What Is the Slump Test?
The slump test is conducted to measure the consistency of concrete in that specific batch. Here, consistency of concrete refers to the workability or fluidity of freshly made concrete, and therefore it is a measure of the ease with which concrete flows.
Therefore, the Concrete slump test also known as the Workability Test of Concrete is used on-site to measure the workability of concrete or the degree of fluidity in the concrete mix.
Generally, loose wet mixes are more workable than drier mixes, but concrete of the same consistency may vary in workability.
The test also shows the change of fluidity of the mix between two batch mixes. The slump test of concrete is widely used in construction for a few apparatus and simple procedures.
The slump is also used to ascertain the effects of plasticizers on their introduction into the concrete mix.
Concrete Slump Test
The Slump test concrete is carried out with the help of a conical cone open at both ends. The slump cone filled with concrete lifted up and the resulting height of concrete spread over the surface shows the degree of fluidity, workability, and consistency of the concrete mix. It also indicates the amount of water added is correct or not.
IS Code for Slump Test
- IS 1199 – 1959 Methods Of Sampling And Analysis Of Concrete
- IS: 7320 -1974 Specification For Concrete Slump Test Apparatus
Principle of Slump test
The Slump cone value of concrete just works on this principle of gravity flow of the surface of the concrete cone which indicates the amount of water added to it. That means how much this mixed concrete is in a condition workable.
Slump Cone Apparatus
The test is carried out using a conical shape metal body known as a slump cone or Abrams cone that is open at both ends and has an attached handle.
The slump cone has an internal dia. 100 mm at the top and 200 mm at the bottom and the total height of the cone is about 300 mm.
How to Measure Slumps of Concrete
The slump value of concrete can be easily measured by using the slump cone test method. In which fresh concrete is poured and filled to the top.
Then the cone is lifted slowly, and the difference between the top of the cone and the top concrete fall is measured as a slump of concrete.
Slump Test Procedure
Slump Cone of concrete procedure,
- First, the slump cone is placed on a hard non – water-absorbing surface. ( metal or concrete)
- The Slump cone is filled with freshly mixed concrete in three layers.
- Each layer of the concrete mix must be tapped with a 2 ft (600 mm)-long bullet-nosed metal rod measuring 5 8 in (16 mm) in diameter.
- After filling the last layer extra concrete must be removed from the top of the cone.
- The slump cone then quickly lifted upward with a twisting effect with both hands. The concrete is then free to fall.
- After free fall the remaining height is known as slump and is measured to the nearest 5 mm if the slump is 100 mm.
Factors affecting Slump Cone Test
The following factors influence concrete Slump value:
• Quality of Fine aggregate, Coarse aggregate, its texture, grading size, moisture content, and shape of it.
• Also affect the water-cement (w/c) ration of concrete.
• Air Content of Concrete and Void ratio of concrete.
• Use of various types of admixtures such as Superplasticizer, Plasticizer admixture, and the sequence of them mixing.
• Time is also an important factor for concrete mixing.
Types of Slump
According to the free fall shape of concrete, the slump is classified into three types termed as true slump, shear slump, or collapse slump.
|In a collapse slump, the concrete collapses completely||In a shear slump the top portion of the concrete shears off and slips sideways||In a true slump, the concrete simply subsides, keeping more or less to shape.|
- If a shear or collapse slump is achieved, a fresh sample should be taken and the test repeated.
- Only a true slump is of any use in the test.
Standard Slump Test Values
|1||0 – 25 mm||Road Construction|
|2||10 – 40 mm||Foundations with light reinforcement|
|3||50 – 90 mm||Normal reinforced concrete placed with vibration|
|4||> 100 mm.||High workability concrete|
- The slump test is not applicable when the aggregate is more than 40 mm.
- This test does not give an accurate result for high-dry and stiff concrete.
- It has a simple apparatus that can be performed in the laboratory as well as on-site.
- It requires fewer apparatus compared to other tests.
- Testing time is too short and gives results quickly;
In conclusion, the slump test is a widely used and reliable method for assessing the workability and consistency of fresh concrete in the construction industry, by measuring the different in height between the initial and final settling of the concrete, the test provides valuable insights into the water content, flow ability and suitability of the concrete for placement and compaction.
The result of the slump test guide construction professional in making necessary adjustment to the concrete mix, ensuring that it meets the desired specification and perform optimally during construction, implementing the slump test contributes to the overall quality, successful execution of concrete based projects.
What is a slump test?
A slump test is a common procedure used in the construction industry to measure the consistency or workability of freshly mixed concrete.
What is the purpose of a slump test?
The main purpose of a slump test is to assess the water content in the concrete mix and determine its ability to flow and compact properly. It helps ensure that the concrete has the desired consistency for the intended application.
How is the slump test result interpreted?
The interpretation of the slump test result depends on the specific requirements of the project or the concrete mix design. Different applications may have different target slump ranges. In general, a higher slump value indicates a more fluid and workable mix, while a lower slump value suggests a stiffer and less workable mix.
Can the slump test be performed on-site?
Yes, the slump test can be performed on-site during the construction process. It is a relatively simple and quick test that can provide immediate feedback on the consistency of the concrete mix, allowing adjustments to be made if necessary.
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