Geopolymer-Concrete-Based Eco-Friendly and Fire-Resistant Concrete Structures: Effect of Exposure to High Temperature at Varying Heating Duration

Abstract

There are concerns towards the vulnerability of geopolymer concrete towards fire. High-temperature conditions instigate physical alterations and chemical reactions in concrete, which progressively breaks down the gel structure of cement. Consequently, the breakdown leads to an increase in tendency of drying shrinkage, changes to colors of aggregates and losses in load-bearing capacity and durability. In the present study, geopolymer concrete samples were exposed to fire at 1000°C at varying heating duration to investigate the effects on mass loss, residual strength and its microstructure properties. Samples with three grades of strength, GEO20, GEO40 and GEO60, were prepared. Six heating durations ranging from 30 to 180 minutes were adopted. Overall, mass losses were less than 3%, ranging from 1.65% as obtained by the low-strength concrete to 2.93% as obtained by the high-strength concrete. For the most part, as heating duration increased, residual strengths decreased, except for when residual strengths of low and medium-strength concrete initially increased at the heating duration of 30–60 minutes, where the exposure to fire facilitated geopolymerization. Analysis of the microstructure reveals that structural integrity of the matrix at high-temperature conditions is adequate. The study investigated the geopolymer concrete is able to resist the exposure to fire and must be seriously considered as an alternative to ordinary-Portland-cement-based concrete for the future of sustainable construction.