Understanding Concrete Workability with the Kelly Ball Test

Concrete, a crucial construction material, must possess optimal workability for effective application. The Kelly Ball Test, often referred to as the ball penetration test, serves as a practical measure of concrete workability. In this exploration, we delve into the test procedure, the apparatus used, and the advantages and drawbacks associated with this method.

Exploring the Kelly Ball Test Apparatus

The apparatus employed for the Kelly Ball Test is depicted in Figure 1. It features a metal ball with a hemispherical shape, weighing approximately 13.6 kilograms (30 pounds) and having a diameter of about 15 cm (6 inches). The flat end of the ball connects to a graduated stem with a handle, while a frame facilitates vertical movement during the test, resting on the concrete surface.

Step-by-Step Procedure of the Kelly Ball Test

The procedure for conducting the Kelly Ball Test unfolds in several steps, ensuring a comprehensive assessment of concrete workability:

1. Concrete Preparation: A considerable amount of freshly mixed concrete is poured into a sufficiently wide container.
2. Container Size: The container should surpass the width required for placing the Kelly Ball apparatus. The depth of the poured concrete should be a minimum of 20 cm.
3. Surface Leveling: Employ suitable equipment to level the concrete surface, preparing it for testing.
4. Apparatus Placement: Position the Kelly Ball apparatus on the leveled surface using the provided handle. Ensure the frame rests on the concrete surface, and the ball’s center is at least 23 cm away from the container edges.
5. Ball Penetration: Release the handle, allowing the ball to penetrate the concrete. Record the penetration value by noting the reading on the graduated stem, rounding to the nearest 0.6 cm (1/4 inch).
6. Multiple Tests: Repeat the procedure at least four times, placing the apparatus at different points on the same concrete sample.
7. Average Reading: Calculate the average value of all the readings obtained to determine the workability of the concrete.

Unveiling Results: Concrete Workability

The workability of concrete is represented by the ball penetration value, which is the average of all the readings obtained during the test.

Advantages of the Kelly Ball Test

The Kelly Ball Workability Test presents notable advantages:

1. Field Compatibility: This test can be effortlessly performed in the field, facilitating on-site assessments.
2. Efficiency: Compared to the slump test, the Kelly Ball Test is quicker and more precise.

Drawbacks of the Kelly Ball Test

However, it’s essential to acknowledge the drawbacks associated with the Kelly Ball Workability Test:

1. Sample Size Requirement: A considerable amount of test sample is needed, which may not always be practical.
2. Surface Leveling Requirement: The concrete sample must be meticulously leveled for accurate test results.
3. Limitation with Coarse Aggregates: The test may not yield accurate results when large-size coarse aggregates are present in the concrete, limiting its widespread use in certain regions.

In conclusion, the Kelly Ball Test offers a valuable perspective on concrete workability, balancing its advantages and drawbacks for practical application in construction scenarios.