Development of polymer-reinforced flax fibre for the strengthening of reinforced concrete.

Abstract

This paper presents the development of new environmentally friendly reinforcement composite materials using technical flax fibres. Flax fibres have low energetic production costs, are biodegradable, cost-effective and have specific mechanical properties comparable to those of glass fibres, making them interesting in the field of composite reinforcement. In this study two different applying methods for concrete strengthening are examined, (1) pre-hardened flax composite strips produced by compression moulding using PA11 or epoxy resins, and (2) handlaid up flexible flax fabrics impregnated on site with ambient temperature curing epoxy resins. Several combinations of matrices and flax fabrics were tested. The composites’ mechanical properties and cohesion were determined through tensile loading and delamination tests. The impregnation quality was assessed through SEM microscopy. The reinforcement ability and the adhesion on concrete substrate of the qualified composites were evaluated through pull-out tests. Different numbers of layers and application methods were tested to determine an optimal use of the composite. The tests show very good concrete/FFRP bonding and high mechanical properties, leading to failures in concrete rather than in the composite or at the interface.