**1.3 Biotechnological approaches**

Biotechnology involves the use of biomineralization in concrete technology. It is a process of mineral formation by living organism in nature. According to the same author, the process can be accomplished by inducing biological mineralization in an open environment as a result of uncontrolled microbial metabolic activity [21]. This process occurs in an anaerobic environment or at toxic-anoxic boundary as avowed by [22]. This is as a result of photosynthesis from bicarbonate solutions which results in carbonate production [45]. Besides, the use of this method is feasible when carbon dioxide is present in the surrounding. It can be inferred from this that photosynthesis pathway can be applied when concrete infrastructure is exposed to carbon dioxide in the presence of light.

Furthermore, the heterotrophic growth of different types of bacteria such as *Arthrobacter*, *Bacillus*, and *Rhodococcus* leads to the production of organic salt and carbonate minerals through urea analysis [46–48]. It also results in the increase in the pH consequently increasing the concentration of carbonate. This process is achieved by the conversion of carbon dioxide to carbonate [13, 49, 50]. Invariably, this aids the calcium carbonate precipitation which plays an active role in the blockage of cracks [51, 52]. Other bacteria used in self-healing technology are shown in **Table 3**.

The major drawback of this approach is the production of ammonium ions (NH4+) through ureolytic activity which results in nitrogen oxide emission into the atmosphere. It is estimated that the remediation of 1 m2 of concrete needs 10 g/L


**Table 2.** *Materials used in encapsulation method of self-healing.*

#### *Use of Sustainable Materials in Self-Healing Concrete DOI: http://dx.doi.org/10.5772/intechopen.86768*


#### **Table 3.**

*Bacteria used in self-healing technology.*


#### **Table 4.**

*Self-healing materials.*

of urea which produces 4.7 g of nitrogen. This amount is about one third of the nitrogen that is produced by each person everyday [52]. Furthermore, the presence of excessive ammonium in the concrete matrix increases the risk of salt damage by converting to nitric acid. Hence, an optimization to find the required amount of urea is beneficial to avoid excessive ammonium emission.

For cement-based materials, different methods can be found in literature (**Table 4**); the first breakthrough involves the use of encapsulated sealant or adhesive [19]. These are stored in fibers [39, 40] or in longer tubes [60]. Filling of the voids and cracks with expansive material can propel carbonation when water percolates [61, 62]. The use of bacteria to stimulate the self-healing mechanism is also a promising alternative [63–65]. Nanotechnology is a unique branch of science that uses nanomaterial in the design, construction, repair, and protection of infrastructures. It deals with the application of the physical world in a small scale by assessing the atom, molar molecule, and similar molecule of material [66–68]. With the increasing development of nanotechnology, the use of tiny nanoparticles and nanomaterial also increased in modern technologies [69].

### **2. Conclusions**

This review assessed the use of self-healing technology for sustainable infrastructural development. Relevant literatures on the use of self-healing technology in concrete technology were assessed. The main concept was to make sure that concrete structure affected by crack regained its mechanical strength by the hydration of the cement particles present in it. Self-healing mechanism using the

#### *Strength of Materials*

autogenous healing, encapsulation of polymeric material, and microbial production of calcium carbonate (biotechnological approaches) was studied. The review revealed that:

