quality of concrete mixing water
Water is a vital ingredient of the concrete mixture. The quantity and quality of water should be controlled to ensure the production of concrete with high strength and durability. The increase in water will adversely affect the compressive strength and durability of a concrete mixture. On the other hand, the presence of impurities in mixing water can affect the setting time of concrete, cause staining on the concrete surface, and reduce the strength of concrete. Water that contaminated with chemicals such as chloride can increase the rate of steel corrosion, and this can cause severe deterioration of the concrete structure.
The potability of water depends on different factors. For example, the drinking water may be considered as unsuitable as mixing water if the concentration of sodium and potassium is high. The high concentration of sodium and potassium can result in an alkali-aggregate reaction. In general, the drinking water is safe to use as mixing water. Also, non-drinking water can be used for producing concrete. In general, water with a ph of 6 to 8 that not tasting saline or brackish (slightly salty) considered suitable. Natural water that contains acids is harmful. Water that contains humic or other organic acids will adversely affect the hardening of concrete.
The presence of algae (non-flowering and typically aquatic plant) in mixing water will result in air-entrainment, and this can reduce the concrete strength.
In some events, where there is a shortage of fresh water. The brackish water is used. The brackish water contains chloride and sulfate. Therefore it should be tested to determine the quantity of these chemicals. The table no:1 showing the allowable quantities of chloride and sulfate.
The seawater has been used as mixing water. The seawater has a total salinity of 3.5%. The use of this water will result in higher early strength but lower strength in the long term. The use of seawater will result in steel corrosion, which will result in the formation of concrete cracking and spalling. Therefore it is not advisable to used seawater.