This statement describes the practices and methods to be used with regards to placing, curing and defect rectification of concrete works.
- Contract specification cast in place in concrete.
- Hazard Analysis table.
- Inspection and Test Plan
- BS 8110
Prior to the placing of any concrete all Q.C. checks are to have been completed and the “approval to concrete” instruction issued by company.
Once delivered to site the concrete will be placed in one of three manners:
- Direct (or chute) discharge,
- Crane and bucket, or
- Concrete pump
The method to be used shall depend on site conditions and pour volume.
The concrete shall be placed in accordance with the Specification for Concrete cast in place and the main points being:
- Concrete is to be placed as close as possible to its final position and not moved laterally by vibration.
- Concrete is not to be over vibrated.
- Concrete is not to be dropped from a height exceeding 2m.
- “Cold joints” of more than 40 minutes shall be avoided.
- Concrete shall be placed not later than one hour after the addition of the mixing water.
- Pumping of concrete shall only be permitted after approval from Consultant.
- If during concreting, rain is imminent sufficient plastic/canvas sheets should be on hand to cover the entire casting area. If seepage water is coming into the excavation in a significant volume or again if rain is imminent a water pump must be in place ready to operate.
After the initial set of the concrete and when the concrete is hard enough to not be damaged by such an action, the exposed concrete surface shall be covered with drenched hessian sacks. These sacks shall be left in position and maintained in a soaked condition for seven days. For formed surfaces the curing shall be applied as described above after the formwork has been removed, or a curing compound shall be applied.
Curing compounds if used shall be approved and of the clear type.
- Construction joints shall be in the locations as indicated in the drawings, or as submitted in a proposal and always at right angles to the structural member’s axis.
- Kickers shall be used at the base of all columns and walls.
- Laitance may be removed once the concrete is hard by light chipping wire brushing.
- Preparation of construction joints shall be done by mechanical chipping taking care not to dislodge the coarse aggregates. This is to be done at least 24 hours after the completion of placing or a concrete surface retarder may be used.
INSPECTION AND REPAIR
- After the removal of formwork the element shall be checked for level, dimensions and surface defects, any non-conformity will be brought to the attention of Company before rectification.
- The action to be take to resolve any non-conformity will be proposed and subsequently approved by Consultant.
- Any patching, grouting or other such compound to be used for rectification works shall be submitted to and approved by Consultant prior to its use.