Potential of oleaginous flax fibre as mortar reinforcement
Natural fibres have been widely used in building materials for centuries and environmental issues lead today to new research in this field. Plant fibre reinforced mortar is one of the rising innovative solutions to develop eco-friendly materials. In this work, the benefits of reinforcing a cementitious or pozzolanic based mortar with oleaginous flax fibre was evaluated and compared with classic polypropylene fibre reinforcement. Fresh state consistency was measured to show the impact of fibre addition and adapt the amount of superplasticizer to maintain the control mortars properties. Standard laboratory bending and compressive mechanical tests were performed on prismatic specimens at 7, 14 and 28 days. Free shrinkage over 28 days was also measured for each composition and the passive ring standard test method was used to determine the age of mortar cracking under restrained shrinkage. Both cementitious and pozzolanic based mortars showed a high flow sensibility when adding polypropylene or oleaginous flax fibres so that superplasticizer was necessary to maintain the fresh state properties. Compressive strength was slightly reduced with both fibres but a higher impact has been noticed at early age with flax ones. In cementitious based mortar, oleaginous flax and polypropylene fibre provided a similar post cracking behavior but the effect of flax reinforcement on pozzolanic based mortar was much more significant. Cracking due to the effect of restrained shrinkage was delayed in each case when adding fibres. Considering these results, oleaginous flax fibre could be a promising eco-friendly solution to replace polypropylene fibre. Further research have to enlighten keys for a better flax fibre distribution in the matrix, to optimize compositions and to evaluate the impact of natural weathering on potential applications.