Experimental Investigation on Bond Behavior of Cement-Matrix–Based Composites for Strengthening of Masonry Structures

Abstract

Fabric-reinforced cementitious matrices have raised a great interest for the external strengthening of historical masonries, representing a valid alternative to fiber-reinforced polymers. As the effectiveness of an external reinforcement firstly depends on the bond performance, this paper presents an experimental investigation, through double-shear tests, on the bond behavior of cement-matrix-based composites reinforced with three different textiles, namely, carbon, polybenzoxazole (PBO), and glass. Textiles and matrix specimens were experimentally tested to correlate mechanical properties of the constituent materials with the global response of the composites. The results of bond tests highlighted that PBO-fiber- and glass-fiber-based composites better exploit the mechanical properties of the textile. Observation of the failure mechanisms highlighted that debonding phenomena occur at the fiber–matrix interface. Furthermore, the effective anchorage lengths were estimated. The values of fracture energy were determined by a fracture-mechanics approach, using the experimental values of debonding loads. Finally, the values of fracture energy were correlated with the mechanical characteristics of the constituent materials.