We know that cement is used for binding the aggregates.So the ingredients in cement should have the property of binding the aggregates.So, Here I am going to write about the composition of cement.
The binding material used in concrete is a mixture of cement and fine aggregate.We call it as mortar.They should have a good adhesive property with aggregates.
The compressive strength of concrete depends upon two factors,
- Strength of aggregate
- Strength of mortar(cement and sand in mix design)
If anyone of these factors fails, then the whole concrete material could fail.We know that the aggregate has higher compressive strength than mortar.
So in order to resist the compressive load acting on the structure, we should make higher compressive strength mortar.
In order to make higher compressive strength mortar.We should use cement which gives high compressive strength.So we must aware the composition of cement used for making concrete for maintaining the structure.
Cement composition or ingredients of cement
Cement contains mainly two units, argillaceous and calcareous materials.Clay is predominating in Argillaceous and lime is predominating in calcareous.
Mainly ingredients of cement consist of lime, clay, iron oxide, silica, alumina etc.At high temperature, they combined with each other to form more complex compounds called bogues compounds.
Coming to our main topic.The different cement composition is described below,
The lime is one of the main cement composition and the chemical formula of lime is Cao.In traditional structures, lime had been used instead of cement, because there is no cement discovered in that period.
The excess amount of lime causes expansion of concrete and consequently results losing its strength.So the excess amount of lime causes a linear decline in compressive strength.
Silica provides strength to the cement by the production of di-calcium silicate and tri-calcium silicate.With the addition of silica, the strength will increase.However, the setting increases with the addition of silica.
The chemical formula of silica is SiO2.Silica in the main ingredient in cement used for making cement.
Alumina provides a quick setting quality to the cement.It reduces the clinkering temperature and excess usage of alumina results in weaker cement.
Iron oxide gives hardness and colour to the cement.The colour of cement should be grey
Calcium Sulphate increases the initial setting time of concrete.
The last composition of cement is magnesia.Magnesia provides colour and hardness to the cement.The more amount of magnesia causes the cement to become unsound.
The below table shows the percentage of ingredient in cement used
So these are the cement composition used for the manufacture of cement.Hope you learned it well.