The Interface Of Sand And Microbe Cement And Its Effect On Properties

Bio-cement, based on microbial induced mineralization, can consolidate the loose particles and would be a novel and sustainable cementing material which is capable of overcoming some disadvantages such as high consumption and evident chemical toxicity. The bio-calcite cement, as one kind of bio-cement, has been investigated widely. Main attention, however, is paid to the preparation and its cemented application in sand. This paper presents a new kind bio-cement based on phosphate-mineralized microbe, and the difference was investigated between the bio-phosphate and bio-calcite cement in the terms of macroscopic cementation performance, the property of the cemented interface and the microcosmic interface between the cemented product and sand particle. The mainly research conclusion and innovation results of the article were list as following four points.The phosphate-mineralized microbe in this paper is able to decompose the selected substrate with the enzyme, and specific phosphate product was synthesized. Analysis results showed that the product was hydroxyapatite. The deposition conditions of bio-phosphate in the solution were optimized and the preliminary recipe was also determined.Cemented sand body samples were studied comparatively in the cementing property such as the strength, permeability, porosity and the content of bio-cement product. The test results indicated that the permeability and porosity of sand body cemented by bio-calcite one were significantly larger than others, while the content of cemented product was the least in such a situation that the strength was very similar. Meanwhile, the microscopic analysis results showed that the distribution pattern of cemented product was obviously dissimilar.The interfacial deposition experiment was conducted on the surface of silica glass and the interface effect was characterized by the disbanding experiment via sonic oscillation. It was showed that the effect was significantly intenser in bio-calcite group than others, and the worst effect occurred in the bio-phosphate calcium one, which was confirmed by the scratch experiment. By comparison, the interfacial bonding strength unit mass of biological calcium was the largest among the experiment groups, which is also consistent with the law of the strength in the cemented sand.The microcosmic interface between the cemented product and sand particle was studied by X-ray photoelectron spectroscopy and nuclear magnetic resonance. The results showed that the chemical environment of the Si atoms were significantly changed and its electron density decreased due to a new bond formed between the cemented product and quartz sand particle, which was the essence of the bio-cement and further clarified the cemented property.