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✔ In construction, creating concrete requires combining four essential components: aggregate, sand, water, and cement.
✔ The strength of the resulting concrete hinges on the ratio of water to cement utilized.
✔ Thus, this communication explores the significance of the water-cement ratio based on code IS 10262:2019.
1. What is the Water Cement Ratio ( w/c ratio )?
✔ The ratio of the weight of water to the weight of cement is a water-cement ratio.
Mathematically,
Water cement ratio = (Weight of water in liters) / ( Weight of cement in kg)
✔ Concrete’s full hydration usually requires approximately 38% water.
✔ As per IS 10262:2019; For nominal mix ( i.e. M10, M15, M20, M25), the w/c ratio varies from 0.4 to 0.6.
| Concrete Grade | Recommended Water-Cement Ratio |
|---|---|
| M10 | 0.6 |
| M15 | 0.55 |
| M20 | 0.5 |
| M25 | 0.45 |
2. What is the history of the Water Cement Ratio?
✔ Duff A. Abrams was the first to develop the notion of the w/c ratio, which had been published in 1918.
✔ Uniform Building Code (1997) specified a maximum of 0.5 w/c ratio for conditions like concrete exposure to freezing, thawing, and humidity.
✔ It also specified a maximum of 0.45 w/c ratio for severe or very severe sulfate conditions.
3. Why Water Cement Ratio Is Important In The Concrete Mix?
✔ The chemical reaction between cement and water ( known as hydration ) produces heat during the reaction, resulting in the hardening of concrete.
✔ Proper hydration reaction is dependent upon the water-cement ratio. Proper hydration results in strong, sound, and durable concrete.
Therefore, using an accurate water cement ratio to strengthen concrete is crucial.
4. How Is Water Cement Ratio Calculated?
✔ As we know,
w/c ratio = weight of water in liters / weight of cement in kg
✔ Here, the amount of water required in concrete mix can also be calculated as follows;
Required amount of water ( in liters) = w/c ratio × weight of cement in kg
✔ Example:
If you want to make M20 concrete with a water cement ratio of 0.5 using 50 kg of cement, how much water do you need to mix the concrete?
soln;
Required amount of water ( in liters) = w/c ratio × weight of cement in kg
= 0.5 * 50
= 25 kg
= 25 L
( 1 kg is equivalent to 1 L )
| Read Also: 26 Types of Concrete |
5. What Happens When Water is not Properly Proportioned with Cement?
✔ When the amount of water used in concrete increases, the cement paste becomes more diluted, resulting in more voids once the water molecules evaporate. These voids can cause various issues, such as cracking, shrinkage, flexural failure, and changes in color due to imbalances in strength and porosity.
✔ Conversely, insufficient water usage can impede the proper binding of the materials and weaken the concrete’s overall strength.
6. W/C ratio for different concrete works
a. For ordinary concrete works: Recommended w/c ratio = 0.4 to 0.6
b. For high-quality concrete works: Recommended w/c ratio = 0.4
c. When 2% plasticizers or superplasticizers are used in high-quality concrete: Commonly 0.35 to 0.40 w/c is used.
( Note: Plasticizers or superplasticizers can increase the flowability and workability of higher-strength concrete.
Mix design is suggested rather than nominal mix if Plasticizers or superplasticizers are used to determine the exact suitable water-cement ratio.)
| Read Also: Grades of Concrete |
| Verified Article By Er. Madhu Krishna Poudel |
