The impurity of mixing water which affects the setting time and strength of concrete - Building Material

The impurity of mixing water which affects the setting time and strength of concrete is _____.

1. sodium sulphates
2. sodium chlorides
3. sodium carbonates and bicarbonates
4. calcium chlorides

Sodium Carbonates and Bicarbonates. Explaination: Sodium carbonates in deionised water accelerates the initial as well as final setting times whereas the other compound sodium bicarbonates retards the initial and final setting times in all concentrations. Sodium carbonates and sodium bicarbonates in deionised water decrease the compressive and tensile strength of concrete specimens significantly at 28 days and 90 days.

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