Construction related cracks
Various types of cracks may be formed during the construction process and changes within the young concrete. The main types are Plastic shrinkage cracks, Plastic settlement cracks, Thermal contraction cracks, Crazing, Long term drying shrinkage cracks and Cracks at joints. The time at which the crack forms will give an indication of the cause, as shown in the Table.
||Typical time of appearance|
|Plastic shrinkage cracks
||Thirty minutes to six hours|
|Plastic settlement cracks
||Ten minutes to three hours|
|Thermal contraction cracks
||One day to two or three weeks|
||One to seven days, sometimes longer|
|Long-term drying shrinkage cracks
||Several weeks or months|
|Cracks at joints
||One day or two or three months|
The occurrence of many of these cracks can be reduced or eliminated by good construction techniques; guidance is given for each type of crack.