What is the quality of water for curing of concrete?
Quality of Water for Concrete
The water used for mixing and curing of concrete should be pure and free from harmful impurities like oils, salts, acids, salts, sugars, organic substances or other harmful substances
Potable water means drinkable water is normally used for satisfactory for mixing concrete
How to check water quality is good for concrete?
If you have a doubt related to the development of strength by using water which is available for creating cement concrete will be found out by compressive strength and initial setting time tests
The average of the comprehensive strength of three or more cube after 28 days curing should not be less than 90 per cent of the average strength of three similar concrete cubes which cast with same materials and cured with distilled water
|source IS CODE 456|
The following guidelines should also be taken into consideration in respect of the quality of water
- For the neutralize the sample of 100 ml water by using phenolphthalein as an indicator, it should not require more than 5 ml of 0.02 normal NaOH. The details of the test are given in IS code: 3025 part 2
- For the normalize the sample of 100 ml water by using the mixed indicator, it should not require more than 52ml of 0.02 normal H2SO4. The details of the test are given in IS CODE: 3025 part 23
Effect of Impurities in water during curing of concrete
- Carbonates and bicarbonates of sodium and potassium (alkali) affect the setting time of concrete.
- While sodium carbonate may result in quick setting, the bicarbonates may either accelerate or retard the setting alkali carbonates and bicarbonates should not exceed 1000 ppm
- slightly salty water contains chlorides and sulphates when chloride does not exceed 500 ppm and SO2 does not exceed 400 ppm the water is harmless
- Weak water contains chlorides and sulfates, while chloride does not more than 500 ppm and SO2 does not more than 400 ppm
- The seawater normally carries 3-4% of dissolved salts, about 75-80% of water is sodium chloride and 15% chloride and sulphate of magnesium.
- The salts present in seawater reduces the strength of concrete by 10 to 20% chlorides causes corrosion of reinforcing steel and efflorescence concrete
- Salts of manganese, zinc, copper, tin and lead cause a marked reduction in strength of concrete
- impurities in the Algae form may also be present in mixing water which is used for concrete or on the surface of aggregate particles. It combines and makes the bond with the cement and reduces the bond capacity between aggregate and cement paste. Algae present in water introduce a large quantity of air in the concrete thus lowering the strength of concrete
- If the amount of sugar is less than 005 % by weight of water there is no adverse effect on the strength of concrete. Sugar content up to 0.15% by the weight of cement retard setting time. When the quantity of sugar exceeds 0.20% by weight of cement, 28-day compressive strength reduce
- The vegetable oils have a detrimental effect on the strength of concrete at later ages. If the concentration of mineral oil is up to 2% by weight of cement a significant increase in strength has been noticed
- Suspended particles of clay and silt are undesireble as they interfere with setting hardening and bond characteristics
Effect of seawater on cement concrete?
- Strength of concrete
- Corrosion of reinforcement