What is Plastic Shrinkage Cracking?

Customers don't like a blemished product - and neither do we. 

That's why we do our best to alert you when conditions are favorable for plastic shrinkage cracking before you place an order for concrete with us.

You probably have some questions, though. We can hear your mind wondering, "Plastic shrinkage what now?"

According to the National Ready Mix Concrete Association, the short answer: Plastic shrinkage cracks form when moisture in the surface concrete evaporates faster than the bleed water in the concrete below the surface, which rises as the concrete sets, can replace it.

Weather conditions - including low relative humidity, winds higher than 5 m.p.h., or high air or concrete temperatures - can speed up surface evaporation and lead to plastic shrinkage cracking. 

Concrete mixtures with slower water bleeding, reduced water content, or delayed setting can also increase the risks of plastic shrinkage cracking.

"Attempts to eliminate plastic shrinkage cracking by modifying the composition to affect bleeding characteristics of a concrete mixture have not been found to be consistently effective," the NRMCA says. "To reduce the potential for plastic shrinkage cracking, it is important to recognize ahead of time, before placement, when weather conditions conducive to plastic shrinkage cracking will exist."

For more info and tips on how to prevent plastic shrinkage cracking, read or purchase the NRMCA's Concrete In Practice publication.