V funnel test and V funnel test at T 5 minutes on Self Compacting Concrete
The V funnel test is a method used to determine the flowability of self-compacting concrete that has a maximum aggregate size of 20mm. The equipment used for this test consists of a V-shaped funnel, which is filled with approximately 12 liters of concrete. The time taken for the concrete to flow through the apparatus is then measured.
In Japan, an alternative type of V-funnel, known as the O funnel, is also used. This funnel has a circular section instead of a V-shape. The O funnel test was developed by Ozawa et al.
After the first flow, the funnel can be refilled with concrete and left for 5 minutes to settle. If the concrete exhibits segregation, then the flow time will significantly increase. The V funnel test is a widely used method for assessing the filling ability of self-compacting concrete, which is an important property for ensuring its proper placement and consolidation during construction.
Assssment of test
The flowability test, despite being intended to gauge the flow properties of concrete, can be influenced by other characteristics of the material. For instance, if there is an excessive amount of coarse aggregate, the result may indicate an issue with the concrete’s ability to flow. This is due to the fact that the test employs an inverted cone shape, which can highlight any blockages or impediments in the concrete. Moreover, a prolonged flow time could be indicative of low deformability resulting from a high paste viscosity or high inter-particle friction. Despite the simplicity of the apparatus, the impact of the funnel angle and wall effect on concrete flow is uncertain.
Equipment
There are several tools that are commonly used in construction and engineering projects. One of these is the V-funnel, which is used to measure the flow rate of concrete. Another essential tool is the bucket, which typically holds around 12 liters and is used to transport materials such as sand and gravel.
A trowel is another important tool, typically made of metal and used for spreading and smoothing materials such as concrete or plaster. A scoop, which is similar to a small shovel, is also commonly used for moving materials around a job site.
Finally, a stopwatch is a simple but essential tool for timing various activities, such as measuring the setting time of concrete or tracking how long it takes workers to complete a task. All of these tools play a crucial role in ensuring that construction and engineering projects are completed safely and efficiently.
Fig 1: V Funnel test Apparatus
Procedure flow time:
To perform a concrete test, it is necessary to use about 12 liters of concrete, which should be sampled normally. The V-funnel should be placed on firm ground and the inside surface of the funnel should be moistened. To ensure that any surplus water drains properly, the trapdoor should be kept open. Once the funnel is filled completely with concrete, without any compaction or tamping, the concrete should be leveled off with a trowel. Then, the trapdoor should be closed and a bucket placed underneath it. Within 10 seconds of filling the apparatus, the trapdoor should be opened to allow the concrete to flow out under gravity. At the moment the trapdoor is opened, the stopwatch should be started, and the time for the complete discharge of the concrete (the flow time) should be recorded. This time is taken to be when light can be seen from above through the funnel. The entire test must be completed within 5 minutes.
Procedure flow time at T5 minutes:
When using the V-funnel for measuring concrete flow time, it is important to avoid cleaning or moistening the inside surface of the funnel gain. After measuring the flow time, close the trapdoor and immediately refill the V-funnel, making sure to place a bucket underneath to catch the concrete. It’s important to fill the apparatus completely with concrete without compacting or tapping, simply using a trowel to strike off the concrete level with the top of the funnel. Five minutes after the second fill of the funnel, open the trapdoor and allow the concrete to flow out under gravity. Start the stopwatch simultaneously when the trapdoor is opened and record the time it takes for the concrete to fully flow out, which is the flow time at T5 minutes. This should be taken when light is seen from above through the funnel.
Interpretation of result:
The purpose of this test is to assess the flow ability of concrete, with shorter flow times indicating greater ease of flow. For Self-Consolidating Concrete (SCC), a flow time of 10 seconds is considered suitable. The test involves using an inverted cone shape, which limits the flow of the concrete. If the flow time is prolonged, it may suggest that the mix is more prone to blocking.
After the concrete has settled for 5 minutes, segregation may occur, resulting in a less continuous flow and an increase in flow time. This can provide an indication of the concrete’s susceptibility to segregation. It is essential to consider the flow ability of concrete during the design and construction stages to ensure the structural integrity and durability of the final product.