Air voids size distribution determined by ultrasonic attenuation

Voids in cement-based materials influence their material properties. While air voids within a certain range are beneficial for freezing-and-thawing resistance, large-size voids decreases strength and durability. This paper proposes a method to quantify the air voids size distribution, which use the concept of ultrasonic wave attenuation. The wave attenuation increases with the inclusion of air voids. Its measurement is compared with a theoretical model, and then three-dimensional information of air voids can be obtained. An application example of cement paste is presented and the results are discussed with the measurement of permeable pores and the result of a microscopical determination.