Strength and post-fire performance of fiber-reinforced alkali-activated fly ash concrete containing granite industry waste

The mechanical properties and the post-fire performance of alkali-activated fly ash (AAF) concrete containing granite industry waste (GW) and polypropylene (PP) fibers were investigated to promote the application of environmentally friendly concrete. The recycled GW proportions of 0, 25, and 50% by weight were used in fine aggregates to replace the natural river sand, and the PP fiber contents of 0, 0.5, and 1.0% by volume were added to the concrete mixtures. The mechanical properties investigated included compressive strength, flexural load–deflection response, and toughness. The post-fire performance was evaluated from the residual compressive strength and weight loss, together with the visual inspection and the scanning electron microscopy (SEM) investigation of the specimens after fire exposure. It was found that the inclusion of PP fibers was effective to improve the flexural performance of AAF concrete, with or without the GW. Based on the toughness of AAF concrete, the optimal percentage for the GW replacement was 25%. After exposure to the ISO-834 standard fire, the results showed that the degradation of AAF concrete manifested itself in the inner core in the form of extensive cracking, particularly for the fiber-reinforced concrete containing the GW. The residual compressive strengths of AAF concrete were reduced to a range of only 25–39% after the fire exposure of 30 min.