Effect of permeability-reducing admixtures on concrete properties at different cement dosages

Abstract

Concrete is the most common building material used worldwide. Significantly high strength values have been achieved owing to developing material technology. Besides compressive strength, durability properties should also be taken into consideration since concrete is exposed to several external effects throughout its service life. Durability properties are mainly associated with the voids in the internal structure and surface of concrete. Even if not exposed to any external effects, concrete contains several pores and micro-cracks. These pores and cracks enlarge with the influence of external effects, and new cracks are developed. Therefore, various methods are used to prevent the permeability of harmful liquids and gases into concrete structures. In this study, permeability-reducing admixtures (PRAs) and various cement dosages were used to produce concrete mixtures. The main purpose is to examine the interaction of these additives with the cement dosage. Workability, compressive strength, and depth of water penetration under pressure tests were conducted to observe the effect of PRA on these parameters. The admixture crystallized in the internal structure of the concrete and created a fuller volume. While the compressive strength increased as a result of the crystallized product, the depth of water penetration decreased. Slump tests revealed that the additive was compatible with all cement dosages, and it did not significantly affect the workability properties of the concrete. Expectedly, the compressive strength increased as the cement dosage increased, while the positive effect of the PRA additive gradually decreased. The PRA additive also contributed to the decrease in the depth of water penetration, but its impact decreased as the cement dosage increased. It was concluded based on present findings that PRA additive, which is the most effective at the lowest cement dosage, increased the compressive strength values by 9.44% at this dosage and decreased the depth of water penetration under pressure by 26.09%.