Improvement of the properties of a sand concrete containing barley straws - Treatment of the barley straws

This work goes within the framework of the valorization of local materials and wastes, such as dune sand, barley straws and aggregate crushing waste. In this context, barley straws have been incorporated in a sand concrete in previous works in order to develop a new lightweight concrete and interesting results have been obtained. However a decrease in the mechanical strength and an increase in the dimensional variations have been recorded. The main objective of the present work is therefore to solve these problems. Indeed, it consists in improving the properties of the barley straws by applying different treatments before using them in order to improve the properties of the optimum composition of the studied lightweight concrete (15 kg/m3 of barley straws). Among several treatments tested, four treatments have proved effective and therefore have been selected for the continuation of this study: the hot water, the gasoil, the varnish and the waste oil. These treatments adhere well to the outer surface of the barley straw and significantly increase its tensile strength without changing much of its mass and dimensions. Introduced in the sand concrete, the straws treated with the hot water gave good improvements in the flexural strength of the composite, they did not change much its density and its thermal characteristics remained acceptable. However, the gasoil was the most effective in reducing the shrinkage of the studied concrete, but no marked improvements in the other properties have been recorded. As to the varnish, this product improved most of the characteristics of the studied concrete, but the rates of increase were lower than those recorded in other treatments. Finally, it should be noted that the waste oil gave relatively good compressive and thermal results, acceptable flexural characteristics, but a high shrinkage and density.