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Fiber-reinforced cementitious matrix (FRCM) composites offer effective reinforcement for masonry structures. The aim of the present investigation was to evaluate the bond behavior between a carbon fiber FRCM and a masonry substrate. A total of 17 single-lap tests are presented. The FRCM had a width of 100 mm and variable bonded length. Load responses are reported together with a discussion of the failure modes in relation to the type of brick and bonded length used. In addition, two clevis grip tensile tests were conducted on FRCM coupons made with the same FRCM system and results are discussed and compared with those of single-lap tests., Paper 293

This study focuses on the effect of the bar diameter of glass fiber-reinforced polymer (GFRP) bars on their bond with concrete using pull-out tests. The investigation involves three nominal bar diameters: 6 mm, 12 mm, and 20 mm and several bonded lengths. Within this study, the pull-out test results for both the 6 mm and 20 mm bars are presented for the first time, whereas the findings for the 12 mm bars were previously reported in a paper by the authors where the effect of the bonded length on the experimental response was assessed. The influence of the bonded length on the bond strength for different diameters is discussed., Paper 308

Reinforced concrete structures are frequently subjected to fatigue loadings. At the interface between FRP and concrete, cyclic loading may induce the formation and coalescence of micro-cracks that result in the interface debonding. The stress transfer mechanism of the FRP-concrete bonded interface is critical to the performance of strengthened elements. This paper reports the preliminary results of an experimental investigation into the static and fatigue behavior of the interfacial bond between carbon fiber-reinforced polymer (CFRP) composite and a concrete substrate. Fatigue and post-fatigue loading curves were obtained to investigate the effect of the load frequency on the specimen response., Paper 229

Glass fiber-reinforced polymer (GFRP) have been employed as internal reinforcement of bridge decks in cold regions, where deicing salts rapidly degrade steel reinforcing bars. Bridge decks should be designed with respect to fatigue loading, which requires the knowledge of the bar and concrete fatigue behavior and of their interaction under cyclic loading. In this paper, the behavior of a GFRP-reinforced concrete slab subjected to a quasi-static 4-point bending test is compared with that of an equal specimen subjected to a fatigue test. These results are also compared with those of pull-out tests of the same bar and concrete., Paper 306

Concrete pull-out tests on glass fiber-reinforced polymer bar with a nominal diameter of 12 mm embedded in concrete were performed. The bonded length ranged from 5 to 20 times the nominal bar diameter. Specimens were tested with two free end conditions: with bar protruding from the bottom of concrete, and with bar cut flush with concrete. Results of pull-out tests were used to calibrate an interfacial cohesive material law (CML). The experimental results obtained indicate that protrusion at the free end significantly influenced the results. Different CMLs are obtained when results of specimens with different bonded lengths are used in the calibration process., Paper 292

Glass fiber-reinforced polymer (GFRP) bars are currently used to reinforce concrete members when durability is the main concern. Indeed, when exposed to aggressive conditions, traditional steel bars rapidly corrode affecting the performance of the reinforced concrete member. GFRP bars are available with various surface treatments, each providing a peculiar GFRP-concrete bond behavior. The GFRP-concrete bond behavior is usually investigated using the pull-out test. In this paper, results of GFRP-concrete pull-out tests are used to calibrate the GFRP-concrete interfacial cohesive material law (CML) that describes the relationship between the bar-concrete interface shear stress and the corresponding slip., Paper 307

Among the different strengthening techniques available to reinforce masonry buildings, the near-surface mounted technique consists in inserting reinforcing elements of high-strength material in grooves realized by removing part of the mortar in the horizontal bed joints of a masonry wall. The present study deals with two experimental campaigns on pull-out tests conducted on twisted steel bars embedded concentrically in mortar cylinders and in the mortar bed joints of masonry wallettes as in in-situ applications. In order to compare the results between cylindrical and masonry specimens, the same bonded lengths are considered.

This publication is part of the proceedings of the Biot-Bažant Conference on Engineering Mechanics and Physics of Porous Materials, which took place virtually on June 1-3, 2021. It contains a one-page abstract and the video of the talk that was given at the conference.

Composites made of fibers embedded in organic or inorganic matrices are efficient systems for reinforcing historical masonry structures to provide strength and ductility with a negligible mass increment. As it is well known, the structural performance of the composites mainly relies on their adhesion to the substrate. There are different methods to test the adhesion of the composite to the substrate: in laboratory direct shear test is the most commonly employed, while on-site the bond between the reinforcement and the substrate is checked by the pull-off test. In this paper, the adhesion of different composites to the same substrate made of fired-clay bricks is investigated by both the shear test and the pull-off test to qualitatively assess the difference in the two methods. Additionally, to investigate whether the bond is affected by the presence of water in the pores, half of the specimens were tested in water saturated conditions. Three different types of matrix (based on epoxy resin, natural hydraulic lime and Portland cement) were used for the composite matrix, without changing the geometry, the type of masonry substrate and the fibers (galvanized steel cords).

This paper presents the results of single-lap direct shear tests on steel reinforced grout (SRG) strips bonded to fired-clay brick and tuff masonry blocks. For this experimental campaign, fifteen masonry blocks were constructed and reinforced with SRG composite strips. Fired-clay bricks and tuff blocks herein employed were collected from demolished historical structures in Modena and Naples (Italy), respectively. Eight out of fifteen blocks were subjected to an artificial weathering procedure to induce salt crystallization, and therefore reproduce the degradation conditions that the buildings could be subjected to during their life. Bond behavior of unconditioned strengthened specimens (i.e. SRG-masonry joints) was compared with the behavior of conditioned joints. Salt distribution, open porosity, and water absorption of brick and tuff masonry units as well as of the SRG composite matrix were analyzed to understand if and how the salt crystallization influenced the adhesion between the SRG strip and the block.

In this study, the behavior of clay masonry columns confined by steel reinforced grout (SRG) composite with a natural hydraulic lime mortar is investigated. An experimental study was carried out to understand the behavior of masonry prisms with a square cross-section confined by SRG composite jackets subjected to a monotonic concentric compressive load. Test parameters considered in this study are the density of steel fibers and column corner radius. The effectiveness of the confinement is studied in terms of load-bearing capacity with respect to unconfined columns.