The aim of this paper is to find out new alternative materials that respond to sustainable development criteria. For this purpose, an original utilization of straw for the design of lightweight aggregate concretes is proposed. Four types of straw were used: three wheat straws and a barley straw. In the present study, the morphology and the porosity of the different straw aggregates was studied by SEM in order to understand their effects on the capillary structure and the hygroscopic behavior. The physical properties such as sorption-desorption isotherms, water absorption coefficient, pH, electrical conductivity and thermo-gravimetric analysis were also studied. As a result, it has been found that this new vegetable material has a very low bulk density, a high water absorption capacity and an excellent hydric regulator. The introduction of the straw in the water tends to make the environment more basic; this observation can slow carbonation of the binder matrix in the presence of the straw.

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This article presents a study on the influence of limestone filler and granular inclusions on the chemical shrinkage of cementitious matrices at very early age (624 h). Measurements of chemical shrinkage and hydration degree are carried out on cement pastes and mortars. During this study, two cement types (CEM 1 and CEM 2), two water-to-cement ratios (W/C = 0.30 and 0.40) and three substitution rates of cement by limestone filler (LF/C = 0; 0.25 and 0.67) are used. The effects of aggregate shape (glass beads and natural sand), aggregate-to-cement mass ratio (A/C = 0.5 and 1) and particle size distribution (D = 1 and 2 mm) on the chemical shrinkage and the hydration rate are quantified. The results obtained show that limestone filler causes an acceleration of both Le Chatelier's contraction and hydration process since the very first hours of hydration. In addition, the chemical shrinkage amplitude is not significantly influenced by the presence of aggregates. Finally, the presence of limestone filler and granular inclusions does not cause significant modification of the quasi-linear relation observed at early age between the chemical shrinkage and the hydration degree of the cementitious matrices.