A new generation of cement, microbe cement, has been developed in response to the ever increasing awareness of environmental protection. Microbe cement is a new strengthening material based on microbiologically induced precipitation of calcium carbonate. This paper confirms the feasibility of binding loose sand particles using microbe cement and details the cementation mechanism of microbe cement. We have also prepared microbe cementitious materials (biosandstones). The compressive strength of the bio-sandstone, which depends on the content of calcium carbonate produced by microbially induced precipitation and the bio-mediated calcite crystal size, could be up to 12 MPa at an age of 20 days. By increasing the precipitated calcite content, the compressive strength and microstructure of bio-sandstone could be improved.
The bio-sandstone, which was cemented by microbe cement, was firstly prepared, and then the microstructure evolution process was studied by X-ray computed tomography(X-CT) technique. The experimental results indicate that the microstructure of bio-sandstone becomes dense with the development of age. The evolution of inner structure at different positions is different due to the different contents of microbial induced precipitation calcite. Besides, the increase rate of microbial induced precipitation calcite gradually decreases because of the reduction of microbe absorption content with the decreasing pore size in bio-sandstone.
Microbe-based cement has been widely reported in recent literatures. It is a new method of consolidating loose fine particles, which relies on the bacterially induced formation of a compatible carbonate precipitation around individual particles and at particle-particle contacts. Materials and cementation procedure are two major factors that influence the cementation performance of microbe-based cement. Besides, there are some other factors related to the performance, such as pH, temperature, metabolism activity, the flushed times of bacterial solution, concentration of substrate and calcium ion, etc., which affect consolidation function. The assessment methods for cementation process are carried out by various techniques. The performance of consolidation loose grains based on microbe-based cement is tested with the help of experiment. In this paper a review is presented on the cementation mechanism of microbe-based cement, techniques utilized to monitor cementation process, the consolidated performance by microbe-based cement and bond factors.
Loose sand particles could be cemented to sandstone by bio-cement(microbial induced magnesium carbonate). The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone cemented by microbial induced magnesium carbonate were tested to characterize the cementation effectiveness. In addition, the formed mineral composition and the microstructure of bio-sandstone were analyzed by X-ray diffraction(XRD) and scanning electron microscopy(SEM), respectively. The experimental results show that the feasibility of binding loose sand particles using microbial induced magnesium carbonate precipitation is available and the acquired compressive strength of bio-sandstone can be excellent at certain ages. Moreover, the compressive strength and the porosity could be improved with the increase of microbial induced magnesium carbonate content. XRD results indicate that the morphology of magnesium carbonate induced by microbe appears as needles and SEM results show that the cementation of loose sand particles to sandstone mainly relies on the microbial induced formation of magnesium carbonate precipitation around individual particles and at particle-particle contacts.
Microbe cementitious material as a binder has been developed due to the ever increasing awareness of environmental protection.The new cementitious material relies on microbiologically induced precipitation of calcium carbonate to bind loose particles or repair surface defects and cracks of cement-based material.This paper elaborates the research on loose sand particles cemented by microbe cement from three aspects:compressive strength,pore structure and microstructure.In addition,the research on restoration surface defects and cracks of cement-based material by microbe cement is introduced from two parameters:surface water absorption and compressive strength recover coefficient.The results show that microbe cementitious material can bind loose particles and repair surface defects or cracks of cement-based material.
