Application Test Research of High Temperature Resistant Epoxy Adhesive in Bonding Layer of Steel Bridge Deck

Abstract:
for orthopaedic steel bridge paving characteristics, self-developed high temperature epoxy resin adhesive, carried out a performance test. The test results show that it not only has good high temperature shear resistance and pull strength, but also has good toughness in a certain temperature range.
keywords: steel bridge paving; epoxy resin adhesive; shear strength; anti-pull strength; toughness In the past ten years, large cross-path orthopaedic steel bridges have been completed and put into operation, such as Guangdong Humen Bridge, Jiangyin Yangtze River Bridge, Xiamen Gate Haiyan Bridge, Nanjing Yangtze River Bridge and Runyang Yangtze River Road Bridge, such as a series of famous bridges . With the exception of a few bridge decks in good condition, most of the bridge surface paving layer has ruts, cracking, displacement and other diseases. The production of ruts is generally considered to be caused by the lack of high temperature stability of the material or structure; Small cracks, vertical and horizontal cracks are caused in part by cracking of the bonding layer, mostly by fatigue damage, mesh cracks are often caused by local stress concentration, and, in a few cases, by improper mixing, and in most cases by the breakdown of the bonding layer, i.e. the bonding layer of the steel bridge interface. It can be seen that the steel bridge interface bonding layer is the key to the steel bridge surface laying layer.
The material used in the existing bonding layer can be divided into three categories according to the construction method and the characteristics of the material: one is a hot-melt bonding material, generally composed of asphalt doped resin and various polymers (e.g. EVA, PE, SBR), the most important feature of this material is that it is easy to soften at high temperatures, the bonding force decreases, the bonding layer becomes weak layer due to softening, resulting in asphalt coating under the traffic load Transfer, cracking and other damage; one is solvent-based bonding material, generally refers to emulsified asphalt and soluble rubber asphalt, this material is easy to soften at high temperatures, and the material contains thermally sensitive substances, when paved at high temperature will release gas, so that the paving layer produces bubbles; Nanjing Yangtze River Bridge using epoxy asphalt as a bonding layer, its paving layer using epoxy asphalt concrete, a better solution to the steel bridge surface paving thermal stability qualitative problem, but epoxy asphalt is expensive, material formulation and construction technology for the United States exclusive, greatly limiting the application of other asphalt concrete in the steel bridge pavement. Epoxy resin adhesives (including epoxy zinc-rich paint), generally composed of epoxy resin, curing agent two groups, at the same time according to the actual needs of modifiers such as tougheners or fillers. At present, more representative is the Shanghai Huitian Chemical Industry New Materials Co. , Ltd. produced 623 epoxy structure glue, its room temperature shear strength of up to 12 MPa, 70 degrees C also has 1.6 MPa, but its high temperature (160 degrees C) shear strength is only about 0.2 MPa. Asphalt mixture high temperature paving bridge surface temperature is often as high as 160 degrees C or higher, in this case, the use of 623 epoxy structure glue and a single particle size of gravel bonding layer due to the sharp decline in their own bonding force, it is easy to produce bonding layer and steel bridge surface separation, while the bonded single particle size stone part is also due to the bonding layer bonding strength of the sharp decline was stripped, Loss of the ability to link asphalt mixtures with steel plates, so that the bonding layer becomes a slip layer, resulting in the spread layer of the spread and cracking and other diseases.
in view of the above situation, Changsha University of Technology steel bridge paving team has developed its own high temperature-resistant epoxy resin adhesive, named "DLERA", and carried out a test of the performance of the force.
1 Orthopaedic Steel Bridge Surface Laying In order to determine whether DLERA meets the requirements for use, it is necessary to put forward corresponding technical indicators. This paper refers to the technical index of the orthopaedic steel bridge surface of Xiling Yangtze River Bridge. According to the information provided by the dam area management department of China Yangtze River Three Gorges Engineering Development Corporation on the structure of the steel box beam of the bridge, as well as the cross-sectional diagram of the structure of the steel box beam, the dynamic calculation model of the orthopaedic steel bridge surface of the Xiling Yangtze River Bridge was established by using an ANSYS large-scale general limited-purpose meta-program, and the calculation and analysis of the bare plate of the steel bridge surface and the maximum pull strain special value of the design paving surface were calculated.
