Publication Price 2022 for SFB 1313 post-doctoral researchers Felix Weinhardt and Johannes Hommel

Congratulations to our SFB 1313 post-doctoral researchers Felix Weinhardt (research project B05) and Johannes Hommel (associated research project CX2)! They received the publication price 2022 of the Faculty 2 of the University of Stuttgart for their publication "Spatiotemporal Distribution of Precipitates and Mineral Phase Transition During Biomineralization Affect Porosity–Permeability Relationships". The ceremony took place at the University of Stuttgart on 7 June 2023.

Authors

• Felix Weinhardt (University of Stuttgart, SFB 1313 research project C04)
• Jingxuan Deng (University of Minnesota, Kang Research Group)
• Johannes Hommel (University of Stuttgart, associated SFB 1313 research project CX2)
• Samaneh Vahid Dastjerdi (University of Stuttgart)
• Robin Gerlach (Montana State University, SFB 1313 external partner, research project C04)
• Holger Steeb (University of Stuttgart, SFB 1313 research projects B05, C05 and Z02)
• Holger Class (University of Stuttgart, SFB 1313 research project C04)

Abstract

Enzymatically induced calcium carbonate precipitation is a promising geotechnique with the potential, for example, to seal leakage pathways in the subsurface or to stabilize soils. Precipitation of calcium carbonate in a porous medium reduces the porosity and, consequently, the permeability. With pseudo-2D microfluidic experiments, including pressure monitoring and, for visualization, optical microscopy and X-ray computed tomography, pore-space alterations were reliably related to corresponding hydraulic responses. The study comprises six experiments with two different pore structures, a simple, quasi-1D structure, and a 2D structure. Using a continuous injection strategy with either constant or step-wise reduced flow rates, we identified key mechanisms that significantly influence the relationship between porosity and permeability. In the quasi-1D structure, the location of precipitates is more relevant to the hydraulic response (pressure gradients) than the overall porosity change. In the quasi-2D structure, this is different, because flow can bypass locally clogged regions, thus leading to steadier porosity–permeability relationships. Moreover, in quasi-2D systems, during continuous injection, preferential flow paths can evolve and remain open. Classical porosity–permeability power-law relationships with constant exponents cannot adequately describe this phenomenon. We furthermore observed coexistence and transformation of different polymorphs of calcium carbonate, namely amorphous calcium carbonate, vaterite, and calcite and discuss their influence on the observed development of preferential flow paths. This has so far not been accounted for in the state-of-the-art approaches for porosity–permeability relationships during calcium carbonate precipitation in porous media.