Effect of salt crystallization on the bond behavior of glass FRCM-masonry joints

The use of fabric-reinforced cementitious matrix (FRCM) composites for reinforcement of existing masonry members has attracted an increasing interest in recent years. FRCM composites are particularly suitable for masonry strengthening and retrofitting due to their ease of installation, reversibility, excellent compatibility with the substrate and vapor permeability. Tensile mechanical properties and bond behavior of FRCM composites were extensively studied. However, limited information is available regarding the durability of FRCM and FRCM-strengthened members, which may represent a critical issue for the effectiveness of the strengthening system. Indeed, existing masonry structures suffer from the presence of moisture, which can come from rising damp, condensation, infiltration of rainwater, etc. Water is often responsible for the presence of salt within the element, which represents a major cause of masonry damage. When the salt crystallization takes place at the interface between the FRCM and the substrate, a possible reduction of the FRCM bond capacity can be observed. In this paper, the effect of salt crystallization on the bond behavior of an FRCM applied onto a masonry substrate is experimentally investigated. The FRCM composite employed comprises a glass open mesh reinforcing textile and a cementitious matrix. FRCM-masonry joints were conditioned in a saline solution to induce salt crystallization in the FRCM, i.e., within the composite strips and at the FRCM-masonry interface. The bond behavior of the FRCM composite before and after the conditioning is investigated with single-lap direct shear tests. The results obtained provide information on the long-term behavior of the glass FRCM composite considered.