Estudo da aderência entre o concreto e barras de polímeros reforçados com fibra de vidro (FRPV)

Abstract

The use of steel as reinforcement in reinforced concrete structures, in construction systems, is, in general, widely spread around the world. Furthermore, under certain environmental conditions, the reinforcement used may be subject to the phenomenon of corrosion, consequently deteriorating. Thus, new materials, such as Glass Fiber Reinforced Polymer (GFRP) rebars, are being introduced in civil construction to replace steel. GFRP bars are, in general, composite materials formed by continuous strands of fibers surrounded by resin. With the increase in its use and applicability in the national market, there is also a need for further studies, both in relation to its behavior, determining its physical and mechanical properties, as well as to regulations and codes, understanding the important factors for dimensioning concrete structures reinforcement, the bond phenomenon. A factor that has decisive effects on its resistance, such as diameter, surface treatment, concrete strength and anchorage length. The sizing, due to the recent introduction of GFRP bars, as mentioned, in reinforced concrete structures, is based on the knowledge already obtained and consolidated on steel bars. Therefore, the present study aims to carry out the pullout test, in accordance with the American standard ASTM D7913/D7913M-14 (2020), with GFRP bars with diameters of 8 mm, 10 mm and 12 mm, inserted in concrete cubes with characteristic strength of 35 Mpa and 50 MPa, in order to obtain the values of bond strength between bars and concrete, comparing the effect of diameter and the influence of concrete strength. Data obtained experimentally were compared with equations found in the Canadian CSA S806-02 (2002), Brazilian CT 303 (2021) and American ACI 440.1 R-15 (2015) standards. In carrying out the experimental program of this work, the materials used in the production of concrete were characterized for the dosage of two compressive strengths of concrete, being 35 MPa and 50 MPa, however the values found experimentally were 35.88 Mpa and 47, 28 MPa. The results obtained show statistically similar bond strengths between the GFRP bars and the concrete, even with the increase in the diameter of the bars, regardless of the compressive strength of the concrete. Another evaluated factor is the resistance of the concrete, the results indicate that there is a tendency in the increase of the adhesion resistance with the increase of the compressive strength of the concrete, however this increase was only significant in this study, for the bars of 8 mm. It is then concluded that, according to the results obtained in this study, with the increase in the compressive strength of the concrete, there is an increase in the bond stress for 8 mm bars, in contrast, the variation in the diameter of the FRPV bars, does not provide significant changes in the bond strength of the structure.