Construction and supervision problems - approx. 36%.
Design defects - approx. 27%.
Ambient conditions (temperature, humidity, etc.) - approx. 21%.
Quality of materials - approx 17%.
In addition, all cracks can be grouped into two broad categories:
Cracks occurring before and during hardening.
Cracks occurring after hardening of concrete.
Avoid by cutting contraction joints along dotted lines.
Shrinkage cracks caused by stress concentration at corners:
Prevent by placing expansion joint along dotted line, or by using reinforcing steel.
Settlement cracks caused by movement of sub-grade or footings.
Cracks due to heaving under the slab through poor drainage of sub-grade.
Expansion cracks:
Prevent by placing expansion joints at dotted lines.
Shrinkage cracks in feathered sections:
Narrow feathered sections should be avoided.Plastic shrinkage cracks:
Due to quick loss of water to dry sub-grade or to the atmosphere.
Shrinkage cracks at door or window corners:
Avoid by use of reinforcing steel or (in solid concrete walls) by careful placement of low-slump concrete.
See that sub-grade is well-compacted.
Check that form work is firm.
Ensure that sub-grade and form work are moist before pouring.
Do not add water to ready-mixed concrete in placing.
Compact low-slump mixes well.
Cut sufficient contraction joints to allow for shrinkage.
Provide expansion joints where necessary.
Start curing as soon as possible.
Maintain proper curing for an adequate period.
By the use of the procedures in this publication and by exercising proper care you will obtain the best performance from your Bamburi concrete.
Bamburi Special Products operates an accredited laboratory with trained technical staff who are available to answer any technical enquiries you may have and assist in designing concrete mixes specifically for your needs.