Concrete cones can be expensive and hard to find. For a hobbyist or the curious, I found this method to be useful.
Note that this is not an accurate way to find slump. For an accurate test, purchasing or building your own slump cone is a must. Note that the walls must not cling to the concrete, and the angle of the sides is important to the test. This will effect the outcome due to wet concretes angle of repose. (thank you sokamiwohali for the heads up!)
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Step 1: Supplies
- 1 quart mixing cup (Can be found in the painting section of any hardware store)
- Tape Measure
- Tamping Rod (This is used to settle the mix, can be any round shaped dowel approx 1/4" round)
- Knife (To cut plastic
- Not Pictured: Concrete, water, mixing supplies
Step 2: Prepping Your Cone
Cut out along the bottom line of your cup with a knife. Easy step here.
Step 3: Mix Your Concrete
- wwBe sure to document all amounts used so that you can recreate your mixture (if successful)
- Also record Humidity and Temperature of the room, and temperature of the water. This does not have to be a number measurement. You may document that the room was humid, or the water was room temperature.
Step 4: Prep Your Cone
Important steps to note:
- Filling the cone must be done in levels, and tamped down after each. It is best to add concrete in 3 steps, and then use your rod to tamp that level flat.
- Be sure to fill the cone to the brim. Low levels will make an inaccurate measurement.
- Use a trowel or level board to level the top of the cone.
Step 5: Removing the Cone
Carefully pull the form straight up. Do not twist the form, the concrete will give after some effort.
Place the cone next to the slumped concrete, place the rod on-top of the cone and over the concrete. Note the distance from the bottom of the rod to the top of the slumped concrete
Note the shape of the final concrete slump. This slump indicates a perfect mix. Move to the next step to learn all the forms of slumped concrete.
Step 6: Concrete Slump
(Image courtesy of http://theconstructor.org/)
- Note the different types of slump. True slump is the target, where collapsed slump will have a weakened integrity.
- If your slump is either Zero or Collapsed, remix your concrete. Zero slump needs more water, where collapsed slump needs more concrete
Step 7: Pour Extra Into Formwork
- Add the slumped concrete and any excess mixed into your formwork (In this case, core samples)
- Tap the side with your trowel to work out any bubbles.