Transactions on Engineering and Computer Science

Abstract 

Self-healing is a concept that has been studied for decades. Self-healing is the ability of cementitious composites to reduce the width of cracks generated due to wear and tear of the material. Of the many self-healing mechanisms, this article reviews and outlines the progress of self-healing in past and recent decades. Primarily, the use of expansive agents for self-healing is discussed in this article. When a cementitious composite fills up the crack with hydration products, expansive or crystalline materials, the composite is said to have undergone autogenous self-healing. Autonomous self-healing refers to the intentional addition of materials to help the composite self-heal. This article delves into these two types of self-healing. At its core, this article studies research on different expansive materials used in self-healing for cementitious composites. The use of magnesium oxide (MgO), quicklime, calcium sulpho-aluminate (Type K), and Sodium Bentonite expansive materials were investigated. Combinations of expansive agents with geomaterials, crystalline additives, swelling minerals in varying proportions were also outlined. Their strength regain, crack sealing and optimum self-healing is subsequently discussed. The use of sand replacing pellets infused with expansive materials for self-healing is studied. Some of the results showed that although self-healing took place, the re-hydration products were unstable proving that a design that had a greater chemical and physical stability is required for effective self-healing. When combinations of expansive agents are used, results show that the composites have a higher crack sealing nature with most cracks being sealed in 14 days. With a new method to improve self-healing, a study was introduced that partially replaced fine aggregates with active granules. The results showed improved crack mouth healing. 

Keywords: Autogenous; Autonomous; Crack; Expansion agent; and Self-healing.