The consistency refers to the flow behavior of fresh concrete. It comes under the category of the rheology of concrete. The normal consistency is determined with the help of a vicat apparatus with a vicat needle. The procedure and the required results for a good quality cement are mentioned.
To determine the quantity of water required to produce a cement paste of standard consistency as per IS: 4031 (Part 4) - 1988.
The standard consistency of a cement paste is defined as that consistency which will permit the Vicat plunger to penetrate to a point 5 to 7mm from the bottom of the Vicat mold.
|Fig.2. Vicat Apparatus with Various Plungers. 10 mm diameter (a) is used for normal consistency|
i) Vicat apparatus conforming to IS: 5513 - 1976ii) Balance, whose permissible variation at a load of 1000g
should be +1.0g
iii) Gauging Trowel conforming to IS: 10086 - 1982
PROCEDUREi) Weight approximately 400g of cement and mix it with a weighed quantity of water. The time of gauging should be between 3 to 5 minutes.
ii) Fill the Vicat mold with paste and level it with a trowel.
iii) Lower the plunger gently till it touches the cement surface.
iv) Release the plunger allowing it to sink into the paste.
v) Note the reading on the gauge.
vi) Repeat the above procedure taking fresh samples of cement and different quantities of water until the reading on the gauge is 5 to 7mm.