Water cement ratio of Concrete !! How to choose W/C ratio?

Water Cement ratio is the relative weight of water to that of cement in the concrete mixture. It is also denoted by W/C ration.

In Concrete, the water-cement ratio determines the final properties of the concrete. The Water-cement ratio is the most important factor behind the strength of concrete.

If a concrete mixture has a high water-cement ratio then it will be workable (easy to work with that concrete) but it will be less stronger as compared to the same concrete with less water-cement ration.

Less workable concrete is stronger. So, while working with cement, the ratio of water must be kept according to the nature of work to get the best result on strength as well as more workable.

You cannot have free choice for choosing the ratio of W/C because the W/C ratio needs about 0.23 to complete the hydration of cement.

If only 23% of water is added while mixing, the concrete will not be workable due to less water. So, we need to use add additional water for workability but with in limit so the strength should not be affected.

In normal concrete, W/C ratio is kept between 0.35 – 0.40 because in this ratio we get good workability without losing a lot of strength.

With the increase in W/C ratio the workability of concrete increases but after one optimum point that workability decreases due to the segregation problem in aggregate and bleeding problems in cement paste.

Relation between Water Cement ratio (W/C) and compressive strength of concrete:

  1. To increases the compressive strength of concrete you need to take a low w/c ratio.
  2. W/C ratio affects the permeability. So less W/c ration concrete is less permeable.
  3. The water-cement ration affects the drying shrinkage and cracking of concrete. If you kept a low W/C ration the drying shrinkage and cracking of concrete will low.
  4. If the w/c ratio chooses by considering workability and strength then there will be less volume change from drying and wetting.
  5. With a low W/C ratio the weather resistance of concrete increases.
  6. W/c ratio determines the concrete and reinforcement bond.

Also, the Curing of concrete helps to gain the required strength and helps to decrease the permeability of hardened concrete.

Also, read the article on Why the curing of concrete is required and different methods of the curing.

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