Step 5: Concrete Slump Test
Performing a slump test will help give you an idea of what the right mix should feel like. Over time you'll develop a feel for it, but in the beginning it helps to keep track of the amount of water you add so you can reproduce the same results throughout projects.
Professional Slump Test Supplies:
- 12" Slump Cone
- Mixed Concrete
- Straight Edge
- Plywood Base Board
1. Moisten the inside of the cone and put it on a smooth, level surface such as a moist piece of plywood or a concrete slab.
2. Fill the cone one-third full with a sample of concrete. Push a rod down into the concrete (called tamping) to help the concrete fully settle and allow any air to escape.
3. Fill the cone until it's two-thirds full, and tamp this layer with the rod.
4. Add more concrete until the cone is slightly over-filled and tamp this layer.
5. Scrape off excess concrete
6. Slowly lift the cone away from the concrete.
7. Put the cone beside the concrete, but not touching it. Rest a straightedge across the cone and measure the distance down to the top of the sample as seen in the photos.
Homebrew Slump Test Supplies:
- 15+ oz. (450+ mL) Plastic Cup
- Pen to poke hole
- Mixed Concrete
2. Fill the cup with freshly mixed concrete and pack it well.
3. Place the filled cup upside-down on a flat, rigid surface.
4. With your hands, carefully vibrate the cup in a steady lifting motion without stopping.
5. Measure the distance of the slump with a ruler.
The ideal slump should be about half the height of the plastic cup. If the mix is too wet, add more bagged concrete mix by the cup.
Hopefully this Instructable has given you some tips that will help when it's time to mix the concrete for your next project. For some easy concrete project ideas, check out our other Instructables.
Feel free to ask questions or offer any tips that haven't been mentioned. Thanks for following!