Cement is one of the most important building material of the present time. It is a dirty greyish...
0Cement is one of the most important building material of the present time. It is a dirty greyish heavy powder containing calcium aluminates and silicates. The important raw materials needed for the manufacture of cement are, limestone, clay and gypsum. The main step in the manufacture of cement is the heating of raw meal or slurry in the rotary kiln at a very high temperature \( 1400-1600^{\circ} \mathrm{C} \). Finally 2 or \( 3 \% \) gypsum is added.
When cement is mixed with water and left as such for some time, it becomes a hard mass. This is known as setting of cement. It is believed that various aluminates and silicates present in the cement form hydrates with water which separate in the form of gel. The gels formed start losing water partly by evaporation and partly by forming hydrates with unhydrated constituents. This results in the formation of a hard mass.
Setting of cement is :
(A) exothermic reaction
(B) endothermic reaction
(C) hydration process
(D) none of these
ЁЯУ▓PW App Link - https://bit.ly/YTAI_PWAP
ЁЯМРPW Website - https://www.pw.live