Optimization of flax shive-cementitious composites: Impact of different aggregate treatments using linseed oil

• Linseed oil and flax shives are used to design lightweight cementitious composites.
• The shives treated with raw and emulsified oil improve the vegetal/matrix compatibility.
• The hydrous and mechanical performances of the composite are improved after shive treatments.
• The shive treatments using linseed oil lead to insulating bearing lightweight concretes.

This study investigates the effect of flax shive treatments on physico-chemical characteristics of shive and physico-mechanical properties of flax shive cementitious composites. In the context of sustainable development and biorefinery, the main objectives of this work are to optimize a lightweight lignocellulosic concrete and to upgrade a product and a by-product of flax transformation, respectively linseed oil and flax shives. To improve the compatibility between cementitious matrix and vegetable aggregates, flax shives have been treated with raw and emulsified linseed oil. A more marked decrease in water absorption capacity and hydro soluble molecule release has been obtained for shives coated with raw linseed oil. Compared to standard shive composite, whatever the linseed oil treatment, the setting times have been reduced, the mechanical strengths improved and the thermal conductivity slightly increased. In the case of dimensional variations, the coating with raw linseed oil has led to a slight better improvement compared to emulsion coating. The flax shive-cementitious composites obtained exhibit the properties of insulating bearing lightweight aggregate concretes.