Assessment of the time-dependent transport properties of cracked ECC accounting for self-healing using XRCT imaging and numerical modeling

Artikel i vetenskaplig tidskrift, 2026

Engineered cementitious composites (ECC) exhibit superior durability performance even after cracking, primarily due to their very low permeability and diffusivity to chlorides. However, accurately quantifying these transport properties is challenging, as they are strongly dependent on factors such as crack tortuosity, fibers bridging the crack, and other microstructural heterogeneities. This paper assesses permeability and diffusion in individual cracks of ECC using X-ray computed tomography (XRCT) imaging and numerical modeling, explicitly incorporating the complex crack morphology and its evolution over time due to self-healing. High-resolution XRCT scans are performed on two different cracked ECC specimens at predefined healing stages. The crack is then segmented and converted into a Finite Element mesh for numerical simulations that are performed directly on the experimentally acquired data. At each healing stage, Stokes flow and chloride diffusion are solved within the crack domain, yielding effective permeability and diffusion coefficients as a function of the healing state. The obtained simulation results were compared against permeability predictions based on experiments using analytical formulas showing that they can differ significantly from numerically derived values. In addition, a parametric study on the impact of the fiber volume fraction showed that permeability decreases by about 8.4% per 1% increase in fiber volume, whereas the diffusion coefficient declines more modestly, by about 2.3% per 1%. By explicitly accounting for self-healing, the exact crack morphology, and bridging fibers, the investigation links microscopic changes in cracks to macroscopic transport parameters relevant for service-life design.