46) The workability of cement concrete can be improved by

• (a) increasing the quantity of cement
• (b) increasing the proportion of coarse aggregate
• (c) increasing the quantity of sand
• (d) all of the above

47) The durability of concrete is proportional to

• (a) sand content
• (b) water-cement ratio
• (c) cement-aggregate ratio
• (d) aggregate-water ratio

48) The maximum water-cement ratio for durable concrete is

• (a) 0.2
• (b) 0.4
• (c) 0.6
• (d) 0.8

49) The durability of cement concrete is usually improved by

• (a) increasing the quantity of coarse sand
• (b) increasing the quantity of cement
• (c) decreasing the water-cement ratio
• (d) decreasing the proportion of fine aggregate

50) Which of the following statement is true?

• (a) workability reduces with time
• (b) workability does not reduce with time
• (c) workability remains constant with time
• (d) none of the above