Improvement of Biomineralization of Sporosarcina pasteurii as Biocementing Material for Concrete Repair by Atmospheric and Room Temperature Plasma Mutagenesis and Response Surface Methodology

Abstract

Microbially induced calcium carbonate precipitation (MICP) has recently become an intelligent and environmentally friendly method for repairing cracks in concrete. To improve on this ability of microbial materials concrete repair, we applied random mutagenesis and optimization of mineralization conditions to improve the quantity and crystal form of microbially precipitated calcium carbonate. Sporosarcina pasteurii ATCC 11859 was used as the starting strain to obtain the mutant with high urease activity by atmospheric and room temperature plasma (ARTP) mutagenesis. Next, we investigated the optimal biomineralization conditions and precipitation crystal form using Plackett-Burman experimental design and response surface methodology (RSM). Biomineralization with 0.73 mol/l calcium chloride, 45 g/l urea, reaction temperature of 45°C, and reaction time of 22 h, significantly increased the amount of precipitated calcium carbonate, which was deposited in the form of calcite crystals. Finally, the repair of concrete using the optimized biomineralization process was evaluated. A comparison of water absorption and adhesion of concrete specimens before and after repairs showed that concrete cracks and surface defects could be efficiently repaired. This study provides a new method to engineer biocementing material for concrete repair.

Keywords: Biomineralization; calcite; calcium carbonate; concrete repair; optimization.

Fig. 1

(A) Comparison of growth and urease activity between Sporosarcina pasteurii ATCC 11859 and mutant B11. (B) The genetic stability of mutant B11.

Fig. 2

The effects of different factors including calcium chloride (A), urea (B), nickel chloride (C), ammonium chloride (D), yeast extract (E), temperature (F), and reaction time (G) on calcium carbonate precipitation and calcite ratio.

Fig. 3. The response surface diagram depicting the influence of the interaction between two factors on the precipitation of calcium carbonate.

(A) Urea and calcium chloride, (B) temperature and urea, (C) temperature and calcium chloride.

Fig. 4

SEM and EDS analysis of calcium carbonate precipitates obtained under optimized condition 1 (A) and optimized condition 2 (B). XRD pattern (C) and FTIR pattern (D) of calcium carbonate precipitate. A and B stand for the precipitates obtained under optimized conditions 1 and 2, respectively. The letters C and V in Fig. 4C stand for calcite and vaterite.

Fig. 5. Visual observation of surface characteristerics of concrete specimens before and after repair.

(A) and (B) were the surface states of concrete specimens with surface defects before and after being repaired. (C) and (D) were the states of concrete specimens with cracks before and after being repaired.

Fig. 6. The changes of bibulous rate (A) and quality loss (B) of the specimens with surface defects after being repaired, and the specimens with concrete cracks after being repaired (C and D).

In the control group, the specimen with surface defect and crack was both repaired without adding bacteria while other conditions remained the same with experimental group.