The effect of reinforcement in the new layer on hygral cracking in hybrid structural elements

In structural elements consisting of concretes of different ages (hybrid elements), hygral deformations induced by drying of the new concrete are restrained by the old concrete. Depending on the amplitude of these deformations and on the degree of restraint of the hybrid element, cracks can be induced in the new concrete layer. An experimental investigation conducted during six months on twelve hybrid elements demonstrated that global displacements are reduced when the reinforcement ratio placed in the new layer is increased. Comparison of the experimental results with a numerical model shows that the presence of reinforcement in the new layer increases the degree of restraint of hygral deformations and the likelihood of localized cracks.