For a good quality cement, the ratio of lime to the total of the...

Cement is made by strongly heating a mixture of lime stone and clay in a rotatory kiln. Lime stone and clay are finely powdered, and a little water is added. For a good quality cement, the ratio of silica (${SiO}_{2}$) to alumina (${Al}_{2}{O}_{3}$) should be between $2 . 5$ and $4$ and the ratio of lime ($CaO$) to the total of the oxides of silicon (${SiO}_{2}$) aluminium (${Al}_{2}{O}_{3}$) and iron (${Fe}_{2}{O}_{3}$) should be as close as possible to $2$. If lime is in excess, the cement cracks during setting. On the other hand, if lime is less than the required, the cement is weak in strength. Therefore, a proper composition of cement must be maintained to get cement of good quality.