Application of coating in anti-carbonization of bridge reservoir

Core Tips: Xiao Yuanhong, Liu Ran, Wu Tao (Tianjin Reservoir Management Office, Tianjin 301900, Tianjin) Abstract: Analyze the causes and effects of the carbonation of the spillway of the Yuqiao Reservoir, and take timely measures to prevent carbonization and ensure the safe operation of the spillway pier. .

1. Analysis and influence of carbonation of gate pier

1.1 Analysis of the Causes of Carbonation of Gate Piers After more than 20 years of application, the bridge pier spillway pier has experienced different degrees of carbonization. The carbonization of the pier refers to the process in which Ca(OH)2 in the concrete reacts with CO2 in the air or CO2 or other acidic substances dissolved in water to become CaCO3 and loses alkalinity.

Factors affecting carbonation of concrete include environmental factors, raw material factors, and construction operation factors. Judging from the spillway pier of Yuqiao Reservoir, in the initial stage of construction, the construction, supervision and construction of the raw materials and construction operations can basically eliminate the latter two factors, so it can be basically determined that the carbonization is caused by environmental factors.

The upper basin of Yanqiao Reservoir is located in the south of Yanshan Mountain. The main weather systems affecting the main wind system include the west wind belt high-altitude trough, the northwest vortex, the typhoon and the typhoon trough, the shear line and the southwest vortex. The basin is basically in the basin area surrounded by mountains, the southwest is the basin outlet, and the northeastern Sanyingying has a 50-100-meter-wide cornice connected to the Weihe River basin, thus providing a corridor for the movement of the air mass. "At the same time, the area is in the warm wind and the windward side. This terrain is conducive to the formation of heavy rain. Therefore, the rainfall in this basin is relatively abundant. It is the rainstorm in the Yanshan area. The average precipitation of the Yuqiao Reservoir is 750 mm. Due to this hydrometeorological condition combined with years of operation, carbonation of the spillway pier is normal.

1.2 Carbonization of the pier affects the carbonization of the pier to reduce the alkalinity of the concrete. At the same time, the amount of hydrogen ions in the concrete pore solution is increased, so that the protection effect of the concrete on the steel bar is weakened. Carbonization is a slow process. When carbonization exceeds the protective layer of concrete, in the presence of water and air, the concrete loses its protective effect on the steel bars, and the steel bars begin to rust. After the steel is corroded, the volume generated by the rust is 2~4 times larger than that of the original, so that the expansion stress is generated on the concrete around the pier. The more serious the rust is, the more the rust is, the larger the expansion force is, and finally the weakening of the grip force of the steel bar is caused. The overall destruction of the pier.

Therefore, the anti-carbonization treatment of the pier is very necessary.

2. Anti-carbonization treatment measures for piers

The anti-carbonization construction of this project is divided into two parts. Firstly, the original pier surface is cut 2cm and then coated with 2cm thick acrylic mortar, and then the surface is coated with ST-9608 anti-carbonization coating.

2.1 Propolis mortar construction Acrylic mortar is the abbreviation of acrylate copolymer emulsion cement mortar. This material has excellent bonding performance, anti-cracking, waterproof, anti-chloride ion penetration, anti-corrosion, anti-freeze, wear-resistant, anti-aging, A new type of face repair material.

Acrylic milk: acrylate copolymer emulsion, this product is milky white liquid, non-toxic, non-corrosive.

(1) Construction process: 1 Process: chiseling concrete——cleaning and moistening------------------------------------------------------------------------------------------------------------------- - Spray curing - Clay mortar seal - spray curing. 2 Concrete base treatment: Cut the concrete to the fresh concrete surface, then rinse it with high-pressure water, remove the dirt, dust, fragments and loose concrete on the repaired surface, then rinse and moisten with clean water to make the concrete base dry. . 3 artificial squeezing: In order to ensure the quality, first use the acrylic syrup to make a primer, then wipe the mortar, using the retreat method: the pressing direction is opposite to the advancing direction of the newly built mortar layer. The thickness is controlled at about 8mm~1cm, and the mortar layer is required to be dense and the surface is smooth and smooth. 4 Maintenance: After 4 hours of squeezing the squeezing mortar, the final setting will occur. At this time, the agricultural sprayer is used for spray curing. After curing for one day, use a brush on the surface of the milk mortar to make a paste. It is required to spread and seal, and continue to spray and maintain after the final slurry is hardened. Maintenance standards: The mortar surface is always kept moist and the curing time is 7 days.

