- The Contractor shall give due notice to the Engineer of the time it is intended to place any concrete and no concrete shall be placed until approval has been obtained from the Engineer.
- Concrete shall not be placed on frozen ground nor shall it be placed in unfavourable conditions, which may be detrimental to the quality and finish of the concrete. Unfavourable conditions shall be deemed to include low temperatures (below 5°C with temperature descending, or below 2°C with temperature ascending), excessively hot, dry conditions, excessively wet conditions, or any conditions making it impractical to work and finish the concrete adequately.
- Immediately before placing the concrete, the foundations shall be lightly dampened, and formwork shall be cleaned out. In all cases surplus water shall be removed before concrete is placed.
- The concrete shall be placed so the coarse aggregate does not separate from the fines, and it shall be thoroughly worked and consolidated into all parts of the formwork, so that no voids or cavities are left. All concrete shall be handled from the mixer, or from the agitator truck mixer, to the place of final deposit as rapidly as is practicable, by methods which prevent segregation.
- Unless otherwise approved, in no case shall more than 30 minutes elapse between discharge of concrete from the mixer/agitator truck and final placement. Under no circumstances shall partially hardened concrete be placed in the work.
- Where a channel is finished with a sand/cement mortar coat, the mortar shall be placed within 2 hours of placing the concrete, provided that when hot dry conditions are prevailing, the allowable time shall be reduced to 1 hour.
- If for any reason a delay of more than 2 hours occurs, an approved PVA bonding agent shall be used to ensure the mortar is adequately bonded to the concrete.
- Before fresh concrete is placed upon or against any concrete which has already hardened, the surface of the hardened concrete shall be thoroughly scabbled, cleaned and cleared of all laitance, loose or foreign material.
Definitions in this section