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. 2015 Oct 13:6:1088.
doi: 10.3389/fmicb.2015.01088. eCollection 2015.

Application of modified-alginate encapsulated carbonate producing bacteria in concrete: a promising strategy for crack self-healing

Jianyun Wang  1 , Arn Mignon  2 , Didier Snoeck  3 , Virginie Wiktor  4 , Sandra Van Vliergerghe  5 , Nico Boon  6 , Nele De Belie  3
Affiliations

Application of modified-alginate encapsulated carbonate producing bacteria in concrete: a promising strategy for crack self-healing

Jianyun Wang et al. Front Microbiol. .

Abstract

Self-healing concrete holds promising benefits to reduce the cost for concrete maintenance and repair as cracks are autonomously repaired without any human intervention. In this study, the application of a carbonate precipitating bacterium Bacillus sphaericus was explored. Regarding the harsh condition in concrete, B. sphaericus spores were first encapsulated into a modified-alginate based hydrogel (AM-H) which was proven to have a good compatibility with the bacteria and concrete regarding the influence on bacterial viability and concrete strength. Experimental results show that the spores were still viable after encapsulation. Encapsulated spores can precipitate a large amount of CaCO3 in/on the hydrogel matrix (around 70% by weight). Encapsulated B. sphaericus spores were added into mortar specimens and bacterial in situ activity was demonstrated by the oxygen consumption on the mimicked crack surface. While specimens with free spores added showed no oxygen consumption. This indicates the efficient protection of the hydrogel for spores in concrete. To conclude, the AM-H encapsulated carbonate precipitating bacteria have great potential to be used for crack self-healing in concrete applications.

Keywords: B. sphaericus spores; bacterial CaCO3; crack self-healing; in situ activity; modified-alginate hydrogel; oxygen consumption.

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Figures

FIGURE 1
FIGURE 1
Scratched surface of the prism.
FIGURE 2
FIGURE 2
Sensor tip just above the surface of the prism.
FIGURE 3
FIGURE 3
Ureolytic activity of non-encapsulated spores (S), modified alginate hydrogel (AM-H), and modified alginate hydrogel encapsulated spores (AM-HS; n = 3).
FIGURE 4
FIGURE 4
Thermogravimetric analysis (TGA) graphs of the samples from AM-HS (A) and AM-H (B) pieces after being immersed in the precipitation medium.
FIGURE 5
FIGURE 5
Scanning electron microscope (SEM) images of the CaCO3 precipitation on/in alginate hydrogel matrix under different magnification [(A) 395x; (B) 2860x).
FIGURE 6
FIGURE 6
Swelling properties of AM-H in de-mineralized water and in cement filtrate.
FIGURE 7
FIGURE 7
Moisture absorption and desorption of AM-H under different relative humidities.
FIGURE 8
FIGURE 8
Mechanical properties of the mortar specimens without and with different dosages of AM-H at the age of 28 days (The chart shows the mean value and standard deviation).
FIGURE 9
FIGURE 9
Oxygen concentration profiles (at certain time intervals) toward the surfaces of different submerged mortar prisms [(A) specimen N; (B) specimen N+AM-H; (C) specimen N+AM-HS; (D) specimen N+S].
FIGURE 10
FIGURE 10
Oxygen consumption in the boundary layer [the 0.5 mm water layer above the investigated location of the different prism surfaces, (A) specimen N; (B) specimen N+AM-H; (C) specimen N+AM-HS; (D) specimen N+S] as time went on.
See this image and copyright information in PMC

References

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