Laser-based ultrasonic evaluation of cement hydration: Fid-Bau Portal

Laser-based ultrasonic evaluation of cement hydration

Tatarin, R. / Erfurt, W.

A scanning, acoustic method was introduced to investigate cement-based materials in a contactless manner during setting and hardening of cement-based materials. Unlike conventional ultrasonic through-transmission methods the ultrasonic excitation is realised opto-acoustically by means of a short-pulsed Nd:YAG-laser. The detection is carried out interferometrically by means of a laser vibrometer. For investigations on cement pastes and mortars a testing mould was developed which permits a laser-induced excitation and -detection of ultrasonic waves. By the selection of an appropriate material and laser beam parameters a reproducible sound excitation was achieved. This allows the determination of the ultrasonic pulse velocity vP as well as the evaluation of the interferometrically collected velocity amplitudes of the longitudinal wave. The results gained in experiments on cement pastes and mortars show that the laser-based method of ultrasonic throughtransmission can be used for a non-destructive, contactless investigation of setting and hardening building materials. In order to describe the material properties the time-dependent and local changes of the ultrasound parameters can be used. The ultrasonic pulse velocity vP and the velocity amplitude of the longitudinal wave allow a continuous evaluation of the hydration kinetics. Using the parameter ultrasonic pulse velocity it became possible to show local variations of the mixture composition of the investigated cement pastes and mortars vertical to the transmission direction. This could be used for example to evaluate the sedimentation stability of such mixtures.