Bushfire-Resistant Lightweight Masonry Blocks with Expanded Perlite Aggregate

During bushfires, one of the building elements that is directly exposed to embers, radiant heat and direct flames is the “wall” element. This study investigated the feasibility of using expanded perlite aggregate in masonry (i.e., cement) blocks to enhance their bushfire resistant characteristics. The chemical, physical, and thermal properties of expanded perlite aggregate were determined first and then masonry block cement mixes were developed by replacing sand in the conventional mix with expanded perlite aggregate by volume at different percentages (100, 80, 60, and 40%). The properties of fresh and hardened cement mixes (slump, density, compressive strength, and water absorption) were measured. The developed masonry blocks were exposed to Bushfire Flame Zone conditions (i.e., 20–842 °C) and the standard fire curve for three hours (i.e., 20–1110 °C) to assess their resistance to bushfires and building fires, respectively. The properties of Cement–Expanded Perlite mixes were compared with those of the standard Cement–Sand mix. The test results showed that the use of perlite aggregate reduced the workability, density, and compressive strength of the cement mix while increasing the water absorption and fire resistance level. All the developed perlite blocks were lightweight and had three hours of fire resistance level (-/180/180). When exposed to bushfire flame zone conditions, the blocks made with 100, 80, and 60% perlite satisfied the maximum ambient surface temperature limit. Of these, masonry blocks made with 60% perlite aggregate are the most suitable for use in external walls of bushfire shelters and residential and commercial buildings in bushfire-prone areas.