Concrete slump test:
The slump test is conducted to measures the consistency of concrete in that specific batch. Here, consistency of concrete refers to workability or fluidity of freshly made concrete, and therefore it is a measure of the ease with which concrete flows.
Therefore, the slump test is used on-site to measure the workability of concrete or 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 mix between two batch mixes. The slump test is widely used in construction to a few apparatus and simple procedure. The slump is also used to ascertain the effects of plasticizers on their introduction in the concrete mix.
The Slump test 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 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.
- 1199 – 1959 METHODS OF SAMPLING AND ANALYSIS OF CONCRETE
- IS: 7320 -1974 SPECIFICATION FOR CONCRETE SLUMP TEST APPARATUS
The test is carried out using a conical shape metal body known as slump cone or Abrams cone that is open at both ends and has an attached handle.
The slump cone has internal dia. 100 mm at top and 200 mm at the bottom and total height of the cone is about 300 mm.
- 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.
- 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.
Read More: CONCRETE MATERIAL CALCULATOR
Interpretation of results:
According to 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.
|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|
- Slump test not applicable when 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 can be performed in the laboratory as well as on-site.
- It requires fewer apparatus compares to other tests.
- Testing time is too short and gives result quickly;
Watch Video: Concrete Slump Test by Utratech Cement