FRESH CONCRETE MONITORED BY ULTRASOUND METHODS

While the requirements regarding the quality control of fresh concrete are nowadays increasing, the methods used for monitoring in-situ at the concreting site are lacking in many ways. They are widely used and for a low budget, but can not be used for reproducible and reliable measurements of the setting and hardening of cementitious materials while they are very limited in terms of control parameters. Systematic investigations as well as the increasing number of damages at the concreting site are demanding a new kind of quality management maybe based on ultrasound. In the last ten years a testing method based on ultrasound was developed at the IWB to control the hardening process of cementitious materials by means of non-destructive testing. It is described how this software called FRESHCON2 is operating and some examples of data and applications are given. First results obtained during a round robin test in collaboration with the Ecole National des Travaux Publics de l’Etat (ENTPE) in Vaulx-en-Velin near Lyon (France) are shown. This test series was suggested by a Rilem Technical Committee ATC (Advanced testing of cement-based materials during setting and hardening) founded in 1999. ÜBERSICHT Trotz gestiegener Anforderungen der Qualitätssicherung im Bauwesen, sind die in der Praxis angewandten Verfahren zur Überwachung in vieler Hin-sicht ungenügend. Zwar sind sie weit verbreitet und vergleichsweise preiswert, jedoch oft auch sehr ungenau und erlauben nur eine stark eingeschränkte Möglichkeit zur Überwachung der Frischbetoneigenschaften. Systematische Untersuchungen und die wachsende Zahl an Schadensfällen scheinen di