Editing Reinforced concrete (section)

===Anticorrosion measures===
In wet and cold climates, reinforced concrete for roads, bridges, parking structures and other structures that may be exposed to [[deicing]] salt may benefit from use of corrosion-resistant reinforcement such as uncoated, low carbon/chromium (micro composite), epoxy-coated, hot dip galvanized or [[stainless steel]] rebar. Good design and a well-chosen concrete mix will provide additional protection for many applications.

Uncoated, low carbon/chromium rebar looks similar to standard carbon steel rebar due to its lack of a coating; its highly corrosion-resistant features are inherent in the steel microstructure. It can be identified by the unique ASTM specified mill marking on its smooth, dark charcoal finish. Epoxy-coated rebar can easily be identified by the light green color of its epoxy coating. Hot dip galvanized rebar may be bright or dull gray depending on length of exposure, and stainless rebar exhibits a typical white metallic sheen that is readily distinguishable from carbon steel reinforcing bar. Reference ASTM standard specifications '''A1035/A1035M''' Standard Specification for Deformed and Plain Low-carbon, Chromium, Steel Bars for Concrete Reinforcement, '''A767''' Standard Specification for Hot Dip Galvanized Reinforcing Bars, '''A775''' Standard Specification for Epoxy Coated Steel Reinforcing Bars and '''A955''' Standard Specification for Deformed and Plain Stainless Bars for Concrete Reinforcement.<!-- [[American Concrete Institute|ACI]] 440 provides information about properties and design of FRP reinforced concrete structures. The Canadian [[Canadian Standards Association|CSA]] 806 and 807 providing the same information in form of a real standard. In addition the Canadian Highway Design Code is the first standard allowing for composites in bridge construction. -->

Another, cheaper way of protecting rebars is coating them with [[zinc phosphate]].<ref>{{cite journal |title=Effect of zinc phosphate chemical conversion coating on corrosion behavior of mild steel in alkaline medium: protection of rebars in reinforced concrete |first1=Florica |last1=Simescu |first2=Hassane |last2=Idrissi |publisher=National Institute for Materials Science |journal=Science and Technology of Advanced Materials |volume=9 |issue=4 |pages=045009 |date=December 19, 2008 |pmc=5099651 |doi=10.1088/1468-6996/9/4/045009 |pmid=27878037 |bibcode=2008STAdM...9d5009S }}</ref> Zinc phosphate slowly reacts with [[calcium]] cations and the [[hydroxyl]] anions present in the cement pore water and forms a stable [[hydroxyapatite]] layer.

Penetrating sealants typically must be applied some time after curing. Sealants include paint, plastic foams, films and [[aluminum foil]], felts or fabric mats sealed with tar, and layers of [[bentonite]] clay, sometimes used to seal roadbeds.

[[Corrosion inhibitor]]s, such as [[calcium nitrite]] [Ca(NO<sub>2</sub>)<sub>2</sub>], can also be added to the water mix before pouring concrete. Generally, 1–2&nbsp;wt.&nbsp;% of [Ca(NO<sub>2</sub>)<sub>2</sub>] with respect to cement weight is needed to prevent corrosion of the rebars. The nitrite anion is a mild [[oxidizer]] that oxidizes the soluble and mobile [[ferrous ion]]s (Fe<sup>2+</sup>) present at the surface of the corroding steel and causes them to precipitate as an insoluble [[ferric hydroxide]] (Fe(OH)<sub>3</sub>). This causes the passivation of steel at the [[anodic]] oxidation sites. Nitrite is a much more active corrosion inhibitor than [[nitrate]], which is a less powerful oxidizer of the divalent iron.