1) A very small of amount of ........... is useful in making sound cement. If it is in excess, it causes the cement to become unsound

• (a) iron oxide
• (b) silica
• (c) sulphur
• (d) alkali

2) Gypsum is added in the manufacture of Portland cement

• (a) while mixing the raw materials
• (b) during burning in the rotary kiln
• (c) at the beginning of grinding the clinker
• (d) at the end of grinding the clinker into powder

3) Gypsum is added in the manufacture of Portland cement in order to

• (a) shorten the setting time of cement
• (b) lengthen the setting time of cement
• (c) decrease the burning temperature
• (d) decrease the grinding time

4) The cementing property in cement is mainly due to

• (a) lime
• (b) silica
• (c) iron oxide
• (d) alumina

5) The setting and hardening of cement paste is mainly due to the hydration and hydrolysis of

• (a) tri-calcium silicate
• (b) di-calcium silicate
• (c) tri-calcium aluminate
• (d) all of the above