Innovative laboratory investigation of problematics in ceramic tilings by means of acoustic and electromagnetic non-destructive techniques

Ceramic materials are assuming a pre-eminent role as elements of external claddings in buildings, for floorings, wall linings and other diversified uses thanks due their characteristics of strength and durability. With respect to traditional ceramic tilings, their use is widely spread in many Countries but the assessment of the health state of existing tilings or the preventive conservation of historic tilings has not yet been properly addressed. The durability of ceramic tilings in real environments is strictly connected to problems which may arise at the time of laying or later in their life-cycle. Most common problematics are cracks or insufficient strength of support, discontinuities at tile/support interface, moisture below the tiles, detachment between adhesive and tiles or between adhesive and support, all of which may occur during or after tile installation. It is evident a lack of appropriate non-destructive testing (NDT) approach for the investigation of these issues on site and the reliability of testing techniques for these purposes has still to be assessed. A laboratory experimental campaign was carried out in Bologna University on several on purpose built ceramic tiling specimens, simulating 7 of the above mentioned defects. The data acquisition was undertaken via acoustic (sonic and impact-echo tests) and electromagnetic (IR thermography and GPR radar) non-destructive diagnostic techniques. A comparison of the outcome from the different techniques was foreseen. In this paper, selected results are presented. One of the aims of the work is to develop a diagnostic procedure to be further used on-site for the verification of the conditions of new or existing tilings