Revealing 3D orientation and strain heterogeneity in calcite generated by bio-cementation

TL;DR

This study employs advanced X-ray imaging techniques to nondestructively analyze the 3D morphology, orientation, and internal strains of calcite in bio-cemented sand, revealing heterogeneity that affects bond strength.

Contribution

It introduces a combined use of micro-tomography, 3DXRD, and DFXM to characterize calcite at multiple scales during bio-cementation, providing new insights into internal strain and microstructure.

Findings

Calcite exhibits anisotropic internal strain and sub-domain structures.

Bio-cementation induces localized strain concentrations during growth.

Microstructural heterogeneity influences bond integrity and load transfer.

Abstract

Bio-cementation uses bacterially induced calcite to bind sand grains, offering a low-carbon approach to soil stabilization. However, the 3D morphology, orientation texture, and internal strain states of individual calcite bonds remain insufficiently characterized. Here, we combine computed micro-tomography, 3D X-ray Diffraction (3DXRD), and Dark-Field X-ray Microscopy (DFXM) to nondestructively characterize grain morphology, crystallographic orientation, and both type II (intergranular) and type III (intragranular) elastic strains in calcite formed at sand-sand contacts during bio-cementation. Tomography establishes the sample morphology and the cemented contact architecture; 3DXRD provides grain-averaged orientation and strain states; and DFXM resolves sub-grain misorientations and localized strain concentrations generated during growth with 100 nm resolution. The combined results show that calcite precipitation through bio-cementation produces anisotropic internal strain and distinct sub-domain structures that can influence bond integrity and load transfer at the macroscopic scale.