SSC JE Civil Engineering 30-Oct-2020 Shift 2 Paper

Concept:The setting and hardening of cement after addition of water is due to hydration of some of the constituent compounds of cement such as Tricalcium aluminate, Tricalcium silicate, Dicalcium silicate, and Tetra calcium aluminoferrite.

Tricalcium silicate $\left(3\mathrm{Ca}.{\mathrm{SiO}}_2\right)$ : This is also called as Alite. This is also responsible for the early strength of the concrete. The cement that has more C­­­­3S content is good for cold weather concreting. The heat of hydration is 500 J/Cal.

Dicalcium Silicate $\left(2\mathrm{CaO}.{\mathrm{SiO}}_2\right)$ : This compound will undergo reaction slowly. It is responsible for the progressive strength of concrete. This is also called as Belite. The heat of hydration is 260 J/Cal.

Tricalcium aluminate $\left(3\mathrm{CaO}.{\mathrm{Al}}_2{\mathrm{O}}_3\right)$ : Celite is the quickest one to react when the water is added to the cement. It is responsible for the flash setting. The increase of this content will help in the manufacture of Quick Setting Cement. The heat of hydration is 865 J/Cal.

Tetra calcium Alumino ferrite $\left(4\mathrm{CaO}.{\mathrm{Al}}_{2.}{\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ : This is called as Felite. The heat of hydration is 420 J/Cal. It has the poorest cementing value but it responsible for long term gain of strength of the cement.