Assessment of porosity of mortar using ultrasonic Rayleigh waves

The relationship between Rayleigh wave velocity at ultrasonic frequencies and porosity is investigated in dry and fully saturated mortar. Porosity is varied by changing the water/cement ratio. Rayleigh wave (RW) pulse velocity is measured accurately using air-coupled ultrasonic transducers as transmitter and receiver. The experimental results are compared with two single-phase models. Due to relatively weak correlation between RW velocity and porosity, measured data and the models are compared using statistical hypothesis tests. Although the parameters of the model are not accurately predicted, these tests conclude on a reasonable agreement between measured data and the models. This result can be useful to develop simplified models of wave propagation in concrete, or to estimate porosity in concrete cover from ultrasonic measurements.