Quantitative characterization of multiple cracks and permeability in coral sand engineered cementitious composites based on micro-computed tomography

Seawater–coral sand engineered cementitious composites (SCECCs) offer an effective solution for marine construction by utilizing local resources, thereby reducing costs and improving efficiency. This study examines the crack characteristics and permeability of SCECCs after loading, which are less understood aspects of these materials. Uniaxial tension tests were performed on SCECC specimens with varying particle sizes and aggregate types. High-resolution micro-computed tomography (micro-CT) and 3D visualization techniques were employed to analyze the formation and distribution of cracks as well as the permeability properties of the material. The findings indicate that as the maximum particle size increases, the volume fraction of cracks decreases. The crack distribution density initially rises and then falls with increasing particle size, while the spacing of cracks show the opposite trend. Specimens with 0.60 mm aggregates demonstrated the most uniform and favorable crack distribution, outperforming similar freshwater–quartz sand ECC mixtures. Key factors influencing the permeability of cracked SCECCs include the pore throat parameters, volume ratios of pores and pore throats across different radii, and the spatial distribution of these structures. The SCECC’s ability to disperse deformation among numerous small cracks significantly enhances its impermeability, making it a highly suitable material for marine engineering applications.