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 0C) 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.

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PurposeThis paper presents the details of a research study on developing composite masonry blocks using two types of mixes, conventional and lightweight mix, to enhance their fire/bushfire resistance and residual compressive strength.Design/methodology/approachComposite masonry blocks (390 × 190 × 90 mm) were fabricated using conventional cement–sand mix as the outer layer and lightweight cement–sand–diatomite mix as the inner layer. Material properties were determined, and all the mixes were proportioned by the absolute volume method. After 28 days of curing, density tests, compression tests before and after fire exposure and fire resistance tests of the developed blocks were conducted, and the results were compared with those of conventional cement–sand and cement–sand–diatomite blocks.FindingsDeveloped composite blocks satisfy density and compressive strength requirements for loadbearing lightweight solid masonry units. Fire resistance of the composite block is –/120/120, and no cracks appeared on the ambient side surface of the block after 3 h of fire exposure. Residual strength of the composite block is higher compared to cement–sand and cement–sand–diatomite blocks and satisfies the loadbearing solid masonry unit strength requirements.Practical implicationsComposite block developed in this research can be suggested as a suitable loadbearing lightweight solid masonry block for several applications in buildings in bushfire prone areas.Originality/valueLimited studies are available for composite masonry blocks in relation to their fire resistance and residual strength.

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