Correlative X-ray Micro-CT and Surface Profilometry for Multiscale 3D Characterization of Sandstone

X-ray micro-computed tomography (micro-CT) has become a widely used non-destructive technique in geosciences for three-dimensional visualization and quantitative analysis of geomaterials. However, in laboratory-based systems, spatial resolution is constrained by a trade-off between sample size, X-ray flux, and focal spot size, with the highest achievable resolutions typically in the micrometer range. In addition, near-surface regions are often affected by imaging artifacts such as beam hardening, cone-beam artifacts, and partial volume effects, which complicate accurate surface characterization. This constraint is particularly significant because many key physical and chemical processes are highly sensitive to the details of surface geometry. Surface properties—including roughness and pore morphology—play a critical role in governing fluid flow, chemical reactions, and mechanical behavior in rocks, making precise measurement essential for understanding geomaterials at multiple scales. 

High-resolution techniques such as FIB-SEM can provide detailed three-dimensional information, but they are destructive and time-consuming. Synchrotron-based X-ray CT offers a non-destructive alternative with higher spatial resolution, although access to synchrotron facilities is limited. Surface profilometry, particularly when combining confocal microscopy and focus variation microscopy, provides an additional non-destructive and time-efficient approach for acquiring high-resolution three-dimensional surface topography. 

This study presents a correlative imaging workflow that integrates laboratory X-ray micro-CT with surface profilometry measurements on Bentheimer sandstone. The micro-CT dataset was acquired at the Ghent University's Center for X-ray Tomography (UGCT) using the CoreTOM (Tescan) with a voxel size of 6.5 μm, while the surface profilometer S neox (Sensofar) achieved a lateral spatial resolution of up to 0.34 μm. The workflow includes data acquisition, registration, and combined multiscale visualization. 

The applicability of this approach is demonstrated by comparing surface modifications before and after nano-silica treatment of Bentheimer sandstone. The correlative dataset reveals morphological changes that cannot be resolved by micro-CT alone, including reduced surface roughness and partial infilling of surface-connected pores. At the same time, micro-CT captures complementary information on the penetration depth and spatial distribution of the treatment products. Together, these observations highlight the added value of integrating surface profilometry with micro-CT for quantitative near-surface characterization of geomaterials. 

Acknowledgment: This abstract is part of project Fluidcontrol (with project number G065224N) which is financed by Research Foundation–Flanders (FWO). Ghent University's Center for X-ray Tomography (BOF.COR.2022.008) and IOF (project FaCT F2021/IOF-Equip/021) are also acknowledged.