3.10 Structures

The structures should be built as per detailed drawings and technical specifications, or as directed by the Engineer. The points to be taken into consideration during their construction are as follows (U.S.D.I., 1981; White, 1977):

1. Having excavated the working pit, plain concrete should be placed immediately if needed.

2. The measurements, location and elevation of forms, etc., should be checked before putting concrete into them.

3. Before casting, the reinforcement should be shown to and checked by the Engineer.

4. All materials used for building and all structures should comply with the relevant specifications. Never use coarse cement (killed cement) for any structures. This may be used for plain concrete.

5. Concrete used for structures should be mixed in a mechanical concrete mixer if available. The mix proportions given in the detailed plans should be adhered to.

6. Before proceeding to place the concrete, the forms should be realigned if necessary and well wetted.

7. Unless otherwise approved, concrete must be placed in a single operation to the full thickness of slabs and walls, with proper compaction.

8. Placed concrete must be protected by approved means from rain, sun and drying winds. Exposed faces of concrete must be kept moist for seven days after placing.

9. The forms must be removed by gradual easing without jarring. The period which must elapse after placing concrete and before easing and removal of the forms may be undertaken, is as follows: