Quality of Water

Quality of Water Quality of water is important because bad quality and impurities in water lead to the following: Interfere with the setting of the cement Affect the strength of the concrete Cause staining of its surface Lead to corrosion of the reinforcement.

Suitability of water include both mixing and curing. Distinction must be made between the effects of mixing water and the attack on hardened concrete by aggressive waters

Quality of Water Water/cement ratio The water–cement ratio is the ratio of the weight of water to the weight of cement used in a concrete mix and has an important influence on the quality of concrete produced. A lower water-cement ratio leads to higher strength and durability, but may make the mix more difficult to place. Placement difficulties can be resolved by using plasticizers or super-plasticizers. -

The water to cement ratio is calculated by dividing the water in one cubic yard of the mix ( in kg) by the cement in the mix (in kg). So if one cubic yard of the mix has 235 kg of water and 470 kg of cement- the mix is a .50 water to cement ratio.

Quality of Water Water used for mixing and curing of concrete should meet the following limits: - pH(degree of acidity) of 6.0 to 8.0 which does not taste saline or brackish. - Salts: should not exceed 500 ppm of chloride ion, and more than 1000 ppm SO₃ - alkali carbonates and bicarbonates should not exceed 1000 ppm.

High solid content in water adversely affect the hardening of concrete High solid content in water adversely affect the hardening of concrete. Such water should be tested. Water used to wash out truck mixers is satisfactory as mixing water because the solids in it are proper concrete ingredients, provided the water used is good water

Quality of Water The effect of sea water on concrete: - Quantity of water in mix is very important and it has a vital influence on strength and other properties - Sea water contain large quantities of chlorides. This cause dampness and efflorescence appearance on the surface of concrete. - Sea water increases the risk of corrosion of the reinforcement. - sea water leads to a slightly higher early strength but a lower long-term strength

- Sea water has a total salinity of about 3.5% - drinking water generally is fit for concrete except when it has a high concentration of sodium or potassium and there is a danger of alkali-aggregate reaction

Quality of Water Curing water - water used for mixing is generally suitable for curing. - iron and organic matter may cause staining, particularly if water evaporates rapidly. - curing of sea water may lead to attack of reinforcement.

Quality of Water Test for suitability of water for mixing: - Compare the setting time of cement and the strength of mortar cubes using the water need to be tested with the corresponding results obtained using good or distilled water. If the tolerance is less than 10% , then the water is suitable for mixing.

Quality of Water Sulfate ion concentration in water means the amount of sulfate ion in mg per liter and should not exceed 1000 ppm. Solid content in water expressed as ppm