Non-destructive measurement techniques determine surface or inner cracks, moisture content during curing, failure etc.. In this paper, we combine two types of NDT methods: elastic waves in the passive (Acoustic Emission, AE) and active (Ultrasonic Testing, UT) form and Millimeter wave (MMW) spectroscopy to investigate physical and chemical parameters of Ferro-cement during curing and cracking. The curing process is experimentally monitored by MMW and UT, while MMW and AE are simultaneously recording the changes regarding the different loading states during bending. It will be shown experimentally that ultrasound identifies changes of stiffness and attenuation inside the material, while the MMWs are more sensitive to the chemical processes in microstructure level and the evaporation at early stage. MMW method can effectively determine surface and inner cracks. Experimental results obtained from both techniques are combined to obtain a precise assessment of the curing and damage properties. In addition, a comparison between contact and non-contact techniques to investigate defect characteristics and some mechanical parameters of specimens are presented.
|Status||Published - 12 sep 2017|