Self-Healing Concrete by Microorganisms in the Altered Pozzolan of Madagascar with Calcium from Crab Wastes

Abstract

Concrete is at a high risk of cracking which threats its durability. Self-healing bacterial concrete has been developed in recent years to tackle this issue and its effectiveness has been massively studied. However, bacteria need carriers and expanded clay is the most used as such, but it reduces concrete strength. Moreover, bacterial culture and immobilization processes are highly expensive; calcium salts also contribute to the high cost of this type of concrete. This work therefore aims to overcome these limitations. Calcium salts were collected from the chitosan production process from crab waste. In addition, we noticed that Betafo pozzolan contains an abundant number of microorganisms, and for the first time, we discovered that those microorganisms have polyextremophilic characters, are resistant to various sterilization methods, and allow the self-healing concrete process. We concluded that calcium salts from the crab, with those microorganisms are able to heal crack up to 350 µm wide, reducing the expenses related to nutrients, and eliminating those related to the growth and the immobilization of bacteria on carrier. Moreover, we pointed out that pozzolan significantly increases compressive strength by 90.04%. However, the behavior of those microorganisms and the pozzolanic reactions need to be further investigated.