Influence of protective coating on flexural behaviour of high strength self-compacting geopolymer concrete beams exposed to standard fire temperature

This paper presents an investigation on the effect of protective coatings of high-strength self-compacting geopolymer concrete (HSGC) when subjected to standard fire conditions. The study involved the use of two types of protective coatings, namely ceramic-wool plaster and alumina-bauxite cement plaster, to insulate 42 beams. The findings of this study reveal that employing geopolymer concrete combined with ceramic-wool and alumina-bauxite protective coatings constitutes a significant advancement in fire-resistant construction materials. Specifically, the application of protective coatings to geopolymer concrete beams introduces an additional layer of insulation and fire resistance, resulting in a reduced rate of temperature rise and prevention of spalling and cracking. Both wool-plaster and powder-plaster coating materials exhibit higher heat resistance properties, displaying 2-4 times greater resistance than specimens without protective coatings. The wool-plaster protective coating significantly enhances the residual load-carrying capacity, achieving 97.8% for fly ash (FA)-blended specimens at 821°C, demonstrating 96.6% and 96.26% for FG (fly ash-ground granulated blast furnace slag) and FM (fly ash-metakaolin) specimens, respectively. Similarly, powder-plaster coated FA and FG specimens exhibit 87.5% and 89.4% residual load-carrying capacity at 821°C, while FM-blended mix specimens exhibit 89.6%. In specimens subjected to 1029°C, the residual load-carrying capacity for wool-plaster coated FA, FG, and FM-based specimens was found to be 75.8%, 72.37%, and 69.62%, respectively. Powder-plaster coated specimens exhibited a similar trend with a residual load-carrying capacity of 67.74%, 64.9%, and 66.82% for FA, FG, and FM blends, respectively. Notably, wool-plaster coated specimens proved superior performance compared to powder-plaster coated ones, retaining 75-85% of their strength after 60 minutes of heating exposure. Conversely, powder-plaster coated specimens retained the same percentage of strength after 30 minutes of heating exposure. However, an increase in heating intensity and duration led to a decrease in the strength of the concrete mix.