Mechanical Properties of Geopolymer Concrete Containing Recycled Rubber as a Partial Replacement of Aggregate

This study explores the mechanical properties of geopolymer concrete incorporating recycled rubber (0-30%) as a partial replacement for natural sand, with varying NaOH molarities (10 M-14 M). The results showed that compressive strength decreased by approximately 47.6%, from 48.5 MPa to 25.4 MPa, as rubber content increased. In contrast, split tensile strength improved by about 41.7% (from 3.67 MPa to 5.2 MPa), and flexural strength increased significantly by 117.6% (from 1.53 MPa to 3.33 MPa) at 30% rubber replacement. The highest overall performance was observed at 14 M NaOH molarity. Scanning Electron Microscopy (SEM) analysis revealed a well-developed microstructure with strong interfacial bonding between rubber particles and the geopolymer matrix, contributing to improved tensile and flexural properties. These findings highlight the potential of utilizing recycled rubber in geopolymer concrete to enhance sustainability in construction practices.