Engineering practice has fully proved that adding rust inhibitor once during the concrete construction process can prevent corrosion for about 50 years, which is basically the same as the design service life of reinforced concrete structures. , and has the characteristics of simple construction, convenient participation, labor and time saving, and low cost. Compared with the epoxy coating steel bar protection method and the cathodic protection method, the cost of adding rust inhibitors is lower and the effect is obvious. However, rust inhibitors are generally chemicals, and some are even toxic substances, which have adverse effects on human health and the construction environment. Therefore, sufficient attention should be paid to the specific application process.
1. Specific provisions in national standards
According to the current national standard “Concrete Admixtures According to the “Application Technical Specifications” (GB50119-2013), the following requirements should be met when adding rust inhibitors to concrete or mortar.
(1) New concrete project
The mix proportion design of concrete mixed with rust inhibitor should comply with The relevant provisions in the current industry standard “Common Concrete Mix Proportion Design Regulations” (JGJ55-2011). When the raw materials or concrete properties change, the concrete mix proportion should be redesigned
(2) Add rust inhibitors or compound rust inhibitors with other admixtures The properties of concrete used should meet the requirements of design and construction.
(3) The mixing, transportation, pouring and maintenance of concrete containing rust inhibitors should comply with the current national standard “Concrete Quality Control Standard” (GB50164-2011) the relevant provisions in.
2. Existing concrete projects
Use concrete or mortar mixed with rust inhibitors When repairing existing reinforced concrete projects, the following regulations should be met.
(1) The corroded, contaminated or neutralized concrete layer should be removed first, and the rust on the surface of the steel bars should be removed before repair.
(2) When the damaged part is small and the repair layer is thin, mortar should be used for repair; when the damaged part is large and the repair layer is thick, mortar should be used for repair. Concrete should be used for repair.
(3) When constructing over a large area, a combination of spraying or spraying can be used.
(4) The maintenance of repaired concrete or mortar should comply with the relevant regulations in the current national standard “Concrete Quality Control Standard” (GB50164-2011).
2. Key points of application technology in construction
Based on the construction experience of concrete projects at home and abroad , during the concrete construction process using rust inhibitors, the following technical points should be mastered.
1. The properties of various concrete rust inhibitors are different, and the roles they play in concrete are also different. In order to give full play to the rust inhibitors added The function of the agent should be used strictly in accordance with the dosage specified in the instruction manual, and field tests should be conducted to verify it.
2. The use method of rust inhibitor is basically the same as other chemical additives. It can be dried or dissolved in the mixing water in advance. When the rust inhibitor is agglomerated, it should be dissolved in the mixing water in advance. No matter which mixing method is used, the mixing time of the concrete should be appropriately extended, generally by about 1 minute.
3. When adding the steel bar rust inhibitor, it should be reduced appropriately, and the construction should be strictly carried out in accordance with the requirements of the general concrete production process, and the vibration should be fully carried out. Ensure the quality and compactness of concrete.
4. For some important reinforced concrete projects that need to be protected, 5% to 10% steel rust inhibitor solution can be applied to the surface of the steel bars, and then Then use concrete containing rust inhibitor for pouring construction.
5. Steel bar rust inhibitor can be used alone or in combination with other admixtures. In order to avoid adverse phenomena such as flocculation or precipitation when used in combination, a compatibility test should be conducted in advance.
6. When steel bar rust inhibitor is used to repair buildings, the loose and damaged concrete must first be thoroughly removed to expose the fresh concrete base surface. Spray 10% to 20% high-concentration rust inhibitor solution on the surface of the rusted or re-welded steel bars, and then repair it with dense concrete mixed with rust inhibitors.
7. Other operations of concrete mixed with rust inhibitors, such as concrete preparation, pouring, maintenance and quality control, should be based on the production process of ordinary concrete. Conduct and strictly abide by relevant standards.
8. During the storage and transportation of powdered rust inhibitors, relevant regulations should be strictly followed to avoid mixed placement, open flames are strictly prohibited, and flammable and explosive materials should be kept away. items and prevent them from being exposed to direct sunlight and stored in the open air.
9. During the storage and transportation of the rust inhibitor, measures should be taken to keep it dry to avoid moisture absorption, and leakage and water immersion are strictly prohibited.
10. Most steel bar rust inhibitors have a certain degree of toxicity. During storage, transportation and use, you must not touch the powder or solution with your hands, nor use it. Solution for cleaning laundry and utensils, staff…You must pay attention to washing your hands before eating.
11. Most anode rust inhibitors are oxidants, which are prone to oxidation and self-ignition in high temperature environments and are difficult to extinguish. Pay attention to fire prevention when storing.
Rebar rust inhibitors should not be used in acidic environments. In addition, nitrite rust inhibitors must not be used in reinforced concrete projects in drinking water systems. , to avoid nitrite poisoning.
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