Importance

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Abstract

Cement compositions and processes for improving the bond between new hydrating cement-based materials and the surface of 'old' cement-based substrates are disclosed. A mechanically and chemically integral bond is created between the surfaces of the cement-based materials by moistening the old cement-based surface, exposing the moist surface to carbon or carbonate sources (such as with carbon dioxide) and then applying a new hydrating cement-based material thereon. The treatment of the surface of the cement-based substrate as described above creates an aqueous phase chemistry thereon which is compatible to the aqueous phase chemistry of the hydrating cement-based materials applied thereafter. The compatibility of the aqueous phase chemistries results in a mechanically and chemically integral bond formed between the surface of the old cement-based surface and the hydrating cement-based materials. The bond interface may be characterized by low calcium hydroxide concentrations, the presence of amorphous, noncrystalline material, a low water/cement ratio, greater than 90% of all voids being less than 0.15 mm. in diameter, and a low total air content of the interface. The present invention is particularly applicable to the repairing, resurfacing and topping of existing concrete highways, roads and surfaces.

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First Claim