Engineered Cementitious Composites: Can Composites Be Accepted as Crack-Free Concrete?

摘要

Because conventional concrete is brittle and tends to crack easily under mechanical and environmental loads, there are concerns with durability. During the past decade, the effort to modify the brittle nature of ordinary concrete has resulted in high-performance fiber-reinforced cementitious composites (HPFRCCs), which are characterized by tensile strain-hardening after first cracking. Engineered cementitious composites (ECCs), a special type of HPFRCC, represent a new concrete material that offers significant potential to reduce the durability problem of concrete structures. Unlike ordinary concrete and fiber-reinforced concrete materials, ECC strain-hardens after first cracking, as do ductile metals, and it demonstrates a strain capacity 300 to 500 times greater than normal concrete. Even at large imposed deformation, crack widths of ECC remain small, less than 80 µm. Apart from unique tensile properties, the relationship between crack characteristics and durability-including transport properties (permeability, absorption, and diffusion); frost resistance with and without deicing salts; performance in a hot and humid environment; performance in a high-alkaline environment, corrosion, and spall resistance; and self-healing of microcracks-is presented. Research results indicate that, because of intrinsic self-control tight crack width, robust self-healing performance, and high tensile strain capacity, many durability challenges confronting concrete can be overcome by using ECCs.