Self-sealing cementitious composites by gelation in-situ: an experimental and modelling study

Abstract

Healable crack widths of cementitious composites are still at micro scale currently, even after specific self-healing agents like bacteria are incorporated. To enlarge the size of healable cracks to macro scale (> 1 mm), in-situ gelation strategy was adopted to develop self-sealing concrete herein. This strategy was achieved by encapsulating sodium alginate which could be released then react with calcium ions to in-situ generate calcium alginate hydrogels within cracks. The characteristics of capsules were investigated, and results revealed that these capsules could endure shear stress during mixing of cementitious composites, rupture when composite cracked and subsequently induce in-situ gelation. Owing to the characteristics of capsules, mortar specimens with the capsules obtained self-sealing capacity for macro cracks. The crack sealing of cementitious composites with capsules was further simulated based on the volume growth kinetics of hydrogels and stereology. The simulation results were generally consistent with the experimental results in this study. To sum up, the experimental and modelling explorations suggested a great potential of macro-scale self-sealing of cracks in cementitious composites via in-situ gelation.