Another approach in predicting the viscosity of concrete from the measurements of cement paste was developed by Struble [47]. She based her model on the Krieger-Dougherty equation. This equation shows that there is an increase in the viscosity of the medium when particles are added. This increase depends on the concentration of the particles:
where [ 
], the intrinsic viscosity, is
equal to 2.5 for spheres, 
is the volume
concentration of particles,
m the maximum packing, the viscosity of the suspension and 0 is the viscosity of the
medium. Therefore, if the viscosity of the cement paste and the concentration
of the aggregates are known, and the maximum packing of the particles is
determined, then the viscosity of the concrete can be calculated. Struble
used a coaxial rheometer with a gap between the cylinders of 0.7 mm. This
gap, although small is not quite as small, as the mean gap between the
aggregates in concrete (0.12 mm to 0.26 mm) [11]. The concrete rheological properties are is measured using a rheometer similar to the BTRHEOM. This model has not been validated for concrete. Struble is currently designing a program to validate the model.