Standard consistency test is to determine the quantity of water required to produce a cement paste of standard consistency.
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 mould when tested as described below.
Needle for initial setting time.
Needle for the final setting time.
Take 400gm of cement in a pan and a weighted quantity of water in a beaker.Prepare a paste of weighed quantity of cement with a weighted quantity of potable or distilled water,taking care that the time of gauging is not less than 3 minutes,nor more than 5 min,and the gauging shall be completed before any sign of setting occurs
The gauging time shall be counted from the time of adding water to the dry cement until commencing to fill the mould.Fill the vicat mould with this paste, the mould resting upon a non-porous plate.After completely filling the mould ,smoothen the surface of the paste,making it level with the top of the mould
The mould may be slightly shaken to expel the air.The cement paste thus prepared is the test block.Place the test block in the mould together with non porous plate under the rod,bearing the plunger.Lower the plunger gently to touch the surface of the cement paste and quickly release;allowing it to sink into the paste .
This operation shall be done immediately after filling the mould.Prepare trial test specimens with varying percentages of water until plunger penetrates to a point 5 to 7 mm from the bottom of the vicat mould,which is read on the scale.Express the water required as percentage by mass of the dry cement to the first place of the decimal.