Experimental Analysis of Creep and Shrinkage of Self-Compacting Concrete with Recycled Concrete Aggregates

The recycling of old concrete from the demolition of concrete structures is necessary for the rational use of natural aggregate resources. Recycled concrete aggregates (RCAs) are the highest quality recycled aggregates as they are the closest to natural aggregates. However, the use of RCAs is always associated with greater fluctuations and usually with a deterioration in workability, mechanical properties and long-term properties. The use of RCA in self-compacting concrete (SCC), where the proportion of aggregate is lower than in conventional concrete, is one way of mitigating the effects of RCAs. In this paper, the effects of coarse and fine RCA are investigated, focusing on dimensional changes due to shrinkage and creep. SCC mixes were developed in which the dolomite aggregates were partially or completely replaced by RCAs and additionally mixes in which 50% of the cement was replaced by fly ash. The average shrinkage strain measured after 180 days increased from 0.34 mm/m for a mix with natural aggregates to 1.04 mm/m for a mix made entirely with RCAs, showing an almost proportional increase in strain with RCA content. At the same age, the creep compliance ranged from 0.07 GPa−1 for the mix with natural aggregates to 0.34 GPa−1 for the mix made entirely with RCAs, and is most strongly correlated with hardened concrete density.