Abstract
With the increasing number of underground engineering construction projects such as coal mining, tunnel, and subway, water inrush disasters occur more and more frequently. Inspired by the phenomenon of microbial mineralization and diagenesis, microbial-induced calcium carbonate precipitation (MICP) is used to repair cracks in cement-based materials, which provides a new idea to solve the problem of water inrush. To investigate the self-healing properties of microbial capsules, this paper selected epoxy resin E-51 cured by DMP-30 as the wall material and Bacillus pasteurii as the core materials for experiments. In this paper, a single-factor method was adopted to determine the optimal preparation process of microbial capsules and the oil-phase separation method to prepare the microbial capsules. The effects of various factors on the experimental results under different core-wall ratios, reaction time, reaction temperatures, and agitation rates were analyzed. Microbial capsules were analyzed by Fourier transform infrared spectroscopy and optical microscopy to explore the functional groups and features of microbial capsules. The experimental results showed that the microbial capsules achieved the best performance with a core-to-wall ratio of 1 : 3, a reaction temperature of 50°C, a reaction time of 40 min, and a stirring rate of 300 rpm. Meanwhile, we determined the spore survival rate of microbial capsules and finally studied the waterproofness, storage stability, and rupture under the pressure of microbial capsules. We concluded that microbial capsules have high-efficiency and self-healing properties.
Highlights
In the underground engineering, microcracks often occur in concrete layer, which reduces the bearing capacity of the concrete structure and affects its durability and waterproofness [1,2,3,4,5,6,7,8]
A more effective method for repairing concrete cracks is microcapsule technology. is technique involves coating the desired material with a suitable material to form a core-wall structure. e material used for coating is called a wall material, and the material to be coated is called a core material. e wall material is usually selected from organic polymer materials and inorganic materials, and the selection of the core material is determined according to the application of the microbial capsules
Precuring of epoxy resin E-51 was carried out according to a control experiment (Table 3). e experiment shows that the curing reaction accelerates with the increase in the temperature of the water bath; and when the temperature of the water bath reaches 50°C, the curing reaction is the fastest
Summary
Microcracks often occur in concrete layer, which reduces the bearing capacity of the concrete structure and affects its durability and waterproofness [1,2,3,4,5,6,7,8]. A more effective method for repairing concrete cracks is microcapsule technology. Is technique involves coating the desired material with a suitable material to form a core-wall structure. E wall material is usually selected from organic polymer materials and inorganic materials, and the selection of the core material is determined according to the application of the microbial capsules. When microcapsule technology applies to the crack repair of concrete, its essence is the use of microorganisms to induce the formation of calcium carbonate. The microbial capsule will break, and microbial metabolism will produce calcium carbonate, thereby repairing the crack. Singh et al [15] found that the crack healing capacity of the calcium lactate-prepared samples significantly improved, in spite that the expanded clay aggregates-based
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