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Mineral Type Impact on Thermal Conductivity of Biocement and Biocemented Sand

Shadi Zeinali, Zarghaam Heidar Rizvi, Frank Wuttke

TL;DR

This paper investigates how CaCO3 polymorphs generated by microbially induced calcium carbonate precipitation (MICP) affect soil thermal conductivity ($TC$) for geothermal applications. It employs biocementation using Sporosarcina pasteurii and selective calcification conditions to produce vaterite- and calcite-rich precipitates across multiple columns, analyzing polymorph content with XRD/Rietveld, LOI, and SEM while measuring $TC$ in dry and saturated states via transient and steady-state methods. Key findings show calcite-rich biocement yields higher $TC$ than vaterite-rich variants, with about a 30% $TC$ improvement when calcite content rises from ~10% to ~90%; organic content and saturation can modulate this effect. The results link microstructure and recrystallization to thermal performance and underscore the importance of polymorph control for predictive geothermal design, suggesting further testing under broader, field-relevant conditions.

Abstract

This study experimentally investigates the influence of CaCO3 polymorphs on the thermal conductivity (TC) of biocement and biocemented sand. Calcite-rich biocements consistently showed higher TC than vaterite-dominated ones, regardless of density or saturation. Vaterite-rich biocement, resulting from rapid precipitation and elevated organic content, yields inherently lower TC. This study shed light on the limited TC improvement observed in vaterite-rich biocemented sand.

Mineral Type Impact on Thermal Conductivity of Biocement and Biocemented Sand

TL;DR

This paper investigates how CaCO3 polymorphs generated by microbially induced calcium carbonate precipitation (MICP) affect soil thermal conductivity () for geothermal applications. It employs biocementation using Sporosarcina pasteurii and selective calcification conditions to produce vaterite- and calcite-rich precipitates across multiple columns, analyzing polymorph content with XRD/Rietveld, LOI, and SEM while measuring in dry and saturated states via transient and steady-state methods. Key findings show calcite-rich biocement yields higher than vaterite-rich variants, with about a 30% improvement when calcite content rises from ~10% to ~90%; organic content and saturation can modulate this effect. The results link microstructure and recrystallization to thermal performance and underscore the importance of polymorph control for predictive geothermal design, suggesting further testing under broader, field-relevant conditions.

Abstract

This study experimentally investigates the influence of CaCO3 polymorphs on the thermal conductivity (TC) of biocement and biocemented sand. Calcite-rich biocements consistently showed higher TC than vaterite-dominated ones, regardless of density or saturation. Vaterite-rich biocement, resulting from rapid precipitation and elevated organic content, yields inherently lower TC. This study shed light on the limited TC improvement observed in vaterite-rich biocemented sand.
Paper Structure (4 sections, 2 figures, 1 table)

This paper contains 4 sections, 2 figures, 1 table.

Table of Contents

  1. Introduction
  2. Materials and Methods
  3. Results and discussion
  4. Conclusion

Figures (2)

  • Figure 1: (a) EC and pH evolution; SEM image of (b) Bioc2-V3, (c) Bioc3-V1 with 50µ m scale bar
  • Figure 2: (a) TC of biocement columns per dry density versus vaterite content, size of the markers is relative to organic content of the samples; (b) XRD, LOI composition of biocement samples.