Abstract
Self-healing cement composites are generally produced by using materials such as inorganic powders, bacteria pellets, and microcapsules. Among them, inorganic powder-type healing materials tend to decrease in healing performance over time because they react relatively quickly. Accordingly, this study encapsulated self-healing inorganic reactive powders in solid capsules (SC) in order to delay their reaction. The capsule surface was coated with a membrane to prevent moisture from permeating it. SC were utilized to provide the self-healing effect to the repair mortar. SC were mixed at three rates (0%, 5%, and 10%) by the binder mass of the repair mortar. The fundamental properties, including rheology, table flow, strength, and length change, and the self-healing performance of the self-healing repair mortar mixes were investigated. It was found that the rheological and mechanical properties of the repair mortar decreased slightly as the amount of SC increased. On the other hand, for a crack width of 0.25 mm and crack inducing age of 28 days, the healing performance of repair mortar specimens containing SC was at least 20 pt% better than that of plain repair mortar after a healing period of 28 days.
Highlights
Smart self-healing materials have emerged worldwide in the construction industry
Cracks in a concrete structure constructed with self-healing materials can be healed at an early stage of cracking, which can greatly reduce the time, effort, and cost required for general structural maintenance
Materials such as minerals [6], bacteria [7,8], superabsorbent polymers (SAPs) [9], and microcapsules [10,11] are being explored for use as self-healing materials
Summary
Smart self-healing materials have emerged worldwide in the construction industry. Self-healing technology has the potential to repair mechanical damage and cracks in concrete structures effectively, even in difficult-to-access structures [2–4]. Self-healing repair methods have been applied to an existing subway tunnel to stop water leaking from cracks [5]. Materials such as minerals [6], bacteria [7,8], superabsorbent polymers (SAPs) [9], and microcapsules [10,11] are being explored for use as self-healing materials. Choi et al [15] fabricated crack self-healing solid capsules encapsulated with cement powder which can react with water in the event of breaking. The impregnation of lightweight aggregates by a liquid self-healing mineral and their subsequent encapsulation in a polymer-based coating layer was suggested as a method for improving the self-healing performance of concrete composites [10]. The inorganic reactive powder used for producing SC consisted of mixing a hauyne-based expansion material, which was calcium sulfoaluminate (CSA; made by Denka Co., Ltd., Tokyo, Japan), and general anhydrite (CaSO4)
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