Compressive strength test of cement

AIM:

Determine the compressive strength of cement as per IS 4031 (Part 6) 1988.

APPARATUS:

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Compressive Strength Cement Testing machine
  1. Vibrating machine confirming to IS: 10080 – 1982.
  2. Poking rod confirming to IS: 10080-1982.
  3. Cube moulds shall be of 70.60 mm
  4. size confirming to IS: 10080-1982.
    Gauging trowel having steel blade 100 to 150 mm in length with straight edge
    weighing 210 + 10 gms.
  5. Balance of capacity 10 Kg and sensitivity 1 gram.

AGE AT TEST:

Tests should be done at recognised ages of the test specimens, usually being 7 and 28 days. The ages should be calculated from the time of the addition of water to the drying of ingredients.

PROCEDURE:

  • Unless otherwise specified this test shall be conducted at a temperature 270 + 20C.
  • Weigh the material required for each cube separately.
  • The quantity of cement, standard sand and water required for each cube are as follows
    Cement = 200gms
    2mm to 1mm – 200gms
    Standard Sand = 600gms 1mm to 500mic – 200gms
    Conforming to IS: 650 –1991. 500mic to 90mic – 200gms
    Water =(P/ 4+ 3) Percentage of combined mass of cement and sand.
    P is the consistency of cement as per IS: 4031 (Part 4) 1988.
  • Place on a nonporous plate, a mixture cement and standard sand.
  • Mix it dry with a trowel for one minute and then with water until the mixture is of uniform colour.
  • The time of mixing shall in any event be not less than 3 minutes and should be the time taken to obtain uniform colour exceeds 4 minutes.
  • In assembling the moulds ready for use, cover the joints between the halves of the
    mould with a thin film of petroleum jelly and apply a similar coating of petroleum jelly between the contact surface of the bottom of the mould and base plate in order to ensure that no water escapes during vibration.
  • Place the assembled mould on the table of the vibration machine and hold it firmly
    in position by means of suitable clamp, attach a hopper of suitable size and shape
    securely at the top of the mould to facilitate filling and hopper shall not be removed until the completion of vibration period.
  • Immediately after fixing the mould in the vibrating machine, place the mortar in the cube mould and prod with the rod.
  • Prod the mortar 20 times in about 8 seconds to ensure elimination of entrapped air
    and honey combing.
  • Place the remaining mortar in the cube mould and prod again as specified for the
    first layer and then compact the mortar by vibration.
  • The period of vibration shall be two minutes at the specified speed of 12000 + 400
    vibrations per minute.
  • Remove the mould from the vibrating machine and cut of the excess mortar with a
    straight edge.
  • Store the test specimens in a place free from vibration, in moist air of at least 90
    percent relative humidity and at a temperature of 27 + 20C for 24 + 1/2 hours from
    the addition of water to the dry ingredients.
  • After this period, mark the specimens and remove from the moulds and unless
    required for test within 24 hours.
  • Immediately submerge the cubes in a clean, fresh water or saturated lime solution
    and keep there until taken out just prior to test.
  • Renew the water or solution in which the specimens are submerged for every seven days, and the temperature of water is maintained with the specified limits.
  • Conduct testing at recognized ages of the specimens, the most usual being 7 and
    28 days.
  • When it may be necessary to obtain the early strength, tests may be conducted at
    the age of 72 + 2 hours.
  • Calculate the ages from the addition of water to the dry ingredients.\Test at least three specimens preferably from different batches at each selected
    age.

CALCULATIONS:

Compressive strength =(Load/Cross sectional area of the specimen)/N / mm²

RESULTS:

Report the individual and the mean results to the second decimal and express in N/ mm²

PRECAUTIONS:-

  • The time of mixing is very important and in no case shall not be less than 3minutes. 
  • Apply the Greece to the mould (inner side of mould)
  • The Temperature of water should be maintained at 27 +/- 2 oC.
  • Mould should be immersed in water fully.
  • The cube should be tested immediately after taking out of water. 
  • Cube should be tested on their side not on their face. 

 

 

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8 Comments

  1. I need tests for X-ray fluorescent, specific gravity, heat of hydration and Scan Electron microscopy on cements

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