Effect of transient drying on mechanical properties of concrete specimens

Initially saturated, cementitious materials are subject to water movements that are responsible for multiple phenomena. Among them, there are drying shrinkage, creep, fluid transport, swelling reactions and cracking-induced changes in mechanical properties. The main objective of this study is therefore to investigate the impact of drying on the behaviour of cementitious materials. For this we carried out two 70-day studies on the material EDF's VeRCoRs project. The studies consist of storing (after almost complete hydration) a batch of specimen under saturated conditions while the second batch is stored in controlled environments of 30% and 45% h(r), respectively. After the drying phase, specimens are tested by the mean of standard mechanical tests. The conclusions are heterogeneous. For instance, on different specimens that are not in water balance, the compressive strength is increased by a maximum of 12% while the tensile strength determined by bending is more dependent on the type of tests. The elastic modulus decreases with desaturation. Finally, the energy dissipated by the cracking increases sharply with drying. These results show that the hygro-mechanical behaviour is complex, depending on the ambient conditions and its duration, the geometry of the specimens and the type of tests. Thus, to take into account the hydric effects on mechanical behaviour, it is necessary to have a numerical modelling approach to take into account the different mechanisms involved. In this perspective, this work provides a significant database that offers the opportunity to test hygro-mechanical models. A necessary step in order to model structures.