(a) Concrete, once place should not be disturbed till the final setting, has taken place. Significance of initial and final setting time: The final setting time should not be more than 10 hours.Thus, the paste has attained such hardness that the needle does not pierce through the paste more than 0.5 mm. (IV) If the needle makes an impression, while the annular collar of the attachment fails to do so, the cement is considered to be finally set. (iii) Lower the attachment to gently cover the surface of the test block. (ii) Replace the square needle by a needle with an annular collar. (i) Take 300 gm of cement and make a cement paste of consistency of 0.85 P. The final setting time is the time elapsed between the moment the water is added to the cement and the time when the paste has completely lost its plasticity and has attained sufficient firmness to resist certain definite pressure.The initial setting time should not be less than 30 minutes for OPC and 60 minutes for low heat cement.(ii) When the needle penetrates only to a depth of 33 to 35 mm from the top (or 5 to 7 mm from the The surface of the test block and quickly release it. (ii) Attach the square needle to the Vicat plunger and lower it gently to make contact with the (i) Take 300 gm of cement and make a cement paste of consistency of 0.85 P It is the time elapsed between the moment that the water is added to the cement, to the time that the paste starts losing its plasticity.This test should be conducted at a constant temperature of 27° +2☌ and a constant humidity of 90%.This percentage is generally denoted by P.That particular percentage of water that allows the plunger to penetrate only to a depth of 33 to 35 from the top (or 5 to 7 mm from the bottom) is known as the percentage of water required to produce a cement paste of normal (standard) consistency.Similarly, conduct the trials with increasingly water/cement ratios till such time the plunger penetrates for a depth of 33 to 35 mm from the top (or 5 to 7 mm from the bottom).Take the reading by noting the depth of penetration of the plunger.The Vicat plunger is brought down to touch the surface of the paste in the mould and quickly released allowing it to sink into the paste by its own weight.The mould is placed under the Vicat plunger.The Vicat mould is filled with the paste, which is levelled off at its top.The time of mixing or gauging should not be less than 3 minutes nor more than 5 minutes and gauging time should be counted from the time of adding water to the dry cement until commencing to fill the mould.Mix a weighed quantity of water (approximately 24% by weight of cement) for the first trial.To prepare the paste, take weighed quantity (300 g) of cement and place it in a crucible.(ii) A needle with an annular collar of 5 mm diameter is used for the final setting time. (i) A square needle with a 1 mm2 cross-section which is attached to the plunger for the initial setting time There are two attachments for the plunger viz: Vicat apparatus assembly consists of a plunger 300 gm in weight with a length of 50 mm and diameter of 10 mm and a mould which is 40 mm deep and 80 mm in diameter. The normal (standard) consistency of a cement paste is defined as that consistency which will permit a Vicat plunger having 10 mm diameter and 50 mm length to penetrate a depth of 33 to 35 mm from the top (or 5 to 7 mm from the bottom) of the mould. Total sulphur content calculated as sulphuric anhydride shall not be more than 2.5% when CA is 5% or less and shall not be more than 3% when C3A is more than 5%.Total loss on ignition shall not be more than 5 per cent.The weight of magnesia shall not be more than 6 per cent.The weight of insoluble residue shall not be more than 4 per cent.The ratio of the percentage of alumina (Al2O3) to that of iron oxide (Fe203) shall not be less than 0.66.Shall not be greater than 1.02 and not less than 0.66. The ratio of the percentage of lime to percentage of silica, alumina, and iron oxide known as Lime Saturation Factor (LSF), when calculated by the formula.(viii) Specific gravity Test (i) Chemical Composition Test Tests on cement are performed in accordance with IS: 4032-1985 and IS: 4031 (Parts 1 to 15)- 1988-99 to assess the following:
#Portland cement specific gravity lab free#
Presence of lumps: Cement should be free from lumps.If a small quantity of cement is thrown in a bucket of water, it should sink and should not float on.If hand is inserted in a bag or heap of cement, it should feel cool.Physical Properties: Cement should feel smooth when rubbed in between the fingers.Colour: Grey color with a light greenish shade.2.3 (iii) (A) Initial Setting Time Test.
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