The approximate amount of silica present in standard cement is:

Correct Answer: 17-25%

Subject: geography

60-65%
17-25%
3-8%
1-3%

Explanation: • Cement contains between 17% and 25% Silica. • Lime is the largest component at 60-65%. • Alumina is 3-8% and Magnesia is 1-3%. • Options A, C, and D represent Lime, Alumina, and Magnesia respectively. • Trick: 'Lime is maximum (60+), Silica is second (approx 20%)'. • Cement was first introduced in England in 1824 by Joseph Aspdin.