Pull-off adhesion testing for concrete repairs

Where one material is bonded to another, the only appropriate test method to measure bond or adhesion is often a peel or pull-off test. For cement-based materials (mortar or concrete) the pull-off test is preferred partly because it is relatively easy to carry out; however, one limitation lies in the difficulties of interpreting the results. This difficulty lies in the fact that not all failures occur at the interface and there is then a question of whether those that fail at the interface only are an accurate reflection of the interface adhesion strength. The current paper seeks to address this issue through a study of the probability of interface adhesion plotted against concrete cohesion failure. It recommends a method for estimating the error between the measured adhesion failures and the theoretical adhesion strength.