Micro-structural and mechanical properties of ultra-high performance engineered cementitious composites (UHP-ECC) incorporation of recycled fine powder (RFP)

The recycled fine-powder (RFP), produced during the recycling process, will induce a serious impact on the environment with improper disposition. A potential green way to reuse RFP is to add it as supplementary cementitious material in concrete. The effects of RFP on the hydration, microstructure, shrinkage and mechanical properties of ultra-high performance engineered cementitious composites (UHP-ECC) with different replacement ratios up to 50% were investigated. The hydration kinetics were compared among the different replacement ratios using the isothermal calorimetry, which demonstrated an accelerating effect of RFP to the hydration of UHP-ECC matrix. The phase development was quantified by the thermal gravimetric analysis and proved the pozzolanic effect of RFP. The compressive and tensile properties of UHP-ECCs were obtained at 3, 7 and 28 days, respectively, to trace their development along the curing ages. The addition of RFP significantly reduced the autogenous shrinkage of UHP-ECC. Besides, the single fiber pullout test was investigated to quantify the influence of RFP at the fiber level. The environmental scanned electron microscope analysis was conducted to study the morphology of PE fiber at the fracture surface.