Self-compacting recycled concretebasic mechanical properties, rheology, robustness and thixotropy

Resumo

This work is focused on the study of hardened and fresh behaviour of self-compacting recycled concrete (SCRC) with different replacement percentages of recycled concrete coarse aggregate (0%, 20%, 50% and 100%). Regarding hardened behaviour (compressive strength, modulus of elasticity and splitting tensile strength), it has been analysed how the incorporation of recycled coarse aggregate affects self-compacting concrete (SCC). To do so, a database was created with published results regarding vibrated recycled concrete. Different correction coefficients were adjusted to adapt code expressions to this type of concrete. Also, specific prediction expressions for vibrated recycled concretes were adjusted as an alternative to code formulations. Lastly, it has been concluded that both the correction coefficients and the specific expressions can be used with the same accuracy in SCRC as in vibrated recycled concrete. Regarding fresh behaviour, the relationships between rheological and empirical parameters were analysed concluding that they show the same trend in SCRC as in SCC. In this context, the research has also studied the specificity of SCRC rheology and its influence on the fresh behaviour over time. The achieved conclusions lead to state that this specificity lies in the extra water added to compensate the recycled aggregate absorption and in the intrinsic characteristics of this aggregate. Moreover, the SCRC robustness has been analysed through sensitivity parameters and a statistical approach, defining which factors affect it to a greater extent and which tests provide more sensitivity when this property is studied. Finally, SCRC thixotropy has been evaluated measuring also its influence on interlayer bond strength.