Self‐Healing of Concrete Cracks by Ceramsite‐Loaded Microorganisms

Abstract

Protective carrier is essential for the self-healing of concrete cracks by microbially induced CaCO 3 precipitation, owing to the harsh conditions in concrete. In this paper, porous ceramsite particles are used as microbial carrier. Heat treatment and NaOH soaking are first employed to improve the loading content of the ceramsite. e viability of bacterial spores is assessed by urea decomposition measurements. en, the self-healing efficiency of concrete cracks by spores is evaluated by a series of tests including compressive strength regain, water uptake, and visual inspection of cracks. Results indicate that heat treatment can improve the loading content of ceramsite while not leading to a reduction of concrete strength by the ceramsite addition. e optimal heating temperature is 750°C. Ceramsite particles act as a shelter and protect spores from high-pH environment in concrete. When nutrients and spores are incorporated in ceramsite particles at the same time, nutrients are well accessible to the cells. e regain ratio of the compressive strength increases over 20%, and the water absorption ratio decreases about 30% compared with the control. e healing ratio of cracks reaches 86%, and the maximum crack width healed is near 0.3 mm.

Research on Improving Concrete Durability by Biomineralization Technology

“…With the increase in environmental protection awareness, these environmentally unfriendly repair materials must be eliminated. In addition, the repair effect of these substances is not very significant due to compatibility issues with the concrete substrate, so researchers from various countries have been working toward environmentally friendly and sustainable repair of biological systems [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

“…Many studies have pointed out that small cracks in concrete can be repaired by themselves based on the continuous hydration of cement or other physical and mechanical behaviors [5,6,10,11,13,14]. In the field of concrete science, this phenomenon is often called "autogenous healing" or "concrete self-healing."…”

“…Therefore, biomineralization can often form an ordered natural organic-inorganic composite material with excellent structure. In view of this, in recent years, microbiologically induced calcium carbonate precipitation (MICP) technology based on microbial mineralization has become a hot topic in concrete self-healing technology and has attracted widespread attention in the academic community [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23].…”

“…Many published studies have confirmed that calcium carbonate precipitates produced by bacteria have been successfully used to repair concrete or limestone surfaces, and that they significantly increase the strength or durability of concrete [6][7][8][10][11][12]15,16]. However, in essence, the bacteria in these studies were applied externally to cracked concrete structures or specimens.…”

Evaluation of Mechanical Parameters of Bacterial Concrete

“…The performance of healing cracks can be enhanced by various parameters viz: biological agents [15][16][17][18][19][20][21], chemical agents [22], encapsulated capsules [23][24][25][26][27] and pozolonic materials [28]. There is an improvement in lifetime of concrete structure by crack healing.…”