Mechanical behaviour of Ultra High Performance Fibre Reinforced Concretes (UHPFRC) at early age, and under restraint

At early age, ultra high performance fibre reinforced concretes (UHPFRC)undergo significant volumes changes (thermal deformation and autogenous shrinkage)related to their composition. These deformations can be restrained by different elements respective to the material (rigid constituents) and the structure (formwork, underlying concrete and reinforcement) during construction. The consequences at material level are the development of tensile stresses that can initiate cracking and increase permeability. Therefore, their initial protective performance can be reduced. This paper presents the evolution of the temperature in various conditions, the degree of hydration, and the response at early age in free and restrained conditions determined by means of an original testing set-up developed at MCS-EPFL (autogenous shrinkage and stress generation) for a UHPFRC.