2 Steel-glue interface shearing, pull-out test to study the success or failure of steel bridge asphalt paving the first problem is how to solve the problem between the paving layer and smooth steel plate surface interface shear resistance is not enough. As can be found from Table 2, the maximum horizontal stress of the steel bridge surface of Xiling Yangtze River Bridge is 1.32 MPa when the water-resistant bonding layer (used as a bonding layer while being used as a waterproof layer) is considered at the least loaded position and when impact is considered. However, in the actual project, the separation between the waterproof bonding layer and the steel plate and the stripping of the stone with which it adheres often occurs during the paving of asphalt mixtures, at this time, the temperature of the steel bridge surface is often as high as 160 degrees C, and the waterproof bonding layer in the high temperature of the bonding force dropped sharply, it is difficult to resist the construction of the upper mechanical equipment applied by the composite force and damage. To this end, this paper requires the interface of steel and glue at 160 degrees C to have shear strength τ1.32 MPa, pull strength of 1.2 MPa. 2.1 Simple shearing, pull test Pull, shear test with coated steel sheet test pieces in the 10-power test machine. The test was conducted at four temperatures: room temperature (25 degrees C to 2 degrees C), medium temperature (70 degrees C to 2 degrees C), high temperature (140 degrees C to 2 degrees C, 160 degrees C to 2 degrees C). The results of the experiment can be found in tables 3 and 4.From Tables 3 and 4, DLERA not only has a high shear and pull strength at normal temperature and medium temperature (70 degrees C), but also maintains a high shear and pull strength at 140 degrees C/160 degrees C, fully meeting the reference indicators proposed in Table 2. 2.2 Round milling test In order to further verify the high temperature stability performance of DLERA, the test room designed the test using rutted test piece molding instrument (wheel mill method), and compared with a certain epoxy resin coiling agent (25 degrees C, 70 degrees C shear strength of 8.96 MPa, 9.40 MPa). The test process is: the steel plate (300 mm x 350 mm x 50 mm) in the direction of length is divided into two parts, one part DLERA, the other part coated with a certain epoxy adhesive. The glue is applied in two layers, the first layer is 0.3 to 0.5 mm, and then the second layer is applied after its initial formation strength, the layer is 0.6 to 0.7 mm thick, while spreading a single grain Basalt with diameter (2.36 to 4.75 mm), asphalt mixture with SMA-13, oil-stone ratio of 6%, mixed with 0.3% fiber, thickness of 3 cm. After the glue is cured, the steel plate is loaded into the rutted test mold (glue facing up), while the asphalt mixture mixed with machine mixing machine and asphalt mixture, mixing temperature and oven temperature control at about 180 degrees C. After mixing well, quickly put the hot mix asphalt mixture into the rutted test mold, after rough flat (surface is 185 degrees C, the bottom temperature is 155 degrees C) quickly lifted on the pressure table, applied 10.5 kN load (wheel width 350 mm, pressure line load of 300 N/cm), crushed 24 times, lifted the test mold immediately crushed asphalt mixture into observation. See Figures 1 and 2 for test parts of steel plates before and after crushing.
From Figure 2, it is clear that the DLERA remains intact, and that part of the surface of a epoxy resin glue removal itself is damaged (due to layering, the damaged part does not pass through the lower layer), and the single grain of stone adhered to it is mostly stripped, leaving a noticeable pit on the adhesive layer. Experiments show that DLERA has good high temperature shear and pull resistance.
3 Bending test Steel bridge panel due to the effect of the load bending deformation, especially in its ribs and the main beam abdominal plate produces a large deformation, and repeated appearance, often lead to the laying layer cracking, especially the interface laying layer such as waterproof bonding layer cracking. When the waterproof layer is cracked, it can lead to a series of consequences, such as rainwater seeping directly into the steel plate, causing the steel plate to rust. With the penetration and diffusion of steel plate rust, the steel-glue interface dissointed from each other, resulting in the slip and cracking of the upper bunk layer. Therefore, it is required that the interface material has good entourage performance to the deformation of the steel plate. The laboratory has designed a simple bending test device, as shown in Figure 3.
test pieces are made of steel plate, layered on its surface, and coated with a second layer of glue while spreading 4.75 to 9.5 mm single-particle stone, to be cured and placed in a simple bending tester (span 22. 7 cm) on, apply the glue face down, test the maximum vertical displacement it can withstand at the design temperature (to hear a crisp cracking sound as the end point of the test), and then calculate the corresponding maximum strain (cross-pull strain) and curvature radius.
By Table 2, Xiling Yangtze River Bridge orthopaedic steel bridge surface bare plate surface in the most unfavourable position produced by the maximum lateral pull should be changed to 332 s, when the comprehensive consideration of the interface material under the effect of load repetition fatigue cracking, this paper is considered to be available as a reference. The test results, the parameters used for the calculation and the calculation results can be found in Table 5.From Table 5, it can be seen that DLERA has good toughness of 0 to 70 degrees C, i.e. anti-bending properties, while the test further shows that as the temperature increases, DLERA will gradually soften, will not appear bending cracking under the condition of high temperature asphalt mixture paving. 4 Conclusion (1) DLERA has good high temperature shear resistance and pull strength, and can better meet the requirements of asphalt paving and crushing on the mechanical properties of the bonding material in the steel interface at a temperature of 160 degrees C. (2) DLERA has good bending resistance at 0 to 70 degrees C, and the higher the temperature (no more than 200 degrees C, otherwise prone to thermal oxidation and destruction), the better its anti-bending properties. However, as the temperature decreases,
DLERA will gradually become brittle and bend and crack under overload. If put into the actual construction, on the one hand, to prevent the destruction of overweight vehicles that is, the implementation of traffic control, on the other hand, we can start from the rational aspects of the laying structure layer, so as to achieve better utilization effect.
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