Concrete Slump Test (The Cheap Way)

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!)

Step 1: Supplies

Supplies needed

- 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.

Comments

[Learnz]

Thank you for sharing.

[sokamiwohali]

I would also like to add about your makeshift "cone"... And this would be, it's not truly a cone. It's a relatively straight side container and thus adds to the difficulty figuring out the slump. So the slump indicated in one of your pictures is wrong. It's not REALLY a 1" slump. It's likely about a 4" slump.

[sokamiwohali]

I apologize for being the Debbie downer here...however, this is NOT at all an accurate way to figure out the slump of concrete... I am a concrete mixer driver... Standards have been set to establish how to measure the slump of your concrete. A 12" cone is required to find the slump, as the measurements in any other standard would be inaccurate (this being your makeshift cone) and would result in poor concrete quality.

So far as adding the concrete to the cone, standards require that you add the concrete to the cone in EXACTLY 3 equal amounts, and to "tamp" them down in between the additions.

For small projects, generally speaking, the slump of concrete is not important, and you're only adding to the time and difficulty of your project. You don't want it soupy, but you don't want it too dry either.