The slump test is a widely used method for determining the workability of concrete, which is a measure of its consistency and ability to flow. The test is conducted according to the guidelines provided by the Indian Standard (IS) code, specifically IS 1199-1959, “Methods of Sampling and Analysis of Concrete.” Below is a step-by-step methodology for performing the slump test as per reference IS code:
Equipment and Materials Required:
- Concrete mix
- Slump cone
- Tamping rod
- Tamping rod with bullet-nose
- Non-absorbent base plate
- Measuring scale
- Graduated tamping rod (optional)
- Preparation of Test Equipment:
- Ensure that the slump cone is clean and free from any hardened concrete.
- Moisten the inner surface of the slump cone before starting the test.
- Sampling of Concrete:
- Collect a representative sample of the concrete to be tested.
- Mixing of Concrete:
- Mix the concrete thoroughly using the appropriate mix design.
- Conducting the Slump Test:
a. Place the slump cone on a smooth, flat, non-absorbent surface.
b. Fill the slump cone with the freshly mixed concrete in three layers, each approximately one-third of the height of the cone.
c. Compact each layer by rodding 25 times using the standard tamping rod. Ensure that the tamping is distributed evenly over the entire cross-section of the concrete.
- Finishing the Slump Cone:
a. Strike off the excess concrete level with the top of the slump cone using the tamping rod.
b. Clean any loose concrete from around the base of the cone.
- Lifting the Slump Cone:
- Lift the slump cone vertically in a smooth and steady manner, ensuring there is no lateral or torsional movement.
- Measurement of Slump:
- Measure the difference in level between the height of the mold and the displaced concrete. This difference is the slump of the concrete and is measured to the nearest 5 mm.
- Recording the Results:
- Record the slump value as the average of three measurements taken at different points around the displaced concrete.
- Interpreting the Results:
- Compare the slump value with the specified range or target slump mentioned in the mix design or project specifications.
- Cleaning the Equipment:
- Clean the slump cone and tamping rod thoroughly after each test.
It’s important to note that the specific requirements and procedures may vary depending on the version of the IS code in use, so always refer to the latest version of the code for accurate and up-to-date information.