Concrete @ your Fingertips

Plucking of surface

This appears as surface material lost upon striking the formwork

Normally occurs when the concrete surface is not of sufficient strength when striking the formwork.  Could be due to cold weather, retarded surface, high cement replacement or a combination thereof.

Allowing the concrete to gain sufficient strength reduces the risk of its occurrence and is generally accepted as being 5MPa.

Acknowledgement: Concrete Society

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Visual Concrete: Control of blemishes