Performance of Sustainable Alkali-Activated Mortar Incorporating Natural Pozzolan, Waste Glass Powder, and Polypropylene Fibers

This research highlights the mechanical performance of alkali-activated polypropylene fiber (PPF) mortar containing natural pozzolan (NP) and waste glass powder (WGP) as partial replacements for cement. A total of 45 mix combinations and 405 samples were prepared by varying the levels of NP, WGP, PPF, and sodium silicate (SS), with sodium hydroxide (SH) as an alkali activator. The levels for these variables are NP (0%, 10%, and 20%) and WGP (0%, 10%, 20%, and 30%) by weight of the cement; PPF (0%, 0.5%, and 1.5%) by volume of mortar; and SS + SH (30%, 40%, and 50%) by weight of the binder. The molarity of the SH solution was kept at 10 M, while the SS/SH ratio was maintained at 2.5. Compressive (f’c), flexural (fr), and split tensile strength (ft) were evaluated at 7, 28, and 90 days. The results showed that strength development is strongly age-dependent, with 85–90% of the total strength achieved at 28 days and continued moderate gains to 90 days. SS + SH was the most significant variable, with 50% of activator content achieving the highest f’c, fr, and ft values. Within the tested ranges of NP (0–20%) and WGP (0–30%), strength showed a decreasing trend with increasing replacement due to dilution. PPF had a very minute effect on f’c but significantly improved fr and ft at 0.5% dosage because of crack-bridging. Correlation analysis confirmed that cement and SS + SH are the most dominant strength-controlling factors. The results suggest that the combined use of NP, WGP, and PPF maintains mechanical performance while reducing cement consumption, highlighting the feasibility of this hybrid alkali-activated mortar as a low-carbon construction material.