Reactive Silicate Coatings for Protecting and Bonding Reinforcing Steel in Cement-Based Composites

摘要

Reinforced concrete (RC) is the major construction material for hardened structures for the Army. As a basis for shelters and for infrastructure reinforced concrete has two drawbacks: the bond between the concrete and its steel reinforcement at the interfacial zone is typically very weak and the increased porosity of the interfacial zone can accelerate penetration of chloride ions to the surface of the embedded steel reducing the time to the initiation of corrosion. Corrosion products from steel occupy a larger volume that the steel that has oxidized. The increase in volume cracks the concrete around the reinforcement and weakens the steel members. When the steel is separated from the surrounding concrete the carrying capacity of the RC structure is compromised. A novel coating that is based on a hydraulically reactive silicate cement blended with a glass enameling frit and fused onto the steel reinforcement has been developed that addresses both the problem of bonding and corrosion. Research has been undertaken to develop basic understanding of how this composite coating performs has shown that when portland cement is used as the cementitious component in the enamel, the hydration reaction that occur in cement paste can be observed taking place in the cement attached to the glassy enamel coating. Grains of reactive calcium silicate that are embedded in the glass hydrate if exposed to water. If the glass fractures the coating is sealed by calcium silicate hydration products from the embedded cement in a 'self-sealing' reaction.