Mechanical behavior of sustainable engineered cementitious composites with construction waste powder as binder and sand replacement

The utilization of recycled powder (RP) obtained from construction waste in the development of sustainable engineered cementitious composites (ECC) has significantly improved their sustainability. This study investigated the mechanical strength of sustainable ECC prepared with three different RPs namely recycled brick powder, recycled paste powder, and recycled concrete powder. The results demonstrated that substituting high portion of cement with RP resulted in a loose microstructure in ECC, but the substitution of silica sand with RP led to a denser microstructure in ECC. Replacing 50% cement and 100% fly ash with RP derived from concrete waste led to a marginal decrease of 39.4% and 20.2% in the compressive strength of ECC, but replacing silica sand with such RP slightly increased the strength of ECC. Besides, recycled brick powder blended ECC shows better strength than the recycled concrete powder blended ECC. Under uniaxial tensile load, the incorporation of RP improved the ductility of ECC, regardless of whether it replaced silica sand or binding materials, while simultaneously reducing the ultimate tensile strength of ECC to varying degrees. Specifically, substituting RP from concrete waste for 50% cement, 100% fly ash, and 100% silica sand caused 145.5%, 55.4%, and 43.6% increase in the ultimate tensile strain of blended ECC, respectively. Particularly, the combine substitution of binder and silica sand with RP is feasible in ECC. More sustainable ECC with good mechanical strength and ductility can be achieved by optimizing the content of RP as binder and sand replacement, and the ECC blended with RP shows good environmental and economic benefits.