Analysis of the corrosion environment of bridges

Bridge is one of the outstanding buildings of mankind, China's bridge history can be traced back more than 6000 years, since the 1990s, China's bridge construction has made remarkable achievements. The development course of Chinese bridge also reflects the evolution experience of chinese bridge anti-corrosion coating from the side.
the 1950s, bridge protection using natural raw materials-based low-grade paint, poor protection performance, some bridges a year later serious corrosion

. Then appeared with zinc palladium white paint, red Dan rust-proof paint and gold-redstone type titanium white powder and long-oil season tetium alcoholic acid resin paint, and achieved good results.
the 1960s, paints made from flaky zinc aluminum powder and synthesized with long-oiled glutatro-tyolate resins were developed. Because flaky zinc aluminum powder reflects ultraviolet light, anti-fading and powder resistance is greatly improved than ever before in gray finishes, and because flaky layers overlap, water vapor is not easy to pass through, enhancing corrosion resistance.
In the 1970s, it further developed the gray cloud ferrooltic acid magnetic paint with international advanced level, which was officially applied to the Yangtze River Bridge in Nanjing and Wuhan, and protected for more than 5 years, becoming the main coating coating of steel bridge in China for the next 20 years.
the 1980s, with the rapid development of transportation, zinc-rich epoxy, inorganic zinc-rich, epoxy cloud iron and acrylic polyurethane were widely used.
Since the 21st century, people have put higher demands on bridge coating, requiring a longer protection period (20 years, 30 years and above), as well as safety, health and environmental protection, in line with the latest environmental requirements, a variety of new anti-corrosion coatings are gradually being applied.
the future, with China's economic development, a batch of larger cross-river bridge construction, China's
bridge will certainly create greater achievements, bridge anti-corrosion coating technology will be developed.
1, the basic structural form of the bridge
Usually, the bridge according to its use or structure, etc. can have the following classification forms.
(1) Classification by use Road bridges, railway bridges, road and railway bridges, walkway bridges and stack bridges for various purposes;
(2) classification of beam bridges (plate beam bridges, box beam bridges, girder bridges, steel bridges), arch bridges, pull bridges, suspension bridges,
(3) according to support parts classification of bridges, continuous bridges, suspension bridges, bridges without support.
2, bridge corrosion environmental analysis
A. Atmospheric corrosion
bridges across rivers or bays, and the corrosion environment is complex. China's vast territory, the geographical location of the bridges is very different, and the corrosion of bridges and the environment is closely related, so according to the temperature and humidity, usually divided into five categories of climate environment.
a, Tropical Wet Hot Zone: Leizhou Peninsula, Hainan Island and Southern Taiwan
b, Subtropical Wet Hot Zone: South of Qinling, Yangtze River Basin, Sichuan, Pearl River Basin, Northern Taiwan and Fujian
c, Subtropical Dry Zone: Tianshan South of Xinjiang, Gobi Desert
d, Temperate Mild Zone: North of Qinling, south of Inner Mongolia, north China, south of North China
e, cold zone dry area: northern Inner Mongolia, Heilongjiang Province
acid rain distribution according to China's environmental monitoring report, acid rain is the most serious area of Chongqing (PH≈4), followed by Guizhou, eastern Yunnan, Guangxi to Hainan Island, and then the middle and lower reaches of the Yangtze River. The reason is that because the local fuel produces more exhaust gas, the acidic gas produced in the northwest and north turns into acid rain with the air flow south. Salt distribution The area with the most salt in the air is 100m near the coast, gradually weakening inland.
the classification of atmospheric corrosion environment, bridge corrosion is not only affected by temperature and humidity, but also related to the corrosion medium of atmospheric environment: chlorine ions, sulfur-containing compounds.
B. Water medium corrosion
bridge is across rivers and lakes, depending on the moisture, usually divided into fresh water corrosion and seawater corrosion.
a, fresh water corrosion: Generally speaking, fresh water corrosion is weak, mainly oxygen-absorbing corrosion, but with the modern industrial emissions of fresh water pollution, will accelerate the corrosion.
b, seawater corrosion: sea water is a variety of salt electrolyte solution, PH between 7.5-8.6, sea water corrosion according to the contact with seawater is divided into splash area, tide difference area, full immersion area and sea mud area. Among them, the splash area is affected by the waves, the frequent impact on the surface of the bridge, wet and dry alternate, is the highest area of anti-corrosion requirements.
c, soil corrosion: the support of the bridge must be based on the soil, soil corrosion of steel and concrete directly affects the safety of the bridge, the soil is composed of gas phase, liquid phase and solid phase complex system, which also survives many soil microorganisms. The main factors affecting soil corrosion are: resistivity, oxygen content, salt, water content, PH, temperature and microorganisms.
3, the bridge overall anti-corrosion coating
"Conley" concrete corrosion-proof materials combine the advantages of osmosis and film-forming concrete protection materials, and through clever molecular design to make the protective materials form a three-way protection system, can effectively improve the service life of concrete, and has a good decorative effect.
The material can penetrate into the concrete 1 to 3mm and react with the active ingredients in the concrete to form a solid silicate structure, while the film coating gives the material good anti-aging performance, high and low temperature resistance, chemical corrosion resistance and color ability. Concrete corrosion-resistant material is a two-component protective material, with excellent resistance to chlorine ion erosion, acid-base erosion, waterproof, breathable, carbon-resistant properties, can effectively improve the service life of concrete structure and improve the appearance of concrete.
Compared with acrylic coatings, silicate coatings and water-based fluorocarbon coatings, concrete corrosion-resistant materials have better water resistance, anti-chloride ion erosion and anti-freeze melting cycle ability, at the same time, Kangli's coating of water vapor through the rate of up to 70%, effectively avoiding the coating drum pack caused by the loss of protection from twilight to failure.
A, "Conley " solidification has a strong water repellent, similar to the lotus leaf effect, thus preventing snow melt agents, chlorides and other harmful media into the bridge to reduce the life of the bridge.
B, "Kangli " effect, left 1 for the use of ", right 1 for the original basic
effect; C, recommended use: bridge structure anti-corrosion protection coating, bridge structure damage repair (need to support the use of concrete thin layer repair glue)
4, marine environment bridge anti-corrosion reinforcement maintenance technology
1. Grass-roots treatment: the use of high-pressure water clearing the grass roots, remove stains and loose tissue.
2. Preparation material: paste the limit device in the appropriate position of the glass fiber plate, and fix the glass fiber plate in the design position of the column after curing.
3. Fixed sleeve: in the limit device bundled with a temporary packing belt, in the glass fiber board yin and yang buckle (or hook) according to 150mm spacing not embroidered steel self-tapping wire.
4. Lower seal: use a compressible seal (the outside of the seal is coated with JGN underwater seal glue), or with a pre-installed water-stopping band to absorb water to expand to the sealing effect.
5. Bottom grout: the preparation of epoxy grout into the bottom of the sleeve 15cm, waiting for the EGM-100S epoxy grout at least 8h curing.
6. Main grout: remixed EGM-100S epoxy grout into the sleeve, to the barrel of water all discharged and filled (if the loss rate of >20%, it is appropriate to use CGM underwater anti-dispersive grout).
7. Jianpo: build a slope with JGN underwater sealing glue (underwater type) and seal the top of the sleeve.
8. Sweep tail: to be completely solidified after the grout to remove to the temporary packaging belt, glass fiber sleeve underwater anti-corrosion reinforcement system completed.
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