The use of ultrasonic pulse velocity measurements to monitor the effectiveness of concrete patch repairs

Abstract

Concrete patch repairing is a fairly new field in the concrete industry, so that there is only a limited number of standards available. Consequently there is also limited application of quality assurance for patch repairs. Curing has a major effect on the quality of the repair work; therefore the manufacturer of patch repair materials has very stringent guidelines with regards to curing methods. The question now is: How can it be ensured that the repair material was cured according to specification? So a need for a cost-effective, nondestructive test for the evaluation of the quality of patch repairing exists. This article presents the results of a research project on the use of ultrasonic pulse velocity to evaluate the quality of curing on concrete patch repairs. As part of the experimental work, three sets of four 1200 mm x 235 mm x 140 mm concrete test specimens were prepared in three concrete strengths (30 MPa, 40 MPa and 50 MPa). The results clearly indicate that there is a decline in the pulse velocities when inadequate curing is performed. This is due to the lower densities and poor strength development of the inadequately cured concrete patch material. This conclusion is supported by the corresponding pull-off tests that were done to determine the bond strength between the in situ concrete and concrete repair material. The measuring of the pulse velocities therefore proved an effective and fast nondestructive method to estimate the quality of concrete patch repairs, and can be used as a quality control method at the early stages of disrepair.