Unlocking concrete's three-dimensional pore structure: a comprehensive micro-CT analysis

Abstract Micro-computed tomography (micro-CT) is widely applied to characterize concrete pore systems; however, analyses are typically limited to global porosity and pore size metrics, providing little insight into the spatial heterogeneity of pores. In particular, three-dimensional, scale-dependent quantification of pore heterogeneity remains largely unexplored. In this study, micro-CT was used to analyze the three-dimensional pore structure of concrete cubes produced with and without the addition of superplasticizer. Beyond conventional porosity descriptors, pore-system heterogeneity was quantified using three-dimensional lacunarity analysis. Pore evolution during curing was investigated, and intact specimens were compared with fractured samples. The results demonstrate that the addition of superplasticizer significantly reduces porosity and average pore size while promoting a more homogeneous pore distribution. Lacunarity reveals a pronounced increase in pore-system heterogeneity during early curing, followed by stabilization, reflecting hydration-driven pore refinement and the increasing dominance of larger detectable pores. Furthermore, fractured regions are shown to be associated with higher contributions from large, spatially heterogeneous pores. The main contribution of this work is the introduction of lacunarity as a robust, scale-sensitive descriptor for concrete pore systems, providing information beyond conventional porosity measures and enabling a more comprehensive understanding of pore structure evolution and fracture-related heterogeneity.