What Is Concrete Slump Test?
What Is Concrete Slump Test?
The concrete slump test is a way to measure the consistency or workability of fresh concrete before it hardens.
The test is done by filling a cone-shaped mold with concrete and measuring how much the concrete settles or “slumps” after the mold is removed.
The test is easy to perform and can be used to check the quality of a batch of concrete or to ensure that different batches of concrete have consistent consistency under field conditions.
A separate test called the flow table or slump-flow test is used for concrete that is too fluid to be tested using the standard slump test.
This test involves using a similar cone-shaped mold, but the mold is placed on a table that allows the concrete to spread out and flow more easily.
The concrete slump test is useful for ensuring that concrete can be easily poured and worked with, which is important for many construction projects.
How Do You Test For Concrete Slump?
The slump test is a method for measuring the consistency of concrete. Before starting the test, you should make sure that the mold, base plate, and all testing materials are clean and free of any debris.
The inside surface of the base and the mold should also be dampened to reduce friction. It’s important to perform the test on a flat, vibration-free surface using fresh, newly mixed concrete. To conduct the test:
- Secure the slump cone to the base plate using the cone tabs or by standing on the foot holds.
- Fill the cone with the concrete sample in three stages, tamping each layer with the steel tamping rod 25 times.
- Level off the top of the cone with the steel tamping rod.
- Lift the cone straight up in a steady motion, without any rotational movement.
- Invert the cone mold and place it next to, but not touching, the concrete sample on the base.
- Measure the difference in height between the cone and the slumped concrete by placing a straight edge across the mold base and measuring the distance from the bottom of the straight edge to the displaced center of the slumped concrete. Record the result to the nearest 1/4 inch.
What Does A Concrete Slump Test Tell You?
The slump test is used to measure the consistency of concrete. The resulting shape of the slumped concrete, or the “slump,” can be classified as a true slump, shear slump, or collapse slump.
Only a true slump is useful in the test, as a shear or collapse slump indicates that the concrete mix is either too wet or has too high of a workability, making the slump test inappropriate.
Different slump ranges are suitable for various purposes: very dry mixes with a slump of 0-25 mm are often used for pavement or road construction, low workability mixes with a slump of 10-40 mm are suitable for lightly reinforced foundations, medium workability mixes with a slump of 50-90 mm are typically used for normal reinforced concrete placed with vibration, and high workability concrete with a slump greater than 100 mm is often used in situations where reinforcing has tight spacing or the concrete needs to flow a long distance.
If a shear or collapse slump is obtained, a new sample should be taken and the test should be repeated.