USE OF GLASS-CERAMIC COATINGS CONTAINING WATER-REACTIVE COMPONENTS AS A BONDING LAYER BETWEEN CONCRETE AND METAL

摘要

Vitreous enamels that were designed to bond tightly to metals can be combined with high-melting-point water-reactive silicate- and aluminate-based ceramics to form a bonding layer between a reinforcing metal and an inorganic cement, such as portland or calcium aluminate cement. Vitreous enamels can bond to a variety of metal surfaces, and a variety of water-reactive ceramics also bond tightly to vitreous enamel. The bond strength from steel to enamel is on the order of 35 MPa. The tensile strength of concrete is typically 10% of the compressive strength. The steel-to-enamel bond is over eight times the tensile strength of structural concrete (compressive strength = 40 MPa). The elevated water content of concrete at the metal surface lowers the bond strength into the range of 2.2 to 2.7 MPa thereby making the interface the weakest bond. Pull-out tests were used to demonstrate that using bonding enamel could produce a 4-fold increase in bond strength and make the interfacial bond strength exceed the tensile strength of the concrete. Using a bonding enamel allows the tensile strength at the interface to match the ultimate tensile strength of the concrete. Tests conducted with composite beams demonstrated an increase in strength in experimental beams made with coated versus uncoated steel tubes was observed after 7 days of curing. In sample beams cured for 28 days, the ultimate loading on the coated beams was increased by over 30% on average. The bonding enamel interfaces allows us to take advantage of the new generation of very-high strength concretes in new concrete-steel composites.