Flow table test-Workability test

AIM 

To determine the workability of concrete mix of given proportion by flow table test

THEORY 

The workability of concrete is measured by examining the flowing property of concrete. The flow test is a simple laboratory test. This test works on the principal of a jolting of the standard mass of concrete and measured by flow of concrete.

The flow test is used to measure the workability of high or very high workable concrete, which eventually would exhibit the collapse of slump. It gives an idea about the quality of the concrete with respect to the consistency and cohesiveness. This workability test is quite simple to perform and is the best for the concrete which has a nominal maximum size of aggregate less than 38 mm. 

APPARATUS

Metal Cone or Mould: Mould is in the form of a frustum of a cone with a base diameter of 250 mm, upper surface diameter of 170 mm and 120 mm height, Flow Table, Trowels, Hand scoop, Scale, Tamping Rod

PROCEDURE

1. Clean all the gritty material or dust from the flow table and from inside the mould.

2. Place the cone in the marked or middle portion of the flow table.

3. Now pour the freshly mixed concrete in the mould in two layers, each layer should be tamped 25 times with tamping rod. If concrete overflows after tamping then level it with the help of a trowel, and excess concrete should be removed off from the table.

4. Then, lift the mould vertically upward and let the concrete stand on its own without support.

5. Thereafter the table is raised and dropped from 12.5 mm height, 15 times in about 15sec.

6. Next, measure the diameter of the spread of concrete in about 6 directions and note down the average.

RESULT

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

Formula for Measuring Concrete Flow= (Spread diameter in cm-25)/25 x100 

INFERENCE
The value of flow test should be in range of 0 to 150 %.

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