KELLY BALL test
In this article, we explained how to determine the workability of freshly mixed concrete by the KELLY BALL test.
Origin
and principle:
This experiment was developed in the United States by Kelly in the 1950s. The test was adopted in the American concrete construction practice, where it was standardized. This is a test based on the measurement of penetration into the new concrete of a larger and heavier hemispherical body (pictured below). The standardized Iribarren test in Spain is a test method based on the same principle.
Application:
The test is suitable for
the assessment of fresh mixes of 'medium' workability. Its range of use is
approximately the same as for the slump test. The test is also applicable to
many special mixes, including lightweight and heavyweight concretes.
Description:
The apparatus consists of a
steel hemispherical plunger (ball) of 14 0.05 kg and 152 mm in diameter, fitted
with a handle graduated at 0.25 in intervals.
The shaft of the handle
passes through a frame that guides the movement of the plunger. The frame
rests on the surface of the concrete. The penetration reading is taken from the
graduated shaft of the handle against the reference level which is the top edge
of the level part of the frame.
Apparatus
1. The Kelly Ball test
apparatus, dimensions are shown on Fig. 4.37b,
2. optional: a suitable
container having a min. depth of approx. 203 mm and a min. diameter of approx.
500 mm to hold the sample of concrete.
Size
of a sample:
Fresh concrete can be
tested directly in-situ in formwork, wheelbarrows, buckets etc. or in any
container holding a sample of at least the minimum size or volume required. The
container or the formwork holding the in-situ concrete must have a depth equal to
the greater of 203 mm or 8 x the max. size of aggregate. The surface available
must be sufficient to accommodate three tests which must be spaced at least 150
mm apart.
Kelly Ball test apparatus
Procedure
1. Level off the surface of the concrete to be tested. Use a
wooden float to smooth the surface, avoiding excessive working and the formation of
laitance or grout.
2. Place the frame of the apparatus on the levelled
surface of the concrete. Check that the handle is in a vertical position and moves
freely through the frame.
3. Lower the plunger until it touches the surface of the
concrete and releases it slowly. Ensure that concrete in the container is not
subject to vibration, jolting or other movements during the test.
4. Once the plunger has come to rest, read the
penetration off the scale on the shaft of the handle against the top edge of
the guiding frame. Read the penetration to the nearest 0.25 in (6 mm), see Fig.
below
The Kelly Ball test apparatus: basic dimensions
5. A minimum of three readings should be taken from each
sample or location. The readings should be taken at points at least 150 mm away
from the previous position of the base of the frame.
A clamp moving along the shaft of the handle may be
fixed at the position indicating the penetration, it makes it possible to read
the result in a more convenient position, after the ball has been removed from
the concrete.
6. If the first three readings did not fall within an interval of 25 mm, additional readings have to be taken until three successive readings come within the interval. No corrections are to be made in case of a slight settlement of the feet of the frame.
7. The result is obtained as the average of the three readings, rounded to the nearest 0.25 in (6 mm).
Interpretation
of test results:
The results of the test are presented as average
penetrations rounded to the nearest 0.25 inches
It is possible to carry out a slump test on a sample of
the concrete mix and obtain a correlation for this particular mix which can be
used to convert results from the Kelly Ball tests into the values of a slump. The
slump is usually between 1.10 to 2.00 times the penetration of the Kelly Ball.
For a given mix a linear relationship such as shown in Fig. below can be
established.
Precision:
No systematic assessment of the precision of the test has
been published as yet. The reliability of the test results appears to decline
with an increasing the maximum size of the aggregate. The properties of the surface
layer depend to some extent on the operator preparing the sample for the test,
the surface layer affects the test results. Tests on concrete that has been segregated should be avoided.
Measurement of workability
by the penetration of the Kelly Ball
The reliability of the results also depends on the
maintenance of the apparatus. The apparatus must be kept clean and the surface
of the ball free of any scratches, rust or oil when in use. The shaft passing
through the frame must be clean and without any distortion which would affect
its free movement.
Relationship between a slump and the penetration of the
Kelly Ball
Advantages
:
· The
test is suitable for the assessment of fresh concrete in situ, without the
necessity to remove samples.
· The
test procedure is simple and rapid, it provides direct results.
· The
apparatus is simple and relatively inexpensive.
Disadvantages:
· A
level concrete surface is required.
· A
level of maintenance higher than normally expected for such a relatively simple
apparatus is required.
· It
is difficult to simulate the movement of the concrete during the test by a
mathematical model.
· The
use of the test is practically limited to the U.S.A.
Standardisation:
U.S.A. ASTM 0360 - 82: Standard Method for Ball Penetration in Fresh Portland Cement Concrete
FAQs
What is the Kelly ball test?
The Kelly ball test is a simple field method for determining the workability of freshly mixed concrete. This is done by measuring the penetration of a 30-pound metal “ball” onto the concrete surface. This test can be performed on on-site concrete and is easier and faster than the slump test.
NATIONAL
STANDARDS
1. IS 1199-1959 (reaffirmed
2008): Methods of Sampling and Analysis of Concrete
2. IS 6461 (Part 10) -1973
(reaffirmed 2011): Glossary of Terms Relating to Cement Concrete; Part 10:
Tests and Testing Apparatus
REFERENCES
Fresh Concrete. Properties
and Tests by P. Bartos
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