Slump Flow Test and T 50 cm Test on Self Compacting Concrete
The slump flow test is a method used to evaluate the ease of horizontal free flow of self compacting concrete without any obstructions. Initially designed in Japan, the test is commonly used to examine the properties of underwater concrete. The test procedure is modeled on the technique utilized for determining the slump. In this method, the diameter of the concrete circle formed after the test is an indicator of the concrete’s filling capacity. By measuring the concrete’s ability to flow freely, the test helps assess the quality and consistency of the self-compacting concrete.
Assessment of Slump Flow Test
This is a straightforward and speedy testing procedure, but it requires two individuals to measure the T50 time accurately. Although it can be performed on-site, a large base plate is needed, and the ground must be level to obtain reliable results.
The test is widely used and provides a sound evaluation of the filling capacity of concrete. However, it does not reveal how well the concrete can pass through reinforcement without creating voids, although it may offer some insight into its ability to resist segregation.
Some may argue that the test’s unrestricted free-flowing nature does not accurately reflect what occurs during concrete construction. Nevertheless, it can still be effectively utilized to evaluate the consistency of ready-mixed concrete supply to a site from one load to the next.
Equipment for Slump Flow Test
The equipment for this task consists of a mould designed in the shape of a truncated cone, with internal dimensions of 200 mm at the base, 100 mm at the top, and a height of 300 mm. Additionally, a base plate made of a sturdy, non-absorbing material, with a minimum area of 700mm square, is provided. The base plate is marked with a circle indicating the central location for the slump cone, as well as another concentric circle with a diameter of 500mm.
A trowel and scoop are also included in the equipment. The trowel can be used for levelling the top surface of the concrete sample, while the scoop is used for placing the sample into the mould. A ruler is also provided for measuring the slump of the concrete.
Optionally, a stopwatch can be used to measure the time taken for the concrete to reach its final slump. Overall, the equipment provided is intended to facilitate the measurement of the slump of a concrete sample, a key parameter in determining the workability and consistency of the material.
Equipment for Slump Flow Test
Procedure of Slump Flow Test on Self Compacting Concrete
To perform a slump test on concrete, it is necessary to use approximately 6 liters of the material. The test requires the base plate and inside of the slump cone to be moistened, after which the base plate should be placed on level and stable ground. Next, the slump cone should be centered on the base plate and held down firmly.
The cone should then be filled with the concrete using a scoop. It is important not to tamp the concrete, but rather strike off the top of the cone level with a trowel. Any excess concrete around the base of the cone should be removed.
The cone should then be raised vertically, allowing the concrete to flow out freely. At the same time, the stopwatch should be started and the time taken for the concrete to reach the 00mm spread circle should be recorded. This time is known as the T50 time, and it provides a secondary indication of flow.
A lower T50 time indicates greater flow ability, and the Brite EuRam research has suggested that a time of 3-7 seconds is acceptable for civil engineering applications, while 2-5 seconds is acceptable for housing applications.
In cases of severe segregation, the coarse aggregate will remain in the center of the concrete pool, while the mortar and cement paste will be at the periphery. Minor segregation can result in a border of mortar without coarse aggregate at the edge of the pool. However, even if neither of these phenomena appear, there is no guarantee that segregation will not occur at a later time, as it is a time-related aspect.