Residual Properties of Geopolymer Concrete for Post-Fire Evaluation of Structures

The research focuses on effectively utilizing industrial by-products, namely fly ash (FA) and ground granulated blast furnace slag (GGBS), to develop sustainable construction materials that can help reduce carbon emissions in the construction industry. Geopolymer mix design using these by-products is identified as a potential solution. The study investigates the impact of different water to binder ratios (W/B) ranging from 0.4 to 0.6 on the residual properties, including compressive strength (CS), of geopolymer concrete (GPC), in accordance with Indian Standard for Alkali activated concrete. Lower W/B ratios were found to result in a more compact and less porous microstructure in the GPC. Additionally, the research explores the post-fire performance of GPC with varying grades (M10, M20, M30, & M40) and different W/B ratios, following the ISO 834 standard fire curve. It was observed that concrete samples exposed to elevated temperatures displayed a more porous microstructure. The mass loss of GPC with 0.4 W/B was found to be 2.3–5.9% and for 0.6 W/B ratio, the loss was found to be 3–6.5%, after exposing to 30-, 60-, 90-, and 120-min of heating. In the case of strength loss, for 0.4 W/B ratio, the loss was 36.81–77.09%, and for 0.6 W/B ratio the loss was 38.3–100%, after exposing to 30-, 60-, 90-, and 120-min of heating. Overall, the findings suggest that optimizing the W/B ratio in geopolymer concrete can enhance its compressive strength, as well as residual properties, and contribute to its suitability as a sustainable construction material. However, the response to elevated temperatures should also be considered to ensure its performance in fire scenarios.