Technical feasibility study of using spent magnesia–chrome refractory bricks in concrete paving blocks

Concrete is a fundamental construction material that poses environmental challenges, particularly concerning aggregate sourcing from natural deposits. Industrial waste materials, such as spent magnesia–chrome refractory bricks (SMCRBs) from metallurgical industries, contain hazardous elements and are often disposed of in landfills, raising environmental concerns. This research investigated the potential of SMCRBs as a partial replacement for natural river sand (NRS) in concrete paving blocks (CPBs). The study evaluated the technical properties of CPBs incorporating SMCRB at various replacement levels (0 %, 15 %, 30 %, 50 %, and 100 % by weight). The technical test results including density, water absorption, compressive and flexural strengths, structural efficiency, porosity, ultrasonic pulse velocity, abrasion resistance, and microstructure indicate that replacing up to 30 % of NRS with SMCRB is viable for producing CPBs suitable for light-traffic pavements. Additionally, the leaching concentrations of chromium and lead in the 30 % SMCRB specimens were significantly below the thresholds established by Indonesian Government Regulation for nonhazardous materials. These findings suggest that incorporating SMCRBs into CPB production not only enhances the technical properties and durability of the blocks but also mitigates environmental impacts by reducing harmful substances in surrounding areas and minimizing pollution of surface and groundwater. • SMCRB use of 30 % feasible for sustainable CPB. • Enhanced CPB properties with 30 % SMCRB. • Cr and Pb significantly below regulatory limits. • Optimal SMCRB replacement identified. • Durability enhanced in light-traffic CPB.