Sprayed high-strength strain-hardening cementitious composite: Anisotropic mechanical properties and fiber distribution characteristics

Abstract

High-strength strain-hardening cementitious composite (HS-SHCC), such as ultra-high performance concrete (UHPC) and high-strength engineered cementitious composites (ECC), is renowned for its exceptional strength, ductility, and durability compared to traditional concrete materials. This study experimentally investigated the anisotropic compressive and flexural responses of sprayed HS-SHCC. Initially, a sprayable HS-SHCC material was developed, which possessed appropriate rheological properties for pumping, spraying, and stacking. HS-SHCC panels were then fabricated via spraying, and specimens were subsequently extracted for compressive and flexural testing. The experimental variables included the load direction and the location of the extracted specimens in the panel. In addition to the mechanical tests, X-ray computer tomography was used to quantify fiber distribution in the sprayed HS-SHCC. The results indicated significant anisotropy in the compressive and flexural behavior of the sprayed HS-SHCC, particularly in flexural strength, which was 70% higher than the cast specimen when loaded in the spray direction. The calculated coefficients for the fiber orientation, number of fibers, and fiber dispersion indicated a planar fiber orientation in the sprayed HS-SHCC, with the highest values for the gravity direction and the lowest for the spraying direction. Furthermore, the mechanical behavior and fiber distribution also depended on the location of the extracted specimens in the panel. Lastly, a probability density distribution was suggested for evaluating fiber orientation in the sprayed HS-SHCC.