Protection of steel rebar

For a many years concrete has been used to protect steel rebar from corrosion. Unfortunatelly, in the most cases it is not enough. To avoid corrosion any agressive substances should not be used when pouring concrete and the environment should be non- agressive. In theory it sounds easy but in real life it is impossible to examine every filler of concrete and to avoid agressiveness of environment in which reinforced concrete will be used. Therefore, more efficient method of protection should be used to prolong life of the rebar without the major maintenance. Consider the most well- known methods of protection. (14)

Moisture in concrete provides alkaline environment which saves the passive state of rebar surface. But concrete also always interacts with environment which may contribute to hardening and sealing, which will strenghten the protective properties. On the other hand agressive environment may destroy structure of concrete and lower its durability. In addition, moisture inside of concrete may change its properties which will lead to loosing of protective properties and acceleration of corrosion process.

Protective paints are relatively cheap method of protection. Rebar is painted before concrete is poured. Paints, which do not contain epoxies are less durable comparing to ones that contain them. It makes epoxy paints a separate method.

Epoxy paints showed better efficiency comparing with other paints but this kind of coating costs significantly more and technology is very hard in the execution. Usually, rebar should be coated in factory conditions. They are sensitive to UV radiation so it is not recommended to use them for uncovered steel.

Figure 6. Epoxy coated rebar (23)

Figure7. Corrosion inhibitor application (24)

Migrating inhibitors are relatively new method of rebar protection. They could be added to liquid as well as hardened concrete. They spread through the cracks and pores, reaching rebar surface. After absorbed by steel, they create a protective monomolecular layer. Corrosion process decelerates, oxygen and moisture can no longer reach the rebar surface through protective layer. (15)

That kind of protection is very efficient: this substances may lower the corrosion rate in 5-13 times. Using this protection before corrosion process occurs may significantly postpone its appearance. (15)

In order to use inhibitors, surface should be cleaned up from oil, dirt and fungus. After that inhibitor could be applied by spraying or by using paint roller. If concrete is very dense, application is divided on 2 stages with 8 hour interval. (15)

Nowadays, use of inhibitors is the most modern way of rebar protection. This technology is already in use in such projects like Burj Khalifa, Pentagon renovation and Singapore metro. (15)

Date: 2015-12-18; view: 859