Slump test(ASTM C143/AASHTO T119) is a simple field test of freshly mixed concrete. This test is very much popular because it is simple to use and can easily measure the consistency of concrete more easily than other test methods.
To perform slump test of a batch of concrete a slump apparatus is required. A slump apparatus is a frustum cone with the following specifications:
Height 305mm( approximately 12.0 inches)
Top Diameter 100 mm(approximately 4.0 inches)
Bottom Diameter 200 mm (apparoximately 8.0 inches)
The apparatus also contains a slump rod. The slump rod is 600 mm (approximately 24 inches) .
How To Perform Slump Test?
Slump test is quite simple and easy to implement in the field. The steps include-
- Place the cone with the smaller dia keeping at top in a non-absorbent hard surface so that the surface does not absorb the water of the concrete. The surface shall be plain as much as possible too.
- Fill the cone to its 1/3 and hit the concrete inside with the slump rod for 25 times. Drop the slump rod from a height of approximately 1 feet. This process compacts the concrete.
- Again fill another 1/3 of the slump cone and repeat the compaction process using the slump rod.
- Fill the last 1/3 again and do the same as step 3. Level the top surface of the concrete.
- Carefully lift off the slump cone vertically so that it does not disturb the concrete inside of it.
How Are Slump Measurements Taken?
Look, you filled a cone of 12 inches with concrete. When you pulled off the slump cone, the frustum structure will change its shape by some degree. Measure the new height of the concrete.
For example, you measured the last height of the concrete is 9 inches. So the slump will be
Slump = cone height(12 inches) – Final Concrete Height (9 inches) = 3 inches or 75 mm