Abstract
In recent years, as a result of the large-scale use of stainless steel bars in production and life, people’s demand for stainless steel bars has increased. However, existing research information on stainless steel bars is scant, especially the lack of research on the mechanical properties of duplex stainless steel bars and the bonding properties of duplex stainless steel bars to concrete. Therefore, this paper selects 177 duplex stainless steel bars with different diameters for room temperature tensile test, and then uses mathematical methods to provide suggestions for the values of their mechanical properties. The test results show that the duplex stainless steel bar has a relatively high tensile strength of 739 MPa, no significant yield phase, and a relatively low modulus of elasticity of 1.43 × 105 MPa. In addition, 33 specimens were designed to study the bonding properties of duplex stainless steel bars to concrete. In this paper, the effects of concrete strength, duplex stainless steel reinforcement diameter, the ratio of concrete cover to reinforcing steel diameter, and relative anchorage length on the bond stress were investigated, and a regression model was established based on the experimental results. The results show that, with the concrete strength concrete strength from C25 to C40, the compressive strength of concrete increased by 56.1%, the bond stress increased by 27%; the relative anchorage length has been increased from 3 to 6, the relative anchorage length has doubled, and the bond stress has increased by 13%; and, the ratio of concrete cover to reinforcing steel diameter increased to a certain range on the bond stress has no significant effect and duplex stainless steel reinforcement diameter has little effect on the bond stress. The ratio of concrete cover to reinforcing steel diameter from 3.3 to 4.5 and the bond stress increased by 24.7%. A ratio of concrete cover to reinforcing steel diameter greater than 4.5 has no significant effect on the bond stress, with the average bond stress value of 20.1 MPa. The duplex stainless steel bar diameter has little effect on the bond stress for the diameters of 12 mm, 16 mm, 25 mm duplex stainless steel bar, and their average bond stress is 19.9 MPa.
Highlights
The corrosion of steel is a common durability problem for reinforced concrete structures, especially for offshore, harbor and hydraulic structures, and bridges in coastal areas, which are under harsh environmental conditions, such as long-term wet or alternating wet and dry conditions
27%; the relative anchorage length has been increased from 3 to 6, the relative anchorage length has doubled, and the bond stress has increased by 13%; and, the ratio of concrete cover to reinforcing steel diameter increased to a certain range on the bond stress has no significant effect and duplex stainless steel reinforcement diameter has little effect on the bond stress
The standard values of tensile strength, elongation after break, elastic modulus, and yield strength of duplex stainless steel bars calculated by substituting the test data into
Summary
The corrosion of steel is a common durability problem for reinforced concrete structures, especially for offshore, harbor and hydraulic structures, and bridges in coastal areas, which are under harsh environmental conditions, such as long-term wet or alternating wet and dry conditions. The corrosion of steel bars affects the normal use of the structure, but it shortens the service life of the structure and even directly endangers the safety of the structure. Repairing these corroded structures requires huge capital investment, but it generates a lot of construction waste, which, in turn, causes a series of environmental problems. Practice has proven that the above-mentioned measures have improved the durability of reinforced concrete structures to varying degrees, but they have not fundamentally solved the problem of steel corrosion [4,5]. Research has showed that the strength of stainless steel bars is relatively high, there is no obvious yield stage, and the elastic modulus is relatively low, which can significantly improve the durability of concrete structures, and it has good economic benefits for whole-life projects
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