Flax and polyparaphenylene benzobisoxazole cementitious composites for the strengthening of masonry elements subjected to eccentric loading

To address the structural problems caused by eccentric loads in unreinforced masonry, three differenttypes of masonry were prepared based on clay bricks bonded with a natural hydraulic lime mortar combinedwith a flax or polyparaphenylene benzobisoxazole (PBO) fabric-reinforced cementitious matrix(FRCM) composite. The mechanical behaviour when subjected to concentric and eccentric loads wasstudied by performing axial compression tests, with eccentric load tests only carried out in instancesof large eccentricities. Analysis of the load–displacement and moment–curvature response revealed thatboth the flax- and PBO-based strengthening systems improve the strength and deformability of masonry.However, compared to the PBO fabric composite, the use of flax fabric provides a greater deformabilitythat helps prevent the composite and substrate debonding.