Strain-hardening mechanism and crack control of hydraulic engineered cementitious composites (HECC): A theoretical and experimental study

Engineered Cementitious Composites (ECC) are characterized by high ductility, durability, multiple cracking, and self-healing properties, making them ideal for addressing cracking and leakage in hydraulic structures such as dam foundations and panel dams. This study explores the strain-hardening mechanism of Hydraulic Engineered Cementitious Composites (HECC), focusing on fiber elongation and crack behavior, and proposes a control theory. A three-stage tensile strain-hardening process is introduced, along with an HECC fiber slip assumption theory. The method for calculating fiber slip pull-out length and the design method for HECC elongation based on this theory are derived through mathematical and theoretical formulations. Crack and elongation control methods are also analyzed. Experimental tensile tests are conducted to validate the proposed fiber slip theory, confirming the rationality of the strain-hardening mechanism and computational model. The results suggest that enhancing the matrix’s initial cracking performance, increasing fiber elastic modulus, reducing matrix elastic modulus, selecting HECC with a large difference between matrix tensile strength and initial cracking strength, and increasing fiber content or reducing fiber diameter are all beneficial for controlling HECC’s elongation and crack propagation. Finally, the material parameters based on control theory were successfully applied in a large-scale hydraulic project, aiming to improve durability and safety. This study provides a theoretical foundation for understanding the role of fibers in concrete and the strain-hardening mechanism of HECC, advancing fiber selection methods and facilitating its application in hydraulic engineering.