Bond Behaviour of Flax and Jute PLA Coated Fibers Embedded in Lime-Based Mortar

The use of natural reinforcement as a substitute for conventional reinforcing fabrics within Textile Reinforced Mortar (TRM) technology is an increasingly addressed topic in research. This choice was made to improve the sustainability of such reinforcement interventions on structures. The main problems encountered with respect to this solution are inherent to the characteristics of the natural fabric itself: in fact, the latter presents on the one hand mechanical characteristics suitable for structural use, in particular for masonry; on the other hand, aspects such as variability in physical and mechanical characteristics and durability represent “weak” points to be investigated and addressed. The study carried out deal with these issues, applying the polymer coating technique to the natural fabric/yarns. However, to avoid compromising the sustainability of the intervention, rather than using conventional polymers (mainly epoxy resin), bio-polymer (Poly-Lactic Acid, PLA) has been chosen. As a matter of fact, although coating/impregnation is a commonly used technique in TRM to improve the characteristics of the reinforcement, the possibility of using bio-polymers has not been effectively addressed yet in the literature. The physical and mechanical characterization of the fabric elements thus treated was then carried out. One of the analyses concerned the study of the bond behaviour between the impregnated fabric-yarns and the lime-based mortar with which the latter will have to interact. Two phases of pull-out tests were then carried out, designing specific test configurations for the required needs, and in these the bond between the fabric and the matrix was recorded by varying different parameters (different impregnation concentrations, different anchoring lengths, different type of natural yarns). The results obtained represented a failure mechanism between impregnated cord and mortar mainly related to the interaction between the matrix and the PLA present on the surface of the cord. In general, however, the behaviour of the fabric presents promising characteristics for use within TRM systems.