Investigating the Impact of Fly Ash Replacement with Portland Cement on Porosity, Water Absorption, and Compressive Strength of Geopolymer Mortars in a Tidal Acid Environment

Abstract

This study examines how Portland cement affects the physical and mechanical properties of geopolymer mortar when exposed to tidal water after 28 days of curing, when used instead of fly ash. Geopolymer, an alternative to concrete, utilizes waste materials to replace Portland cement. However, it has a relatively slow setting time. This study evaluated the influence of varying levels of Portland cement replacement on the setting time, water absorption, porosity, sorptivity, and compressive strength by replacing fly ash with Portland cement at levels of 0%, 5%, 7%, and 10%. The specimens were cured for 24 h at 100 °C after molding. After 28 days, the specimens were exposed to an artificial acidic environment with a pH of 3 for one month. The results showed that replacing fly ash with Portland cement reduced the initial and final setting times. The water absorption, porosity, and sorptivity increased as the percentage of Portland cement replacement rose, while the compressive strength of the geopolymer mortar improved with 7% and 10% Portland cement replacements.