Preparation of low-cost green engineered cementitious composites (ECC) using gold tailings and unoiled PVA fiber

The current study aims to establish low-cost green engineered cementitious composites (ECC) using gold tailings, unoiled PVA fiber and large-volume fly ash. Through compression test, four point bending test, direct tensile test, matrix fracture toughness test and single-crack tensile test, the mechanical properties of ECC were explored. It is found that incorporation of gold tailings leads to the enhanced compressive strength and reduced ductility. When quartz sand was fully replaced by gold tailings, the compressive strength increased by 19.5%, the strain capacity decreased by 22.3%, the deflection decreased by 15.8% but no obvious change occurred in first crack stress as well as tensile strength. A rougher surface of unoiled PVA leads to reduced slip hardening response. At micro-scale, replacement of the quartz sand using gold tailings leads to higher complementary energy (Jb') available for strain hardening during the crack development and reduced matrix fracture energy (Jtip) for crack initiation. This contributes to the increased pseudo strain-hardening PSHE (=Jb'/Jtip) index and ductility. When fiber content is 2.0%, the values of PSHS (=& sigma;0/& sigma;fc) index reached 1.2, which ensures the saturated multi-joint cracking behavior.