Soon after mixing, the concrete has to be transported and placed in the moulds. A maximum time limit of 1½ hours is allowed between the moment of actual mixing and placing of concrete. It should never be disturbed once the setting has commenced.
While transporting and placing of concrete, care should be taken to avoid segregation and loss of water added.
The surface on which the concrete is to be placed should be cleaned, prepared and well watered. The formwork or moulds should be given a coating of grease or some other material to prevent adhesion of concrete. Concrete should always be laid in even and thin layers and each layer should be well compacted before the next is placed, usually layers of 15–45 cm thickness is adopted. Concrete should never be thrown from a height. Concrete pumps are also now available to place the concrete. The reinforcement should be kept in a fixed position and should never be disturbed.
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