or flaking / chipping /

Spalling:
are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure (as in a ball bearing). ...
http://en.wikipedia.org/wiki/Spalling

Splitting
especially of wood) cut or ripped longitudinally with the grain; "we bought split logs for the fireplace"; divided: separated into parts or portions
http://wordnetweb.princeton.edu/perl/webwn?s=split

Flaking:
a small fragment of something broken off from the whole;

"wall spalling" image examples:
http://www.123rf.com/photo_17343401_spalling-of-the-brick-wa...
http://activerain.com/blogsview/1391224/spalling-concrete-du...
http://flickrhivemind.net/Tags/spalling/Interesting

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