Abstract
Reinforced concrete crack repair and maintenance costs are around 84% to 125% higher than construction costs, which emphasises the need to increase the infrastructure service life. Prolongation of the designed service life of concrete structures can have significant economic and ecological benefits by minimising the maintenance actions and related increase of carbon and energy expenditure, making it more sustainable. Different mechanisms such as diffusion, permeation and capillary action are responsible for the transport of fluids inside the concrete, which can impact on the structure service life. This paper presents data on microbially induced repair and self-healing solutions for cementitious materials available in the contemporary literature and compares results of compressive strength test and capillary water absorption test, which are relevant to their sealing and mechanical characteristics. The results of the repair and self-healing solutions (relative to unassisted recovery processes) were “normalized.” Externally applied bacteria-based solutions can improve the compressive strength of cementitious materials from 13% to 27%. The internal solution based solely on bacterial suspension had 19% improvement efficacy. Results also show that “hybrid” solutions, based on both bio-based and non-bio-based components, whether externally or internally applied, have the potential for best repair results, synergistically combining their benefits.
Highlights
Concrete structures and buildings compose the vast majority of constructions currently in service
This paper presents an attempt to compare data on repair and self-healing solutions for cementitious materials available in the contemporary literature, according to the criteria used in the research conducted by the authors
In order to evaluate the effects of remediation agents, both mechanical and sealing properties should be taken into account
Summary
Concrete structures and buildings compose the vast majority of constructions currently in service. There have been several extensive review papers written on internal self-healing approaches, but only a few papers have considered externally applied bacteria-based agents or materials for concrete repair [33,43,44,45,46], which emphasises the fact that the research in this field is still in its early stages Another option for utilising MICP is to treat already formed cracks with a bio-agent containing suitable bacteria and nutrients. In case of a bio-agent based on bacteria and nutrients, the agent per se does not act as sealant, but induces the bulk material (concrete or cementitious matrix) to seal/heal itself It can be, argued that this novel repair technique employs self-healing/self-sealing processes, and that RILEM at the time they were drawing up the definitions of self-healing had not yet encountered this specific technique. There is concern about them not being environmentally friendly
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