Abstract
Abstract The article describes an experimental study on the bond–slip performance between the pultruded glass fiber-reinforced polymer (GFRP) tube and the nano-CaCO3 concrete. Taking the nano-CaCO3 concrete strength and GFRP tube thickness as primary parameters, nine specimens were designed and tested to study the influence of these parameters on the bond strength of the specimens. Besides, three specimens filled with the ordinary concrete were also tested by using the push-out tests to make comparisons with the bond performance of the specimens filled with nano-CaCO3 concrete. A total of four push-out tests were conducted on each specimen. The experimental results indicate that there are two types of axial load–slip curves for each specimen in four push-out tests. Moreover, comparison of the results of the push-out tests in the same direction shows that the bond failure load of the specimen decreases with the increase in the number of push-out tests. Based on the analysis of the test results, it is shown that the bond performance between the GFRP tube and the nano-CaCO3 concrete is better than that between the GFRP tube and the ordinary concrete. Furthermore, as the nano-CaCO3 concrete strength increases, the bond strength of the specimens decreases, indicating that the concrete strength has a negative effect on the bond strength. When the nano-CaCO3 concrete strength is relatively smaller (C20), the bond strength of the specimens decreases with the increase in the thickness of the GFRP tube. However, when the nano-CaCO3 concrete strength is relatively larger (C30 and C40), the bond strength of the specimens increases as the thickness of the GFRP tube increases.
Highlights
In recent years, with the rapid development of nanotechnology, more and more nanomaterials have been developed
A slight sound was produced during the loading process of the specimens, which was likely to be the friction sound caused by the slip between the inner concrete and the pultruded glass fiber-reinforced polymer (GFRP) tube
A small segment δ in where T is the thickness of the GFRP tube; EG is the elastic modulus of the GFRP tube; b is the side length of the GFRP tube; τ is the shear bond strength between the GFRP tube and the concrete; N is the ultimate bond failure load between the GFRP tube and the concrete, which is equal to the bond failure load in the first pushout test; and l1 is the length of the contact surface
Summary
With the rapid development of nanotechnology, more and more nanomaterials have been developed. When the nano-CaCO3 is added into the ordinary concrete, the bond performance between the core concrete and the GFRP tube might be significantly enhanced owing to the tiny structural unit of nano-CaCO3. Based on the existing bond strength models, Lu et al [33] proposed a series of new bond–slip models by the combination of the finite element results and the test results These models were recommended for future use in the numerical modeling of the FRP-strengthened reinforced concrete structures. Many researchers have investigated the bond–slip performance between the ordinary concrete and the FRP materials, little experimental study and theoretical analysis have been carried out on the bond–slip performance between the nanoCaCO3 concrete and the GFRP tube. This article can provide a good reference for further relevant research studies and contribute to the practical application of nano-CaCO3 concrete-filled GFRP structures in the engineering construction fields
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