Fire performance of sustainable concrete bricks with combustible recycled waste in masonry systems

Purpose Incorporating recycled waste materials, such as eco-aggregates, in sustainable construction practices reduces landfill waste and environmental impact. However, these materials are typically combustible and could pose fire concerns, necessitating research into their fire properties. This study examines the fire safety implications of incorporating crumb rubber (CR) and plastic eco-aggregates (RESIN8) for the production of sustainable concrete bricks (SCB) at replacement ratios of 5%–50%. Design/methodology/approach A series of fire behaviour and resistance tests, including cone calorimeter at various irradiances, elevated temperature material at ambient and post-fire conditions and fire-resistance furnace tests at International Organization for Standardization 834 fire exposure, were conducted. Findings SCBs with 50% CR showed ignition at irradiance levels of 35 kW m−2 and 50 kW m−2, while with 40% CR ignited only at 50 kW m−2. Conversely, RESIN8-incorporated SCB ignited solely at the 50% replacement ratio. No other samples ignited. Post-fire SCBs exhibited strength reductions of up to 75% at high replacement levels. Residual strengths decreased by up to 82% after heating samples to constant temperatures of 200 °C–600 °C. Non-load-bearing masonry walls achieved a 2 h fire-resistance rating, with no cracks or holes formed and effective insulation properties with potential smoke production at medium to higher replacement ratios. Practical implications Incorporating 20%–30% eco-aggregate replacement in SCB can offer an optimal balance of sustainability and minimised fire risk. Originality/value This study provides critical data for performance-based fire design, which has been lacking for sustainable masonry systems based on uniquely quantified ignition properties, fire performance and post-fire structural integrity.