The cracks that are found in concrete are a common occurrence. This is based on lower tensile strength. It is found that the concrete would be impacted by cracks and this would allow the fluids to flow through, making the whole concreate of no use. In the cases where the micro-cracks grow, there will be a lot of issues in the use of the concrete. It is imperative to control the cracks and control the width in order to treat the cracks as soon as they are formed. Based on the costs involved in the maintenance and the repair of the concrete structures, the focus of the development has been about self-healing concrete. The self-healing of the cracks in the concrete leads to lengthier service life of concrete structure. These would make the material more durable and increase the life of the concrete. There is considerable research that is done to achieve this paradigm using different methods.

Autogenous healing

The concrete has the property of “autogenous healing capacity”. The concrete has un-hydrated cement which is present in the matrix. Whenever water interacts with the cement, there is further hydration that occurs. The CaCO3 crystals are formed when the CO2 interacts with the Ca2+. These two methods are used to heal the smaller cracks. To enhance the healing mechanism, the microfibers are added to the mixture. This addition of the microfiber in the concrete causes multiple cracking to occur. This is based on the use of autogenous healing.

Superabsorbent polymers (SAP)

These SAPs are the hydrogels and they are able to consumer larger amount of the fluids. This is used to retain their structure without the process of dissolving. At times when the cracks occur, SAP has been observed that whenever it is exposed to humid environment, it swells. This swelling is defined as the reaction to partly close the cracks and cause prevention from the intrusion of the potentially harmful substances. After swelling process occurs, the SAP particles generally desorb the compounds and provide more fluid for the surrounding matrix for them. This invariably leads to the internal curing. There is further requirement of hydration and the precipitation of the CaCO3. This causes the cracks to close completely. The PH level in the concrete drops from 12.8. It is imperative to investigate the pH sensitive hydrogels. This causes the swelling of the cracks that occur and the fresh water penetrates.

Bacterial spores

The cracks are observed to be healing from the use of the calcium carbonate by utilizing the bacterial micro-organisms. The organisms are observed and entrenched in the concrete matrix. After the immobilization of the diatomaceous, the earth in the microcapsule shows cracks. This would start the precipitation of CaCO3. This causes the crack to occur. This crack happens whenever the bacterial cell is coated with another layer of CaCO3. This results in the crack filling. The CaCO3 precipitation has been observed to be immobilized on diatomaceous earth of the silica gel.