ABSTRACT
Delayed deformations of concrete are known to induce a risk of cracking in structures and excessive bending. Delayed deformations are mainly of two types: shrinkage and creep. The shrinkage tests were carried out for two substitution rates of natural aggregates with 30% and 100% recycled aggregates (RA). State-of-art and the experimental results show that shrinkage and creep generally increase when RA are incorporated in concrete, due to a higher amount of the cement paste. Differences in micro-cracking are 188observed very locally on the concrete’s skin. Three-point bending creep tests show the same conclusions. It is difficult to distinguish natural concrete from recycled concrete at macroscopic scale. Two types of modelling have been used to describe the mechanisms associated with shrinkage and creep. The first, conducted at macroscopic scale on a homogeneous material, shows that damage seems more severe in the concrete’s skin subjected to desiccation. The second, carried out at mesoscopic scale to evaluate the creep, allows considering the influence of the attached old mortar. This modelling makes it possible to better understand the influence of RA on the location of micro-cracks. Experimental fatigue tests have been conducted within RECYBÉTON. They show that the endurance of concrete slightly decreases when RA are introduced.
