WORKABILITY TESTS OF CONCRETE Submitted By – Kamal Sharma Class – D2CEC2 College Roll No. – 140332

Scope and Significance WORKABILITY TEST OF CONCRETE BY VEE-BEE CONSISTOMETER METHOD (IS-1199-1956) Objective To determine the workability of freshly mixed concrete by using of Vee – Bee consistometer apparatus. Scope and Significance The workability of fresh concrete is a composite property, which includes the diverse requirements of stability, mobility, compactability, placeability and finishability. There are different methods for measuring the workability. Each of them measures only a particular aspect of it and there is really no unique test, which measures workability of concrete in its totality. This test gives an indication of the mobility and

to some extent of the compactibility of freshly mixed concrete to some extent of the compactibility of freshly mixed concrete. The test measures the relative effort required to change a mass of concrete from one definite shape to another (i.e., from conical to cylindrical) by means of vibration. The amount of effort (called remoulding effort) is taken as the time in seconds, required to complete the change. The results of this test are of value when studying the mobility of the masses of concrete made with varying amounts of water, cement and with various types of grading of aggregate. The time required for complete remoulding in seconds is considered as a measure of workability and is expressed as the number of Vee-Bee seconds. The method is suitable for dry concrete. For concrete of slump in excess of 50mm, the remoulding is so quick that the time cannot measured.

Vee-Bee Consistometer

Apparatus Procedure Cylindrical container, Vee-Bee apparatus (consisting of vibrating table, slump cone) Standard tamping rod, Stop watch and trowels. Procedure (1) Place the slump cone in the cylindrical container of the consistometer. Fill the cone in four layers, each approximately one quarter of the height of the cone. Tamp each layer with twenty-five strokes of the rounded end of the tamping rod. The strokes are distributed in a uniform manner over the cross-section of the cone and for the second and subsequent layers the tamping bar should

penetrate into the underlying layer penetrate into the underlying layer. After the top layer has been tamped, struck off level the concrete with a trowel making the cone exactly filled. (2) Move the glass disc attached to the swivel arm and place it just on the top of the slump cone in the cylindrical container. Adjust the glass disc so as to touch the top of the concrete cone, and note the initial reading on the graduated rod. (3) Remove the cone from the concrete immediately by raising it slowly and carefully in the vertical direction. Lower the transparent disc on the top of concrete. Note down the reading on the graduated rod. (4) Determine the slump by taking the difference between the readings on the graduated rod recorded in the steps (2) and (3) above.

Observations and Calculation (5) Switch on the electrical vibrations and start the stopwatch. Allow the concrete to remould by spreading out in the cylindrical container. The vibrations are continued until the concrete is completely remoulded, i.e, the surfaces becomes horizontal and the whole concrete surface adheres uniformly to the transparent disc. (6) Record the time required for complete remoulding seconds which measures the workability expressed as number of Vee-Bee seconds. Observations and Calculation Initial reading on the graduated rod, a Final reading on the graduated rod, b Slump = (b) – (a), in cm Time for complete remoulding, seconds

Results Standard Values The consistency of the concrete is reported in seconds. Standard Values

COMPACTION FACTOR TEST AIM To study the workability of concrete. APPARATUS Compaction factor apparatus’ trowels, hand scoop (15.2 cm long), a rod of steel or other suitable material (1.6 cm diameter, 61 cm long rounded at one end ) and a balance. SAMPLING Concrete mix (M15) is prepared as per mix design in the laboratory.

PROCEDURE (I)Place the concrete sample gently in the upper hopper to its brim using the hand scoop and level it. (ii) Cover the cylinder (iii) Open the trap door at the bottom of the upper hopper so that concrete fall in to the lower hopper .Push the concrete sticking on its sides gently with the road. (iv) Open the trap door of the lower hopper and allow the concrete to fall in to the cylinder below (v) Cut of the excess of concrete above the top level of cylinder using trowels and level it. (vi) Clean the outside of the cylinder. (vii) Weight the cylinder with concrete to the nearest 10 g. This weight is known as the weight of partially compacted concrete (wi).

(viii) Empty the cylinder and then refill it with the same concrete mix in layers approximately 5cm deep, each layer being heavily rammed to obtain full compaction. (ix) Level the top surface. (x) Weigh the cylinder with fully compacted. This weight is known as the weight of fully compacted concrete (w2). (xi) Find the weight of empty cylinder (W). CALCULATION The compaction factor is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete. It shall normally to be stated to the nearest second decimal place. Compaction Factor= (W1-W2 / W2-W)

Slump Test This test is carried out with a mould called slump cone whose top diameter is 10cm, bottom diameter is 20 cm and height is 30 cm. the test may be performed in the following steps: 1. Place the slump mould on a smooth flat and non-absorbent surface. 2. Mix the dry ingredients of the concrete thoroughly till a uniform colour is obtained and then add the required quantity of water. 3. Place the mixed concrete in the mould to about one-fourth of its height.

4. Compact the concrete 25 times with the help of a tamping rod uniformly all over the area. 5. Place the concrete in the mould about half of its height and compact it again. 6. Place the concrete upto its three fourth height and then upto its top. Compact each layer 25 times with the help of tamping rod uniformly. For the second subsequent layers, the tamping rod should penetrate into underlying layers. 7. Strike off the top surface of mould with a trowel or tamping rod so that the mould is filled to its top. 8. Remove the mould immediately, ensuring its movement in vertical direction. 9. When the settlement of concrete stops, measure the subsidence of the concrete in millimeters which is the required slump of the concrete.

Suitability of Slump Test: The slump test is suitable only for the concrete of high or medium workability.

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