Performance of Glass-Based Hot Mix Asphalt Mixtures Produced from Locally Sourced Recycled Crushed Glass

Abstract

This study presents the Marshall Mix Design and comparative performance evaluation of hot mix asphalt (HMA) incorporating recycled crushed glass as a partial fine aggregate replacement at seven levels ranging from 0% (conventional control) to 30% by mass of the fine aggregate fraction. Penetration-grade 60/70 bitumen and locally sourced aggregates conforming to ASTM and BS standards were employed. Marshall Stability, Flow, Bulk Density, Voids in Mix (VIM), and Voids Filled with Bitumen (VFB) were determined at the Optimum Binder Content (OBC) for each mix series. Indirect Tensile Strength (ITS) was estimated using an empirical model derived from Marshall parameters (Hicks, 1991; Kiggundu & Roberts, 1988), and Tensile Strength Ratio (TSR) was predicted from a volumetric relationship with VIM (Lu & Harvey, 2006). It is acknowledged that these are empirical approximations not directly validated for glass-modified mixes, and conclusions regarding tensile strength and moisture susceptibility should be interpreted accordingly. The 5% recycled glass mix yielded the highest Marshall Stability (11.56 kN), best-controlled flow (2.48 mm), highest estimated ITS (1.039 MPa), and highest Multi-Criteria Performance Index (MCPI = 0.960). All mixes maintained estimated TSR values above 80% across TSR model coefficient sensitivity scenarios (k = 2, 3, and 4), confirming adequate moisture resistance across the full 0 to 30% replacement range. The optimal recycled glass content is recommended at 5 to 10% because the best mechanical properties, environmental and economic improvements were recorded at that range of replacement.