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Mon, Aug. 19

Ask the contractor: Sealant helps keep walkways from eroding

We are approaching our winter weather, and our weather can take a toll on more than just our cars and our attitudes. Concrete walks, driveways and steps all take a pounding from the elements and the de-icing chemicals that we apply.

The most common winter damage to concrete is scaling - the flaking or peeling away of the surface mortar. Scaling can leave the concrete looking pockmarked and will expose the stones in the concrete mix. Minor scaling can be merely a cosmetic flaw, but if left unchecked, it can turn a smooth concrete walk into a rough gravel path.

Scaling is caused by cycles of freezing and thawing. Water is absorbed into very fine capillary spaces in the concrete. When the temperature drops, this absorbed water freezes and expands. Such expansion creates pressure that forces flakes or mortar loose from the surface, and you can often see where mortar has "popped," leaving holes.

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Q: Should we consider sealing our pavers?-Dee M. Prescott

A: In talking with Brian Peterson of Diversified Concrete Crafters and Ty Smith of Yavapai Block, both recommend sealing of pavers. Paver sealing is not nearly as critical as sealing concrete, but is nonetheless recommended. It is always good to keep moisture out of concrete and although pavers are a much denser material - 9,000 psi vs. concrete at 2,500 or 3,000 psi - sealing will help hold the paver color and will keep efflorescence at bay. Sealers limit the water that is absorbed by the material and, in a majority of cases, will help reduce scaling of concrete.

For existing concrete that shows signs of scaling, sealing can be an effective remedy. There are many products available to help protect the concrete and other items such as pavers. These surface treatments are usually penetrating sealers made from silane, siloxane or other materials. Avoid sealers that prevent water in the concrete from evaporating. These materials may seal the surface of the concrete or pavers, but they also can trap moisture that is absorbed from the ground below. Use a sealer that allows the concrete to breathe so this moisture can evaporate.

Other winter hazards to concrete come from chemicals used to melt snow and ice. De-icers can worsen scaling by increasing freeze-thaw cycles. De-icers sold as safe for grass and shrubs can chemically attack concrete. These products usually contain ammonium nitrate or ammonium sulfate. They are fine for landscaping but can destroy concrete.

Removal of compacted snow and ice with shovels or snow blowers isn't always easy or effective. The use of a chemical de-icer may be needed to facilitate removal. In order to be effective, de-icers must first attract or come into contact with sufficient moisture to form a liquid brine. The brine has a lower freezing point than water, which causes ice and snow to dissolve on contact. De-icing agents penetrate downward through the ice and snow layer until they reach pavement. Once on the pavement, the brine spreads outward to break the bond between the ice and snow and the pavement. After sufficient loosening, the ice and snow can be removed by shoveling or plowing.

Calcium magnesium acetate, or CMA, is a salt-free de-icing agent made from acetic acid and dolomitic lime. Although this de-icing compound is more expensive than most salts or combination de-icers, it is less damaging to the driveway surface and plants, making it suitable for use in environmentally sensitive areas.

Physical removal of snow and ice, using a shovel, plow or snow blower, will greatly reduce the need for salt, abrasives or other removal methods. Frequent or timely removal of snow will help to prevent the formation of a packed snow or ice layer on the driveway.

Yavapai County Contractors Association (YCCA) is a professional association representing licensed, bonded and insured contractors, suppliers, distributors and business entities. Call YCCA for information on hiring a contractor at 778-0040. Submit questions to ycca@cableone.net or through www.ycca.org.

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