Reinforcement effects on the tensile properties of seawater sea-sand engineered cementitious composites reinforced with multi-scale hybrid fibers

Abstract

The preparation of seawater sea-sand engineered cementitious composites (SS-ECC) holds great potential for development in coastal and marine infrastructure. To improve its compressive strength and tensile properties, this study investigated the crack characteristics, micro-mechanics, fibers reinforcement index, and micro-structure of SS-ECC using a multi-scale hybrid fibers system consisting of CaCO3 whiskers, PE fibers, and stainless steel fibers (SSF). The aim was to gain an in-depth understanding of the reinforcement effects of multi-scale hybrid fibers. The results showed that CaCO3 whiskers increased the number of cracks and the stability of crack evolution in SS-ECC during the ultimate tensile state by bridging the matrix micro-cracks, improving the matrix micro-structure, and filling the interfacial transition zones between the macroscopic fibers (PE fibers and SSF) and the matrix. Additionally, it reduced the crack width and spacing. These combined effects increased the compressive strength, tensile strength, and tensile strain capacity of SS-ECC by 12.8%, 15.7%, and 11.9%, respectively. Finally, the reinforcement effects of multi-scale hybrid fibers were analyzed based on the pseudo-strain hardening performance indices, fibers reinforcement index, and hybrid coefficient. This analysis provides reference and insight for the design of multi-scale hybrid fibers SS-ECC with a high comprehensive performance (σcσtε/w) index.