Using linseed oil as flax fibre coating for fibre-reinforced cementitious composite

In recent years, many studies have focused on the mix-design and characterization of cementitious composites reinforced with plant fibres. It appears that in the fresh state, the morphology and the hydrophilic nature of these fibres significantly affect the rheology of the material. In the hardened state, the mechanical performances of the composites are lower than that of composites reinforced with standard fibres (glass, synthetic, etc.). These poor mechanical performances are mainly due to weak neo-formed fibre/matrix interface. Indeed, the high-water absorption capacity causes swelling/shrinkage of the fibre within the matrix, which subsequently generates an unbounded interface. In order to address these issues, numerous studies have been carried out over the past few years on compatibilisation treatments applied to plant fibres. In most cases, these are chemical treatments to leach the fibre, which often have a significant environmental impact. This work examines the influence of a coating treatment with linseed oil applied to flax fibres on the properties of cementitious composites. The first part of this study deals with the optimisation of this treatment. The second part focuses on the effect of this treatment on the properties of the composite in the fresh and hardened states. The results showed a noticeable improvement in the workability of the treated fibre composites. The linseed oil coating treatment can also significantly improve the flexural strength of the composite, depending on the mix-design. Flax fibres and linseed oil can also slightly enhance the thermal insulation properties of the material.