Placing of fresh concrete on a rigid support such as a metal beam or a section of existing concrete frequently results in the appearance of cracks. The origin of these cracks is associated to parameters that are relatively vague for the engineer. In reality, the shrinkage of the new layer of concrete is restricted, causing an internal state of residual stresses in the structure. These residual stresses are the cause of the cracking of the early age concrete and diminish the resistance of the hybrid structure. In addition, they make the structure more susceptible to damage under service loads.
The long term goal is to find new solutions that diminish the cracking dangers and the residual stresses caused by the restricted shrinkage of the new material.
An in depth study of the behaviour of early age concrete will be conducted with the goal of understanding the processes involved and to identify the principal parameters.
Two series of laboratory tests on hybrid elements and their numerical simulations will be used to find a model that can predict the physical and mechanical behaviour of early age concrete. This model will be validated by means of in situ tests that will be representative of the construction or modification of structures.