Using Ultrasound for In-Service Assessment of Rendered Walls

Abstract

Ultrasound has been widely used for the diagnostic testing of structural elements, but little research has been done and no specific standard exists for its application to nonstructural materials such as mortars. These mortar coatings are usually applied on walls with more than one layer; therefore, the ultrasound technique needs more investigation to better understand the results for rendered walls and in-service conditions. This study discusses the use of this technique, using the indirect method, in assessing the performance of cement-based mortars. Experimental work was carried out in the laboratory and in situ for this purpose. It was possible to relate the pulse velocity to the mechanical properties of the mortars, proposing criteria to support the in-service performance. It was also possible to characterize the presence and severity of various anomalies, mainly discontinuities. Finally, when this technique was combined with others (on rendered walls or on extracted samples), the in-service diagnostic testing under real in-service conditions was less susceptible to subjectivity. The results showed that this technique has a great potential to characterize the in-service performance of renders and to help the diagnosis of degradation. The specific factors influencing this technique for renders should be emphasized and separated from applications in concrete.