Measurements Of Workability For Fresh Concrete

Different methods determine the workability or consistency of freshly prepared concrete. This is usually done to determine the workability of the finished concrete. Measurements Of Workability For Fresh Concrete.

Measurements Of Workability For Fresh Concrete

Different methods determine the workability or consistency of freshly prepared concrete. The following are the commonly used procedures among them.

1 – (Slump Test)

2 – (Compaction factor Test)

3 – (Vee-Bee Test)

Slump Test

This is usually done to determine the workability of the finished concrete. The apparatus used for this network Slump Cone is called. It is made of steel. Its height is 30 cm -1 12 inches). It is 10 cm (14 in) in diameter at the top and 20 cm (8 in) in diameter at the base. A transparent glass plate is placed under it and a stand is used to take its reading. 16 mm (5/8 in) diameter 60 cm (24 in. long) for pressing the concrete into it.

The concrete that performs the slump test is filled in a slump cone. To fill the cone, a 7.5 cm (3 inch) thick layer is pressed into the alloy 25 times with the help of a rod. Nowadays the work of rahane is done with the help of a Vibrating table. After the cone is filled and compacted, the excess concrete on its upper edge is formed with the help of a leaver. The cone is then lifted very slowly and the amount of slump under the concrete is determined with the help of a stand. Slump values ​​suitable for concrete prepared for various types of concrete works are shown below.

Values of Slump

Type of construction                                                                   Slump

(Inches)                  (mm)

Reinforced foundation walls and footings                                          25-75                      1-3
Plain footings, caissons, and substructure walls                                 25-75                      1-3
Beams and reinforced walls                                                                  25-100                    1-4
Building columns                                                                                   25-100                     1-4
Pavements and slabs                                                                              25-75                      1-3
Mass concrete                                                                                         25-50                      1-2

 

Compaction Factor Test

It is a motor test to determine the workability of fresh concrete. In this intention, as a result of known work (Work), the amount of giving (Compaction) of concrete is determined. This quantity is called the compaction factor. This factor density after a practical section of fresh concrete Density) and the density of this concrete after 100% tension is relative to (Density). For the reliability of this net, it is necessary that the maximum size of aggregates (Aggregates) in concrete be used up to 4 cm (1/2-1 inch).

The device used for this test is called Compaction Factor Apparatus. This device consists of two hoppers and a number of cylinders. These three are placed on top of each other. While the cylinder is placed at the bottom. Their inner surface is smooth. The wings of the hoppers are hinged with the help of which the concrete in them is removed from below. Can be taken out.

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Compaction Factor Apparatus

1-Upper Hopper

2-Lower Hopper

3-Cylinder

Description                                                                                  Dimension

Upper hopper, A                                                                                            CM                            IN

Top internal diameter                                                                                  25.4                            10
Bottom internal diameter                                                                           12.7                              5
Internal height                                                                                             27.9                             11

Lower hopper.B

Top internal diameter                                                                                  22.9                               9
Bottom internal diameter                                                                           12.7                                5
Internal Height                                                                                             22.9                                9
Cylinder. C
Internal diameter                                                                                         15.2                                 6
Internal Height                                                                                             30.5                                12
Distance between the bottom of the upper hopper and the top of the  20.3                                8
lower hopper.
Distance between the bottom of the lower hopper and the top of           20.3                               8
the cylinder.

Dimensions of the Compaction Factor Apparatus

To determine the workability of the fresh concrete, the sample concrete is poured into the upper hole And is filled slowly. After that, the hinge on its hinge is opened. Through this process, the cigarette is filled from the upper lobe to the lower lobe. During this time, Nigrit becomes somewhat compact. After that, the hinge of the hopper is also opened, thus the concrete is filled in the cylinder. The excess concrete falling on the cylinder is made with the help of float or sugar. After that, by finding the volume and weight of this cylinder, the density of the cylinder in it is found. The cylinder is then 100% filled with the same concrete in four layers as per the standard method. And its density is also known and the packing factor is known with the help of the following formula is done.

Comparison between compaction factor and slump

Compaction Factor   =  D/D

where. D1 =  Density of partially compacted concrete after dropping from the hopper.

            D2 =-Density of concrete with 100 percent compaction

Description of workability                  Compaction factor              Corresponding Sharp(mm)
Very low                                                              0.78                                           0  – 25     
Low                                                                      0.85                                           25-50       
Medium                                                               0.92                                           50 – 100   
High                                                                     0.95                                           100 – 175 

Comparison between compaction factor and slump.

Comparison factor 0.95% = high

                               0.92% = medium 

                               0.85% = low workability

Vee-Bee Test

It is a modern net for determining the quality of fresh concrete. This net is suitable for hard-type concrete. Given the instrument used in this intention. B. Called the Upper Minis (Vee Bee Apparatus). This device consists of a cylinder.

Vee Bee Test  0-3 seconds = medium

                     10 -15 seconds = low 

                     18 – 30 second = very low workability,

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