strength retention, less than 5% mass loss, and approximately 93% retained strength under partial and full fuel immersion. These outcomes demonstrate the potential of SBA–NS-based SFP as a sustainable and durable pavement solution suitable for heavy‑duty and fuel‑exposed applications.