FLOW TABLE TEST OF CONCRETE TO TEST WORKABILITY

Workability is a complex property of concrete which directly impacts on Concrete strength, quality and appearance and it also determines how easily freshly made concrete can be mixed, placed, compacted and finished with the minimum to no loss concerning homogeneity.

To test the freshly mixed concrete workability, the following tests are usually performed on field and lab.

Flow table test of concrete

In this test the workability of concrete is determined by examining the flowing property of fresh concrete. It also determines the Quality of Concrete concerning its consistency, cohesiveness and the proneness to segregation. The flow test is used for high workability concrete (with a slump of more that 175 mm).

Apparatus of Flow Table Test

Flow table made of metal having thickness 1.5mm and dimensions 750mmx 750mm, tamping rod made of hardwood, Scoop, Centimeter Scale, Metal Cone or mould (Lower Dia = 20cm, upper Dia = 13 cm, Height of Cone = 20cm). The middle portion of flow table is marked with a concentric circle of dia 200mm to place a metal cone on it. 

Procedure of flow table test

1. Prepare concrete as per mix design and place the flow table on a horizontal surface.

2. Clean the dust or other gritty material on Flow table and Sprinkle a hand of water on it.

3. Now place the metal cone at the middle portion of the flow table and stand on it.

4. Pour the freshly mixed concrete in the mould comprising two layers; each layer should be stamped with tamping rod for 25times. After tamping the last layer, the overflowed concrete on the cone is struck off using a trowel.

5. Slowly, lift the mould vertically up & let concrete stand on its own without any support.

6. The flow table is raised at the height of 12.5mm and dropped. The same is repeated for 15times in 15secs.

7. Measure the spread of concrete in Diameter using centimeter scale horizontally and vertically. The arithmetic mean of the two diameters shall be the measurement of flow in millimeters.

Formula for Flow value of concrete

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The percentage increase in the average diameter of the spreading concrete over the base diameter of the mould is called the flow of concrete