Sulfate Acid Corrosion Mechanism of Biogeomaterial Based on MICP Technology

Abstract

Biogeomaterials are developed based on microbially induced calcite precipitation (MICP) technology, which is a recent innovation in civil engineering. Acid pollution, such as large amounts of distributed sulphate saline soil on site and acid leachate from an industry factory site, has been considered when using new biogeomaterials. The purpose of this study was to evaluate the stability of the anticorrosion and corrosion properties of a biogeomaterial as well as the induced corrosion mechanism in a sulfate acid environment. The mechanical properties and pore characteristics of this biogeomaterial were examined via unconfined compressive strength and microscopic characteristic testing. The fractal characteristics of pore size were also investigated in various corrosion stages. The results show that dynamic equilibrium is maintained between two crystals that exist in different stages of corrosion, resulting in the different acid corrosion properties of the biogeomaterial. As a bonding material and strength supplement, calcium carbonate crystals induced from MICP were constantly dissolved when corrosion began. The porosity of the biomaterial increased gradually while its mechanical properties decreased dramatically. Furthermore, calcium sulfate crystals, a new chemical product having a larger volume and lower mechanical strength than calcium carbonate crystals, was generated from the dissolution of calcium carbonate crystals. It is concluded that the ability of a biogeomaterial to resist sulfuric acid corrosion is not as weak as expected because of the formation of slightly soluble calcium sulfate. This finding provides important insight into the corrosion resistance of biogeomaterials in sulfuric acid environments.