Physical, mechanical, thermal and fire behaviour of recycled aggregate concrete block wall system with rice husk insulation

This study comprehensively investigated the physical, mechanical, thermal, and fire performance of hollow blocks made from recycled aggregate concrete containing rice husk ash as a replacement of Portland cement (hereafter abbreviated as block), as well as the wall system constructed using hollow blocks filled with rice husk insulation. Fire resistance test on hollow/insulated block wall assemblies, compression test on individual hollow blocks before and after fire resistance test, and thermal transmittance coefficient test on hollow/insulated block wall assemblies were conducted. The mechanical properties and fire performance of the block wall system were also compared with the commercial clay brick (hereafter abbreviated as brick) wall system. Additionally, the thermal behaviour of the block wall system insulated with rice husk board was also compared with that of the system insulated with commercial wood fibre board. It was found that the developed hollow block exhibited remarkably higher compressive strength, E-modulus, and strain capacity compared to the commercial hollow brick. The block also showed superior endurance against thermal expansion and maintenance of integrity at elevated temperatures. However, the temperature development on the exterior of hollow block wall was observed to increase more rapidly compared to the hollow brick wall when subjected to elevated temperatures. With the rice husk insulation, the block wall met the criteria for the F 90 classification as per DIN 4102-2, with a temperature increase of 75 ± 2 K after 90 min of testing. The systems constructed with blocks insulated with rice husk or wood fibre exhibit significantly higher thermal transmittance coefficients compared to those built with hollow blocks. However, no significant difference in thermal transmittance coefficient was observed between the system insulated with rice husk and the system insulated wood fibre.