Capillary of engineered cementitious composites using steel slag aggregate

The durability loss of hydraulic concrete structures due to capillary suction has become a global concern. Engineered cementitious composites (ECCs) offer a promising solution to extend the service life of these structures and reduce maintenance costs. However, the limited availability and high cost of micro-silica sand (MSS), a key component in ECC production, hinder its widespread application. Therefore, it is essential to identify alternative materials that can replace MSS. This study investigates the capillary transport properties of economic ECCs incorporating steel slag (SS) as an aggregate. Key properties, including compressive strength, absorption, void content, capillary water absorption, and chloride transport characteristics, were evaluated. The phase development and microstructural characteristics of the matrix were analysed using XRD and SEM observations, confirming the potential cementitious activity of SS. The incorporation of SS was found to refine the pore structure, enhance compressive strength, and improve resistance to capillary transport. At a 50 % SS substitution rate, the 28-day compressive strength of ECCs increased by 7.01 %, while the initial water absorption rate and chloride diffusion coefficient decreased by 21.86 % and 21.24 %, respectively. However, a higher content of polyvinyl alcohol (PVA) fibres adversely affected the capillary transport properties of ECCs. Based on the experimental results, an ECC mixture containing 1.5 % PVA fibres and 50 % SS is recommended for hydraulic concrete structures. Nonetheless, the application of ECC mixtures in hydraulic structures with stringent early-age strength requirements is constrained by the slower development of strength and durability. This study provides insights into the resource-efficient utilisation of SS in high-performance construction materials.