Investigating the mechanical and microstructure properties of fibre-reinforced lightweight concrete under elevated temperatures

This study investigated the mechanical properties and elevated temperatures of lightweight concrete (LWC) incorporating polypropylene fibre (PPF) and glass fibre (GF). The experimental research used five types of concrete mixtures, which were produced to indicate the effects of PPF and GF. Fibres were added in two ratios (i.e. 0.2 % and 0.4 %) by volume of concrete. A lightweight pumice aggregate was used as a coarse aggregate with a ratio of 65 %. The fresh and hardened LWC properties, such as slump, unit weight, compressive, tensile and flexural strengths, of LWC were analysed. Compressive, flexural strengths and microstructural analysis were investigated under elevated temperatures at ambient temperature, 200 °C, 400 °C and 600 °C for 2 h of exposure time. Flexural and tensile strengths increased by 53 % and 38 % for mixtures containing 0.4 % GF, respectively. Compressive and flexural strengths of the LWC exposed to elevated temperature were improved by adding GF. PPF increased the number of pores of the concrete structure, and elevated temperature resulted in numerous cracks owing to the evaporation of numerous fibres and the replacement of air voids. Consequently, a considerable reduction in compressive and flexural strengths was observed.