What Causes Concrete Flatwork Damage?
Freeze/thaw cycles during cold months are the most common cause of damage to the surface of concrete flatwork. Concrete is a porous material that will absorb moisture at the surface. When the absorbed moisture freezes, in exerts a tremendous expansive force, which weakens the surface and sometimes leads to scaling. Concrete less than one year old, and particularly concrete poured after November 1st, is particularly vulnerable to freeze/thaw cycle damage.
About De-icing Products
De-icing products can be composed of a variety of different chemicals that are harmful to concrete. State, county and municipality street departments frequently use magnesium chloride based materials in the past, a chemical that exacerbates the probability of damage to concrete as a result of snow and water drippings from vehicles.
The most damaging effect of using de-icers is not the chemicals themselves, rather that they increase the number of freeze/thaw cycles experienced by flatwork during cold months.
Repetitive cycles amplify the weakening effects caused by freezing moisture at the surface of the concrete. As a general rule, de-icing products should not be applied to exterior concrete flatwork that is less than one year old.
Liberty Ready Mix prides itself on providing quality products to its customers. We use concrete mixes for exterior flatwork that meet or exceed industry standards for compressive strength and air-entrainment. Air-entrained concrete mixes contain tiny air bubbles that provide spaces within the concrete for expanding water to move into, thereby reducing the expansive stresses associated with freezing moisture in the concrete.
Protecting Your Exterior Flatwork
You should inform all of your customers to take the following precautions. This will help to reduce the number of call backs that you get, in turn reducing tear-out and replacement losses.
- Do not use any de-icing products in the first cold weather season under any circumstances. Again, using these products exacerbates the weakening effects of freezing moisture on concrete surfaces by increasing the number of freeze/thaw cycles.
- Never use any de-icing products containing ammonium nitrate, ammonium sulfate or magnesium chloride. These agents chemically attack concrete and cause damage above and beyond the effects of freeze/thaw cycles.
- Do not park vehicles on driveways. Snow and water contaminated with road salt and de-icers will drip from vehicles leaving concentrated areas of salt or de-icer brine that will facilitate multiple freeze/thaw cycles at the surface of the concrete.
- Minimize vehicle traffic on the driveway until cold months have passed for any concrete poured after November 1. Concrete requires an ambient temperature of 50 degrees of 30 days for the curing process to complete. If the ground is frozen, as it often is after November 1, the compressive strength of concrete is at a minimum. A weak concrete surface combined with uneven areas of frost-heaved sub-base can lead to severe damage when subjected to the stress caused by the weight of an automobile.
- Apply a protective sealer to the surface of the concrete. Liberty Ready Mix would be happy to assist you with more information about sealers and their application.