Experimental Investigation on Bond Properties of SRP/SRG–masonry systems

Reinforcing technique, for strengthening or retrofitting existing structures, using FRP bonded to structural members are the topics of several studies presented in the literature. The main obstacles to a widespread use of FRP remain its relatively high cost and lack of confidence in long-term durability as well as fire endurance. In particular, the former factor, i.e. cost, is very important because of the scale of necessary repairs and upgrades of the existing civil infrastructure. As an example, 180,000 bridges in the USA are considered deficient with the cost of repair or replacement estimated at $20 billion. Recently a new family of composite materials have been considered in order to overcome the mentioned shortcoming of FRPs, they are made of high strength twisted steel wires impregnated with polymeric resin (referred to as steel reinforced polymer, SRP) or with cementitious grout (referred to as steel reinforced grout, SRG). Steel reinforced polymers (SRP) are currently considered for several applications in civil engineering such as bridge and building repair. The problem of bond between FRP and substrate has been already dealt with by different authors and several design guidelines are available nowdays, such as the ACI 440.2R-02 (ACI 440) in the United States, the Fib-Bulletin 14 (2001) in Europe, the recently published TR55 (2004) in the United Kingdom, and the Italian CNR document. Referring to masonry structures available researches on the use of SRP/SRG are lacking for the authors knowledge, comprising the interface behaviour. Bond between SRP/SRG reinforcement and masonry depends on several parameters, as masonry mechanical properties, bonded length and type of reinforcement, i.e. matrix and fibres. The goal of this work is the analysis of bond performance when SRP/SRG are used for strengthening masonry elements. At this aim a direct shear test was performed analysing the influence of both matrix and density of the reinforcement on the interface behaviour. Obtained experimental results are compared and discussed.