(2) Refer to the ratio of the latex mortar.

The latex mortar is prepared from the ratio of ash to sand ratio of 1:1 to 1:1.5, and the ratio of 1:0.45 to 1:0.725 acrylate (coating) is 2:1 (3) propylene mortar.

According to the mix ratio, weigh them separately. First mix the water and the milk, mix the cement and sand evenly or pour into the mixing tray, then slowly pour the mixture into the mixture of cement and sand and mix it by hand. The amount of one mixing is controlled by cement at 10kg. It is appropriate.

2.2ST-9608 anti-carbonization coating construction (1) coating preparation: anti-carbonization coating is divided into two parts: the primer and the surface coating.

1 Primer preparation: The base coat material is two-component, the component A is milky white emulsion, and the B component is gray or reddish powder. The ratio of the component is: A:B=1:1.8~2.2.

2 top layer coating: the surface layer coating is used directly, and the coating is fully stirred evenly before use.

(2) Base treatment: Since the construction of the acrylic mortar has been carried out before the construction of the ST-9608 coating, the base layer treatment of the ST-9608 only needs to be applied to the wet dew surface, and the surface is first wiped with a rag or the like. Dry, and then re-construction; on the dry surface, sprinkle water on the surface before spraying to keep the concrete surface moderately moist to ensure the quality of the coating construction.

(3) Undercoating construction: The base layer can be inspected to meet the requirements of anti-corrosion coating construction, and the primer coating construction can be carried out.

The primer is scraped from top to bottom with a plastic plate. The batch is scraped in the same direction, and the back and forth are resolutely prevented to ensure the integrity of the polymer coating network and the flatness of the coating. The batch speed is controlled during the process to avoid a large number of bubbles and affect the quality. The undercoat layer is applied in 3 times, and the coating of each batch of scraping is smooth, no obvious scraping marks are transferred, and the total thickness is controlled at about 300 um. After one batch of scraping, the curing is about 2 hours, and the surface is hard formed into a film without removing the powder. After passing the inspection, the second coating is carried out. In order to ensure the thickness of the undercoat layer, the quality inspectors shall check the thickness at any time. In addition, the primer (A+B) shall be not less than 1.5 kg per square meter during construction. After the construction of the undercoat layer is completed, the surface should be substantially smooth, flat, and free of obvious scratches.

(4) Top coat construction: After the construction of the base coat is completed, after the inspection and inspection, it meets the requirements of the surface paint construction, and then the next process, that is, the construction of the surface paint. The surface coating is made of a roller brush, and the batch scraping surface of the undercoat surface is smoothed by sandpaper before construction. The drum dipping is suitable. Roll the board on the board before rolling to prevent the paint from sagged on the wall. The direction of the brush is from top to bottom, and the speed is moderate to avoid generating a lot of air bubbles. Each roller brush should be separated by 2 hours, which is based on the dryness of the coating film. The surface is coated twice, and the paint is rolled again. When the athletes are active, the construction personnel ensure that the coating film is not damaged.

(5) Maintenance: In order to ensure the quality of the anti-carbonization coating, ensure the curing period of at least 2 days, and care for the person during the curing period to avoid heavy pressure, impact and immersion in the water.

3. Conclusion

The application of acrylic latex mortar and ST-9608 anti-carbonization coating in the anti-carbonization treatment of the bridge spillway pier has indeed received good results, increasing the long-term effectiveness of the pier and ensuring the overall safety of the spillway project.

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