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Adding water to ready-mixed concrete

Generally, it is not a good idea to add extra water to ready-mixed concrete once it has arrived on site.

However, under certain circumstances, it may be permissible for water to be added to a load of stiff ready-mixed concrete in order to achieve the specified consistence class.

This is in accordance with BS 8500 and applies when:

• the slump is less than the lower limit of the consistence class
• the quantity of added water is controlled by being measured accurately and is recorded on the delivery docket
• the stiffness is not due to an excessive delay since batching
• the amount of water added does not exceed any specified limit for water:cement ratio.

Acknowledgement: the concrete Society

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Concrete practice
- guidance on the practical aspects of concreting - GCG8

Control and conformity of water to binder ratio in fresh concrete