To determine the initial setting time of cement. This test is required to understand the time cement takes for initial setting between mixing and transporting and placing of concrete.
Vicat apparatus, needle for initial setting time, stop watch.
Take 400 gm of cement in a pan. Prepare a neat cement paste by adding 0.85 times the water required to give a paste of standard consistency by the previous test. Start a stop watch at the instant when water is added to the cement. Keep the vicat mould on a non porous plate and fill the cement paste in it. After completely filling the mould, it should be shaken slightly to expel the air. Smooth off the surface of the paste making it level with the top of the mould.
Place the test block and the non porous plate under the rod bearing the needle having 1sq.mm.cross section. Lower the needle gently till in contact with the surface of the test block and quickly release allowing it to penetrate in to the test block.(When vicat apparatus with dash pot is used, place the mould filled with cement paste and the non absorbent plate on the base of the vicat apparatus .Raise the in the beginning the needle will completely pierce the block. Repeat the procedure until the needle fails to pierce block for 5+-0.5mm measured from the bottom of the mould. The period elapsing between the time when water is added to the cement and the time at which the needle fails to pierce the test block by 5+-0.5mm is the initial testing time.
The initial setting time of the given sample of cement=……………..min
OBSERVATIONS AND CALCULATIONS
Weight of cement taken (g) = _________
Quantity of water added to cement = 0.85 X Quantity of water required for standard consistency = _______
|SL. NO.||TIME (min)|
(measured from the instant of adding water to cement)
|DEPTH OF PENETRATION|