121) The dry process of mixing is usually employed in the manufacture of Portland cement when the raw material is

• (a) blast furnace slag
• (b) chalk
• (c) clay
• (d) all of these

122) The clinker is formed at a temperature of

• (a) 500ºC
• (b) 1000ºC
• (c) 1200ºC
• (d) 1500ºC

123) The amount of gypsum, usually, added in the manufacture of cement is

• (a) 0.1 to 0.5%
• (b) 0.5 to 1%
• (c) 1 to 3%
• (d) 3 to 5%

124) Which of the following compounds of portland cement reacts immediately with water and sets early?

• (a) dicalcium silicate
• (b) tetra calcium alumino ferrite
• (c) triclacium aluminate
• (d) tricalcium silicate

125) The percentage of sulphur trioxide in ordinary portland cement is

• (a) 3.5 % to 9 %
• (b) 17 % to 25 %
• (c) 1 % to 2 %
• (d) 60 % to 65 %