Concrete @ your Fingertips

Non-ferrous metals in concrete

Copper
Copper is generally immune from attack by caustic alkalis and not affected by contact with lime or calcium hydroxide. It can be safely embedded in fresh concrete with no disruptive action occurring even when the concrete is saturated, provided chlorides are not present. Admixtures containing chlorides should not be used in the concrete.

Brass
Primarily an alloy of copper and zinc, but iron, aluminium, manganese, nickel, tin and lead are frequently added. There is likely to be a slight attack from fresh concrete which results in a protective coating on the metal. Once hardened , further attack is unlikely unless chlorides are present in the concrete, e.g. from admixtures.

Aluminium
Aluminium is attacked by alkaline solutions, e.g. calcium hydroxide, and thus strong initial attack by fresh concrete will occur with the evolution of hydrogen. This can lead to hydrogen embrittlement of the steel in prestressed concrete and should be avoided in this application. Cracking or spalling may occur but the attack should reduce once the concrete hardens; however, it may be activated again if moist conditions prevail. The presence of calcium chloride in the concrete may increase the severity.

Bronze
Primarily an alloy of copper and tin, although the name is sometimes applied to other alloys not containing tin. Reaction similar to that of copper.

Zinc
Zinc is attacked by alkaline solutions e.g. calcium hydroxide and thus initial attack by fresh concrete will occur with the evolution of hydrogen. It is not as strong as the attack on aluminium. Cracking or spalling is less likely unless a large surface area is available to react. Attack should cease once the concrete hardens, but may be activated again if moist conditions prevail. A protective zinc coating on steel bars may reduce the bond strength to concrete.

Tin
Attack similar to zinc.

Acknowledgement: The Concrete Society