To Determine the Normal Consistency of Ordinary Portland Cement (O.P.C) by Using Vicat’s Apparatus (VA) With Plunger Attachment

To Determine the Normal Consistency of Ordinary Portland Cement (O.P.C) by Using Vicat’s Apparatus (VA) With Plunger Attachment.

INTRODUCTION:

The water requirement for various tests of cement depends on the normal Consistency of the cement, which itself depends upon the compound composition and fineness of the cement. This is a test to estimate the quantity of mixing water to form a paste of normal consistency defined as the percentage water requirement of the cement paste, the viscosity of which will be such that the Vicat’s plunger penetrates up to a point 5 to 7 mm from the bottom of the Vicat’s 4-6 mm 00 5-6mm mould.

MATERIALS REQUIRED:

• Ordinary Portland cement (O.P.C) & water.

APPARATUS REQUIRED:

• Vicat’s apparatus with a plunger (10mm diameter) attachment, mould (Depth 40mm, upper Dia = 100mm, base Dia =150mm), glass plate, Spatula, bowls, and measuring cylinders. Ordinary Portland Cement (O.P.C) & water.

THEORY:

Normal Consistency of Cement: To find the initial & final setting time of cement we prepare a cement paste in which standard consistency is used. It is therefore necessary to determine for any given cement, the water content of the paste which will produce the desired consistency. The consistency of cement is measured by V.A. using a plunger of 10mm diameter. A trial paste of cement and water is mixed in a prescribed manner and placed in the mould. The plunger is then brought into contact with the top surface of the mould in such a way that it just touches the top but does not penetrate it. This plunger is then released and is allowed to penetrate the cement paste under its weight. The penetration of the plunger depends upon the consistency. According to its British standard of measuring (4550 part, 3rd section, 1978) the standard consistency will occur when the plunger penetrates up to the point of (5+1) mm from the bottom of the mould. In O.P.C. water ratio should be from 0.25 to 0.33 and the normal consistency value should range between 26% to 33%.

Procedure.

1. Prepare a cement paste by taking 400g of cement mixed with different water contents.
2. Mix the water into the cement uniformly with the help of a spatula.
3. Now put the cement paste into the mould & support it with the help of a glass plate at the bottom.
4. By using a spatula level the surface of the paste, which is placed in the mould.
5. Place the mould in the V.A.
6. Touch down the surface of the cement paste and note down the initial reading.
7. Release the plunger into the paste and note down its reading.
8. Repeat this whole procedure by reducing the water-cement ratio of 0.38, 0.36, 0.34, 0.32, 0.30, 0.28, and 0.26.
9. Calculate the water content by using the following formula.
   Water Content = W/C Ratio x cement content

Pre-Cautions:

Observations:

Review Questions

1. What are the factors that affect the test of normal consistency?
2. Why normal consistency is determined?
3. State the importance of normal consistency.