**6. Conclusion**

Wall slip of particulate systems is well known and is rather a rule than an exception. Here, we are encountering it also in a clay-only system, like natural fluid mud (with a sporadic settling solid, if any). The aggregate structure might similarly be a bit different at the wall and apparently also slips at low shear rates.

With complex mixtures, it is often not possible to apply the ideal measuring geometry: wider gaps are necessary and different (surface) geometries. In that case, direct outcomes of rotoviscometer need to be post-processed for rheological characterisation and/or vane testing is necessary complementary to testing with elements with better-defined shear rates.

Exploring in detail the low shear behaviour of yield shear thinning fluids by plotting the results as viscosity graphs accentuates measuring difficulties; care should be exercised not to interpret as (bulk) rheology.

*Rheology, Rheometry and Wall Slip DOI: http://dx.doi.org/10.5772/intechopen.108048*

It is unknown what is causing the wall slip of fluid muds, but whatever the cause, the first sign of yielding is not the static yield stress for application in rheological calculations.

Since wall slip of mixtures may constitute an efficient way of transport (pumping of fresh mortar is based on that), it would be worth systematically investigating if/ how wall slip in rotoviscometers compares with wall slip in capillary viscometers, at least in the absence of coarse solids.
