The evaluation of viscosity using a novel viscometer for SCC: Fid-Bau Portal

The evaluation of viscosity using a novel viscometer for SCC

Gregori, Amedeo / Sun, Zhihui / Douglas, Raissa P. / Shah, Surenda P. / Bonen, David

A falling/pulling ball viscometer was designed. A scale with a nominal accuracy of 0.001 g, an elastic tensile spring, and steel balls are the major components of this viscometer. The viscosity calculation is based on the velocity of the ball and the exert forces. The calibration should also be valid for non-Newtonian fluids if the material behaves according to Bingham model. For a Bingham material, drag force is linearly related to the velocity of the moving ball. Self-consolidating concrete (SCC) pastes were made of ordinary type I Portland cement and two types of superplasticizers: polynaphthalene sulfonate based and polycarboxylate based. A steel ball with a one inch diameter was used. The measured velocity of the falling ball decreased from a value close to 4 mm/s to a value very close to 0. Within this region, the drag force is linearly related to the velocity, so that cement pastes behave as Bingham materials. The measured viscosity of a SCC paste sample was 2.94 Pa.s. In order to check the validity of the falling ball viscometer, a commercial co-axial rheometer was used as a reference. Although the absolute values of viscosities that were obtained with the two devices are different, the trend is similar. The falling ball viscometer gives higher values of viscosities. The measurement can be improved by using liquids with lower viscosity to calibrate the system. It appears that the viscosity of cement paste, mortar and concrete can be measured by using steel balls with different sizes. The system might be further improved by changing the shape of the steel balls. The advantages of such a system are related to its low cost, simplicity, and the possibility of using this viscometer in a field.