Evaluation of self-compacting recycled concrete robustness by statistical approach

Abstract

[Abstract:] The use of self-compacting recycled concrete appears as to be a very interesting technology for the sustainable construction future. However, one of the major obstacles to a more widespread use of self-compacting concrete is to obtain a robust material. Therefore, the emphasis of this work is placed on analysing both practice and theory to understand the properties that control and assess self-compacting recycled concrete robustness. Hence, forty-nine different mixes were produced with several replacement percentages of recycled concrete coarse aggregate (0, 20, 50 or 100%) and with two different mixing procedures (all aggregates in dry-state conditions or recycled aggregate with a 3% of natural moisture). The experimental program consisted of making, in the fresh state, rheological tests (a stress growth test and a flow curve test) and empirical characterization tests (slump flow, V-funnel, L-box, J-Ring and sieve segregation) at 15, 45 and 90 min from cement-water contact. In the hardened state, compressive strength was measured at 3, 7 and 28 days. All results were analysed using a statistical approach based on Kendall’s coefficient of concordance and Spearman’s rank correlation. This approach allowed us to successfully identify six key properties that can be measured to evaluate SCRC robustness (capacity of the material to tolerate certain variations in material characteristics and mixture parameters). For each mix, a ranking that defines its robustness category was obtained by considering all properties. Also, it showed that water control is the key factor that affects SCRC robustness.