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Temporary shutters are used where large areas or large volumes of concrete have to be replaced and a formed finish is required. Correct design of shutters is extremely important. They have to be capable of being erected quickly before the bonding aid or substrate dries out. They have to be well sealed against the adjacent concrete and may require intermediate openings (letter boxes) for to facilitate concrete placing and poker vibrator insertion.
The repair material may be a proprietary flowing concrete or a conventional concrete, depending on the size of the repair and the complexity of the reinforcement. Normal concretes are used where the sections are similar to those found in conventional construction. Minimum thickness for flowing concrete (which requires less vibration) is around 50 mm but will depend on reinforcement congestion.
Placing of conventional concrete follows normal concreting practice except that it may be necessary to use smaller vibrators in thin sections. Intermediate access points for introducing concrete and inserting pokers may be needed. These are sealed off as the concrete reaches them. The pour should be completed in one continuous operation to avoid cold joints.
Good curing is essential for successful repairs. It should be started as early as possible and maintained for at least seven days.
Acknowledgement: The Concrete Society
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