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Objective and Theory of Vee-Bee Test on Concrete
The main goal of the Vee-Bee test is to figure out how workable newly mixed concrete is. The Vee-Bee test determines the mobility and compactibility of freshly mixed concrete. The Vee-bee test is used to determine the relative effort required to alter the mass of concrete from one shape to another. That is, according to the test, after undergoing a vibration procedure, the conical shape is transformed into a cylindrical shape. The effort is measured using a timer that counts down in seconds. The remoulding effort is the amount of work measured in seconds. The time it takes to completely remould anything is a measure of its workability, and it’s measured in Vee-Bee seconds.
The experiment is named after V Bahrmer, a Swedish developer. Dry concrete can also be used with this procedure. The remoulding activity will be so quick for concrete with a slump value greater than 50mm that time measurement will be impossible.
Apparatus for Vee-Bee test
As indicated in 1, the Vee-Bee test instrument consists of a Vee-Bee consistometer as per IS: 119 – 1959. A vibrating table is supported and mounted on elastic supports as part of the device. A sheet metal slump cone, a weighing scale, a cylindrical container, a standard iron tamping rod, and trowels are also included.In the Vee-Bee Test for Concrete Workability, a Consistometer is used. 1: Consistometer used in the Vee-Bee Concrete Test 1 shows a vibrating table with dimensions of 380mm in length and 260mm in width. It is supported on a rubber shock absorber above the level of the floor at a height of 305mm. Underneath the table is a vibrator. The vibrator is powered by electricity. The entire stated assembly is in place.
shows a sheet metal slump cone mould with openings on both ends that is placed in a cylindrical container. With the help of wing nuts, the cylinder container is secured to the vibration table. The height of the cone employed in the arrangement is 300mm, with top and bottom diameters of 200 and 100mm, respectively. A swivel arm holder is included in the base. It has another swivel arm with a funnel and a guide sleeve that is fastened into it.For the swivel arm, separation from the vibrating table is feasible. Through the guide sleeve, a graded rod is attached to the swivel arm. Screwing the transparent disc into the graded rod is possible.The economic downturn.
Procedure of Vee-Bee Test on Concrete
Step 1: The sheet metal slump cone is first inserted into the cylinder container, which is then placed within the consistometer. Four layers of concrete are used to fill the cone. Each concrete layer is a quarter of the cone’s height. After pouring, each layer is tamped twenty-five times with a normal tamping rod. The rounded end of the rod is used for tamping.The strokes are evenly scattered over the canvas. The second and subsequent layers of concrete must be penetrated by the strokes used for the second and later layers of concrete.With the use of a trowel, the concrete is struck off to make it level after the last layer has been placed and compacted. As a result.
Step 2: The glass disc attached to the swivel arm is moved and set on top of the slump cone inside the cylindrical container after the concrete cone has been prepared. The glass disc must be positioned such that it meets the top of the concrete level, and the reading must be taken using the graduated rod.
Step 3: Immediately remove the cylindrical cone by carefully rising it in the vertical direction. The reading is taken once the transparent disc on top of the concrete is moved to its new location.
4th Step:The slump is determined by the difference between the values measured in steps 3 and 4.
Step 5: The electrical vibrator is now turned on, and the stop watch must be started at the same time. In the cylindrical container, the concrete is allowed to spread out. The vibration will remain until the concrete is remoulded. When the concrete surface becomes horizontal and the concrete surface adheres equally to the glass disc, this is the stage.
Step 6: Calculate the time required for complete remoulding in seconds. This time in seconds is used to determine the fresh concrete’s workability. Vee-Bee seconds are used to measure time.Vee-Bee Test Observation and Calculations Before unmolding, take a reading from the graduated rod (a) in mm.After removing the mould, the final reading on the graduated rod
Precautions Necessary in Vee-Bee Test
Before pouring the concrete mix, make sure the mould is clean and dry on the inside. When applying the strokes to the layers, it’s important to make sure they’re distributed evenly across all of them. This allows the full impact of the strokes to be felt. The slump cone should be pulled upward in such a way that it does not disturb the concrete cone in any way. The vee-bee tests must be carried out at a safe distance from any other source of vibration other than the one specified in the test. The remoulding of concrete is complete when the clear disc rider completely covers the concrete and all holes and cavities in the concrete surface are gone.
The Vee-Bee test replicates the procedure that a freshly mixed concrete undergoes in its natural form. When compared to other tests, such as the slump test and the compaction factor test, the Vee bee test has this benefit. The completeness of the remoulding is determined visually, which can make measuring the end-point difficult and hence lead to inaccuracies. The higher the workability of the concrete mix, the greater the probability of error. As a result, the Vee-Bee time in this mix is decreased. The phenomena of remoulding is discovered to be very swift in concrete mixes with a slump value greater than 125mm, and the time cannot be measured.
Vee-Bee Test to Determine Workability of Concrete using Consistometer
This problem can be solved in some cases by using an automatic operational device that records the movement time. In general, the Vee-bee test is ideal for concrete mixes with a low or extremely low workability value.The slump test method is the most popular test to determine concrete workability among the three workability tests specified by IS: 119 -1959, namely the slump test, the compaction factor test, and the Vee-bee test. According to American Concrete Institute 211, the Vee-bee time in seconds for varying workability is shown in the table below (ACI Committee 211).
IS: 119 – 1959 covers the Vee bee consistometer test, which is named after Swedish creator V Bahrmer. By conducting vibrations, we assess the proportional effort exerted by concrete to transform from one specific shape to another definite shape (Conical to cylindrical). This effort is referred to as remoulding effort and is quantified in ‘t’ seconds (time) or Vee bee Secs. As a metric of concrete workability, the time it takes for the concrete to completely remould is calculated and displayed as Vee bee Secs. This test is normally done on dry concrete and should not be used on very wet concrete. Where measuring the slump value, concrete with a slump value more than 50mm remoulds more quickly.
The transparent glass disc attached to a swivel arm is moved and put on the top surface of the concrete after it has been filled in the slump cone. Assign a “initial reading” to the reading from the graduated scale.
The test measures the relative effort required to change a mass of concrete.
Explanation: 2-5 sec is the Vee-Bee time for the medium degree of workability and 10-20 sec is for very low.
Vee Bee Consistometer Test as per IS Code 1199.