The potential impact of size effects on compressive strength for the estimation of the Young's modulus of concrete

International audienceConcrete, a highly heterogeneous material, exhibits a clear size-dependence of its compressive strength. As the Young's modulus is generally assumed to be proportional to the compressive strength, this would, in principle, implies a dependence on sample size for this modulus. However, the elastic modulus is directly related to linear elastic deformation, while the compressive strength results from strongly non-linear processes due to the progressive development of damage and microcracking. In other words, the elastic modulus, a material-dependent parameter, should not depend on the sample size, unlike the compressive strength. Here we show, from an extensive experimental program including non-destructive and destructive tests carried out on 527 cylindrical concrete specimens with three different concrete mixtures and four different sizes, the sizeindependence of elastic properties of concrete regardless of the concrete mixes. This is in full contrast with the size-dependence of the compressive strength, and implies that (i) there is no direct proportionality between the elastic modulus (linear property) and the compressive strength (nonlinear property) of concrete, and (ii) the use of empirical expressions given in building codes (e.g