For concrete contractors, the concrete slump range is an important factor to consider when placing concrete. While a high slump may allow the concrete to be placed more easily, it is not necessarily a good thing if you’re trying to produce a quality slab that will hold up to traffic and weathering.
Fortunately, there are other ways to measure concrete mix consistency beyond the slump test. For example, you can use a concrete flow test to determine the consistency of your concrete mix, which may be helpful if you’re looking for an indicator of strength.
In recent years, the National Ready Mixed Concrete Association and American Concrete Institute have been advocating for performance specifications instead of prescriptive ones, and they believe that slump requirements should be eliminated from these types of specifications. This is because a concrete producer and contractor should be jointly responsible for setting fresh concrete workability expectations and agreeing on how to meet these requirements.
To perform a concrete slump test, you need a slump cone, a steel rod and a measuring stick. Place the slump cone on a level surface and fill it with concrete in three layers, making sure to tamp each layer down 25 times with a steel tamping rod. When you’re finished, remove the slump cone and observe how far the concrete sinks down, or slumps. Measure the distance from the top of the slump cone to the base and note this as the slump number.