AUTHOR=He Jia , Mao Xunyu , Zhou Yundong , Tang Qiang TITLE=Cementation of Sand With Enzyme-Induced Carbonate Precipitation (EICP) Using Concrete-Extracted Calcium JOURNAL=Frontiers in Physics VOLUME=9 YEAR=2022 URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2021.825356 DOI=10.3389/fphy.2021.825356 ISSN=2296-424X ABSTRACT=

Calcium carbonate precipitation and crystallization induced by urease enzyme to solidify soil is known as biocement technology. The uses of waste and cheap materials can make this technology more cost-effective and practical for applications. In this study, calcium ions were obtained by dissolving waste concretes in acidic liquid. Sand columns were treated by enzyme-induced carbonate precipitation (EICP) with either concrete-extracted calcium or reagent calcium for comparison. Compressive strengths, calcium carbonate contents, and microscopic analysis on the treated sand were carried out. It was found that the compressive strength of the former could reach 833 kPa in the dry state and 204 kPa in the wet state after 5 times of EICP treatment, both of which were higher than that of the latter. The calcium carbonate contents could reach 2–3% after 3–5 times of treatment. Based on the scanning electron microscope (SEM) and X-ray diffractometer (XRD) analyses, the crystal type of calcium carbonate produced in sand was calcite. The comparative results showed that the treatment effect using concrete-extracted calcium was similar or better than that using reagent calcium.