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

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The study evaluates whether the Marsh Funnel—a simple field device that measures the time required for 946 mL of fluid to drain—is suitable for measuring grout suspensions, which are often non-Newtonian. Researchers compared Marsh Funnel measurements with Fann Viscometer results for four Newtonian fluids and seven grout suspensions.<br /><br />The Fann Viscometer results showed that Newtonian fluids have constant viscosity and no yield stress, while the grout suspensions exhibited shear-thinning behavior and yield stress. Their rheological properties varied with water-to-cement ratio (w:c).<br /><br />For Newtonian fluids, the effective Marsh Funnel viscosity generally increased as the test progressed, indicating that flow was faster during the initial portion. The difference between early and late measurements—termed internal bias—increased with Marsh Funnel viscosity. Grout suspensions also showed changing effective viscosity during the test, with flow behavior dependent on w:c. Lower w:c mixtures had higher viscosity and slower initial flow.<br /><br />Comparisons with the Fann Viscometer suggest that the Marsh Funnel is most appropriate for low-viscosity, low-yield-stress suspensions, such as grouts with higher w:c ratios. For these materials, Marsh Funnel estimates aligned with Fann apparent viscosities at low shear rates. Results did not agree as well for higher-viscosity, higher-yield-stress grouts with lower w:c ratios.<br /><br />Overall, the Marsh Funnel correlates well with Fann measurements for Newtonian fluids and can provide quick, useful onsite quality-control checks between grout batches. However, engineers should use caution when applying it to grouts with low w:c ratios, because the test may be biased and may not reliably represent their rheological behavior.

Keywords

Marsh Funnel

grout suspensions

Fann Viscometer

rheology

Newtonian fluids

shear-thinning

yield stress

water-to-cement ratio

viscosity

quality control