Abstract: In order to prepare fully recycled coarse aggregate self-compacting concrete that meets the requirements of workability, 11 groups of fully recycled coarse aggregate self-compacting concrete mixtures were prepared with fly ash content (20%, 30%, 40%, 50%, 70%, mass fraction) and water-binder ratio (0.36, 0.40, 0.45) as design variables. The workability tests such as slump expansion, flow time T₅₀₀ and J-ring expansion were carried out, and the effects of fly ash content and water-binder ratio on the workability of fully recycled coarse aggregate self-compacting concrete were analyzed. The results show that the fluidity of fully recycled coarse aggregate self-compacting concrete can be improved by adding appropriate amount of fly ash. When the content of fly ash reaches 30% (mass fraction), the slump expansion of concrete reaches 755.0 mm. When the content of fly ash increases from 20% to 40%, the filling performance of concrete decreases, and the segregation rate decreases first and then increases. It is suggested that the reasonable content of fly ash in fully recycled coarse aggregate self-compacting concrete is 20%~30%. Based on the experimental results, a nonlinear regression model for the slump expansion of fully recycled coarse aggregate self-compacting concrete is established, and the calculated values are in good agreement with the experimental values.

Key words: recycled coarse aggregate concrete, self-compacting concrete, fly ash, water-binder ratio, workability, slump expansion