3. Materials and methods
3.1. Materials
Carboxy Methyl Cellulose (CMC) was tested and is generally regarded as an ideal non-Newtonian power-law fluid for experimental work, especially when ultrasonic tests are concerned as CMC offers excellent wave scattering/reflection and minimal attenuation [13]. The CMC (Protea Chemicals, Bryanston, South Africa, http://www.proteachemicals.co.za) solutions used were 3.25% and 7% w/w. Bentonite powder (Protea Chemicals) was mixed with water to obtain different concentrations of bentonite:water suspensions. The concentrations tested were 6.9% and 8% w/w. Dry kaolin powder (Protea Chemicals) was used to prepare a kaolin:water suspension of 17% v/v. Kaolin suspensions attenuate the ultrasonic energy significantly [13] and was thus used to test the limitations of profile measurements using different ultrasonic transducers.