Effect of fine recycled concrete aggregate incorporation rates on rheological and mechanical properties of self-compacting mortar

This study examines the impact of replacing dune sand [DS] with fine recycled concrete aggregate [FRCA] on the properties of self-compacting mortar [SCM] at incorporation rates of 0 %, 25 %, 50 %, 75 %, and 100 %. The methodological approach is based on the mini-cone test [slump-flow] and the measurement of flow time using the V-funnel, complemented by yield stress [τ0] estimations through the inclined plane test [IP], the Coussot–Roussel model, and the Chateau–Ovarlez [C–O] model. The effect of structural build-up with rest periods of 10, 20, and 30 minutes was also examined. A reference mix containing 1 % superplasticizer and meeting EFNARC criteria was first selected before the progressive substitution of DS by FRCA. The results highlight, on the one hand, a granular densification related to the presence of fines and the broader particle size distribution of FRCA, leading to an increase in dry packing density [Φ] from 0.55 to 0.62 as FRCA content increased from 0 % to 100 %. On the other hand, workability decreased with higher FRCA content; the slump flow diminished, while the V-funnel flow time tended to increase. From a rheological perspective, the yield stress τ0 increased both with the FRCA content and with rest time. The C–O model, which integrates packing density and aggregate volume fraction, provided estimations close to those of the IP test, while the Roussel-Coussot model proved more sensitive to variations in the spread diameter. Finally, in the hardened state, compressive strength decreased significantly with substitution. Compared to the reference sample [0 % FRCA], losses reached about 9 % at 50 % and 33.8 % at 100 %, with a similar trend observed in flexural strength.