Determination of the normal consistency of hydraulic cement

Standard test method for the determination of the normal consistency of hydraulic cement.

(ASTM C 187-04)

Purpose:

  • To determine of the normal consistancy of hydraulic cement.
  • To determine the amount of water required to prepare hydrualic cement pastes for testing.

Apparatus:

  • Vicat’s apparatus
  • Plunger(dia = 10mm, length = 50mm)
  • Weighing balance
  • Glass plate and trowel
  • Spatula and safety gloves

Related Theory:

Consistency:

The thickness or viscosity of the cement paste is called consistency. It is the ratio of thickness of water to the mass of cement expressed as percentage.

Standard cement paste:

It is the cement paste for which the 10mm diameter plunger in a standard VICAT’S test penetrates to such an extent that its distance from the bottom is 10±1mm. the normal consistency of cement is 28%.

Normal consistency:

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

Test Specifications:

Air temperature:

  • Air temperature 20 – 27.5 ͦ C
  • Water temperature 23 ± 2 ͦ C

Humidity:

  • Humidity should not be less than 50%.

Procedure:

  • Take 650g of cement and mix it with 26% of water by weight of dry cement. The Gauging time should not be more than 4min ±15 sec.
  • Fill the Vicat mould with paste and level it with trowel.
  • Lower the plunger gently till it touches the cement surface.
  • Release the plunger allowing it to sink into the paste.
  • Note the reading on the gauge.
  • Repeat the above procedure taking fresh samples of cement and different quantities of water until the reading on the gauge is 10±1mm.

Precautions:

  • Gauging time should be strictly observed
  • Room temp. 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.

Observation and calculation:

Weight of cement= 650g

Sr. No. Weight of cement (g) Percentage of water by weight of dry cement (g) W/C Vicat penetration (mm)
1 650 175.5 0.27 16
2 650 169 0.26 11
3 650 169 0.26 10

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 11mm
  • The standard penetration is observed at 26% water by weight which is the between the range of ASTM
  • 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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