Experimental Investingation of the Methods of Evaluating the Bond Between Repair Materials and Concrete Substrate

In the field of repair and strengthening of concrete structures, the need often arises to place new concrete next to old, i.e. existing concrete. Examples of these applications include highway structures where concrete overlays are used and in repair of corossion-damaged concrete structures, where the deteriorated concrete must be replaced with new concrete. In these application, the bond between the old and new concrete usually presents a weak link in the repaired structure. Several tests are available to measure the bond strength. However, little infor,ation is available on comparison of these various tests methods and the resulting bond strength values. As demonstrated in this paper, the measured bond strength is greatly dependent on the test method. With the proliferation of chemical bonding agents, the design engineer is often faced with selecting the bond strength of a particular product based on the data reporied by the manufacturer. Depending on the test method used, the reported bond strength may significantly overestimate the true strength of the product. therefore, there is a need to compare different tests for measuring bond strength and establish a relarionship among the values obtained from each test.