Post-Fire Performance of Binary-Blended Geopolymer Concrete Structural Members

Owing to the ever-increasing climate crisis, it is essential that the construction sector endeavors to reduce its contribution to global carbon emissions. The cement and associated by-products used in the production of concrete are a significant contributor to the carbon footprint in construction, and there should be replaced by suitable and more sustainable materials if and where possible. Such materials, sometimes called ‘green’ materials, include geopolymer concrete (GPC), which can reduce or eliminate the use of cement in concrete mix design. Although significant research focus has been given to GPC in recent years, there is very limited data on the post-fire behaviour. Accordingly, in the current paper, three different types of binary-blended GPC elements were cast and subjected to a standard fire for various durations. These included a mix made up of 100% fly ash (FA), another using FA and ground granulated blast furnace slag (FG) and a third combination comprising FA and metakaolin (FM). The test specimens were examined under a variety of conditions, after cooling. The test results illustrate that GPC beams deform in a similar manner to cement-based concrete beams at ambient temperature and therefore, the deformations can be evaluated through a strain compatibility methodology. However, the same does not apply to GPC beams following exposure to fire conditions as the structural behaviour was shown to degrade with increased temperature exposure. All of the post-fire tests were supplemented with image analysis to measure the influence that elevated temperature has on the concrete quality. The results show that the FG blended mix provides an effective yet more sustainable concrete mix compared to the FA and FM blended mixes.