Kelly ball test also called as a ball penetration test is performed on freshly mixed concrete to measure its workability. It is a quick simple field test and is considered as an alternative to the slump test. The test procedure of the kelly ball test, its advantages and drawbacks are explained in this article.
Kelly Ball Test Apparatus
The Kelly ball apparatus is as shown in fig 1. It consists of a metal ball which is in hemispherical shape and weighs about 13.6 kilograms (30 pounds). The diameter of the metal ball is about 15 cm (6 inches).
The flat end of the metal ball is attached to a graduated stem with handle. A frame is arranged between the ball and stem in such a way that the stem can slide through it when the ball moves vertically. The frame generally rests on the concrete surface during testing.
Test Procedure of Kelly Ball Test
The test procedure of the Kelly ball workability test as follows.
- A large amount of freshly mixed concrete is taken and is poured into a container.
- The container should be more than wide enough to place the Kelly ball apparatus in it.
- The depth of poured concrete should be at least 20 cm.
- Level the concrete surface using suitable equipment.
- Place the Kelly ball apparatus on the leveled concrete surface using handle provided.
- The apparatus should be placed in such a way that the frame should rest on the concrete surface and also the center of the metal ball should be at least 23 cm away from any edge of the container.
- Now release the handle and allow the ball to penetrate through concrete and note down the penetration value by observing the reading on the graduated stem. The observation should be taken to the nearest 0.6 cm (1/4 inch).
- Repeat the above procedure for 4 more times by placing the apparatus at different points on the same test sample.
- The workability of concrete is the average value of all the readings obtained.
Result for Kelly Ball Test
Workability of concrete = Ball penetration value = Average of all the readings obtained
Advantages of Kelly Ball Test
Advantages of the kelly ball workability test are as follows.
- This test can be performed in the field.
- It is quicker and precise test compared to the slump test.
Drawbacks of Kelly Ball Test
Drawbacks of the kelly ball workability test are as follows.
- A large amount of test sample is required to perform the test.
- The test sample of concrete must be leveled to perform the test.
- This test may not give accurate results when large size coarse aggregates are used in the concrete. Hence, it is not widely used in many countries.