Below is a brief method statement that describes the practices and methods with regards to concrete placing, curing and defect rectification.
Below is list of reference documents useful for this method statement.
- Contract specification cast in place in concrete.
- Hazard Analysis table.
- Inspection and Test Plan
- BS 8110
Methods of Concrete placing, curing and defect rectification
Concrete Placement:
Complete all quality control checks before placing of any concrete and obtain the “approval to concrete” instruction from the client.
After delivery at site, place the concrete in one of three manners:
- Direct (or chute) discharge,
- Crane and bucket, or
- Concrete pump
The method of concrete placement depends on site conditions and pour volume.
Place the concrete in accordance with the specification for concrete cast in place. Following are some main points to consider:
- Place the concrete is as close as possible to its final position and not moved laterally by vibration.
- Do not over vibrate the concrete.
- Never drop the concrete from a height exceeding 2 meters.
- Avoid the “Cold joints” of more than 40 minutes.
- Place the concrete not later than one hour after the addition of the mixing water.
- Allow the pumping of concrete after approval from consultant / client.
- 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.
Curing of Concrete in Place
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 apply the curing as above after the removal of formwork, or apply a curing compound. Make sure to use the curing compounds as per the client approval and ensure it is of the clear type.
Finishing of Building Construction Joints
- Make sure that all the construction joints are in the locations as indicated in the drawings, or as per the proposal and always at right angles to the structural member’s axis.
- Use kickers at the base of all columns and walls.
- Remove the laitance as applicable once the concrete is hard by light chipping wire brushing.
- Prepare the construction joints 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 & Concrete 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 consultant before rectification.
- The action to be taken 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.