Recycling air-cooled blast furnace slag in fiber reinforced alkali-activated mortar

Fiber reinforced alkali-activated materials (FR-AAM) present as one type of sustainable and resilient materials. However, the thermal degradation mechanism of FR-AAM remains unclear. In this study, FR-AAM incorporating air-cooled blast furnace slag (ACBF), ground granulated blast furnace slag (GGBS) and different types of fibers (steel, glass, and polypropylene) are produced and exposed to elevated temperatures. Test results show that ACBF (replacing 30% of river sand) improved the thermal resistance of FR-AAM due to the ameliorated interfacial transition zone (ITZ) and channels for the release of vapor pressure. Relatively, steel fibers better retain mechanical performance, whilst polypropylene fibers better provide channels for the release of vapor pressure after melting. Gel decomposition and micro crack development are the main causes for the thermal deterioration of FR-AAM. Based on non-destructive tests, damage degree is proposed to quantitatively evaluate the usability and deterioration coefficient (K) is adopted to controll the strength retention of FR-AAM at high temperatures. Economically and environmentally, the development of FR-AAM is promising in shaping a sustainable and resilient future.