COMPARISON BETWEEN CEMENT AND LIME

Although cement and lime are cementing materials, they have different features and properties:

1. The colour of cement is grey, whereas lime is white or greyish white in colour.
2. Lime slakes immediately when it comes into contact with water, but cement does not slake when it comes into contact with water.
3. Cement paste sets during a definite period of time, whereas lime takes more time to set.
4. Cements are of different types, a suitable one can be selected to fit in for a given environment. But lime can not fit in for all environments.
5. Cement has extremely high strength compared to lime.
6. Lime has a better flexibility property than cement which acts as a rigid material.

SALIENT POINTS

1. Cement is made from limestone and clay in a powder form, which on addition of the requisite quantity of water is capable of hardening.
2. The main ingredients in the manufacture of cement are lime, silica, alumina and other oxides.
3. Lime is the main constituent which contributes to the strength. Its proportion has to be properly maintained so as to make the cement sound and strong.
4. Silica contributes to the strength of cement due to the formation of dicalcium and tricalcium silicates.
5. The quick-setting quality is imparted by alumina to the cement.
6. Iron oxide provides colour, hardness and strength to the cement.
7. Correct quantity of magnesium oxide imparts hardness and colour to the cement.
8. Sulphur trioxide makes the cement sound when present in small quantities.
9. The fineness of cement is a measure of the size of particles of cement. It is expressed as the specific surface of cement.
10. When water is added to cement and mixed, it forms a paste, which gradually becomes less plastic and finally forms a hard material. The time taken for the entire process is called the setting time, which is divided into the initial setting time and the final setting time.
11. Initial setting time is regarded as the time when the cement paste losses its plasticity.
12. Final setting time is the time elapsed between the time of water addition to the cement to the time when the paste has completely lost its plasticity.
13. Cement that has less expansive qualities when mixed with water is termed as the soundness.
14. Strength of cement is generally assessed from compression tests on cement-mortar cubes (1:3) with an area of 500 mm².
15. Reaction of silicates and aluminates of cement with water forms a binding medium which solidifies into a hardened mass which is termed as hydration.
16. Heat of hydration is defined as the quantity of heat (in calories/gram of hydrated cement) liberated on complete hydration at a particular temperature.
17. Specific gravity of Ordinary Portland Cement is around 3.15.
18. Loss on ignition is the loss in weight due to ignition of cement at high temperature. Loss in weight is a measure of the freshness of cement.
19. An inactive part of cement is called the insoluble residue.
20. Production of cement is performed in three stages, viz., (i) Mixing of raw materials in the correct proportion, (ii) Burning of the mixture and (iii) Grinding.
21. There are two processes in the manufacture of cement, viz., the wet process and the dry process, depending upon whether the mixing and grinding of raw materials are done in wet or dry conditions.
22. Major complex compounds formed due to chemical compositions are: tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite.
23. Grades of Ordinary Portland Cement are: 33-Grade, 43-Grade and 53-Grade.