An exploratory study on high-volume fly ash concrete incorporating silica fume subjected to thermal loads

In this study, cement has been partially replaced with a Class F fly ash (FA) at a level of 70% to produce high-volume fly ash (HVFA) concrete (F70). F70 was modified by partially replacing FA with silica fume (SF) at levels of 10% and 20%, by weight. All HVFA concrete types were compared to the neat Portland cement (PC) concrete. After curing, the specimens were exposed to elevated temperatures ranging from 400 °C to 1000 °C with an interval of 200 °C. Weight and compressive strength before and after firing have been thoroughly explored. The various decomposition phases formed were identified using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated higher relative strength of all HVFA concrete types. F70 exhibited the highest relative strength. The SF blends exhibited good fire performance up to 600 °C, then severe degradation in the residual strength was observed at 800 and 1000 °C.