Early Age Sealing Capacity of Structural Mortar with Integral Crystalline Waterproofing Admixture

Crystalline admixtures embedded in concrete may react in the presence of water and generate thin crystals able to fill pores, capillaries and micro-cracks. Once the concrete has dried, the crystalline chemicals sit dormant until another dose of water starts the crystallization again. The research aims to analyses the early age self-sealing effect of a crystalline admixture at a dosage rate of 1–3% of the cement mass. Specimens made with two types of gravel were pre-loaded with three-point bending to up to 90% of the ultimate capacity, and conditioned through wet–dry cycles. Micro-crack closure was measured with a microscope after pre-loading, and after 1 day, 4 days, 8 days, 14 days and 20 days of wet–dry exposure. The results show that an admixture content of 3% achieves the best early self-sealing performance. These results are also confirmed by probabilistic analyses, which also emphasize the self-sealing potential of lower ICW contents.