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Testing of cements


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Testing of cements

  1. 1. Free Powerpoint Templates Page 1 Free Powerpoint Templates TESTING OF CEMENT
  3. 3. Free Powerpoint Templates Page 3  Open the bag and take a good look at the cement, then it should not contain any visible lumps.  Colour of cement should be greenish grey.  Should get cool feeling when thrusted.  When we touch the cement, it should give a smooth &not a gritty feeling.  When we throw the cement on a bucket full of water before it sinks the particles should flow.  When we make a stiff paste of cement & cut it with sharp edges & kept on a glass plate under water there wont be any disturbance to the shape& should get strength after 24hours. FIELD TEST
  4. 4. Free Powerpoint Templates Page 4 LABORATORY TESTS  Fineness test  Standard consistency test  Setting time test  Strength test  Soundness test  Heat of hydration test  Chemical composition test
  5. 5. Free Powerpoint Templates Page 5 • The fineness of cement has an important bearing on the rate of hydration, rate of gain of strength, evolution of heat. • Finer cement offers greater surface area. • Disadvantage of fine grinding is that it is susceptible to air set & early deterioration. • Maximum no. of particles in a sample of cement<100microns. • The smallest particle should have a size if 1.5microns. • Large particle should have a size of 10microns. FINENESS TEST
  6. 6. Free Powerpoint Templates Page 6 Fineness of cement is tested in two ways. • By sieving. • By determination specific surface by air permeability
  7. 7. Free Powerpoint Templates Page 7 • Take correctly 100grams of cement on a standard IS sieve No.9 • Break down the air-set lumps & sieve it &weigh it. • This weight shall not exceed 10% for ordinary cement. • Sieve test is rarely used. • The weight of the residue should not exceed 10% for ordinary cement. SIEVE TEST
  8. 8. Free Powerpoint Templates Page 8  Principle of air permeability method is in observing the time taken for a fixed quantity of air to flow through compacted cement bed of specified dimension and porosity. PROCEDURE:  cement required to make a cement bed of porosity 0.475 is calculated.  pass on the air slowly at constant velocity. Adjust the rate of air flow until the flowmeter shows a difference in level of 30-50cm. Repeat these observation for constant h1/h2. specified air flow. STANDARD PERMEABILITY TEST
  9. 9. Free Powerpoint Templates Page 9
  10. 10. Free Powerpoint Templates Page 10 The 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 to a depth of 33- 35 mm from the top of the mould. STATNDARD CONSISTENCY TEST USE Used to find out the percentage of water required to produce a cement paste of standard consistency. This is also called normal consistency (CPNC).
  11. 11. Free Powerpoint Templates Page 11 •For first trial, take about 500gms of cement & water of r%. •Fill it in Vicat’s mould with in 3-5min. •After filling, shake the mould to expel air. •A standard plunger, 10 mm diameter, 50 mm long is attached and brought down to touch the surface of the paste and quickly released. •Note the reading according to depth of penetration of the plunger.
  12. 12. Free Powerpoint Templates Page 12 •Conduct trials continuously by taking different water cement ratios till the plunger penetrates for a depth of 33-35mm from top. • This particular percentage is known as percentage of water required to produce cement paste of standard consistency. This is usually denoted as ‘P’. SUITABLE CONDITIONS: Conducted in a constant temperature of 27º±2ºC. Constant Humidity 90%.
  13. 13. Free Powerpoint Templates Page 13 An arbitraty division has been made for the setting time of cement as  Initial setting time  Final setting time. SETTING TIME TEST
  14. 14. Free Powerpoint Templates Page 14  The time elapsed between the moment that the water is added to the cement, to the time that the paste starts losing its plasticity.  Normally a minimum of 30min has maintained for mixing & handling operations.  It should not be less than 30min. INITIAL SETTING TIME
  15. 15. Free Powerpoint Templates Page 15 FINAL SETTING TIME  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.  It should not exceed 10hours. So that it is avoided from least vulnerable to damages from external activities.
  16. 16. Free Powerpoint Templates Page 16 PROCEDURE:  Vicat apparatus is used for finding the setting time  Take 500gms of cement and add about 0.85p  The paste should be filled within 3-5 minutes.  Initial and final setting time is noted.
  17. 17. Free Powerpoint Templates Page 17 STRENGTH TEST  This is the most important of all properties of hardened cement.  Due to excessive shrinkage and cracking the strength tests are not made on neat cement paste.  Standard sand is used for finding the strength of cement.
  18. 18. Free Powerpoint Templates Page 18  Take sand and cement (i.e., 1:3 ratio of cement and sand) Mix them for 1min, then add water of quantity(P/4)+3.0%.  Mix three ingredients thoroughly until the mixture is of uniform colour.  The time of mixing should not be<3min and >4min.Then the mortar is filled into a cube mould of 7.06cm. Compact the mortar.  Keep the compacted cube in the mould at a temperature of 27°C ± 2°C and at least 90 per cent relative humidity for 24 hours.  After 24hours the cubes are removed & immersed in clean fresh water until taken for testing.
  19. 19. Free Powerpoint Templates Page 19 SOUNDNESS TEST  It is very important that the cement after setting shall not undergo any appreciable change of volume.  This test is to ensure that the cement does not show any subsequent expansions.  The unsoundness in cement is due to the presence of excess of lime combined with acidic oxide at the kiln.  This is due to high proportion of magnesia & calcium sulphate.  Therefore magnesia content in cement is limited to 6%.
  20. 20. Free Powerpoint Templates Page 20
  21. 21. Free Powerpoint Templates Page 21 HEAT OF HYDRATION  cement with water is an exothermic reaction  Heat of hydration will be found out using thermos flask  About 120 calories of heat is generated in the hydration of 1 gm of cement  Temperature rise of about 50°C is observed and this causes serious expansion of the body of dam.
  22. 22. Free Powerpoint Templates Page 22 To avoid this :  Lean mix  puzzolanic cement  Artificial cooling materials  incorporation of pipe system in the body of dam and applying cold brine solutions. Tests :  To be carried out only in low heat cement  vaccum flask method for short duration and adiabatic calorimeter for longer period  should not exceed 65 cal/gm at 7 days and should be less than 75 cal/gm at 28 days
  23. 23. Free Powerpoint Templates Page 23 CHEMICAL COMPOSITION TEST Ratio of percentage of lime to percentage of silica,alumina and iron oxide when calculated by Cao-0.7So3 ————————————— 2.8SiO ₂ +1.2Al ₂ O ₃+0.65Fe ₂ O ₃ Should not be greater than 1.02 and not less than 0.66 This is called LIME SATURATION FACTOR PERCENT