Self-healing concrete is a new type of concrete. It imitates the automatic healing of body wounds by the secretion of some kind of material. To create self-healing concrete, some special materials (such as fibers or capsules), which contain some adhesive liquids, are dispensed into the concrete mix. When cracks happen, the fibers or capsules will break and the liquid contained in them will then heal the crack at once. However, self-healing concrete is only at the research stage. Its application in the concrete industry is still some way off.

After construction, concrete cracks, weathers, leaks, and bends. Self-healing concrete contains limestone producing bacteria that repairs the crack when it comes into contact with air and water. Along with concrete, this self-healing bacteria can repair mortar for already existing structures. Repetitive dry and wet cycles with a width of 0.05 to 0.1mm completely seal cracks. The self-healing product acts as a capillary, and the water particles go through the cracks. Then, these water particles soak and hydrate the cement, causing it to expand, thus filling the crack. However, if cracks are greater than the width of approximately 0.1mm, other reconstructive work will be required. Self-healing of cracks in concrete would contribute to a longer service life of concrete structures and would make the material not only more durable but also more sustainable

Self-healing concrete is prepared in two ways:

1. By direct application:

After you mix the concrete, add calcium and bacterial spores to the mix. The process of sealing cracks occurs when water comes into contact with this bacteria, then they germinate on calcium lactate, and the production of limestone creates self-healing concrete.

2. By encapsulation in lightweight concrete:

The bacteria and calcium lactate are in clay pellets and mixed in with concrete preparations. Only about 6% of the clay pellets are actually included for making self-healing concrete. When there is a crack in the structure, the clay pellets break down, the bacteria germinate and feed on the calcium lactate and produce limestone.