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Slump Flow Test and T 50 cm Test on Self Compacting Concrete
The slump flow test is used assess the horizontal free flow of self compacting concrete in the absence of obstructions. It was first developed in Japan for use in assessment of underwater concrete.
The test method is based on the test method for determining the slump. T is the diameter of the concrete circle is a measure for the filling ability of the concrete.
Assessment of Slump Flow Test
This is a simple, rapid test procedure, though two people are needed if the T50 time is to be measured. It can be used on site, though the size of the base plate is somewhat unwieldy and level ground is essential.
It is the most commonly used test, and gives a good assessment of filling ability. It gives no indication of the ability of the concrete to pass between reinforcement without booking, but may give some indication of resistance to segregation.
It can be argued that the completely free flow, unrestrained by any foundries, is not representative of what happens in concrete construction, but the test can be profitably be used to assess the consistency of supply of supply of ready-mixed concrete to a site from load to load.
Equipment for Slump Flow Test
The apparatus is show in figure;
- Mould in the shape of a truncated cone with the internal dimensions 200 mm diameter at the base, 100mm diameter at the top and a height of 300 mm.
- Base plate of a stiff non-absorbing material, at least 700mm square, marked with a circle marking the central location for the slump cone, and a further concentric circle of 500mm diameter
Procedure of Slump Flow Test on Self Compacting Concrete
About 6 liter of concrete is needed to perform the test, sampled normally. Moisten the base plate and inside of slump cone, place base plate on level stable ground and the slump cone centrally on the base plate and hold down firmly.
Fill the cone with the scoop. Do not tamp, simply strike off the concrete level with the top of the cone with the trowel.
Remove any surplus concrete from around the base of the cone. Raise the cone vertically and allow the concrete to flow out freely.
Simultaneously, start the stopwatch and record the time taken for the concrete to reach the 00mm spread circle (This is the T50 time).floatable test, might be appropriate.
The T50 time is secondary indication of flow. A lower time indicates greater flow ability. The Brite EuRam research suggested that a time of 3-7 seconds is acceptable for civil engineering applications, and 2-5 seconds for housing applications.
In case of severe segregation most coarse aggregate will remain in the centre of the pool of concrete and mortar and cement paste at the concrete periphery. In case of minor segregation a border of mortar without coarse aggregate can occur at the edge of the pool of concrete. If none of these phenomena appear it is no assurance that segregation will not occur since this is a time related aspect that can occur after a longer period.