Question

Fill in the blanks with an appropriate option:

The water cement ratio directly affects the strength of the concrete mix. The typical w/c ratio for different grades of concrete varies between ________ to _________ .

1. 0.4 - 0.6
2. 0.9 - 1.2
3. 1.2 - 1.5
4. 1.5 - 2.0

Answer 1

Correct Answer - Option 1 : 0.4 - 0.6

Concepts:

Water cement ratio is the ratio of weight of water to the weight​of cement. Its normal value lies between 0.4 to 0.6 as per IS code 10262 (2009) for nominal mixes.

However, maximum strength is derived at W/C = 0.4 at which minimum capillary cavities are expected to form.

When it decreased to less than 0.4, there is improper consistency and resulting in honeycombed structure. 

If W/C is more than 0.6, the increase in volume of hydrated products will not be able to occupy the space already filled with water. Hence porosity increases and strength decreases.