61) Excess of silica in the clay

• (a) makes the brick brittle and weak
• (b) makes the brick crack and wrap on drying
• (c) changes the colour of the brick from red to yellow
• (d) improves impermeability and durability of the brick

62) The colour of brick depends upon the amount of iron oxide present in the clay.

• (a) Correct
• (b) Incorrect

63) Which of the following constituent, when present in excess quantity in clay causes the bricks to melt and distort during burning ?

• (a) Alumina
• (b) Silica
• (c) Lime
• (d) Alkalies

64) The alkaline salt present in the bricks, absorbs moisture from the air which on drying

• (a) leaves pores and makes the bricks porous
• (b) leaves high powder deposit on the brick
• (c) makes the bricks brittle and weak
• (d) all of the above

65) The standard size of a masonary brick without mortar is

• (a) 20 × 10 × 10 cm
• (b) 19 × 9 × 9 cm
• (c) 22 × 10 × 9 cm
• (d) 21 × 9 × 4 cm