21) The rocks having alumina and clay as their main constituent are called

• (a) silicious rock
• (b) argillaceous rock
• (c) sedimentary rock
• (d) none of these

22) Which of the following stone is damp-proofing

• (a) Slate
• (b) Marble
• (c) Laterite
• (d) Granite

23) Sandstone consists of

• (a) quartz and lime
• (b) quartz and silica
• (c) quartz, lime and silica
• (d) silica, lime and alumina

24) Marble contains mostly lime and silica.

• (a) True
• (b) False

25) The compressive strength of granite is

• (a) 50 to 70 MN/m2
• (b) 70 to 130 MN/m2
• (c) 130 to 170 MN/m2
• (d) 170 to 200 MN/m2