This work is devoted to the study of fresh and hardened properties of concrete containing recycled gravel. Four formulations were studied, the concrete of reference and three concretes containing recycled gravel with 30, 65 and 100 % replacement ratios. All materials were formulated on the basis of S4 class of flowability and a target C35 class of compressive strength according to the standard EN 206-1. The paper first presents the mix design method which was based on the optimization of cementitious paste and granular skeleton, then discusses experimental results. The results show that the elastic modulus and the tensile strength decrease while the peak strain in compression increases. Correlation with the water porosity is also established. The validity of analytical expressions proposed by Eurocode 2 is also discussed. The obtained results, together with results from the literature, show that these relationships do not predict adequately the mechanical properties as well as the stress–strain curve of tested materials. New expressions were established to predict the elastic modulus and the peak strain from the compressive strength of natural concrete. It was found that the proposed relationship E–f _c is applicable for any type of concrete while the effect of substitution has to be introduced into the stress–strain (ε _c1–f _c) relationship for recycled aggregate concrete. For the full stress–strain curve, the model of Carreira and Chu seems more adequate.

This study concerns the frost durability of an ordinary concrete without air-entraining agents. The water—cement ratio and the quantity of cement were chosen within the limitations imposed by the French standard. Physical and mechanical characteristics evolutions during freezing—thawing cycles have been followed. The obtained results show that the reduction in the mechanical resistance and the elastic modulus is accompanied by an increase in the intrinsic permeability. The damage is characterized by a scalar parameter, D_f, due to frost action with which the resistance reduction as well as the permeability evolution may be described as a function of crack development. The pore liquid phase pressure, generated during ice formation, was also calculated by an inverse poroelastic analysis based on strains recorded during freezing—thawing cycles. A negative pore pressure of 25 MPa at a temperature of -15^° C resulting in an effective stress representing 25% of the compressive strength was found.