Abstract
Crystalline admixtures (CAs) are new materials for promoting self-healing in concrete materials to repair concrete cracks. They have been applied to tunnel, reservoir dam, road, and bridge projects. The fundamental research and development of CAs are needed concerning their practical engineering applications. This paper reviews the current research progress of commercial CAs, including self-made CA healing cracks; the composition of CA; healing reaction mechanism; the composition of healing products; distribution characteristics of healing products; the influence of service environment and crack characteristics on the healing performance of CA; and coupling healing performance of CA with fiber, expansive agent, and superabsorbent polymers. The current research findings are summarized, and future research recommendations are provided to promote the development of high-performance cement matrix composites.
Highlights
Cracking is an unavoidable phenomenon in concrete structures
In order to promote the development of cement-based composites with crystalline admixtures (CAs) and improve the concrete durability, this paper presents a review on the reaction mechanism of CA; composition and distribution of healing products; the influence of service environment and crack characteristics on the healing performance of CA; and synergetic healing performance of CA with fibers, CA
Through the SEM-EDS test, Sisomphon et al [36] found that the healing products of specimens mixed with CA and calcium sulfoaluminate based expansive additive (CSA) were mainly CaCO3, C-S-H, and ettringite
Summary
Cracking is an unavoidable phenomenon in concrete structures. In the process of concrete strength development, external or internal cracking is inevitable. In recent years, adding some substances in cement-based materials to make the structure self-healing without intervention has gradually become the focus of research, because this method can significantly improve the durability and sustainability of the structure. The healing mechanism is as follows: (1) Partially hydrated cement particles and other cementitious materials (pulverized fly ash, blast furnace slag, and so on) on the crack surface will further hydrate, and C-S-H, Aft, and portlandite may exist in the healing products. In order to promote the development of cement-based composites with CAs and improve the concrete durability, this paper presents a review on the reaction mechanism of CA; composition and distribution of healing products; the influence of service environment and crack characteristics on the healing performance of CA; and synergetic healing performance of CA with fibers, CA. It is difficult to obtain valuable results from these tests
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