Greetings!
 The phone call every concrete contractor dreads is the one from an angry customer complaining that the surface of their new driveway or sidewalk is flaking away. This ugly condition, called "spalling," is one of the most common ailments with concrete, occurring most often in climates exposed to freeze-thaw conditions and the destructive effects of snow and ice. Most of these surface failures on concrete slabs are little more than cosmetic, but they can be costly to fix. The good news is that spalling is easy to prevent, if you understand its causes and take some precautions. Here is advice on keeping your concrete slabs free of flaking and your customers happy.
Jim Peterson,
The Concrete Network
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Use the Right Concrete Mix
The concrete you start with is the most important factor in avoiding spalling. A durable, low-permeability concrete mix that's placed and finished properly
should be able to handle typical freeze-thaw cycles for decades without spalling. See The Correct Concrete Driveway Mix.
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Add More Air
Concrete
is naturally porous, so if water gets in and freezes, the expansion pressure can cause a weak surface to break off in flakes. (Water expands up to 9% in volume when it freezes!) Proper air entrainment can prevent this problem by producing tiny air cells, or "escape hatches," that relieve this internal pressure. The solution is simple: Ask your ready-mix producer to add an air-entraining admixture to the fresh concrete at the batch plant. Learn more: Protect Against Freeze-Thaw Cycles.
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Don't Overdo It
Don't be an overachiever when it comes to finishing your concrete slabs. Overworking the surface with a steel trowel, especially if bleed water is still present, can create a weak surface that won't be able to handle freeze-thaw expansion and the effects of deicing salts. See Proper Finishing Techniques.
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Apply a Sealer
Sealers are a great way to protect concrete from spalling
deterioration, says concrete expert Chris Sullivan. A good-quality sealer designed for use on exterior
concrete will help minimize water saturation and protect against salt
damage. A sealer can provide other benefits as well. Learn more.
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