Non-destructive testing of fresh cementitious materials (ultrasound)

(finished project, researcher: Nicolas Robeyst, for more information contact prof. dr. ir. Nele De Belie)

Setting of concrete refers to the gradual transition from the initial liquid-like state to a load-bearing solid material. With conventional equipment such as the Vicat needle apparatus and the penetrometer, setting is monitored by the change in penetration resistance of a standard needle. Since these methods are destructive and little accurate in the presence of larger aggregates, non-destructive techniques, such as the ultrasonic method, were introduced to observe the changing material properties of early-age concrete. The research focused on the optimization of the wave through-transmission technique, the extraction of additional information such as wave energy and frequency content and the correct interpretation of the results. Based on the characteristic points in the velocity and energy graphs, the relation between ultrasonic measurements and setting times was fixed into practical criteria. Moreover, the microstructure development was described with the aid of computer simulations (CEMHYD3D) and correlated with the ultrasonic parameters.
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Measurement set-up (FreshCon): (a) computer with DAQ card, (b) amplifier, (c) piezoelectric sensor, (d) container, (e) preamplifier and (f) semi-adiabatic calorimeter.

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BSE-image of hydrated cement paste containing blast-furnace slag at the age of 2 days. Left: original image – middle: segmented image – right: simulated hydrated cement paste.