Correct Answer - Option 4 : 6
Explanation:
Property of water used for making concrete:
a) As per IS 456:2000 Ph of water is > 6 and water 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.
b) Natural water or freshwater rarely contains more than 2000 ppm of dissolved solids and is generally suitable for making concrete.
c) Water contaminated with industrial wastes, but free of suspended solids is also suitable at low concentrations for making concrete.
d) Much larger contents of the impurities, in natural water can be tolerated except for the alkali carbonates and bicarbonates which may have significant effects even less than or equal to 2000 ppm.
e) Other inorganic impurities of possible industrial origin, that may be detrimental at moderate concentrations are sulfides, iodides, phosphates, arsenates, borates, and compounds of lead, zinc, copper, tin, and manganese are adversely affected.