A method of reducing plastic shrinkage cracking in concrete compositions
that includes a) combining 3-40 volume percent cement, 5-50 volume
percent fine aggregate, 5-50 volume percent coarse aggregate, and 10-22
volume percent water to form a concrete mixture; b) during or after (a),
adding 1.5-40 volume percent of prepuff particles to the concrete mixture
to form a concrete composition; c) placing the concrete composition in a
form; and d) allowing the concrete to set and harden to form a hardened
concrete article substantially free of plastic shrinkage cracking. The
prepuff particles have an average particle diameter of from 0.2 mm to 8
mm, a bulk density of from 0.02 g/cc to 0.64 g/cc, an aspect ratio of
from 1 to 3. The concrete composition has a density of from about 40 to
about 135 lb./ft.sup.3.