Self-healing concrete techniques and performance, A review

Abstract

Modern society faces the duality of rapidly expanding structure, making concrete one of the world's most traded materials. However, cement manufacturing can pollute the environment by releasing approximately one tonne of CO2 for every tonne of cement produced. Concrete cracks can provide superior access for aggressive substances such as chlorides and sulfates, resulting in structural deterioration. So, to fix concrete cracks, different traditional methods were used, which use cement and some chemical agents that are hazardous to the environment. Because of the environmental issues and sustainability challenges associated with cement and concrete, it is preferable to reduce the amount of cement used by developing promising and unique solutions to enable quick crack healing in concrete and extend the structure's lifetime. Therefore, incorporating self-healing mechanisms into construction materials has been proposed to improve their performance and durability while reducing the need for maintenance and repair. This review assesses the performance and causes of autogenous and autonomous self-healing techniques. The autogenous technique occurs naturally due to inherent material properties, while the autonomous technique uses various healing agents, such as chemical or biological substances. Both techniques rely on forming calcium carbonate (CaCO3) crystals as the principal agent for concrete healing. Previous findings showed that the autogenous technique has limited efficacy in repairing larger cracks with a width exceeding 0.3mm. In contrast, autonomous techniques have shown successful repai of cracks exceeding 2mm in width. The application of an autonomous methodology in the field of concrete has resulted in significant results, such as effectively repairing large cracks, enhancing structural integrity, and substantially decreasing permeability levels from high to exceedingly low levels

Innovative Strategies for Enhanced Concrete Durability: A Comparative Analysis of Autogenous and Autonomous Self-healing Mechanisms

“…The autogenous technique enhances natural crack healing, using only the material's original components. As per RILEM (Alazhari et al 2016;Ghazy et al 2023;Lahmann et al 2023;Van Tittelboom et al, 2013a), autogenous self-healing can be attributed to three main causes: physical, mechanical, or chemical. The physical cause can be attributed to the volume increase of the hydrated cement paste near the crack face, leading to the expansion of calcium silicate hydrate gel (C-S-H) (Ghazy et al 2023;Ter Heide 2005).…”

“…As per RILEM (Alazhari et al 2016;Ghazy et al 2023;Lahmann et al 2023;Van Tittelboom et al, 2013a), autogenous self-healing can be attributed to three main causes: physical, mechanical, or chemical. The physical cause can be attributed to the volume increase of the hydrated cement paste near the crack face, leading to the expansion of calcium silicate hydrate gel (C-S-H) (Ghazy et al 2023;Ter Heide 2005). The mechanical cause, also known as the self-tightening technique, only involves filling the cracks with tiny particles or small impurities, with no involvement of chemical reactions (De Rooij et al 2013;Ter Heide 2005;Toader et al, 2020).…”