In this post, you will get water-cement ratio formula, water-cement ratio table, and calculation for Mortar. The water cement ratio is the ratio between the weight of water to the weight of cement used in the concrete mix. or the amount of water that we used in the cement concrete.
It is one of the major factors but not the only one influencing the strength of concrete. It is responsible mainly for the porosity of the hardest cement paste.
It was first developed by Duff A. Abrams in 1918. Abram’s equation for water cement ratio:
Where,
S = Compressive Strength
W/C = Water Cement Ratio
Why we should maintain water-cement ratio?
We know that the water-cement ratio directly affects the strength of concrete. If we use the limited amount of water for concrete then it will decrease the workability of concrete and so it will cause honeycomb in concrete.
If we add more water than required then it may cause bleeding in concrete which reduces the strength of concrete in a bad manner.
Water cement ratio Table
Calculation for Water Cement Ratio
For proper workability, the water-cement ratio varies from 0.4–0.6. However, maximum strength is derived at w/c = 0.4 at which minimum capillary are expected to form.
In arriving at the water-cement ratio values it is assumed that aggregates are saturated with the surfaces in dry condition. Suitable adjustment should be made for dry aggregates, Sometimes cement-water ratio versus strength.
Normally, water cement ratio is calculated as :
Water cement ratio formula
Water-Cement Ratio = Weight of water/ Weight of cement.
Let us calculate water quantity for 1 bag of cement.
1 bag of cement = 50 kg
Assuming W/C ratio = 0.50
Water-Cement Ratio = Quantity of water/ Quantity of cement
Quantity of water = W/C ratio * Quantity of cement
Quantity of water= 0.50 * 50
= 25 kg (ltr).
Water Cement Ratio in Mortar:
Mortar may be defined as a paste (capable of setting and hardening) obtained by adding water to a mixture of fine aggregates such as sand and binding materials, e.g., clay, gypsum, lime, or cement or their combinations. For the calculation of the quantity of sand, cement, and water in a mortar,
Quantity of Mortar
Assuming, volume of mortar = 1 meter cube
Mix ratio = 1:4
Dry volume of mortar = wet volume * 1.33
= 1*1.33
= 1.33 meter cube.
Quantity of cement
Quantity of cement = ( dry volume of mortar * cement ratio) / (sum of ratio)
Density of cement = 1440 kg/meter cube
1 bag of cement contains 50 kg of cement.
Number of bag = 383.04/ 50
=7.661.
Quantity of sand
Here, cement:sand :: 1:4
Therefore,
Weight of sand = 1.064 * 1920
Since, (1 Meter Cube=35.3147cubic feet)
=2042.88kg
If divided by 1000 => 2.0428 tonnes
Quantity of water
Here, water cement ratio = 0.50
Water Cement ratio = weight of water / weight of cement
Weight of water = 383.04*0.5
= 191.52 kg (ltr)
From above method, we can calculate the quantity of sand, cement and water in mortar.
Water Cement ratio of different grade of Concrete – Table
Normally, we used the water-cement ratio falls under 0.4 to 0.6 per IS Code 10262(2009) for nominal mix i.e. M7.5, M10,M15,M20,M25.
Here, M denotes Mix and Number denotes characteristics compressive strength of concrete of 150 mm cube after 28 days.
| Concrete Grade | Mix Ratio | Water/Cement Ratio |
| M7.5 | 1:4:8 | 0.40 |
| M10 | 1:3:6 | 0.45 |
| M15 | 1:2:4 | 0.50 |
| M20 | 1:1.5:3 | 0.55 |
| M25 | 1:1:2 | 0.60 |
I hope this post remains helpful for you.
Happy Learning – Civil Concept
Contributed by,
Civil Engineer – Suraj Khatri
Read Also,
Soundness test of cement- Procedure (By Le-Chatelier Method)
Fineness test of cement | Formula with Table of Calculation
Different grades of cement- IS Codes, Compressive Strength, Uses
