Slump cone test determination for workability of concrete | types of slumps | procedure and results of slump cone test of concrete

Slump cone test is the process of determining the workability of concrete to check the consistency as per the grade of the concrete. As per the Indian standards, the slump is determined according to IS: 1199 – 1959 code. For better concrete strength, the value of the slump is taken in between 25mm to 50mm in the building construction. In article you can able to learn about the complete concepts related to the types of slumps used for the concrete, what are the factors effecting on the slump value, experimental procedure to find the slump cone test and calculation of workability as per test results.

Factors affecting the slump cone test of concrete

1. Water cement ratio of concrete
2. Material properties
3. Use of admixture
4. Testing time after mixing
5. Void ratio and air content in concrete

Water cement ratio of concrete

The water cement ratio is the amount of water and cement content used in the concrete mix as per the considered grade of concrete. If the water content is, high the concrete mix becomes the slurry mix then the value of the slump is high and in the same process if the water content is less than the value of slump is less.

Material properties

The properties of materials like fineness of cement, specific gravity of cement, fineness modulus of aggregates and specific gravity of aggregates also influence the value of the workability. For example if the fineness of material increases then the value of slump is observed as high because of the less bonding between the materials.

Use of admixture

Admixtures are generally used in the concrete to reduce the water content for mix. By using the admixture in the concrete we can able, to convert the slurry mix concrete to normal concrete in order to achieve the better strength results at the same time the value of slump decreases from higher to lower value.

Testing time after mixing

The testing time of the concrete is another important factor affects the slump value. It is the time interval between the mixing the concrete to the mixing the concrete. If the testing time of the concrete increases then the value of the slump is decreases because with increasing the time the will set and leads to decrease in the water concrete because of this reason the value of the slump decreases.

Void ratio and air content in concrete

The voids ration and air content are used in the determination of workability of concrete. If the voids ratio and air content increases then they filled with water hence the value of the slump will be observed as high and in the same process if the value of the value of voids ratio and air content decreases then the intensity of workability decreases as per the considered grade of the concrete.

Types of slumps used in the workability of concrete

The slump values are classified as three types according to the type of concrete

1. True slump
2. Shear slump
3. Collapsible slump

1. True slump

This type of slump mainly used in the construction of the structures. The intensity of workability value is less in this case because of the better bonding between the materials. Sometimes it will get zero slump value in this type of slump.

2. Shear slump

The shear slump is acceptable in low strength buildings and structures and the value of the slump is high then true slump and less than collapsible slump. Because of the less bonding between the concrete materials the values of slump increases.

3. Collapsible slump

The collapsible slump value is not acceptable in the construction industry. In this the value of slump high, the main reason of increase in the value of the slump is segregation between the aggregates.

Apparatus used in the slump cone test

The following are the apparatus used to determine the workability of the concrete as per the

1. Slump cone (top diameter 10cm, bottom diameter 20cm and height is 30cm)
2. Tampering rod (16mm diameter and 600mm length)
3. Flat bottom
4. Steel rule

Experimental procedure to determine slump cone test

The following procedure is used to determine the workability of concrete as per the slump cone test.

1. Calculate the mix design initially based on the materials properties and grade of the concrete.
2. Now apply the lubricant to the slump cone and flat bottom plate and place them on the flat ground.
3. Mix the materials properly in order to obtain the proper concrete mix.
4. Now fill the slump cone with 1^st 1/3 of the concrete mix and compact it with the help of the tampering rod with 25blows.
5. After this fill the 2^nd 1/3 concrete and compact with another 25blows. Finally final 1/3 concrete and compact with another 25 blows.
6. Now remove the slump cone and measure the value of concrete fall from the initial position to secondary position.
7. The distance of variation of concrete position is the value of slump.

Results of slump cone test values

The below table values shows the type and value of slump used in the concrete

Type of workability	Slump in mm
Very low	0 to 25mm
Low	25mm to 50mm
Medium	50mm to 100mm
High	100mm to 175mm

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Conclusions of slump cone test for determination of workability types of slumps

Well now, the above-explained concepts are related to the definition of slump, types of slumps and experimental procedure to fine the concrete workability values. The slump cone value types are true slump, shear slump and collapsible slump.  The factors affecting the slump values is water cement ratio of concrete, material properties, use of admixture, testing time after mixing and void ratio and air content in concrete.

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