Abstract: Novel methods and compositions are disclosed for bonding a hydrating cement-based overlay onto a cement-based substrate. An integral bond is created between the overlay and the substrate by maximizing capillary suction through properly preparing the substrate and designing the overlay. The integral bond has an interface strength at least substantially similar to the substrate strength. The substrate is prepared to optimize the capillary suction by cleaning and optimal water saturation. Properly designing the overlay for optimal capillary suction involves optimizing the water/cement ratio of each layer of the overlay. A low water/cement ratio is generally optimal. In addition to incorporating a low amount of water, the water to cement ratio is minimized through the use of dispersants and mixing techniques. The design of the overlay can also include silica fume to increase the strength of the interface bond.

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.