The bubbles allow space for absorbed water to expand when it freezes, which protects the concrete against scaling (flaking) when it alternately freezes and thaws.
(The bubbles; allow; space for absorbed water) Context(The bubbles allow,List([0, 17))):(The bubbles; allow space for absorbed water to expand; T:when it freezes) (it; alternately freezes; ) (it; freezes; )
The bubbles allow,List([0, 17))
The bubbles The bubbles it it
allow allow space for absorbed water to expand alternately freezes freezes
space for absorbed water
T:when it freezes