Question

Which one of the following is an important ingredients of Portland cement?

• A. Dicalcium silicate
• B. Tricalcium aluminate
• C. Monocalcium silicate
• D. (a) and (b) above.

Answer 1

The correct option is D (a) and (b) above.

The important ingredients of Portland cement are Dicalcium silicate $\left(C{a}_{2}Si{O}_4\right)$, Tricalcium silicate $\left(C{a}_{3}Si{O}_5\right)$, Tricalcium aluminate $\left(C{a}_{3}A{l}_2{O}_6\right)$,
Hence, the correct answer is option (d).

Theory
Portland Cement:
Cement is an important building material. It was first introduced in England in 1824 by Joseph Aspdin. It is also called Portland cement because it resembles the natural limestone quarried in the Isle of Portland, England.

For a good quality cement,
$\frac{Si{O}_2}{A{l}_2{O}_3}=2.5-4$
$\frac{CaO}{Si{O}_2+A{l}_2{O}_3+F{e}_2{O}_3}$~2

Composition of Portland cement:
$CaO50-60\%$
$Si{O}_{2}20-25\%$
$A{l}_2{O}_{3}5-10\%$
$MgO2-3\%$
$F{e}_2{O}_{3}1-2\%$
$S{O}_{3}1-2\%$

Preparation:
Strong heating of Clay and lime. They fuse and react to form ‘cement clinker’. This clinker is mixed with 2-3% by weight of gypsum to form cement.

Important ingredients of Portland cement:
Dicalcium silicate $C{a}_{2}Si{O}_{4}26\%$
Tricalcium silicate$C{a}_{3}Si{O}_{5}51\%$
Tricalcium aluminate$C{a}_{3}A{l}_2{O}_{6}11\%$
The setting of cement:
When mixed with water, the setting of cement takes place to give a hard mass due to the hydration of the molecules of the constituents and their rearrangement. The purpose of adding gypsum is only to slow down the process of setting the cement so that it gets sufficiently hardened.
Uses:
It is used in concrete and reinforced concrete, in plastering, and in the construction of bridges, dams, and buildings.