Effect of Coupling Media on Ultrasonic Pulse Velocity in Concrete: A Preliminary Investigation
Measurement of the ultrasonic pulse velocity (UPV) is an important tool in diagnostic examination of concrete. In this method piezoelectric transducers are normally held in direct contact with the concrete surface. The current study aims to test the hypothesis that a preferential coupling effect might exist i.e. that the speed of sound measured depends on the couplant used. In this study, different coupling media of varying acoustic impedance were placed between the transducers and concrete samples made with constant aggregate content but with different compressive strengths. The preliminary results show that using coupling materials (both solid and a range of liquid substances) has an effect on the pulse velocity measured in a given concrete. The effect varies depending on the material used. The UPV measurements with solid coupling were higher than these from the liquid coupling at all strength levels. The tests using couplants generally recorded lower UPV values than the conventional test, except when carbon fiber composite was used, which retuned higher values. Analysis of variances (ANOVA) was performed to confirm that there are statistically significant differences between the measurements recorded using a conventional system and a coupled system.
 Raouf, Z.A. and M. ALsamari, Nondestructive Test of Concrete. 1999, United Arab Emirates: Alsareqah Universtiy
 Ohdaira, E. and N. Masuzawa, Water content and its effect on ultrasound propagation in concrete—the possibility of NDE. Ultrasonics, 2000. 38: p. 546-552.
 Lin, Y.C., C.P. Lai, and T. Yen, Prediction of ultrasonic pulse velocity (UPV) in concrete. Aci Materials Journal, 2003. 100(1): p. 21-28.
 Abo-Qudais, S.A., Effect of concrete mixing parameters on propagation of ultrasonic waves. Construction and Building Materials, 2005. 19(4): p. 257-263.
 Lin, Y.C., et al., Investigation of pulse velocity-strength relationship of hardened concrete. Aci Materials Journal, 2007. 104(4): p. 344-350.
 Trtnik, G., F. Kavcic, and G. Turk, Prediction of concrete strength using ultrasonic pulse velocity and artificial neural networks. Ultrasonics, 2009. 49(1): p. 53-60.
 Purnell, P., et al., Noncontact ultrasonic diagnostics in concrete: A preliminary investigation. Cement and Concrete Research, 2004. 34(7): p. 1185-1188.
 Berriman, J., et al., Humidity and aggregate content correction factors for air-coupled ultrasonic evaluation of concrete. Ultrasonics, 2005. 43(4): p. 211-7.
 Cetrangolo, G.P. and J.S. Popovics, Inspection of Concrete Using Air-Coupled Ultrasonic Pulse Velocity. Aci Materials Journal, 2010. 107(2): p. 155-163.
 Chimenti, D.E., Review of air-coupled ultrasonic materials characterization. Ultrasonics, 2014. 54(7): p. 1804-16.
 Galan, A., J. Perlakiová, and P. Šilhan, Combined ultrasound methods of concrete testing. Vol. 34. 1990: Elsevier Amsterdam.
 Lomax, R.G. and D.L. Hahs-Vaughn, Statistical concepts: a second course. 2013: Routledge.