09492 Reactive Silicate Coatings for Protecting and Bonding Reinforcing Steel in Cement-Based Composites

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Product Number: 51300-09492-SG

ISBN: 09492 2009 CP

Author: Vincent F. Hock, Charles A. Weiss, Sean W. Morefield and Philip G. Malone

Publication Date: 2009

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Engineered glass-ceramic coatings that contain hydraulically reactive calcium silicates have been shown to be remarkably effective in increasing the bond strength between reinforcing steel and the surrounding concrete or mortar. The coatings are a mixture of portland cement and alkaline-resistant basecoat glass enamel. X-ray diffraction patterns indicate that all of the major reactive compounds, such as dicalcium silicate and tricalcium silicate and the ferrites and even gypsum survived the firing of the frit-cement mixture onto steel. When exposed to water the cement grains in contact with water hydrated to form gel products similar to those produced in hydrating normal cement paste. The hydration of the layer of cement appears to remove the “wall effect” and the bond strength between the concrete and steel is increased up to four times that developed with uncoated steel. The enamel over the steel isolates the metal and produces durable corrosion protection. A SEM study of cracks purposely produced in the enamel indicates the embedded cement grains will hydrate when moisture contacts them and produce hydration products that can fill fractures and raise the pH at the steel surface.

Keywords: vitreous enamel, portland cement, reinforcing steel, concrete