As a typical brittle material, concrete exhibits strain softening under tensile load. The unfavorable failure mode can adversely affect the mechanical properties and durability of engineering structure. By material design on a micro scale, strain hardening cementitious composites (SHCC)were developed by designing materials on a microscopic scale and considering the interaction between fiber, matrix and fiber/matrix interface. This is a new type of high performance fiber reinforced cementitious composites. Compared with the traditional fiber reinforced concrete, SHCC has two significant advantages: one is tensile strain hardening, and the other is the multiple micro-cracks before failure. High ductility makes it excellent in mechanical properties, and tight cracks effectively ensure durability. In recent years, the relevant research works have made great progress. At the initial stage of research, the material design theory guides it to achieve the desired results. The fiber-bridging law is the theoretical basis of SHCC. In order to achieve strain hardening, two criteria must be satisfied-strength criterion and energy criterion. After the material design is refined, various mechanical performance indicators can provide key information for engineering applications. High strength and high toughness material is one of the unremitting pursuits of researchers. At present, SHCC with compressive strength up to 115 MPa and ultimate tensile strain of 8% has been successfully designed. Moreover, most crack widths are maintained under 100 μm with the crack spacing less than 2 mm. Research on the fracture properties of SHCC is challenging, and there is still a lack of effective analytical methods in the multi-cracking stage. The split Hopkinson pressure bar test showed that SHCC is a strain rate dependence material, and the peak stress increased obviously with the increase of strain rate. Subjected to fatigue loading, SHCC exhibited ductile failure characteristics and relatively high fatigue life. At the same time, considering the long service life of engineering structure, the durability of materials cannot be ignored. The amount of water permeation decreased sharply due to the small crack width of SHCC. The permeability coefficient was only 2.10×10-7 m/s at 2% tensile strain level; besides, its self-hea-ling behavior can further reduce the permeability. SHCC also provides the possibility of application under extreme temperature conditions. After 300 freeze-thaw cycles, the performance of SHCC remained at a high level; after high temperature, the melted fibers leaved small channels to release vapor pressure, avoiding explosive spalling. In addition, the actual engineering can objectively and truly reflect the material properties. SHCC has been successfully applied in ordinary concrete beam reinforcement, masonry structure reinforcement, pavement engineering and dam repair. This paper introduces the design concept of SHCC, the basic criteria to be satisfied and the selection of raw materials, firstly. Then, the latest research achievements in the basic mechanical performance and durability of SHCC are presented separately. Additionally, the repair and reinforcement engineering structure and its engineering application using SHCC are summarized. Finally, the problems in the current SHCC research are discussed and the further research directions are proposed. © 2019, Materials Review Magazine. All right reserved.
