= Slump test for yield stress
A <slump test for yield stress> probes a material by allowing a molded sample to deform under its own weight. Fill a known mold on a level support, remove the mold, and measure the decrease in height or the spread of the final deposit. <Gravity> supplies the driving <stress>; resistance associated with the <yield stress> can arrest the motion before the sample becomes a thin layer.
The measured distance is not itself a <stress>. Inferring <yield stress> requires a calibrated relation or a mechanical model using the initial geometry, final shape and <density>. The final slump alone generally cannot identify both <yield stress> and <dynamic viscosity>: a time-resolved measurement provides additional information. A modified concrete test, for example, records the <time> required for a specified fall as well as the final slump.<Modified Slump Test to Measure Rheological Parameters of Fresh Concrete>[pp. 241–247, abstract and apparatus: final slump and additional time measurement for rheological parameter estimation]{ref} The procedure is useful as a simple field measurement, with interpretation dependent on sample history and geometry.
Back to article page
