Sprayable engineered cementitious composites (ECC) using calcined clay limestone cement (LC3) and PP fiber

Abstract

Sprayable engineered cementitious composites (ECC) has demonstrated in field applications as a promising repair material. However, the large cement dosage that leads to a high carbon footprint and potential restrained shrinkage cracking suggests needed improvements. In this study, a sprayable ECC was developed using calcined clay limestone cement (LC3), calcium sulfoaluminate (CSA) expansive additive and polypropylene (PP) fiber to increase the material greenness and durability. The sprayability and mechanical performance were examined by the flow table and uniaxial tension tests. The one-time build-up thickness achieved was 45 mm for vertical spraying and 35 mm for overhead spraying at 20–30 min rest-time, and up to 80 mm for vertical spraying at 50 min rest-time. The ECC had a comparable strength but higher tensile strain capacity (5.7%) and reduced crack width (30 μm at 1% tensile strain) when sprayed, in comparison to specimens prepared by casting. A spray-repaired layered ECC-concrete composite revealed multiple cracking and strain-hardening performance under flexural loading. The advantages of low carbon, low shrinkage, low cost, and ultra-high ductility of the developed sprayable ECC promote broader applications in infrastructure repair.