Range of Concrete and Mortar ph? 1

[jheidt2543]

Can some one tell me or direct me to a reference that has the "normal" range of ph for concrete and masonry mortar made with Type I Portland cememt?

Thanks in advance for your help.

 

[kenvlach]

The pH is at least 12, most likely about 12.5.

From HOT-DIP GALVANIZING FOR CORROSION HOT-DIP GALVANIZING FOR CORROSION PREVENTION: A guide to specifying & inspecting hot-dip galvanized reinforcing steel. p. 3:

"Under normal conditions, concrete is alkaline (pH of about 12.5) due to the presence of calcium hydroxide. In such an environment, a passivating iron-oxide film forms on the steel, causing almost complete corrosion inhibition.
As the pH of the concrete surrounding the reinforcement is reduced by the intrusion of salts, leaching or carbonation, the system becomes active and corrosion proceeds...In the presence of oxygen, inhibition of iron corrosion occurs at a pH of 12.0. But as the pH is reduced, the corrosion rate increases. With reduction of pH to 11.5, the iron corrosion rate increases by as much as five times the rate at a pH of 12.0."
The complete article can be downloaded from the American Galvanizers Association website,

http://www.galvanizeit.org