Strengthening of masonry using natural fibers bonding with highly deformable adhesives

Abstract

Strengthening of cracked masonries of poor construction using composite materials of high strength and stiff adhesives of low deformability, like lime and cement mortars or epoxy resins, does not increase significantly the capacity of masonries in seismic areas. This is because of the stress concentration occurrence. The use of highly deformable materials as adhesive and matrix allows reducing peaks of stress concentration in weak brittle substrates, causing increase of composite strengthening efficiency. In the paper, there were tested masonry units (bricks Rosso Vivo - A6R55W) strengthened by GFRP, BFRP, CFRP and BBFRP fibers bonded on epoxy resin and highly deformable polymer PS. The Single Lap Shear Test was used for comparison of stiff and deformable matrix and adhesive materials, bonding various fibers to the brittle substrate. The significant strength increase of the tested masonry specimens was obtained in the case of the use of highly deformable interface materials than of barely deformable bonding materials. Lower level of the shear stress in the substrate results in increasing of load capacity of masonries, thus applying of the highly deformable polymer PS as a matrix and an adhesive to the weak masonry substrate is more advantageous than classically using stiff epoxy adhesives. It was confirmed by other laboratory and insitu tests, in which GFRP and BFRP grids bonded on the polymer PS adhesive were applied for strengthening of masonry and concrete structural elements.