This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
123. Tests have been made to find the value of Portland cement concrete as a protection of steel or iron from corrosion. Nearly all of these tests have been of short duration (from a few weeks to several months); but they have clearly shown, when the steel or iron is properly imbedded in concrete, that on being removed therefrom it is clean and bright. Steel removed from concrete containing cracks or voids usually shows rust at the points where the voids or cracks occur; but if the steel has been completely covered with concrete, there is no corrosion. Tests have shown that if corroded steel is imbedded in concrete, the concrete will remove the rust. To secure the best results, the concrete should be mixed quite wet, and care should be taken to have the steel thoroughly imbedded in the con-crete.