A unified failure envelope from the evaluation of concrete repair bond tests

Abstract

This paper compares the core pull-off and slant-shear tests with the patch test (see Magazine of Concrete Research, September 1993 v45 n164) as methods of evaluating the bond of shallow concrete patch repairs. The effects of repair material properties, surface roughness and soundness, moisture condition and artificial partial debonding on bond performance are described, with reference to both physical tests and material modelling. The pull-off and patch tests were found to be sensitive to surface roughness and soundness and to incomplete bonding. In contrast, the slant-shear test was found to be insensitive to changes in surface roughness and soundness, and with rough surfaces was also relatively insensitive to partial debonding. The bond strength values obtained from the two tests are not directly comparable because of the different stress rates along the repair interface. A bond failure envelope is proposed which enables a meaningful comparison of information from different test methods to be made. Bond failure envelopes are presented for the two plain sand- cement mortars, which emphasize the superior bond performance of the one with the higher water-cement ratio. Bond failure envelopes for the two polymer-modified materials could not be established because bond failure did not occur. (A)