Estimation of the Adherence of Mortars Using Ultrasound

Mortars are subjected to severe external stresses such as freezing, thawing, and drying during their lifetime. These stresses can lead to a loss of adhesion between the support and the mortar. The strength of the substrates with respect to their ability to receive a coating (mortar) is characterized in particular by the value of minimum tear resistance of the surface to be coated. In this work, the use of a non-destructive method which is both fast and easy to implement is employed to evaluate this support-mortar adhesion. The first method is based on the measurement of the velocities of the surface ultrasonic waves and the second by tearing tests using a specific dynamometer. The determination of the adhesion strength concerned two different supports (concrete beam and masonry block) coated with two types of mortar (a prepared cement mortar and a ready-to-use mortar) with two different thicknesses for each mortar (1 and 2 cm, respectively). The results of the two methods are then correlated for an estimation of the adhesion of the mortars.