A Closer Look at the Potential Bias in the Marsh Funnel Viscosity Measurements-Paper

Paper

Pdf Summary

The study evaluates whether the Marsh Funnel provides reliable viscosity estimates for grouts, especially non-Newtonian suspensions that may have yield stress. Researchers tested four Newtonian fluids and seven bentonite or cement-based grout mixes, comparing Marsh Funnel results with measurements from a Fann Model 35 viscometer.<br /><br />To investigate changes during flow, the Marsh Funnel test was divided into four volume intervals. The time for each interval was converted to an equivalent full-test viscosity. For most materials, the first interval indicated faster flow than later intervals. This initial-flow bias increased with viscosity for Newtonian fluids. Grouts with substantial yield stress behaved differently: their initial flow was especially slow, reflecting the stress required to start the material flowing.<br /><br />Marsh Funnel measurements corresponded reasonably well with Fann viscometer results for Newtonian fluids and grouts with minimal yield stress. At very high Newtonian-fluid viscosities, the funnel showed a slight tendency to overestimate. For grouts with higher yield stress, however, it substantially underestimated apparent viscosity at relevant shear rates.<br /><br />The authors conclude that the Marsh Funnel remains useful for rapid, onsite batch-to-batch quality control. However, it represents fluidity through a single flow-time measurement, not viscosity across a range of shear conditions. Its results should therefore be used cautiously when selecting grout mixes, particularly low water-to-cement-ratio mixes with significant yield stress.

Keywords

Marsh Funnel

viscosity

grout

non-Newtonian

yield stress

bentonite

cement-based grout

Fann Model 35

fluidity

shear rate