foundation system of burj al arab

Plastic Settlement Cracks in Concrete

Cracking can develop also over obstructions to uniform settlement, e.g., reinforcement or large aggregate particles. This is called plastic settlement.

Details of plastic settlement

Location of appearance

1) In case of over reinforcement member it is generally located in deep section.

2) Where changing in section is inevitable they are seen frequently like waffle slabs.

3) In case of arching they appear at top of column.
Causes
Excess bleeding generally results plastic settlement cracking. Rapid early drying conditions also helps such cracks to be pronounced. Also as stated above over reinforcements and large size aggregate produce differential settlement and finally plastic settlement cracking. Plastic settlement cracking can occur also at normal temperatures but, in hot weather, plastic shrinkage cracking and plastic settlement cracking are sometimes confused with one another.

Arrival time
They are normally appeared within 10 min. to 3 hr of concrete placement.


Remedy

The plastic settlement cracking can be avoided by the use of dry mix, good compaction, and by not allowing too fast build-up of concrete. Reduction of bleeding or revibrating arrest such types of cracking.

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