If you are working in a small to medium size company then you must see this scenario every day.
Every contract labour working on concrete placement tries to pour extra water to the concrete. Is that what makes them happy? Absolutely.
Because with the optimum watercement ratio the concrete mixture or cement mortar will look dense and weigh more to transfer (via cementpond). So they all try to add water to them which makes the concrete less hardened and the cement pond looks full which is easy to transport.
Is this correct? Absolutely not. Adding too much water affects the quality of the concrete or cement mortar.
In this post, we are going to discuss
 What is the watercement ratio?
 Role of Water in Concrete
 Effect of watercement ratio on concrete strength
 Workability of concrete
 How to calculate the watercement ratio
 Minimum watercement ratio table
 Water cement ratio formula
 Example Calculation of water quantity for concrete
What is Water Cement Ratio?
The ratio between the water weight to the cement weight is known as the watercement ratio or W/C Ratio.
Role of Water in Concrete or Cement Mortar
As you all know concrete is a macro content which consists of Cement, Sand and coarse aggregates.
To make a concrete mixture to withstand required compressive strength, Cement needs to react with other micro materials such as sand, coarse aggregate.
Water, when mixed with cement, reacts and forms cement paste (chemical process) which will bind the other micro materials to form a hardened concrete.
Adding water to the concrete beyond this limit will affect the cement paste strength and eventually breaks the concrete strength.
Effect of Water Cement Ratio on Concrete Strength
As stated earlier adding too much water will affect the concrete quality. The coarse aggregate and fine aggregates will freely move in the concrete which will be resulted in
 Aggregate segregation – The density of aggregates high compared to water. So the extra water will float above the concrete and make the uneven coarse aggregate segregation.
 Concrete Honeycomb formation – The excess water content will be vaporized after placing the concrete and forms honeycomb formation.
Minimum Water Cement Ratio Table – IS code 10262
Water is the critical element that makes or breaks the concrete quality. To obtain perfect concrete, we need the minimum watercement ratio
Exposure  Plain Cement Concrete  Reinforced Cement Concrete  
IS 10262  Minimum Cement Content  Water Cement Ratio  Grade  Minimum Cement Content  Water Cement Ratio  Grade 
Mild  220  0.6  300  0.55  M_{20}  
Moderate  240  0.6  M_{15}  300  0.5  M_{25} 
Severe  250  0.5  M_{20}  320  0.45  M_{30} 
Very Severe  260  0.45  M_{20}  340  0.45  M_{35} 
Extreme  280  0.4  M_{25}  360  0.4  M_{40} 
How to Calculate Water Cement Ratio?

Example Calculation of water quantity for concrete
This calculation applies only for the nominal mix.
From Example, Calculate Water Cement Ratio for M_{20} RCC
From the table, we know the watercement ratio is 0.55 for M_{20}
We take 0.55 as a ratio of W/C. M_{20} is a volumetric mixing, so we have to take 0.55 of water in volume of cement.
Therefore, the unit weight of cement = 1440 kg/m^{3}.
Quantity of water = 0.55 x 50/1.44 = 19.1 Liters (1 bag cement = 50 Kg)
So the required quantity of water is 19.1 Liters per cement bag.
For Easy calculation Refer Unit weight of materials.
6 Comments
Thanks for useful knowledge…..
Thank you!. Stay in connect
Thanks for the information..
Glad!… you are welcome.
This does not look correct. Looking at some other sites, it seems that the ratio is specified as a volumetric calculation, not by mass. Since the cement has a density of 1.44, the water added should be 0.55 x 50 / 1.44 (because 50kg of cement occupies 50/1.44 litres of volume). I would be interested in your comments.
Hello John, Thanks for the suggestion. You are right. We have updated the same.