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 (e c1 -f c ) relationship for recycled aggregate concrete. For the full stress-strain curve, the model of Carreira and Chu seems more adequate.

The paper presents the results of an experimental program carried out on 96 concrete pullout specimens prepared with natural and recycled aggregates using 10 and 12 mm diameter deformed steel bars. Steel rebars were concentrically embedded in pullout specimens with two embedded length of 5 and 10 times the rebar diameter. The present work includes six recycled concrete aggregate mixtures and two conventional concrete mixtures with C25/30 and C35/45 target class of compressive strength and S4 class of workability. For both series, specimens were fabricated with different incorporation ratios of fine and coarse recycled aggregates and only coarse recycled aggregates. Tensile load was applied gradually until the pullout failure occurred and the slip between the rebar and concrete was measured at the free and loaded ends for each loading level. Furthermore, systematic observations of failure surface have been made at both macroscopic and microscopic scales. Test results showed that for the same class of compressive strength the bond strength and related failure mechanisms remain very close and the obtained values are, at least, four times higher than the predicted values by Eurocode 2. The experimental results of this study, together with an extensive number of results reported in the literature, were used to describe the variation of bond strength with concrete compressive strength, embedded length, and concrete cover. In addition, an analytical bond‐slip relationship is proposed and the parameters of bond‐slip law were calibrated by an optimization algorithm.

For radiative heat transfer applications, in particular in homogenized phases of porous media, an exhaustive and accurate validity criterion of the radiative Fourier law, depending only on the logarithmic derivative of the temperature field and an effective absorption coefficient, accounting for possible multiple scattering phenomena, has been established for a semitransparent medium. This effective absorption coefficient is expressed as a function of the absorption coefficient, the albedo, and the scattering asymmetry parameter. The criterion can be applied to semitransparent media that do not follow Beer's laws related to extinction, absorption, and scattering.