Tailoring crack width control of LC3-based engineered cementitious composites (ECC) via fiber hybridization: From micromechanics design to macro investigation

As a class of strain-hardening cement-based material, Engineered Cementitious Composites (ECC) feature high tensile ductility and multiple cracking. However, ECCs reinforced with hydrophobic fibers attain high ductility but also exhibit larger crack widths caused by the weak bonding of the fiber/matrix interface, attenuating the durability potential of resulting infrastructures. This research aims at tailoring the crack width control ability of ECC through hybridizing hydrophilic PVA and hydrophobic PP fiber. A systematic design procedure was proposed based on the micromechanical analysis with a multi-scale investigation. Experimental results verified the hypothesized composite ductility enhancement by PP fiber and strength enhancement and crack width reduction by PVA fiber. Tight crack width of 50 μm at 2 % tensile strain can be achieved by a fiber hybridization ratio of 1:1 to ensure extreme durability. Changes in the microstructure of the matrix, associated with fresh property alteration due to fiber hybridization, were captured by micro CT scanning. Finally, the trade-off between mechanical performance, durability, and material sustainability was investigated for optimal material design. This research demonstrates that hybridizing PVA fiber with PP fiber holds promise to enhance material sustainability while maintaining the advantageous characteristics of ductile ECC and tight crack width for extreme durability.