Abstract
Bio-grout, a new ground improvement method, has been recently developed to improve the mechanical properties, decrease the permeability of porous materials, reinforce or repair cementitious materials and modify the properties of soil or sand. Bio-grout production depends on microbially induced calcite precipitation (MICP), which is driven mainly by an enzyme, urease. However, urease-based MICP process produces excessive ammonia, in addition to secondary pollution generated by urea that is used as substrate in it. In the present study, we reported asparaginase-based MICP process for sand bio-grout development using Bacillus megaterium, and results were also compared with urease-based bio-grouts. The asparaginase activity led to significantly less ammonia production compared to urease without compromising with desired properties of a novel grout. The UCS of bio-grout was obtained at 980 kPa, while the permeability was decreased substantially. The mineralogical composition of precipitated substance was identified as calcite using XRD and the crystal morphology was observed under SEM. The mass percentage of calcite in bio-grout was calculated by thermogravimetric analysis and XCT verified calcite precipitation in it. The results confirmed that biocalcification by means of bacterial asparaginase is a potential solution for geotechnical problems. The asparaginase-based MICP process could be of wider acceptance in future.
Highlights
Bio-grout, a new ground improvement method, has been recently developed to improve the mechanical properties, decrease the permeability of porous materials, reinforce or repair cementitious materials and modify the properties of soil or sand
The problem associated with urease driven microbially induced calcite precipitation (MICP) process is the production of excessive ammonia, which has a negative impact on human health and the environment when the concentration of ammonia and ammonium is higher than safety threshold[12]
In order to solve such problems, the present study focuses on MICP process driven by asparaginase enzyme with commercially available asparagine as substrate
Summary
Bio-grout, a new ground improvement method, has been recently developed to improve the mechanical properties, decrease the permeability of porous materials, reinforce or repair cementitious materials and modify the properties of soil or sand. Bio-grout production depends on microbially induced calcite precipitation (MICP), which is driven mainly by an enzyme, urease. Bio-grout has been developed based on biological activity as a new ground improvement technology with potential to use with cementitious materials[5]. It could improve the mechanical properties (strength, stiffness, cohesion, friction), decrease the permeability of porous materials, reinforce or www.nature.com/scientificreports/. Bio-grout mainly depends on microbially induced calcite precipitation (MICP), carried out by urease producing bacteria During this process, bacteria hydrolyze a substrate, urea by producing an enzyme, urease that leads to increment in pH by the production of ammonium ions. Urea is widely used as substrate in the MICP process and because of its agricultural use and being raw material for fertilizer production, economic viability may not be associated with it, in addition to secondary pollutant nature of urea[13]
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