Effect of a Crystalline Admixture on the Permeability Properties of Concrete and the Resistance to Corrosion of Embedded Steel

Reinforced concrete structure durability hinges on concrete permeability, which relies on the characteristics of the inner porous network. Harmful ions and gases can accelerate steel corrosion. Permeability-reducing admixtures (PRA), including crystalline admixtures (CA), are commonly used to mitigate this. This study examines a commercial CA's impact on durability-related aspects in concrete specimens. Two concrete mixtures with matching proportions were prepared: a reference mix and another mix with a commercial crystalline admixture. Several properties were studied, such as compressive strength, density, porosity, electrical resistivity, water absorption capacity, chloride diffusion, air permeability, and corrosion resistance. The studied admixture in concrete yields several positive outcomes such as a slight reduction in mixing water, a potential 6% increase in concrete's compressive strength and the development of a denser and less permeable structure with 3% lower porosity and water absorption than the reference mix. Electrical resistivity improves by 10%. Unidirectional chloride diffusion tests show no differences. Air permeability decreases by from 36% to 55%, and the water absorption rate diminishes by 23%. The admixture potentially reduces the scatter in corrosion initiation periods for steel reinforcements, delaying corrosion onset by around 60 days, although more extensive experiments are needed for definitive conclusions.