Case 4
- Introduction
- Causes of Defects
- Good Practices
- Standards
- Maintenance and Diagnostics
- Remedial
- Similar Cases
- References
Good Practices
Ensure that the concrete mix is appropriate and to the specifications specified. Use good quality concrete with low permeability. Ensure that the concrete mix is appropriate for construction. Mix concrete properly on site. Use a container, not a shovel, to measure each part of materials used in the mix. Add only enough water to obtain an even, workable mix. If the concrete is ready mix, it shall comply with SS 289. Check for quality of concrete before placing (SS 78). e.g. water cement ratio, slump test, etc.
Placing of concrete plays a vital role to have dense, good quality concrete. Concrete should be placed as close as possible to its final location with the forms to prevent excessive movement. The drop of the concrete must be as near to vertical as possible. The free fall distance of concrete in wall should be limited to 4′ to 6′. Otherwise, the concrete will segregate and may lead to problems like rock pocket and honeycomb.
Only proper placing method should be used, e.g., chute, bucket, concrete pump or buggy. After concrete is placed, it is immediately consolidated with the course directly below. The immersion vibrator is to be held vertically and should pass through the top course, penetrating a few inches into the course below. The vibrator is immersed at regular intervals into the course for period or 5 to 15 seconds. Over vibration will cause water and paste to flow to the surface.