Natural rubber latex and steel fiber modified metakaolin-fly ash geopolymer for sustainable ballistic-resistant construction applications

This study evaluates mechanical performance of metakaolin-fly ash (MK-FA) geopolymers modified with steel fiber and Natural Rubber Latex (NRL) for potential ballistic-resistant construction applications. Geopolymers were prepared with MK:FA ratios from 20:80 to 50:50, and modified with steel fiber and NRL at 1% and 2% by precursor weight and cured at 75 °C for 24–72 h, followed by ambient curing, with mechanical properties evaluated at 7 and 14 days. The MK:FA = 30:70 mix with 1% steel fiber exhibited compressive strengths of 31.82–33.39 MPa at 7 days and 37.38–39.39 MPa at 14 days, which are higher than the thresholds for ballistic-resistant walls with thicknesses of 560 mm and 305 mm, respectively. Overall, the combination of 1% steel fiber and 1% NRL in the MK:FA = 30:70 geopolymer provided the optimum balance between strength, toughness, and microstructural integrity. • Performance of metakaolin–fly ash (MK–FA) geopolymers modified with natural rubber latex (NRL) and steel fibers was investigated. • MK:FA = 30:70 with 1% NRL and 1% steel fiber achieve the highest compressive strength, flexural strength, and modulus of resilience. • Optimized geopolymer mix satisfies compressive strength requirements for ballistic-resistant walls with thicknesses of 560 mm and 305 mm. • Increasing NRL or steel fiber content beyond 1% reduces mechanical performance due to inhibited geopolymerization and fiber agglomeration. • Scanning electron microscopy and X-ray diffraction analyses reveal 1% NRL enhances matrix cohesion, fiber–matrix bonding, and microstructural densification.