The bond between the cement paste and steel reinforcement in concrete structures is typically very weak. Enameling the steel reinforcement with a Jow-melting point vitreous enamel that contains calcium silicates and calcium aluminoferrites raises the bond strength by a factor of approximately two to four times the normal bond adhesion. An X-ray diffraction study and SEM imaging and a microanalytical examination of the bonding enamel layer indicates the calcium silicates and calcium aluminoferrites fused into the enamel react with the moisture in the fresh mortar and form a calcium silicate hydrate surface that adheres to the surrounding paste. The increased bond strength demonstrates that the enamel-cement coating acts as a coupling layer and attaches the hardening calcium silicate gel layer to the steel. During hydration, the composite cement-glass layer reacts with water that accumulates at the interface and appears to prevent the usual weakly-cemented layer from occurring in the adjacent paste. Additionally the bonding enamel can be applied to provide a durable chemically-resistant layer to protect the steel from oxidation.
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