Structure first, anti-corrosion second. The importance of concrete anticorrosion can be seen. What exactly does corrosion of concrete mean? What factors can cause concrete to corrode? What are the outstanding advantages of silane impregnation technology in concrete anticorrosion? How do you rate the best silane impregnated coatings?
1. What does concrete corrosion mean?
U.S. Federal Highway Administration (FHWA): More than 50% of the nearly 600,000 bridges in the United States suffer from corrosion of steel bars, requiring $75 billion in maintenance costs each year, accounting for 1.25% of the total annual construction cost.
According to statistics, Japan currently only spends 40 billion yen per year on the maintenance of concrete structures, and about 12.4% of reinforced concrete structures are damaged due to corrosion of steel bars. The Shinkansen, which Japan is proud of, has been in use for less than 10 years, and there are large areas of concrete cracking and erosion.
In addition, due to concrete corrosion, the internal structural performance of the bridge deteriorated, eventually leading to a collapse accident (as shown in the figure below).
To sum up, the harm of concrete corrosion is huge, which is mainly reflected in: significantly shortening the service life of concrete, reducing the safety factor of concrete structures, leading to safety accidents and huge economic losses.
2. What factors can lead to concrete corrosion?
Affected by the physical, chemical and biological erosion of the environment, the concrete structure will deteriorate and the service life of the building structure will be shortened. The main factors affecting the durability of concrete are: corrosion of chloride ions, corrosion of steel bars, freeze-thaw cycles, carbonation, alkali-aggregate reaction, and surface biological erosion.
3. What are the outstanding advantages of silane impregnation technology in concrete anticorrosion?
Silane is a penetrating impregnating agent with excellent performance. It has a small molecular structure. It penetrates deep into the concrete capillary wall and reacts with hydrated cement to form a polysiloxane interpenetrating network structure. Through a strong chemical bonding reaction, it gives the concrete surface The microstructure has long-term hydrophobicity and maintains the function of breathing and ventilation, which greatly reduces the intrusion of water and harmful chloride ions, etc., and ensures that the concrete structure is free from corrosion.
4. How to choose silane impregnated coating?
Silane impregnation coatings refer to small molecule silanes, the most common being isobutyltriethoxysilane, n-octyltriethoxysilane, and isooctyltriethoxysilane. However, in the field of anti-corrosion, silicone waterproofing agents and silane impregnated coatings are often mixed together.
When choosing silane impregnated coatings, only look at his lotus leaf effect or water drop effect. As a result, the final anti-corrosion cannot meet the expected requirements, thus doubting the silane impregnation technology.
“Lotus leaf effect” means that water can produce the same effect as lotus leaves on the base surface, that is, water droplets roll. The lotus leaf effect is the easiest to observe, but also the most deceptive. The main reasons are: 1. Whether the lotus leaf effect is obvious or not is directly affected by the interfacial tension of the base surface, the length of the molecular chain, the structure of the hydrophobic group, the roughness of the base surface, etc. will all affect the lotus leaf effect. Second, waterproof and hydrophobic are two concepts. Hydrophobic is the apparent contact angle CA>90°. Waterproof is the ability to resist water erosion.
How to evaluate the quality of silane impregnated coating?
Impregnation depth: the effective depth at which the silane impregnated coating penetrates into the concrete.
Water absorption: It is the most authoritative measure of silane waterproof performance. Specifically, it refers to the weight percentage increased by soaking in water for a certain period of time at a certain temperature.
Chloride absorption reduction effect: Measures the resistance to chloride ion attack of silane impregnated coatings.
The above three indicators are the most basic and important indicators to measure the effect of silane impregnated coating after construction. It is clearly stipulated in JTJ275-2000 “Technical Code for Corrosion Protection of Concrete Structures in Harbor Engineering”, CCES 01-2004 “Guidelines for Durability Design and Construction of Concrete Structures”, and JTS153-2015 “Durability Design Standards for Water Transport Engineering Structures”.
As for the effect of the material itself, the most core index – the effective substance content: liquid requirements > 98.9%; paste requirements > 80%. Now many material suppliers provide significantly lower effective content than this standard, the most direct impact is that the durability cannot meet the design requirements. Therefore, the selection of a good silane impregnated coating must pay attention to the above indicators. A good silane impregnated coating is the guarantee of anti-corrosion effect.