Valorisation of platinum slag aggregate as sand replacement in water-cured one-part geopolymer concrete: Mechanical and durability performance

Using waste materials in concrete production is a sustainable approach to mitigate carbon emissions, reduce waste and environmental pollution, lower costs, and conserve natural resources. Hence, this study investigates one-part geopolymer concrete (OGPC) produced with ground granulated Corex slag and metakaolin as binders, and platinum slag aggregate (PSA) as a replacement for natural sand up to 100 % in 25 % increments. The workability, density, mechanical properties (elastic modulus, compressive, flexural, and splitting tensile strengths), durability, and microstructure of the mixes were evaluated. Results show that 100 % PSA increased workability and density (28-day) by 23.8 % and 2.7 %, respectively. Compressive strength improved by 4.7 % at 50 % PSA but decreased by 8.5 % at 75 % and 100 % PSA (28 days). Flexural and splitting tensile strengths at 25–50 % PSA were comparable to the control, with minimal reductions at higher contents. Additionally, 25 % PSA enhanced the elastic modulus. However, increasing PSA content significantly increased water absorption, porosity, and sorptivity due to microcracks and a weak interfacial transition zone, as revealed by SEM analysis, due to the glossy surface of the PSA. Conclusively, this study demonstrates that PSA can be used as a sustainable partial replacement for natural sand in OGPC, particularly at a 25–50 % replacement level. This offers a cost-effective, environmentally friendly solution for the construction industry, while promoting waste reuse and reducing dependence on natural resources. • Impact of waste platinum slag aggregate on mechanical and durability properties of geopolymer concrete is investigated. • Adding platinum slag aggregate increases the workability and the hardened density of the concrete. • Compressive strength of 29.4 MPa was obtained for the control, while 25 % platinum slag yielded comparable control strength. • Flexural and splitting tensile strength results also follow the compressive strength trend. • The durability properties reduce with an increase in platinum slag aggregate content.