Measurement of workability
(1) Slump Test
(2) Compaction Factor Test
(3) Vee Bee consistometer Test
(1) Slump Test
Slump Test or slump cone test is to determine the workability or consistency of concrete mix prepared at the laboratory or the construction site during the progress of the work. Concrete slump test is carried out from batch to batch to check the uniform quality of concrete during construction.
The slump test is the most simple workability test for concrete, involves low cost and provides immediate results. Due to this fact, it has been widely used for workability tests since 1922. The slump is carried out as per procedures mentioned in ASTM C143 in the United States, IS: 1199 – 1959 in India and EN 12350-2 in Europe.
Generally concrete slump value is used to find the workability, which indicates water-cement ratio, but there are various factors including properties of materials, mixing methods, dosage, admixtures etc. also affect the concrete slump value.
2) Compaction Factor Test
Compaction factor test is the workability test for concrete conducted in laboratory. The compaction factor is the ratio of weights of partially compacted to fully compacted concrete. It was developed by Road Research Laboratory in United Kingdom and is used to determine the workability of concrete.
The compaction factor test is used for concrete which have low workability for which slump test is not suitable.
Proceedure
Place the concrete sample gently in the upper hopper to its brim using the hand scoop and level it.
Cover the cylinder.
Open the trapdoor at the bottom of the upper hopper so that concrete fall into the lower hopper. Push the concrete sticking on its sides gently with the road.
Open the trapdoor of the lower hopper and allow the concrete to fall into the cylinder below.
Cut of the excess of concrete above the top level of cylinder using trowels and level it.
Clean the outside of the cylinder.
Weight the cylinder with concrete to the nearest 10 g. This weight is known as the weight of partially compacted concrete (W1).
Empty the cylinder and then refill it with the same concrete mix in layers approximately 5 cm deep, each layer being heavily rammed to obtain full compaction.
Level the top surface.
Weigh the cylinder with fully compacted. This weight is known as the weight of fully compacted concrete (W2).
Find the weight of empty cylinder (W)
3) Vee Bee consistometer Test
The main objective of Vee-Bee test is to determine the workability of the freshly mixed concrete. The Vee-Bee test gives an indication about the mobility and the compactibility aspect of the freshly mixed concrete.
Vee-bee test carries out the relative effort measurement to change the mass of the concrete from a definite shape to the other. That is, as per the test, from the conical shape to the cylindrical shape by undergoing vibration process.
The measurement of the effort is done by time measurement in seconds. The amount of work measured in seconds is called as the remolding effort. The time required for the complete remolding is a measure of the workability and is expressed in the Vee-Bee seconds.
The experiment is named after the developer V Bahrmer of Sweden. The method can be also applied for dry concrete. For concrete that have slump value more than 50mm, the remolding activity will be so fast that the measurement of time is not possible.
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