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Wednesday, March 30, 2011

TEST FOR CONSISTENCY


TEST FOR CONSISTENCY




Aim:

To the standard consistency of the cement

Apparatus Required
1. Vicat apparatus with 10mm plunger and mould
2. Stop watch
3. Measuring jar
4. Trowel
5. Balance

Procedure:

  1. Weigh 400gms of cement on a large non – porous platform and make it a heap with a depression in the centre to hold the mixing water.
  2. Find out the volume of water to give a percentage of 25 by weight of dry cement and this amount carefully to the cement.
  3. Mix the cement and water together thoroughly. The process of mixing shall include kneading and threading. The total time elapsed from the moment of adding water to the moment when mixing is completed shall not be less that four minutes.
  4. Fill the mould completely with the cement paste and strike off the surplus paste and level with the top of the mould. Slightly tap the mould with the content to drive out any trapped air.
  5. Keep the mould under the vicat plunger such that the plunger touches the surfaces of cement paste and support the moving rod by the plunger of the dash pot and then release the rod.
  6. After the plunger has come to rest, note the reading against the index.
  7. Repeat the experiment with trial paste varying the percentage of water till the plunger comes to rest between 5mm and 7mm from the bottom of the mould.
  8. Tabulate observations and report the amount of water to permit the plunger to come to rest between 5mm and 7mm from the bottom as a percentage of dry weight of cement and express this as the percentage for standard consistency.
  
Result:

The standard consistency of the given cement paste is =




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