Specific gravity of cement viva questions and answeres.
viva questions and answeres.
1. Define specific gravity of cement ?
The specific gravity of cement is the ratio of the weight of a given volume of cement to the weight of an equal volume of water.
2. What are the factors affecting the specific gravity of cement ?
Factors affecting specific gravity of cement are
- Materials used in manufacture of cement like limestone, shells, chalk, shale, clay, slate, blast furnace slag, silica sand, and iron ore.
- Humidity.
- Moisture content
- Temperature and Pressure.
3. Why is kerosene used instead of water in the specific gravity test ?
Cement reacts with water in exothermic reaction forming calcium silicate hydrate (C-S-H) and calcium hydroxide ca(OH)2. The cement reaction with water hinders the accuracy of the test. Hence, cement specific gravity is determined with reference to a non-reactive liquid like kerosene or diesel.
4. What is the use of specific gravity of cement ?
The specific gravity test is used in quality assessment of cement. Specific gravity of some deleterious materials will be low which is unsuitable for used in concrete mix. The high moisture containing cement will have high specific gravity which also unsuitable for application in building.
5. Is specific gravity of cement constant ?
Specific gravity varies from the time of production to application in structures. When the cement bag is exposed to air containing moisture, its specific gravity goes on increasing. The finer cement particles absorb water from air and solidify.
6. List the apparatus used in specific gravity of cement test ?
The apparatus used in specific gravity of cement are Le-Chatelier Flask, trowel, measuring jar, weighing balance, plate, rubber glove and kerosene.
7. If the air bubbles are not completely removed from the flask, how the results will be affected ?
Cement contains finely grained particles of micron size. Air gets entrapped between these particles, completely removing from the flask is impossible. The entrapped air will result in error measurement of equal volume of cement and kerosene.
8. Why is it necessary to keep the temperature of test chamber constant during this experiment ?
Cement is made up of like limestone, shells, chalk, shale, clay, slate, blast furnace slag, silica sand, and iron ore. These materials volume will be different for different temperature and pressure. Maintaining a constant temperature and pressure is necessary to ensure the consistency of test.
9. What are precautions need to be taken while performing specific gravity cement test?
- Only kerosene which is free of water is to be used.
- All air bubbles shall be eliminated in filling the apparatus and inserting the stopper.
- Weighing is to be done quickly after filling the apparatus and shall be accurate to 0.1 mg.
- Precautions are to be taken to prevent expansion and overflow of the contents resulting from the heat of the hand when wiping the surface of the apparatus.
Refrence
1. Brooks, J.J & Neville A. M. (2019). Concrete Technology (2nd ed.). Pearson Publishers Pvt Ltd. click here
2. Shetty, M. S & Jain, A. K. ( 2018). Concrete Technology: Theory And Practice (8thed.).S Chand Publishers Pvt Ltd.
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