Experimental study on shear behavior of masonry walls strengthened by bio-coated lime-based flax-TRM systems

The growing need to reduce the environmental impact of the construction sector has stimulated the development of more sustainable materials and strengthening techniques for existing structures. In this context, Natural Textile Reinforced Mortar (N-TRM) systems have recently attracted increasing attention as a promising alternative to conventional strengthening solutions, combining mechanical effectiveness with the use of renewable resources. This paper investigates an innovative flax-based N-TRM system, in which the textile reinforcement is coated with a biodegradable Poly Lactic Acid (PLA) polymer. An experimental campaign was carried out at different scales, including yarns, textile strips, TRM composites and masonry wall specimens, in order to evaluate both the material properties and the structural performance of the proposed solution. Particular attention was devoted to diagonal compression tests on masonry panels, aimed at assessing the shear behaviour of strengthened walls. A total of twelve specimens were tested, including unreinforced masonry walls, strengthened with a basalt-TRM system and with the proposed bio-coated flax N-TRM. The results demonstrated the effectiveness of the proposed strengthening solution in improving the shear response of masonry walls. Compared to conventional systems, the flax-coated N-TRM exhibited enhanced deformation capacity and a more distributed cracking pattern, highlighting its potential as a sustainable and effective retrofitting solution for masonry structures.