Cement - A Concreting Material

Hi,

Fresh Concrete is a material formed by mixing cementing material, coarse aggregates, fine aggregates and water in some definite proportion and which after curing of the required period forms a hard material like stone known as concrete.

Cement: 
Setting times of cement: 
(a) Initial Setting Time: Initial setting time is the time required by cement to start setting. So it is the time which is utilized for the mixing, transporting and placing of the cement concrete.
 Initial setting time is adjusted by mixing Gypsum to cement.
If gypsum is not added then cement will set as soon as water is added to it. BIS code recommends a initial setting time not less than 30 minutes.

(b)Final Setting time: Final setting time is the time after which cement starts gaining strength. BIS code recommends a final setting time not more than 10 hours.

Image source: Google Images

(c) Progressive hardening and strengthening of cement.

Compounds of cement(Bogue's compounds):
After the burning of the raw material there is a formation of the compounds like tri-calcium silicate, di-calcium silicate, Tri-calcium aluminate and tetra-calcium alumino ferrate.

Tricalcium silicate and dicalcium silicate are compounds which are responsible for the early strength and ultimate strength of the cement respectively. Tricalcium aluminate is responsible for almost all the un-desirable properties of cement.

So, the four Bogue's compounds are :
1)Tri-calcium silicate
2)Di-calcium silicate
3)Tri-calcium aluminate
4)Tetra-calcium alumino ferrate

Thanks!

Reference:
1.GK Publishers - GATE 2013 - Civil Engineering.
2. Google Maharaj