Water, natural or treated, used for mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials or other substances that may be deleterious to concrete or steel.
Potable water is generally considered satisfactory for mixing concrete. As a guide the following concentrations represent the maximum permissible values:
a) To neutralize 100 ml sample of water, using phenolphthalein as an indicator, it should not require more than 5 ml of 0.02 normal NaOH. The details of test are given in 7.1 of good practice [6-5A(13)].
b) To neutralize 100 ml sample of water, using mixed indicator, it should not require more than 25 ml of 0.02 normal . The details of test shall be as given in 7 of good practice [6-5A(13)].
c) Permissible limits for solids shall be as given in Table 1.
| Sl No. | Parameter | Tested as Per | Permissible Limit Max |
|---|---|---|---|
| (1) | (2) | (3) | (4) |
| i) | Organic | Good practice [6-5A(13)] | 200 mg/l |
| ii) | Inorganic | Good practice [6-5A(13)] | 3 000 mg/l |
| iii) | Sulphates (as SO3) | Good practice [6-5A(13)] | 400 mg/l |
| iv) | Chlorides (as Cl) | Good practice [6-5A(13)] | 2 000 mg/l for concrete not containing embedded steel and 500 mg/l for reinforced concrete work |
| v) | Suspended matter | Good practice [6-5A(13)] | 2 000 mg/l |
4.4.1 In case of doubt regarding development of strength, the suitability of water for making concrete shall be ascertained by the compressive strength and initial setting time tests specified in 4.4.1.2 and 4.4.1.3.
4.4.1.1 The sample of water taken for testing shall represent the water proposed to be used for concreting,
due account being paid to seasonal variation. The sample shall not receive any treatment before testing other than that envisaged in the regular supply of water proposed for use in concrete. The sample shall be stored in a clean container previously rinsed out with similar water.
4.4.1.2 Average 28 days compressive strength of at least three 150 mm concrete cubes prepared with water proposed to be used shall not be less than 90 percent of the average of strength of three similar concrete cubes prepared with distilled water. The cubes shall be prepared, cured and tested in accordance with good practice [6-5A(14)].
4.4.1.3 The initial setting time of test block made with the appropriate cement and the water proposed to be used shall not be less than 30 min and shall not differ by ± 30 min from the initial setting time of control test block prepared with the same cement and distilled water. The test blocks shall be prepared and tested in accordance with the good practice [6-5A(15)].
4.4.2 The pH value of water shall be not less than 6.
4.4.3 Sea Water
Sea water shall not be used for mixing or curing of concrete because of presence of harmful salts. Under unavoidable circumstances sea water may be used for mixing or curing in plain concrete with no embedded steel after having given due consideration to possible disadvantages and precautions including use of appropriate cement system.
4.4.4 Water found satisfactory for mixing is also suitable for curing concrete. However, water used for curing should not produce any objectionable stain or unsightly deposit on the concrete surface.