Plastic shrinkage cracking, by definition, is cracking that occurs while the
concrete is still plastic. It is actually a desiccation problem, very
similar to the dried soil shown in this photo. If water is evaporating from
the concrete surface faster than it is being supplied by bleeding, tensile
stresses will develop in the concrete. Ultimately, these stresses will be
greater than the very small ability of the still-plastic concrete to resist
the stresses and cracking will result.
The Silica Fume Association
38860 Sierra Lane, Lovettsville, VA 20180
Tel: 540.257.4224 Fax: 540.822.9456