Rheology Study of Fresh Self-compacting Concrete Made Using Recycled Fine Aggregates

The paper herein presents the results of an experimental work carried out to investigate the rheological behaviour of self-compacting concrete (SCC) mixes, which were produced by replacing natural sand with recycled fine aggregate (RFA) and using supplementary cementitious materials. A cross-vane rotating type rheometer has been used to evaluate the rheological parameters of the mixes. A total of 5 different SCC mixes having varying RFA content (0%, 50% and 100%) and binder composition (30% fly ash with 10% silica fume and 40% fly ash without silica fume) have been investigated. The results showed that the yield stress of the SCCs increased with increase in the RFA content in the mixes, and it reduced when fly ash content was increased keeping RFA content constant. The mixes with 100% RFA content resulted in very high shear stress and it increases at higher rate with respect to time. Bingham parameters were obtained and linear correlation with high correlation coefficient value were found, which confirmed that the fresh self-compacting concrete having RFA can be properly modelled as a Bingham fluid. The thixotropy of the SCCs was evaluated in terms of breakdown area and drop in apparent viscosity. A strong correlation is found between breakdown area and drop in apparent viscosity at vane rotation speed from 0.1 rps to 0.4 rps.