The Effect of Polypropylene Fiber Addition on the Compressive Strength and Ultrasonic Pulse Velocity of Low-Temperature Cured AlkaliActivated Slag

Abstract

Portland cement (PC) has long been a predominant binder material in the construction industry, but it is also a major contributor to carbon dioxide emissions. Alkali-activated materials (AAMs) have emerged as an environmentally friendly alternative in the construction industry. AAMs are formulated by activating aluminosilicate-based materials with alkali activators, offering potential environmental benefits by reducing carbon dioxide emissions compared to traditional PC-based binders. Due to its ability for continuous hydration at low temperatures, alkali-activated slag (AAS) stands as a promising binder material for winter construction applications. High alkali dosage (Na2O%) dosage and alkali modulus in AAS production may result in the occurrence of shrinkage cracks. This study employed 0.3% polypropylene fiber (PP) by volume to mitigate the potential negative impact of cracks, which may arise from elevated Na2O%, on the mechanical properties of AAS. AAS mortars were manufactured with Na2O% of 7% and 9%. Ultrasonic pulse velocity and compressive strength tests were conducted on samples aged 7 and 28 days. The results showed that the compressive strength increased with an increase in Na2O%. The sample with 7% Na2O% exhibited better strength development with increasing curing time compared to its 9% counterpart. There was a decrease in compressive strength with PP substitution.