Determining moisture content in concrete under simulated precipitation using ultrasonic propagation time measurements

The use of ultrasound is recognised as a means to obtain information about concrete with non-destructive testing. Various aspects of the material can be characterised. However, the scientific literature in this area is quite sparse. The present paper therefore addresses the issue of moisture content, and related compressive strength, in a systematic experimental manner. The moisture content profiles of 24 concrete cubes under constant simulated precipitation over 24h were investigated using ultrasonic methods. Different values of water/cement ratio, duration of pre-curing vibration and curing regime were used. The propagation time of ultrasonic compression wave pulses gave a good correlation with gravimetric moisture content and it was found that the type of curing and the amount of vibration had the greatest impact on the propagation time of the ultrasonic wave. The moisture diffusion coefficient was estimated using a simple finite difference model and good agreement was achieved with experimental measurements.