Question

In portland cement, the percentage of $A{l}_2{O}_3$ is:

• A. $50\%$
• B. $20\%$
• C. $5\%$
• D. $10\%$

Answer 1

Answer: (C)

$5\%$

The chief chemical constituents of Portland cement are as follows:

Lime $\left(CaO\right)$ ------------ 60 to 67%

Silica $\left(Si{O}_2\right)$ --------- 17 to 25%

Alumina $\left(A{l}_2{O}_3\right)$ ------ 3 to 8%

Iron oxide $\left(F{e}_2{O}_3\right)$ ------ 0.5 to 6%

Magnesia $\left(MgO\right)$ ------ 0.1 to 4%

Sulphur trioxide $\left(S{O}_3\right)$ ------- 1 to 3%

Soda and/or Potash $(N{a}_{2}O+K_{2}O)$ -------- 0.5 to 1.3%

So, option C is the correct answer.