The equipment is made up of a flow table with a diameter of roughly 76 cm and concentric circles marked on it. The following internal dimensions are employed in a smooth metal casting mould in the shape of a frustum of a cone. The base measures 25 cm in diameter, the upper surface measures 17 cm in diameter, and the cone stands 12 cm tall.

The table’s centre is firmly secured and filled in two levels. Each layer is tamped 25 times with a 1.6 cm diameter tamping rod that is 61 cm long and rounded at the lower tamping end. top layer is equally rodded, and the excess concrete that has overflowed the mould is removed. The concrete is pulled vertically upward from the mould and stands on its own. In around 15 seconds, the table is raised and dropped 12.5 mm 15 times. The spread concrete’s diameter is measured to the nearest 5 mm in six directions. It is indicated the average spread.

Consistometer Test using Vee Bee

This is a good laboratory test for determining the workability of concrete indirectly. A vibrating table, a metal pot, a sheet metal cone, and a standard iron rod are used in this test.

The slump test is carried out as described above, with the slump cone being placed inside the sheet metal cylindrical pot of the consistometer. The swivel arm’s glass disc is spun and positioned on top of the concrete in the pot. The electrical vibrator is then turned on, and a stopwatch is started at the same time.

The vibration continues until the conical shape of the concrete vanishes and the concrete takes on a cylindrical shape. This can be determined by looking at the transparency of the glass disc from the top.

The stop watch is turned off as soon as the concrete has entirely assumed a cylindrical shape.

Vee Bee Degree is the amount of time it takes for the shape of concrete to change from slump cone to cylindrical in seconds.

This method is very suitable for very dry concrete whose slump value cannot be measured by Slump Test, but the vibration is too vigorous for concrete with a slump greater than about 50 mm.

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The compacting factor test is primarily intended for laboratory usage, although it can also be applied in the field.

It is more precise and sensitive than the slump test, and it is especially beneficial for very low workability concrete mixtures, which are commonly employed when concrete is compacted by vibration.

Premise:

This test is based on the principle of determining the degree of compaction accomplished by allowing concrete to fall through a standard height with a standard amount of work. The density ratio, or the ratio of the density actually attained in the test to the density of the same concrete fully compacted, is used to determine the degree of compaction, also known as the compacting factor.

Compacting Factor Test Procedure

1. The concrete sample to be analysed is filled to the brim in the upper hopper.
2. The concrete falls into the bottom hopper after the trap-door is opened.
3. The bottom hopper’s trap door is then opened, allowing the concrete to fall into the cylinder.
4. If the concrete is dry-mix, it is unlikely that it will fall when the trapdoor is opened.
5. In this scenario, a little poke with a rod may be necessary to get the concrete moving.
6. The extra concrete that remains over the cylinder’s top level is subsequently chopped away with plane blades included with the apparatus.
7. The cylinder’s exterior has been scrubbed clean. The concrete is precisely filled to the cylinder’s top level. It’s weighted to the tenth of a gramme. “Weight of partially compacted concrete” is the name given to this weight.
8. The cylinder is then emptied and refilled with concrete from the same sample in 5 cm thick layers.
9. To achieve thorough compaction, the strata are severely rammed or, preferably, vibrated.
10. The fully compacted concrete’s top surface is then carefully struck off level with the cylinder’s top and weighed to the closest 10 grams. “Weight of thoroughly compacted concrete” is the name given to this weight.

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It is not good for extremely wet or extremely dry concrete. It does not account for all aspects that influence workability, nor is it always indicative of the concrete’s placability.

However, it is useful as a control test because it indicates the consistency of concrete from batch to batch.

The slump test apparatus mainly consists of a metallic mould in the shape of a frustum of a cone with the internal dimensions as follows:

• 20 cm bottom diameter
• 10 cm top diameter
• 30 cm in height

The copper sheet for the mould should not be thinner than 1.6 mm in thickness. Suitable guides for vertical lifting are sometimes included with the mould. A steel tamping rod with a bullet end and a diameter of 16 mm is used to tamp the concrete.

Before starting the test, the internal surface of the mould is completely cleaned and free of excess moisture and adherence of any old set concrete.

Slump test procedure:

1. The mould is put on a non-absorbent, smooth, horizontal, solid surface.
2. The mould is then filled in four stages, each about 1/4 of the way up the mold’s height.
3. The tamping rod is used to tamp each layer 25 times, uniformly distributing the strokes across the cross section.
4. The concrete is struck off level using a trowel and tamping rod after the top layer has been rodded. The mould is immediately removed from the concrete by slowly and carefully elevating it vertically.
5. This permits the concrete to settle. Concrete SLUMP is the term for this type of subsidence.
6. The level difference between the mold’s height and the highest point of the subsiding concrete is measured. Slump of Concrete is the variation in height in millimetres.

It is important to note that:

1. True slump occurs when the concrete slumps evenly.
2. Shear slump occurs when one half of a cone slides down.
3. The difference in height between the height of the mould and the average value of the subsidence is used to calculate the slump value in a shear slump.
4. Shear slump indicates that the concrete is non-cohesive and has segregation characteristics.

The slump test is suitable for slumps of medium to low workability, with slumps ranging from 5 to 260 mm. However, the test fails to distinguish between stiff mixes with zero slump and moist mixes with a collapse slump. It only applies to concrete with aggregates smaller than 38 mm (1.5 inch).

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