Acids and Alkalies:

The water contaminated by industrial waste is generally highly acidic or alkaline. Use of such water is strictly avoided for manufacturing of concrete, as it will adversely affect the hydration process. The pH of water should be in the range of 4.5 to 8.5. Generally, as thumbs rule it is preferred to have pH value more than 6.0.

Algae:

Algae may be present in the water or on the surface of aggregates. The presence of algae in either form is harmful for the strength of concrete as it causes large quantity of entrained air in the concrete. Use of such aggregates and water with algae should be avoided for manufacturing of concrete.

Organic Materials:

The presence of organic material is generally restricted to 3000-ppm. Particularly, the presence of humic acid or such organic acids is harmful to the strength of concrete as they adversely affect the hardening process of concrete. The presence of even 780-ppm of humic acid has been observed as seriously damaging the strength of concrete.