Study on the influence of magnesium/calcium ratios on bio-cemented sandy soils

Xiaohao Sun, Linchang Miao, Hengxing Wang, Ziming Cao, Linyu Wu, Jian Chu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

7 Citations (Scopus)

Abstract

Microbially induced carbonate precipitation (MICP) has been extensively studied as a promising technique for soil stabilization. However, the heterogeneity in bio-cementation always hampers the application of MICP. Seawater contains more magnesium ions (Mg2+) than calcium ions (Ca2+) and using magnesium for bio-cementation might be more cost-effective in coastal cities. In this study, the microbially induced magnesium and calcium precipitation (MIMCP) treatment was proposed to solve the problem of heterogeneity, where the urea-magnesium-calcium solution was used as the cementation solution with various Mg2+/Ca2+ ratios. The influences of Mg2+/Ca2+ ratios on pH, bio-flocculation, and chemical conversion efficiency were studied. The sand bio-cementation tests were subsequently conducted to compare the treatment effects with different Mg2+/Ca2+ ratios. Results showed that the increase in Mg2+/Ca2+ ratios resulted in lower pH levels and smaller percentages of bio-flocculation. The higher Mg2+/Ca2+ ratio also provided a longer lag period, regardless of biomass concentrations; however, the chemical conversion efficiency decreased. Furthermore, the increased Mg2+/Ca2+ ratios resulted in a small difference in UCS and contents of precipitation at different parts of bio-cemented soils, achieving better homogeneity in bio-cementation. However, the strength significantly decreased at an Mg2+ concentration over 0.8 M due to much smaller contents of precipitation. In addition, with increased Mg2+/Ca2+ ratios, more aragonite in calcium precipitation was produced. The proposed MIMCP method in this study was significant to improve the homogeneity of bio-cemented soil in practical engineering applications.

Original languageEnglish
JournalActa Geotechnica
DOIs
Publication statusAccepted/In press - 2024

Keywords

  • Bio-cementation
  • Ca ratios
  • Homogeneity
  • Mg
  • Sand stabilization
  • UCS

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Earth and Planetary Sciences (miscellaneous)

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