Techniques and Methodologies of Biomineralization in the Healing of Concrete Cracks

Abstract

Concrete structures have become common all over the world, however the mateiral undergoes a cracking process, allowing the entrance of deleterious agents. Some countries are now spending more money on recovering existing structures than on building new ones. Thus, in the last decade, researchers have evaluated techniques to promote the self-healing of concrete. It is known that the concrete has a small healing capacity due to the late hydration of anhydrous cement partickes, but it is limited to small cracks and it increases the consumption of cement, which generates financial and environmental disadvantages. In the search for more promising techniques, it has been studied the use of bacteria for the production of biominerals, which heal the cracks, reduce the permeability and the water absorption, and increase the compressive strenght. This study aims to present the state-of-art of this technique, approaching the species used and the methodology of insertion of the microorganisms in the concrete matrix. Among the taxonomic genus studied, there are advantages in the use of bactéria of the genus Bacillus, because they have physiology resistant to aggressive environments. As for the insertion of the bacteria in the concrete, advantages and disadvantages are presented in relation to their encapsulation in lightweight aggregates and their direct addition in the kneading water of the concrete. Gaps were still to be studied, such as the reduction of costs involved in the preparation of the material, improvement of design methodologies, simplification of the construction processes, verification of the durability of this concrete, and study of the inactive life in the bactéria within the hardened concrete.