Water mixed in concrete need not be distilled water. In many cases it is said that water used in concrete should be drinkable. Dissolved impurities in water should not be more than 2000 parts per million (PPM). Water mixing in concrete should be of good quality. Bad quality of water affects concrete. High quantity of potassium and sodium is dangerous as it may start alkali-aggregate reaction. pH value of water should be between 6.0 to 8.0. Algae should not be present in the water. Sea water should not be used for concrete work.
Effect of bad quality of water in concrete
- Alkali carbonate water can retard or accelerate setting and 28-day strength when total dissolved salts exceed 1000 ppm. Can also aggravate alkali–aggregate reaction.
- Chloride present in concrete may lead to Corrosion of reinforcing steel. Chloride can enter the mix through admixtures, aggregates, cement, and mixing water, so limits are expressed in terms of total free chloride ions.
- Sulfate can cause expansive reaction and deterioration.
- Sea water can accelerate strength gain but reduces ultimate strength. Can aggravate alkali reaction.
- Oils present in concrete may reduce the strength of the concrete.
- Algae can reduce hydration and entrain air. Do not use water containing algae.
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