Preventing plastic settlements cracks
The tendency for plastic settlement cracks to form may be reduced by adjusting the concrete mix, for example by avoiding gap-graded fine aggregate and reducing the water content, and by appropriate workmanship and control of vibration. Particular care will be required for tall elements. In some cases, plastic settlement cracks can be eliminated, rather than prevented, by careful re-vibration of the concrete after they have formed. However, it is important to ensure that the concrete is not over-vibrated.