Effect of High Temperature on the Microstructure ad Mechanical Properties of Eco-Friendly Hybrid Fibre Reinforced Geopolymer Concrete (HFRGPC): An Experimental and Modelling Study

Abstract

This study aims to investigate the effects of metakaolin (MK) and natural zeolite (NZ) on the properties of a fibre reinforced fly ash-based geopolymer concrete containing 100% recycled coarse aggregate from crushed specimens of laboratory. Polypropylene fibre (PF) with volume fractions of 0, 0.5, 1, and 1.5% and steel fibre with constant volume fraction as reinforcement in geopolymer concrete (HFRGPC) were added into the mixes to improve the overall mechanical properties. In this study, workability, compressive strength, splitting tensile strength and modulus of elasticity tests were conducted to investigate the behaviours of HFRGPC at room temperature. Moreover, the fire resistance of the HFRGPC mixes with optimum value of PF is studied in term of residual compressive strength. The results indicate that the combined effect of the 20% MK substitution and 1% PF inclusion in the HFRGPC mixes exhibited the largest compressive strength (52.7 MPa), modules of elasticity (30.6 GPa), and splitting tensile strength (5.7 MPa). In addition, the HFRGPC containing 20% MK and 1% PF maintained the residual compressive strength of 32.64 MPa at 700 °C, and thus recording a minimum strength loss of 38%. Subsequently, a robust machine learning model is developed to formulate the compressive strengths of HFRGPC under high temperature. Results indicated that the machine learning-based prediction model provide powerful tools to simulate the compressive strength of HFRGPC subjected to different temperatures. The results of ANOVA also show that temperature has a major influence on the compressive strength of HFRGPC, with percent contributions of 71.98% and the lowest contribution related to NZ with 5.52%.