What is the Concrete Slump Test?

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Concrete Slump Test:

The concrete slump test is a measure of the workability of fresh concrete. More specifically, this test is performed to measures the consistency of the fresh concrete.

This method of test to be adopted, either in the laboratory or during the progress of work in the field where the nominal maximum size of aggregate does not exceed 38 mm using slump test apparatus.

Courtesy - 123rf

Apparatus:

01. Mould:

The mould for the test specimen shall be in the form of the frustum of a cone. The mould has the following internal dimensions:

Dimensions

cm

Bottom Diameter

20

Top Diameter

10

Height

30

The mould shall be made of metal (brass or aluminium shall not be used ) of at least 1.6 mm ( or 16 BG ) thickness .The top and bottom of mould shall be open and at right angles to the axis of the cone.

The mould shall have a smooth internal surface. The mould shall be provided with suitable foot pieces and handles to facilitate lifting it from the moulded concrete test specimen in a vertical direction as required by the test. A mould provided with a suitable guide attachment may be used.

02. Tamping Rod:

The tamping rod shall be of steel or other suitable material, 16 mm in diameter, 0.6 m long and rounded at one end.

03. Scale Measurement:

A good quality of scale is used to measure the difference of the slump.

Procedure:

The internal surface of the mould shall be thoroughly cleaned and freed from superfluous moisture and any set concrete before testing.

The mould shall be placed on a smooth, horizontal, rigid and non-absorbent surface. The mould being firmly held in place while it is being filled.

The mould shall be filled in four layers, each layer is approximately one-quarter of the height of the mould. Each layer shall be tamped with 25 strokes of the rounded end of the tamping rod. The strokes shall be distributed in a uniform manner over the cross-section of the mould.

Also Read : Ready Mix Concrete (RMC):High Speed Construction without Sacrificing Quality

The bottom layer shall be tamped throughout its depth. After the top layer has been rodded, the concrete shall be struck off level with a trowel or the tamping rod, so that the mould is exactly filled.

If mortar may have leaked out between the mould and the base plate, shall be cleaned away. Then, the mould shall be removed from the concrete immediately by raising it carefully and slowly in a vertical direction. This allows the concrete to drop and the slump shall be measured immediately by temping rod shall be placed over the cone and determine the difference between the height of the mould and that of the highest point of the specimen being tested. The decree in height of slump is measured with a scale. The above test shall be carried out at a place free from vibration or shock, and within a period of two minutes after sampling.

The slump measured shall be recorded in terms of milli-metres. Any slump specimen, which collapses laterally and gives incorrect result and if this happens, the test shall be repeated with another sample. If, in the repeat test, the specimen should shear, the slump shall be measured and the measurement of that the specimen sheared shall be recorded.

Also Read:

What is Compaction of Concrete?
What is Concrete Mix Design?
Weigh Batching vs Volume Batching
Do’s & Dont’s While Practices With Concrete

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