Robustness of self-compacting recycled concrete: analysis of sensitivity parameters

Abstract

This work is focused on understanding the origin of the lower robustness detected in self-compacting recycled concretes and on identifying the parameters affecting this property to a greater extent. A reference concrete (0%) and three recycled concretes were studied. The replacement percentages of natural with recycled coarse aggregate were 20, 50 and 100% (by volume). Each baseline mix was modified using two levels of water (± W: − 3, + 3%), two levels of superplasticizer (± S: − 5, + 5%) and two levels of cement (± C: − 3, + 3%). The analysis is focused on the sensitivity parameters calculated with the variations of the results of different tests obtained with the modified mixes. Four industrial tests and two rheological tests were made at a mix age of 15 and 45 min. It could be concluded that self-compacting recycled concretes present the “Rheological parameter— $$\varnothing /\varnothing_{\hbox{max} }$$ ” curves with higher slope than the ones of conventional self-compacting concrete. Then, when high percentages of recycled coarse aggregate are used, and when long term self-compacting behaviour is required, there is a greater possibility to reach the high slope region of high slope curves causing high rheological changes and low robustness.