Effect of limestone powder on mechanical strength, durability and drying shrinkage of alkali-activated slag pastes

The use of limestone powder (LSP) as a cement replacement is used in abundant applications due to its low cost and wide availability. Adversely, the use of LSP as a part of the precursors of alkali-activated materials (AAMs) is still in the developing stage. This scarcity of studies opened the door and encouraged the researchers for more investigations. Thus, this paper studied the effect of various amounts of LSP on some properties of alkali-activated slag (AAS) pastes activated with NaOH and Na₂SiO₃ solution. Slag was partially replaced with LSP at ratios of 15–60 wt%. The effects of LSP on mechanical strength, water absorption, chloride penetration permeability, drying shrinkage were studied. Advanced apparatuses were applied to detect the changes in crystalline phases, hydration products and microstructure of the pastes with and without the inclusion of LSP. The results confirmed that 15% LSP was the optimum amount, which is responsible for the highest mechanical strength, lowest water absorption and lowest charge passed. The drying shrinkage was mitigated with the inclusion of LSP. The inclusion of 15% LSP enhanced the 28-day compressive strength and flexural strength by 11.41% and 13.7%, respectively, while the water absorption, charge passed and drying shrinkage were decreased.