Slump Cone Test | Workability Test
Concrete slump cone test
Slump Cone Test is the most commonly used method of measuring the consistency of concrete work where the nominal maximum size of the aggregate does not exceed 38 millimeters.
This method can be employed either in the laboratory or at the site.
Apparatus is required for slump test,the mold for the test specimen is in the form of the frustum of a cone having the bottom diameter of 20 centimeters top diameter 10 centimeters and height of the cone is 30 centimeters.
A metal plate of thickness 1.6 millimeters is used as a base,a tamping rod of 16 millimeters diameter and 0.6 meters long is used.
Step-by-step procedure for concrete slump cone test
- The internal surface of the mold should be thoroughly clean and freed from moisture and any set concrete before commencing the test.
- The mole is placed on the smooth metal plate.
- The mold is filled in four layers each approximately one quarter of the height of the mold.
- Each layer should be pampered with 25 strokes with tamping rod such that the strokes are distributed over the cross-section.
- After the top layer is filled the concrete is struck off level should be removed from the concrete by slowly raising in the vertical direction
- Now you will notice concrete tends to subside this subsidence is referred as slump of concrete.
- This slump value is then measured by the difference of the height of the mold and that of the highest point of the specimen.
- This difference in hiding is taken as slump of concrete.
- The pattern of a slump is displayed on the picture below.
- The slump value and it’s acceptable usage are tabulated on the picture below
Interview Questions Based On Slump Cone Test Or Workability Test
Q1.What is slump cone size?
Q2. What is the technical name of slump cone
Q3.What is the size of tamping rod
Ans.16mm dia and length 600mm
Q4.How many layers slump cone is filled
Q5.How many times concrete should be tamped in slump cone?
Q6.Should oil or any lubricant is used before filling concrete?
Q7.What should be the maximum value of slump for light constructions like slab?
Ans.25 to 75mm
Q8.What should be the maximum value of slump for heavy construction?
Ans.50 to 100mm
Q9.How many type of slumps you can get?
True Slump,Zero Slump,Shear Slump,Collapse Slump
Q10.What if you get shear slump?
Ans.Concrete Should Be Reprepared
What is the principle behind Slump Cone Test
Slump cone test is based on the behavior of frustum or slump cone under the action of gravity.
It is an on site test to check the consistency and Workability of concrete to be used.By this test you can quickly see if the concrete is good for your construction purpose or not.
Precautions Before Taking Slump Cone Test
You must clean the debris from the surface where you will conduct slump cone test,so that the apparatus will be in level.
Clean the base plate of Cone if it is covered with dirt or concrete.
Types of Slump
The slump which after removing the frustum mentains its shape more or less like frustum or cone is known as True Slump.
This type of slump is most preferred.
The slump which collapses After Removing the frustum is known as Collapse Slump.
In this case water cement ration is greater than 0.5 or in other words it’s very high.This test is not required for such mixes.
The slump which just slides down while keeping half portion erect after removing frustum is known as shear slump.
In this case concrete should be again prepared.
The slump which mentains the actual shape of frustum is known as zero slump.
Water Cement Ratio in this case is very low and it has almost no Workability
Permissible Values Of Slump As Per Indian Standard Code
Below is the table according to which slump depends on the placing conditions and values are given below