The influence of calcium oxide doses as an activator on the compressive strength and mechanical characteristics of cement-free mortar containing ground granulated blast furnace slag

Abstract In the construction industry, cement-based materials as aggregate binding agent are still widely used. Due to the environmental concern, researchers are working to create eco-friendly cement-free binding materials. Calcium oxide (CaO) is a reactive earth metal oxide that could serve as a potential activator for ground granulated blast furnace slag (GGBFS). In this experimental study, the cement-free mortar was produced by using GGBFS as the base material and CaO as an activator with varied doses of 5%, 15%, and 25% with a fixed water-to-binder ratio (w/b) of 0.4. The results showed that the 28-day compressive strength values of the mixture with an amount of CaO of 5%, 15%, and 25% were 21.45, 32.03, and 25.80 MPa. Moreover, the values of bulk density and porosity of free-cement mortar at the age of 28 days ranged between 1.932 - 1.939 g/cm 3 and 22.66% - 24.95%, respectively. According to the research findings, the optimal additional CaO amount of 15% exhibited the series’ highest compressive strength and lowest porosity.