Mixture Design, Processing, and Properties of Sprayed Strain-Hardening Cementitious Composites: A Review

Strain-hardening cementitious composite (SHCC), also known as engineered cementitious composite (ECC), is a cementitious composite with high ductility, which shows strain-hardening behavior with saturated multiple cracking under direct tension. Sprayed SHCC is a type of SHCC sprayed at high speeds through a nozzle onto the surface of a substrate, which is widely used for structural reinforcement and repair applications. There are several review articles on SHCC for conventional cast applications; however, a comprehensive review and analysis of sprayed SHCC is lacking. To address this, this paper aims to compare the design principles and performance of cast and sprayed SHCC and to review the application and spraying processes of sprayed SHCC. This comprehensive review examines the theoretical foundations, material design principles, performance characteristics, and practical applications of sprayed SHCC. The mixture design theory is thoroughly analyzed, and the fundamental properties of sprayed SHCC are discussed, including pumpability, sprayability, and their evaluation methods. The review investigates the transition zone between substrate and sprayed SHCC overlay, interface failure modes, shear-slip behavior, and various influencing factors, with comparisons to conventional cast SHCC. Current applications of sprayed SHCC in infrastructure repair, strengthening, and durability control are discussed, demonstrating the practical viability and advantages of this technology. This state-of-the-art review is expected to offer valuable insights into further development and wider applications of sprayed SHCC in the construction industry.