Bushfire Resistance of Lightweight Masonry Blocks Made with Diatomite Aggregate

Abstract

‘Diatomite’ is a naturally occurring soft material that contains fossilized skeletal remains of diatoms. It is lightweight, and the porous structure of the aggregate possesses low thermal conductivity. This study was aimed at developing masonry (i.e., cement) blocks using diatomite aggregate and assessing their suitability for use in bushfire shelters and external walls of buildings in bushfire-prone areas. First, the chemical and physical properties of mix components (i.e., cement, sand, and diatomite aggregate) were determined. Then masonry block cement mixes including a cement-sand (i.e., standard) and three different cement-diatomite (i.e., diatomite) mixes were developed by absolute volume method. The properties of fresh mixes; slump and fresh density and properties of hardened mixes; density, compressive strength, and water absorption were investigated, while bushfire and building fire resistance of developed masonry blocks were examined by exposing them to the standard fire curve for 30 min and three hours, respectively. The obtained results from this experimental study showed that diatomite mixes have a negative correlation between the amount of diatomite aggregate and the density and compressive strength, while a positive correlation for water absorption and bushfire and building fire resistance. All the developed diatomite blocks are ultralightweight, loadbearing, and have three hours of building fire resistance. Further, the obtained results were compared with those of the standard and two other previously developed lightweight masonry blocks/mixes using expanded perlite and pumice aggregates. In comparison to the standard and other diatomite, expanded perlite, and pumice blocks, blocks made with 60% of diatomite aggregate are recommended for use in bushfire shelters and other buildings in bushfire-prone areas.