Self-healing of concrete containing commercial bacteria by means of water and chlorides permeability

Abstract

Microbial-induced calcium precipitation (MICP) has shown adequate potential to act as a healing product through Calcium Carbonate (CaCO3) precipitation inside cracks. This work studies the self-healing capability of conventional concrete incorporating two dosages of Bacillus subtilis encapsulated in diatomaceous earth and a liquid solution consisting of a combination of Bacillus, denitrifying, and photosynthetic bacteria. The two bacterial agents used are commercial or industrial products from other sectors. For these mixes, disks of size ϕ100×50 mm were pre-cracked at the age of 21 days by splitting test until reaching residual cracks of 100 to 450 µm. At the age of 28 days, self-healing was promoted during 28 days in three exposures, continuous water immersion at 20°C, a high humidity environment at 20°C and 95% of relative humidity, and 7 days immersed in water at 20°C and 21 days in the high humidity environment. Self-healing was analyzed with water permeability by comparing the results before and after healing. Afterward, chlorides’ penetration was performed to study the possible healing protection on cracked disks compared to uncracked reference disks. As a result, after 7 days of immersion in water, the mixes with bacteria presented acceptable healing results. Some healed cracks could also significantly reduce the penetration of chlorides towards the interior of the concrete matrix.

Self-Healing Capability of Conventional, High-Performance, and Ultra High-Performance Concrete with Commercial Bacteria Characterized by Means of Water and Chloride Penetration

“…A modified water penetration test proposed in previous studies [56,57] was performed by measuring the penetration of sodium chloride through the crack's path and the concrete surface by using its reaction with silver nitrate as a pigmentation method to detect the penetration.…”

“…As expected, specimens healed in HC had P 0 values like the reference of uncracked specimens (Ref P 0 ). Research on selfhealing already reported the substantial effect of water in healing [41,57], and Escoffres et al [69] proposed that specimens healed in a humidity chamber can be used as references since in practice, HC do not promote healing. Healed HPC specimens had a penetration below 2 mm in all mixes, as in the uncracked specimens.…”

The influence of sepiolite on the self-healing capability of concrete by means of water permeability

“…A modified chloride permeability test presented in previous studies [17,18] was performed. This test provides information about the penetration of chlorides throughout the healed crack path and the matrix.…”

Conditions for CaCO3 Biomineralization by Trichoderma Reesei with the Perspective of Developing Fungi‐Mediated Self‐Healing Concrete

“…These polymers can absorb large amounts of water and their consequent swelling capacity allows them to (partially) block cracks. [3,[8][9][10][11] Additionally, they can release this water in drier periods, thereby promoting the concrete's autogenous self-healing mechanisms. [9][10][11] The crack size that can be healed is however limited as well to cracks <0.2 mm.…”

“…[3,[8][9][10][11] Additionally, they can release this water in drier periods, thereby promoting the concrete's autogenous self-healing mechanisms. [9][10][11] The crack size that can be healed is however limited as well to cracks <0.2 mm. [8] Autonomous self-healing methods require a self-healing agent, such as specific bacteria and fungi capable of CaCO 3 -producing biomineralization.…”