Many slurry rheograms do not follow the Bingham model, but are curved (convex upwards) at low-strain rates Alternate models such as the yield-power law (YPL), provide a good fit to the low-strain rate data, but they tend to underestimate apparent viscosities at high-strain rates The current paper considers a hybrid theological model consisting of a cubic-spline fit to the low-strain rate data merging into a Bingham linear model above a limiting strain rate This model predicts turbulent flow well, depending only on the area difference between the Bingham rheogram and the cubic spline