Recycled aggregate with GGBS geopolymer concrete behaviour on elevated temperatures

Purpose This study explored the effects of incorporating RA into geopolymer concrete, particularly examining its performance under ambient and elevated temperatures ranging from ambient temperature to 700°C. Design/methodology/approach The current study incorporates RA to replace conventional aggregates in the mix, with replacement levels ranging from 0 to 50%. Each mix designation is identified by a unique ID: RA0, RA10, RA20, RA30, RA40 and RA50, representing the percentage of RA used. The alkaline-to-binder ratio adopted for this study is 0.43. Findings The compressive strength starts at 50.51 MPa for 0% RA and decreases to 39.12 MPa for 50% RA after 28 days. It is highest with 0% RA and diminishes as the RA content increases. All mixes show a slight increase in compressive strength when heated to 100°C. However, the compressive strength starts to decrease for all mixes at 300°C. At 700°C, there is a drastic drop in compressive strength for all mixes, indicating significant structural degradation at this temperature. Originality/value The study evaluates the qualitative impact of RA on the properties of geopolymer concrete when exposed to severe temperatures. The experimental setup included several tests to assess the concrete mixes' mechanical properties and responses. Specifically, the researchers conducted compressive, flexural and split tensile strength tests.