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Every concrete design follows a specific amount of water quantity. But there are some important sources of water other than the designed that can contribute to an increase in water content of the concrete. This unknown water content is detrimental to the strength of the concrete.
Important water sources that contribute to the water content of the concrete are explained one by one in this article.
1. Aggregate Free Moisture
The aggregate consists of moisture which can account for 10 to 40 percent of the total moisture of concrete. Hence, the aggregate free moisture content is very crucial in the concrete design.
2. Batch Water
Batch water is the water that is either measured by weight or volume in order to mix the concrete. This water accounts for 60 to 90 percent of the total water content in concrete. This is the designed water quantity.
3. Water in Admixtures
Most of the admixtures used in concrete consist of some amount of water content along with their other active ingredients. For a given volume of admixture, the water content is very small which can be easily measured. This water content must be accurately taken into account during the concrete mix design.
4. Water from the Mixing Drum
Some amount of water is added to the drum before the batching starts. It is not always possible to measure this water. Hence, it is necessary to completely empty out the drum after washing before it is loaded with a concrete mix.
5. Water from Ice
Construction areas with freezing temperatures ought to have a presence of ice during the concrete mixing process. One pound of ice is equal to one pound of water.
6. Water Addition by Unskilled People
This issue is mainly observed in the ready mix concrete manufacturing in trucks. When the driver finds that at the site the slump is less than the target, he may add water without proper skill. The water addition is mainly measured by an electronic meter or a sight tube on the truck show this. But all the additions are not shown in this sight tube. The sight tube does not show the water amount added before the tank was loaded.
Another mistake is from the contractor's side, where he can open the water valve leading to the drum, in order to increase the slump. The problem worsens when he does this without the driver or the inspector observing.
All the possible sources have to be kept in mind while designing and concrete manufacturing in order to prevent the water from some of the unplanned sources mentioned above.
Also Read: Determination of Water Content of Concrete
Also Read: What is pH of water used in Concrete