Hybrid natural TRM systems with short flax and jute fibers for masonry strengthening: multiscale investigation of crack control and structural response

Abstract The present paper proposes the results of a multi-scale experimental campaign aimed at investigating the mechanical and structural response of Textile Reinforced Mortar (TRM) systems incorporating natural fibers and natural textile, also referred as Natural Textile Reinforced Mortar (nTRM), for existing masonry structures which can represent a promising alternative to conventional composites, combining structural effectiveness with environmental sustainability. More specifically, the natural TRM composite systems under investigation analyzed herein consider the possible combination of pre-treated flax textiles and short fibers (made of either jute or flax) employed as spread reinforcement. As a matter of principle, the application of hybrid (i.e., combination of textile and short fibers) is proposed as a possible strategy to optimize the overall amount of reinforcement by reducing the optimal number of textile layers while improving mechanical performance through the crack-bridging effect of the short fibers. The mechanical response of the proposed systems is evaluated through four-point bending tests meanwhile diagonal compression tests on reinforced masonry walls are executed to evaluate the structural response of the masonry elements. The results provide insight into the role of fiber type, fiber treatment and reinforcement configuration on strength, ductility, and crack control. The proposed approach highlights the potential of flax- and jute-based hybrid natural TRM systems as effective strengthening solutions for masonry structures, offering a material-efficient alternative to conventional synthetic reinforcement systems.