Method for increasing or decreasing bond strength between concrete and

Abstract

A process for adjusting the steel-to-concrete bond strength in a hardened concrete structure having embedded steel elements. A source of DC voltage, preferably in the range of 5-40 volts, is connected at its negative side to the embedded steel and at its positive side to an external distributed electrode formed on the surface of the concrete structure. The external electrode may, for example, be a self-adherent electrolytic mass of moist pulp fiber, a conductive coating, or the like. Application of voltage to the structure and the resulting current flow between embedded steel and the external electrode, initially results in a progressive reduction in the steel-to-concrete bond strength. This can be particularly useful in connection with pre-tensioned or post-tensioned structures. Continued application of the voltage results in a progressive increase in bond strength, ultimately reaching a maximum strength significantly above initial values. This is useful in reinforced concrete structures, to improve the bond between the concrete and the reinforcing steel. By reference to pre-established database values, the process may be easily controlled to realize targeted modifications in bond strength. Significant improvement can also be achieved in the sealing of the interface between steel and concrete, to prevent seepage of contaminating liquids or gases along the interface.