Plastic Shrinkage Cracks
Loss of
water by evaporation from the surface of concrete or by the absorption by
aggregate or sub grade is believed to be the main reasons of plastic
shrinkage. The loss of water results in the reduction of volume.
The factors affecting
the plastic shrinkage are (i) Ambient temperature (ii) Relative humidity (iii)
Wind velocity (iv)Temperature of concrete.
The preventive measures
for plastic shrinkage are listed below:
- Dampening of sub grade and forms
- Controlling the wind velocity by erection
of windbreaks
- Minimizing placing and finishing time
- Using membrane curing, begin curing as soon
as possible after finishing
- Using mono molecular films (evaporation
retarders) or fog spray immediately after the screeding to maintain the
water/cement ratio at the surface
- Using surface dry aggregates
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