Fresh and hardened properties of self-compacting concrete using silicon carbide waste as a viscosity-modifying agent

The aim of this paper was to evaluate the preparation of self-compacting concrete (SCC) with silicon carbide waste (SCW) as an alternative of the viscosity-modifying agent. Fresh properties like flowability, viscosity, filling and passing abilities as well as segregation resistance were measured while hardened properties such as strength, drying shrinkage, water absorption and chloride permeability were determined. The mechanisms responsible for the performance variations were explored by X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and nitrogen adsorption analyses. Results show that SCW improves the viscosity, filling and passing abilities, segregation resistance and flowability retention of SCC at proper replacement ratios although superplasticizer demand is increased. Besides, strength, drying shrinkage, water absorption and chloride permeability are closely related to SCW amount. Specifically, drying shrinkage, initial absorption and chloride permeability decreases as SCW increases and SCW improves strengths and final absorption at ratio no less than 15%. It is proved that SCW has porous structure with high water absorption, mainly accounting for its viscosity regulating performance. Water absorption and chloride impermeability improvement of SCC can be explained by the microstructure densification. Drying shrinkage is reduced due to the high water absorption and timely releasing ability of SCW. And the combined effects of internal curing, reinforcing filling and further hydration promotion of SCW boost the strength development of SCC. These results favor the reutilization of SCW and the sustainable development of cement and concrete industries. (C) 2018 Elsevier Ltd. All rights reserved.