Experimental Investigation on the Mechanical and Bond Properties of GFRP Anchors Adopted in FRCM-Masonry Strengthening

The strengthening and retrofitting of existing masonry built heritage has become an increasingly important issue in the last decades. Among the innovative solutions developed by the construction industry, the application of externally bonded fabric-reinforced cementitious matrix (FRCM) composites attracted a great interest, proving to be an easy, effective, and cost-efficient strengthening/retrofitting technique. FRCM composites were shown to be particularly suitable for applications on masonry due to the good compatibility between the composite inorganic matrix and the masonry substrate, which also promotes their durability. A crucial point for the effectiveness of externally bonded FRCM is the bond within the composite strip and between the composite and substrate. Indeed, composite debonding is the commonly observed failure mode. In order to improve the bond with the substrate, connectors (anchors) can be used to improve the bond capacity of the FRCM composite. In this paper, the mechanical and bond properties of a glass fiber reinforced polymer (GFRP) anchor spike, designed for FRCM strengthening, are investigated. First, tensile tests are performed to determine the elastic modulus and tensile strength of the anchor. Then, the anchor-masonry bond behavior is experimentally investigated using pull-out tests. Three different masonry substrates, namely a solid clay brick masonry, a tuff block masonry, and a stone masonry were adopted in the pull-out tests. The results show the influence of the substrate type on the anchor-masonry bond capacity and failure mode observed.