Influence of curing environment on concrete with crystalline admixture

The study investigated the influence of crystalline additives and the curing environment on the mechanical properties of concrete. Crystalline admixtures totaling 3, 5, and 7 % of the cement content were added to fresh concrete. Curing variables included atmospheric curing and moist curing. The final specimens were tested for compressive strength, splitting tensile strength, and modulus of elasticity. Scanning electron microscope (SEM) imaging and X-ray fluorescence spectrometry analysis assisted in verifying the results. For concretes with crystalline admixture, the test results showed greater improvement in the mechanical properties of concrete subjected to moist curing than concrete subjected to atmospheric curing. The compressive and splitting tensile strengths of the specimens exceeded those of the control group, indicating that the additive can enhance mechanical properties. The addition of 3 % provided the most advantageous effects. However, the addition of the admixture decreased the modulus of elasticity of the concrete. SEM imaging revealed the results of the reaction between the crystalline admixture and the cement paste; a number of needle-like crystals were apparent and are likely the primary reason for the enhanced mechanical properties.