Fire behaviour, thermal insulation and acoustic performance of wood-cement boards containing recycled automotive rubber

The growing demand for sustainable construction materials and effective recycling of automotive waste has stimulated the development of innovative composite products. This study investigates the effect of recycled rubber and tire granulates from the automotive industry on the fire behaviour, thermophysical properties, and acoustic performance of wood–cement boards and wood–cement/EPS composite boards. Recycled elastomeric fillers were incorporated at concentrations of 10 wt.% and 20 wt.%, and the resulting composites were evaluated using standardized fire, thermal, and acoustic testing methods. The results showed that the cement matrix retained its dominant fire-protective function despite the presence of recycled fillers. The reference WCB did not ignite at a heat flux of 50 kW·m⁻² and exhibited a pHRR of only 12.07 kW·m⁻². The incorporation of 10 wt.% tire granulate increased pHRR to 79.01 kW·m⁻², while substantially higher values were observed at 20 wt.% (171.73 kW·m⁻²). Thermal conductivity of the modified WCB remained within 0.076–0.086 W·m⁻¹·K⁻¹, indicating only a limited deterioration in thermal insulation performance. In wood–cement/EPS boards, the maximum reduction in normalized thermal resistance was only 3.2%. Acoustically, boards containing 10 wt.% tire granulate retained favourable sound absorption, approaching the reference board at higher frequencies. Overall, the 10 wt.% tire granulate modification provided the most favourable balance between fire behaviour, thermal insulation, acoustic performance, and automotive waste valorization, demonstrating its potential for sustainable building applications.