Concrete surfaces are frequently reinforced with embedded rebar. While rebar can greatly increase the structural strength of a concrete surface, it is susceptible to corrosion over time. In fact, the corrosion of embedded rebar materials is one of the major factors behind concrete deterioration.
The lifespan of a concrete surface can be increased if rebar corrosion is prevented. The following are six ways that rebar corrosion can be prevented or minimized:
1. Watertight concrete coverings
Rebar will become susceptible to corrosion if it is exposed to water. Watertight concrete can be produced that has a minimal water-cement ratio when the concrete is being mixed. A low water-cement ratio can help to consolidate and cure a concrete well, thus rendering the resulting concrete less permeable to moisture.
2. Cathodic protection
Corrosion is the result of an electrochemical process. Cathodic protection involves making a metal surface function as an electrochemical cell's cathode. This typically means that a sacrificial anode must be attached to the rebar in some way so that the sacrificial anode corrodes instead of the rebar.
Different sealers can be used on reinforced concrete to prevent rebar from corroding. These sealers could come in the form of epoxy coatings, acrylic products, linseed oil emulsions, or silane sprays.
4. Concrete overlays
When a polymer concrete overlay is used as a corrosion prevention method, reinforced concrete can be rendered for the most part impermeable to both water and chlorides. Methods of using concrete overlays to prevent corrosion include using latex modified concrete or adding silica fume to the concrete mixture to both slow down carbonation and reduce the amount of chlorides that are present.
5. Corrosion resistant rebar
There are types of rebar available that are coated with epoxy. This coating makes corrosion impossible or highly unlikely. If stainless steel rebar is used, the chance of corrosion is already significantly lowered. However, stainless steel is sometimes considered too expensive to be used as a rebar material. One more affordable option is glass-fiber reinforced plastic rebar, which provides effective reinforcement in environments that are prone to corrosion.
6. Chloride content
The American Concrete Institute's ACI 318-08 building code calls attention to the relationship between chloride content and corrosion. This building code limits chloride content depending on cement weight.
According to ACI 318-08, the content of water-soluble chloride ion content in concrete mix cannot exceed 0.30 percent in environments where concrete is exposed to moisture but is not exposed to other chloride sources. The same building code dictates that chloride content can reach as high as 1 percent in reinforced concrete that is protected from moisture.
Keeping chloride content well below these requirements will offer even better corrosion prevention in reinforced concrete. For more information, contact a concrete restoration company in your area, such as Epoxy Stone Inc.