What Does The Slump Test Measure in Concrete?
What Does The Slump Test Measure in Concrete?
The slump test determines the consistency of new concrete prior to setting. It is used to test the workability of newly mixed concrete and, as a result, the ease with which concrete flows. It can also be used to detect a poorly mixed batch.
The test is conducted by filling a mold with fresh concrete, then removing the mold and measuring the height of the resulting concrete column. The height of the column is an indicator of the consistency of the concrete mix – a higher column indicates a more fluid mix, while a lower column indicates a more stiff mix.
While the slump test is a relatively simple test, it can provide valuable information about the quality of a concrete mix. When used in conjunction with other tests, such as the compressive strength test, it can help ensure that concrete is of the proper strength and workability for the intended use.
How Is The Workability Of Concrete By Slump Test Determined?
The slump test is used to assess the workability of new concrete. The IS: 1199 – 1959 slump test is used. A slump cone and Tamping rod are the tools used for slump testing. The slump test procedure for determining the workability of new concrete.
· The inside surface of the mould is carefully cleaned and a light layer of oil is applied.
· Place the mould on a smooth, flat, firm, and nonabsorbent surface.
· The mould is then filled with newly mixed concrete in four levels, each one-fourth the height of the mould.
· The rounded end of the tamping rod is used to tamp each layer 25 times (strokes are distributed evenly over the cross-section).
· After the top layer is rodded, the concrete is troweled off the level.
· The mould is immediately withdrawn from the concrete by slowly elevating it vertically.
· The level difference between the mould’s height and the highest point of the subsiding concrete is measured.
· The difference in height in mm represents the concrete’s slump.
Is The Slump Test Suitable For Any Concrete?
The slump test is appropriate for slumps of medium to low workability, with a slump range of 5 – 260 mm. However, the test fails to establish the difference in workability in stiff mixes with zero slump or moist mixes with a collapse slump.
It is restricted to concrete made with particles less than 38 mm in size (1.5 inches). When the aggregate size exceeds 40 mm, the slump test is inapplicable.
For high-dry and stiff concrete, this test does not provide a reliable result. For example, the slump of concrete that sets in high-dry conditions may be zero. In such cases, the test is not applicable.
The slump test is suitable for most concrete, with the exception of high-dry and stiff concrete. The most common slump range of 5 – 260 mm is applicable to a wide variety of cement types, aggregates, and water-cement ratios.
What Happens If Concrete Fails The Slump Test?
If concrete fails the slump test, it means that the concrete is not workable and has a high water-cement ratio. This can be due to a number of factors, such as too much water in the mix, not enough aggregate, or too much air entrained in the concrete.
When the concrete has a high water-cement ratio, the workability of the concrete is increased but the durability of the concrete is decreased. This is because excessive water forms voids in the concrete, which reduces the strength of the concrete.
If the measured slump or air content exceeds the required limitations, a check test on another piece of the same sample must be performed promptly. In the case of a second failure, the concrete is regarded to have failed the specification criteria.
What Tools Are Used For The Slump Test Of Concrete?
Slump testing necessitates the use of specific equipment. These test kit sets are widely available on the market. The test equipment must meet the aforementioned requirements. The following items are commonly used during slump testing:
Mould.
The mould has the shape of a cone frustum. The cone is also known as the droop cone or the Abrams cone. Steel, plastic, and other materials are used to make slump cones. It stands 12 inches tall (30 cm). The base hole measures 8 inches (20 cm) in diameter, while the top opening measures 4 inches (10 cm).
Base Plate.
The base plate might be constructed of aluminium, polymer, steel, or another material. It might come with a holding attachment.
Tamping Rod.
Steel temping rod is used in the slump test. Tamping rods are typically 24″ long and 5/8″ in diameter. Steel temping rod is used in the slump test. Tamping rods are typically 24″ long and 5/8″ in diameter.
Tape Measure
For measuring, a standard tap should be used.
