Abstract
The interfacial transition zone (ITZ) around aggregates in concrete is a weak area with higher porosity than the matrix; it breaks easily under stress and is not conducive to the durability of concrete. However, the ITZ in concrete is full of calcium hydroxide crystals, which can provide the calcium source required for biomineralization. In view of this, this study aims to use the biological activity (i.e., biomineralization technology) existing in nature to enhance the ITZ in concrete and repair concrete cracks to improve the strength and durability of concrete. In this study, the bacterial strain Sporosarcina pasteurii, which is environmentally friendly, was selected. In addition, lightweight aggregate was used as a bacterial carrier. The bacteria were first sporulated. To protect the strains, the biological species were fixed in porous lightweight aggregates. These lightweight aggregates were then used as concrete aggregates. The planned tests included concrete engineering properties (i.e., compressive strength, chloride ion penetration, and water permeability tests) and residual strength after crack repair. The test results show that the use of lightweight aggregate as a carrier and the implantation of Sporosarcina pasteurii can induce biomineralization, strengthen the ITZ, and repair small internal cracks in concrete, thereby improving the strength and durability of the concrete.
Highlights
Concrete is a composite material that is constituted by its basic elements
The development of biomineralization technology will provide the basis for high-quality concrete and improve the durability of reinforced concrete structures
Biomineralized lightweight aggregate concrete can significantly increase its early strength due to biomineralization, and its 7 day strength was increased by about 33% compared with the control group
Summary
Concrete is a composite material that is constituted by its basic elements. Due to its excellent properties and relatively cheap cost, concrete has become the most commonly used building material in the world. Durable concrete will retain its original form, quality, and serviceability when exposed to the environment [1]. Deformations in concrete occur as a result of the material’s response to external loads and the environment [2]. The resulting cracks can reduce the durability of concrete structures. The issue of how to extend the life of concrete structures has been the focus of research by experts in the concrete field in various countries around the world
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