On the characterization of microstructural characteristics and mechanical behaviour of mortar modified by flax fibre residues

In this study, we explore how the addition of flax fibre residues affects the microstructure and mechanical properties of modified mortars. Flax fibre residues from the individualization process are considered as fillers. Various formulations of mortar are adjusted by incorporating different proportions and sizes of flax fibre residues. The workability of fresh modified mortars is assessed through flow table experiments. X-ray µ-tomography is employed to investigate microstructural changes, focusing on pore content and the 3D spatial arrangement and content of natural residues. Mechanical performance is evaluated through compression tests conducted at different curing times. The findings indicate that flax residues can serve as effective substitutes, resulting in moderate loss in mechanical strength if the particle size is kept below 3 mm. Optimal formulations are found to require sieving of residues particle sizes resulting in small particles of 1 mm for an overall weight content of 5 % in the total weight of the cement used in the mix. These results demonstrate superior mechanical performance compared to all other tested conditions within only 7 curing days. • Flax residues enhance mortar's microstructure with minimal strength loss. • Optimal flax size: 1 mm, content: 5 %, best at 7 days curing. • Flax offers eco-friendly, strong reinforcement in construction. • X-ray tomography used to analyse mortar's 3D microstructure. • Compression tests confirm flax-modified mortar's viability.