Effect of ultra-fine limestone powder on leaching resistance of cement mortar

[Display omitted] •The method for cement mortar leaching tests under continuous immersion and wet/dry cycles was proposed.•Stone powder is not conducive to mortar resistance to calcium corrosion under wet/dry cycles.•The dissolution rate deviates from Fick's law under wet/dry cycles. This study investigated the effect of ultrafine limestone powder on the calcium leaching performance of cement mortar. Ammonium chloride solution (3 mol/L) was used as the accelerated medium with a controlled pH disposal, and leaching tests of cement mortar were conducted using continuous immersion and wet/dry cycles. The evolution laws of the leaching depth, calcium ion dissolution, compressive strength, flexural strength, porosity, physical phase composition and microstructure were analyzed. The results show that with the expansion of the leaching area, the mechanical properties of the mortar in the leaching environment deteriorate and the porosity increases. The coupling effect of wet/dry cycles and leaching can significantly increase the deterioration rate of mortar, and the dissolution rate gradually deviates from Fick's law. An appropriate amount of ultrafine limestone powder can reduce the porosity and improve the density of the micro-structure, thus inhibiting the leaching damage of mortar in an immersion environment. However, this degrades the structural properties of the wet/dry leaching coupling environment, and the structural properties of the mortar deteriorate faster with an increase in the ultrafine stone powder admixture.