High-temperature behaviour and strength modelling of GGBS–Dolomite and GGBS–fly ash–dolomite rubberised geopolymer concretes

GGBS–Dolomite rubberised geopolymer concrete (GDR-GPC), an innovative eco-friendly material, exhibiting excellent mechanical performance at ambient temperatures; however, its behaviour under elevated temperatures remains uncertain. Previous studies on GDR-GPC demonstrated that the optimum energy absorption capacity under impact loading occurs with 10–20 % crumb rubber (CR) content. Another investigation revealed that while GDR-GPC performs well mechanically, its high-temperature resistance is limited. To address this limitation, fly ash was incorporated into the mix to form a new geopolymer concrete (GPC), GGBS–fly ash–dolomite rubberised geopolymer concrete (GFDR-GPC), exhibiting improved thermal stability. In this study, a further enhancement was achieved by developing GFDR-GPC to determine the optimal CR content for high-temperature performance. Comparative analyses between GDR-GPC and GFDR-GPC were conducted based on mass loss, compressive strength (CS), splitting tensile strength (SS), ultrasonic pulse velocity (UPV). The main test variables were temperature (26°C–700°C) and CR content (0 %, 5 %, 10 %, and 20 %). Results showed that GFDR-GPC experienced low strength degradation than GDR-GPC at elevated temperatures. The strength retention rate of GFDR-GPC after exposure to 700°C ranged from 0.340 to 0.211, while tensile strength retention ranged from 0.148 to 0.08. To evaluate the influence of CR on the microstructure, SEM-EDS, TGA, FTIR, and TEM analyses were performed on the control (GDR-GPC0) and rubberised (GDR-GPC20) samples. The findings contribute to understanding the thermal behaviour of rubberized geopolymer concretes and introduce reliable empirical models to predict their strength performance under elevated temperatures.