# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DcuXK_FgO4L
- **Gondola URL:** https://gondola.cc/posts/70003067-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/a84386a275.jpg
- **Posted:** 2026-09-01T00:24:06.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Flip the cone upside down and the concrete spreads exactly the same distance. It just takes nearly twice as long to get there.

The slump flow test uses the same Abrams cone as the century-old slump test. Three hundred millimetres tall, two hundred across the wide end, one hundred across the narrow end. For self-compacting concrete the cone is filled in a single lift with no rodding, lifted vertically, and the mix allowed to spread into a pancake under its own weight. The mean of two perpendicular diameters is the slump flow.

ASTM C1611 permits two orientations, and this is where it becomes interesting.

- Procedure A stands the cone upright, wide end down. Filling the 100 mm opening needs a funnel, and a technician must stand on the foot pieces to stop the mix escaping
- Procedure B inverts the cone, narrow end down. Concrete is poured straight into the 200 mm opening. One person, no funnel, no foot tabs

Inter-laboratory work at the Nordic Innovation Centre found no meaningful difference in final spread between the two. That is not an accident. The spread is a yield stress measurement. Flow ceases when the gravity-driven shear stress falls below the yield stress of the paste, and that terminal condition depends on volume and rheology, not on the shape of the vessel that held it.

The time to reach the 500 mm circle is a different animal. T50 probes plastic viscosity, and viscosity is always measured against a starting geometry. Inverted, the concrete begins on a 100 mm footprint and discharges through a narrow throat. Further to travel, tighter aperture. One study on limestone-filler SCC reported a conversion factor near 1.9 between the two procedures.

Same fluid. Same instrument. A number that almost doubles.

Report the orientation, or the viscosity class means nothing.

#stemantics #concrete #civilengineering #materialsscience #rheology

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## Tags

concrete, materialsscience, civilengineering, stemantics, rheology

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