Steel bridge structure is indispensable in building materials. In coastal Bridges, cross-sea Bridges and other facilities, inevitably appeared some cracks in reinforced concrete, or gap when erosion by salt water or acid rain caused by steel corrosion of reinforced concrete. Domestic and international bridge structure damage caused by steel corrosion damage is very surprising. To solve this problem on international studies for a variety of methods, including using epoxy resin coated steel bar (hereinafter referred to as the coated steel) is a kind of more effective prevention of rebar corrosion. Even in the salt of the worst cases, penetrate into the concrete due to the coating on the surface of steel form the electric insulation, can protect the steel from the erosion of chloride ions. Coated steel has excellent chemical corrosion resistance, high adhesion, coating and metal after the formation of dry shrink, ductility, can effectively block the erosion of the material, can prolong the service life of buildings more than 50 years, avoid the inconvenience due to maintenance or dismantled and expensive cost, so since the 1970 s in the United States for the first time to use, in the United States, Japan, Europe and the far east, the Middle East and other countries and regions has been widely applied, but in our country since the 1990 s to start.
The performance of the coating on steel and ordinary steel difference:
2.1 binding performance: the use of coating for steel and concrete bonding performance caused a certain adverse effect. Foreign scholars of ribbed steel bar, belt hook reinforced after the coating and concrete bonding anchorage performance and lap performance were studied, the experiment in the main beam end pull out, beam reinforced lap performance and creep, etc.
Grip of 2.2: the experiment proved that the coating reinforced when coating thickness more than 0.22 mm, its grip of general reduced 15% can be achieved by using small diameter steel bar, increasing concrete protective layer thickness, configuration of stirrup, extend the anchoring and binding length, increasing concrete strength and other measures to solve.
2.3 crack, deformation and rigidity: due to the bonding strength of coating steel decreases, the width of cracks. In contrast test beam at the university of Texas, in the reinforced overlap area not hooped conditions, coating of steel beam and compared with ordinary reinforced beam crack width and spacing increases by about 50%. In addition, also measure the deformation of the beam in the test beam reinforced epoxy coating on did not affect the rigidity of the beam. Coating steel with ordinary steel in crack width differences will decreases with the increase of repeated load loading times. Using coating reinforced the component did not change significantly early stiffness, as close to the limit load and stirrup is large, with a coating of steel components relative to the stiffness with less rigidity of ordinary steel components. Coating steel with ordinary steel in deformation and stiffness differences will decreases with the increase of repeated load loading times.
Refractory performance: 2.4 the results show that the coating steel has similar refractory to ordinary reinforced performance.
Conclusion: coated steel bar in North America, especially in the United States the use of more than 30 years, continuously improve the manufacturing process, improve quality, increase dosage, prices are falling. General than ordinary steel increases in the cost of domestic coating steel 2000 ~ 2500 yuan/t, for bridge engineering, increase the cost of about 2% of the total cost of bridge construction. Coating reinforced assembly, processing, handling and bundle and the possible damage to the coating problems in concrete pouring, can by direct contact with coated steel parts for non-metallic parts and change the way of concrete vibratory measures to deal with.
