HOW TO DETERMINE STANDARD CONSISTENCY OF CEMENT PASTE?

Test Standard Reference

IS:4031(Part 4):1988-Methods of physical tests for hydraulic cement (Determination of consistency of standard cement paste)

Overview

Standard consistency of a cement paste is defined as that consistency which will permit a vicat plunger having 10 mm dia and 50 mm length to penetrate to a depth of 33-35 mm from top of the mould.

Apparatus

Measuring Instruments

NAME CAPACITY / RANGE / SIZE ACCURACY / LEAST COUNT
Vicat apparatus Should be made as per IS:5513  —
Balance 1000 g 1 g
Measuring cylinder 100 ml 1 ml
Vicat Apparatus Specification
Vicat Apparatus Specification

Other accessories

Tray, glass plate

Environmental Condition

Temperature 27 ± 20 C
Humidity 65 ± 5 %

Procedure

  1. Take 400 g of cement and place it in the enameled tray.
  2. Mix about 25% water by weight of dry cement thoroughly to get a cement paste. Total time taken to obtain thoroughly mixed water cement paste i.e. “Gauging time” should not be more than 3 to 5 minutes.
  3. Fill the vicat mould, resting upon a glass plate, with this cement paste.
  4. After filling the mould completely, smoothen the surface of the paste, making it level with top of the mould.
  5. Place the whole assembly (i.e. mould + cement paste + glass plate) under the rod bearing plunger.
  6. Lower the plunger gently so as to touch the surface of the test block and quickly release the plunger allowing it to sink into the paste.
  7. Measure the depth of penetration and record it.
  8. Prepare trial pastes with varying percentages of water content and follow the steps (2 to 7) as described above, until the depth of penetration becomes 33 to 35 mm.

Calculation

Calculate percentage of water (P) by weight of dry cement required to prepare cement paste of standard consistency by following formula, and express it to the first place of decimal.

P = W/C

Where,

W=Quantity of water added

C=Quantity of cement used

Precautions

  • Gauging time should be strictly observed
  • Room temperature should be well maintained as per test requirement.
  • All apparatus used should be clean.
  • The experiment should be performed away from vibrations and other disturbances.

 

 

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