Contribution to the development of a sand concrete lightened by the addition of barley straws

•The barley straws can be introduced into a cement matrix.•Improvement of lightness, thermal properties, deformability and tensile strength.•Barley straws do not alter the development of microstructural species of concrete.•At the vicinity of the vegetal material only calcium species are observed.•Economical composite and more efficient in thermal insulation and energy saving. It is an experimental work that aims to study an eventual contribution to the development of a eco-lightweight concrete destined to be used in arid environments by using local and renewable materials and waste. Its main objective is the assessment of the effect of the addition of barley straws on the physico-mechanical properties and the microstructure of a concrete which consists only of sand as main aggregate. Indeed, the study was devoted, firstly to determine the optimal composition of sand concrete based on barley straws by researching a good compromise between compactness and workability, and secondly, to study its physical, mechanical, thermal and microstructural properties. The obtained results showed that the addition of barley straws to the sand concrete significantly improves its thermo-physical properties. According to the quantity of straws introduced in the sand concrete, the improvements in the flexural strength have reached 6%. Significant improvements have also been recorded in other properties, such as lightness, deformability, ductility, toughness and thermal characteristics. However, the increase of barley content decreases the compressive strength and increases the dimensional variations. But it should be noted that obtaining acceptable strength values is possible according to the straw content and the shrinkage values are in general less than the recommended limit for wood concretes. As to the microstructure of the studied composite, the SEM analysis showed that the presence of lignocellulosic aggregates did not alter the development of species within the cementitious matrix. Moreover, and contrary to the case of wood aggregates, only calcium species are observed in the vicinity of the lignocellulosic material, there are no silica species. Finally, it should be also noted the easy introduction of the cementitious material inside the tubular pores of some straws.