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.

This paper aims to study the effect of long-term soaking and leaching on the stability properties of fine-grained soil with and without gypsum content, in relation to changes of the mechanical properties and permeability. The soil samples were stabilized with 3% lime and cured for 28 days at 20°C. The cured samples were subjected to soaking for different period extended to 180 days. Also, permeability values of stabilized and unstabilized soil samples were measured under 30 days of leaching. Results showed that the long-term soaking has strong effect on the unconfined compressive strength, wave velocity and volume change of the stabilized soil samples. These properties are degraded when compared with initial properties of the unsoaked samples. Moreover, the results indicate that an increase in gypsum content have significant effects on stability properties of soil samples. The leaching test revealed a marked increase in permeability values of unstabilized soil samples and, to a lesser extent, in the permeability of stabilized samples. The results also showed that the permeability of soil samples is highly related to the quantity of gypsum during the leaching test; however, the lower the gypsum content, the lower the permeability.