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

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The presentation examined potential bias in Marsh funnel viscosity measurements for grout suspensions, comparing the field test with a laboratory fan viscometer. Researchers tested four Newtonian fluids and seven grout mixes containing bentonite or different cements. The fan viscometer showed that the grout suspensions were shear-thinning, with yield stresses especially in mixes with lower water-to-cement ratios.<br /><br />Marsh funnel measurements generally increased during each test. For Newtonian fluids, funnel readings correlated closely with fan-viscometer viscosities. For non-Newtonian grouts, however, the funnel underestimated the apparent viscosity of low water-to-cement mixes, particularly those with yield stress. The authors concluded that the Marsh funnel remains useful for quick field quality control, but engineers should be cautious when using it to select dense, low water-to-cement grouts.<br /><br />Discussion raised possible improvements, including accounting for changing fluid head, estimating shear rates in the funnel, testing stable or plasticized mixes, and analyzing grout behavior with power-law models.

Keywords

Marsh funnel

grout viscosity

shear-thinning

yield stress

fan viscometer