Exp 1 Consistency of cement

Experiment No. 1:

Standard test method for the determination of the normal consistency of the hydraulic cement. (BS-12)

Scope & Significance:

amount of water is then used in making the cement paste for the other cement acceptance quality tests. This test  is used to find out the percentage of amount of water at which the standard consistency is achieved. This known like;vcat

  • Initial setting time
  • Final setting time
  • Soundness test

Related theory:

Consistency

The thickness or the viscosity of the cement paste is called consistency.

Cement Paste

The viscous mass obtained by mixing cement with water is known as cement paste.

Standard Cement Paste

It is the cement paste for which the 10mm diameter plunger in a standard VICAT test penetrates to such an extent that its distance from the bottom is 5-7mm.

Standard/Normal Consistency

It is the thickness or the viscosity of the standard paste and is expressed as the percentage of weight of water.

Apparatus:Consistency of cementVicat-Apparatus

  • Reference Masses and Devices for Determining Mass
  • VICAT Apparatus
  • Plunger with 10mm diameter and 50mm length
  • Glass graduates (200mL or 250mL capacity)
  • Spatula
  • Glass plate trowel
  • Stop watch

Test Specifications:

Temperature & Humidity

The temperature of the air in the vicinity should be between 20-27.5 °C. The temperature of the mixing water should be 23±2 °C.The relative humidity of the laboratory should not be less than 50%.

Amount of Cement

Amount of cement required for the test according to various specifications are mentioned below.

BS-12               = 500gm

ASTM C-187  = 650gm

Mixing Time

The cement paste must be properly mixed and placed in the test specimen within a maximum time of 4±1/4 min from the instant when cement and water were initially brought in contact.

Procedure:

Mix 650gm of cement with a measured quantity of water and make a cement paste as per the standard procedure. Put the cement paste in the ring of the vicat apparatus and remove the excess paste with the help of a trowel. Center the paste confined in the ring, resting on the plate, under the plunger rod  and bring the plunger end in contact with the surface of the paste, Pull the hydraulic jack so that some amount of energy is stored in it and when released that stored energy is transferred to the cement paste.This must not exceed 30 s after completion of mixing. The apparatus shall be free of all vibrations during the test. The paste of normal consistency is achieved when the rod settles to a point such that it is 4-7mm above the bottom surface in 30 s after being released. Make trial pastes with varying percentages of water until the normal consistency is obtained. Make each trial with fresh cement.

Observations & Results:

 Cement Brand =    S.R.MAPPLE LEAF  

Sr. #

Weight of Cement

Trial

Moisture Content

Weight/Volume of Water

Temperature

Mixing Time

Scale Reading

 

(gm)

(%)

(1gm = 1mL)

(°C)

(min)

(mm)

1

    500

28

140

14

4

6

2

500

28

140

14

4

17

3

500

27

135

14

4

28

4

500

28.5

142.5

14

4

8

Achieved Standard Consistency =…28….%

Comments:

  • This experiment tells us the amount of water content at which we can obtain the maximum strength of cement.
  • The achieved Standard Consistency is coming within the range of water( 26% to 33% ) So, the standard consistency of cement paste is 28%.
  • Moreover the temperature and humidity values were not in the specified range.
  • This test also gives us information that how much amount of water is enough to prepare a paste of cement before using it at the site at the time of construction.





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