Loose Sand Particles Cemented by Chem/Bio-BaHPO₄ Powder

Abstract

Bacillus subtilis was selected as the suitable microorganism, which could produce alkaline phosphatase and constantly hydrolyzed phosphate monoester in the mixture solution of bacteria with substrate, and then the PO₄ ^3- was obtained. Bio-phosphate cement was prepared by alkaline earth element (Ba) ions reacting with PO₄ ^3- in the mixture solution. Structure, size and thermal properties of the bio-phosphate cement were characterized by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis. The average crystallite sizes of chem-BaHPO₄ and bio-BaHPO₄ corresponded to 11.99 and 24.13 μm, respectively. Chem-BaHPO₄ and bio-BaHPO₄ were then adopted to bind loose sand particles. The results indicated that loose sand particles can be well cemented by the bio-BaHPO₄ powder into a bio-sandstone with a certain mechanical properties, and the average compressive strength of the bio-sandstones can be up to 0.83 MPa when the curing time was 14 d. Along with the method in future studies, there will be multiple new opportunities for engineering applications, for instance, the treatment of sandy soil foundation, remediation of heavy metals in contaminated soil, and so on.

Keywords

Bacillus subtilis / bio-phosphate cement / X-ray techniques / scanning electron microscope / compressive strength