Resurfacers Can Renew Worn Concrete

In the past, when a concrete patio or driveway started to show serious signs of aging, using a jackhammer or bringing in a bulldozer were the only repair options. Today there are more practical alternatives.

Polymer-based cement resurfacers are formulated to transform cracked, spalled, weatherworn concrete to like-new condition. The top dressing we used, Ardex All-Purpose Concrete Resurfacer, is made of portland cement and high-performance polymers. It’s mixed with water and applied with a steel trowel, squeegee or push broom to a thickness of only 1/16 of an inch.

One 20-pound bag costs about $25 and covers 50 to 60 square feet. (The average concrete driveway is about 500 square feet.)

Besides patios and driveways, Ardex can be used to resurface concrete stairs, sidewalks, garage floors and most vertical surfaces.

For our project, we resurfaced a 9,527-foot driveway and 3,518-foot walkway using six bags of Ardex.

It took two people five hours to complete the job. The work isn’t particularly difficult, but the pace is frenetic. Once the water is mixed in, you have less than 30 minutes to apply the concrete dressing.

For optimum results, work on a day with low humidity, no rain and an air temperature ranging between 70 and 75 degrees Fahrenheit. The surface temperature of the existing concrete must be at least 50 degrees Fahrenheit.

Ardex will bond only to clean, dry surfaces.

First, rinse the concrete with a garden hose or, better yet, a pressure washer. Then use a stiff-bristle push broom to sweep away all dirt, dust and debris. Clean off grease and oil stains with TSP (trisodium phosphate); don’t use any sort of solvent, sealer or primer.

Allow the surface to dry completely. Next, patch all cracks, crevices and holes to ensure that the resurfaced concrete will be completely smooth.

For hairline cracks up to one-eighth inch wide, mix four parts of Ardex to one part water. Force the thick paste into the cracks with a putty knife.

For larger cracks up to half an inch wide, use concrete-repair caulk. Squeeze the caulk into the cracks with a caulking gun, and smooth it with a putty knife. Fill cracks wider than half an inch with masonry mortar mix ($3 per 60-pound bag).

Large concrete slabs are typically divided into sections by expansion joints, which help control cracking. The one-half- to three-quarters-inch-wide joints are usually filled with asphalt-saturated felt, a wood 1-by-4 or a plastic channel. These joints must remain exposed to allow the slab to expand and contract; don’t cover them with the cement top dressing. Mask each expansion joint with a strip of duct tape.

Ardex must be mixed quickly and then applied immediately. Use a 650-rpm, one-half-inch drill motor and a heavy-duty mixing paddle to mix the concrete dressing to a smooth consistency. Pour exactly 2 1/2 quarts of water into a clean 5-gallon bucket. Dump in a 20-pound bag of the resurfacer and mix continuously for two minutes.

Lift out the paddle and stand it in a bucket of clean water. Pour the dressing onto the slab and immediately spread it; have a helper mix the next batch.

For small areas, such as walks or stairs, use a flat steel trowel. Press hard to force the dressing into every tiny hole and crevice. Next, draw a medium-bristle broom across the wet area to create a textured, slip-resistant surface.

When working a larger area, like a patio or driveway, spread the dressing with a long-handle squeegee. Again, press down hard to fill all surface imperfections. Follow up with the push broom. Pull up the tape from the expansion joints immediately after sweeping the surface.

The surface can be walked on after about two hours, but don’t drive your car on it for at least six hours. After 24 hours, protect the new surface with a clear, waterborne masonry sealer.