How to Resurface Concrete

closeup hand construction plastering wet cement on the loft wall

 

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Compared to many home improvement and repair projects, resurfacing concrete is a relatively easy task that can be done with concrete resurfacing products available at any home improvement center or hardware store. Resurfacing is a good option when the surface of a concrete slab or structure is cosmetically marred but in otherwise good shape. Resurfacers will not correct deep cracking or heaving, but they can cover over routine flaking of a concrete surface or small pits due to spalling. A concrete slab that has been damaged by road salts, for example, can be renewed quite easily with a coating of resurfacer.

If you take the time to prepare properly, apply the resurfacer carefully according to manufacturer instructions, and allow the resurfacer plenty of time to cure, you'll be rewarded with a garage floor, driveway, sidewalk or patio that looks as good as new.

Tools and Materials

Concrete resurfacing products are sold in bags of dry mix and are available at just about any home improvement center or hardware store. The only essential tool is a long-handled squeegee that sells for just a few dollars. Other optional tools that may make the work easier include a power washer for cleaning the cement before resurfacing, and a paddle attachment for a 1/2-inch drill, which will make it easier to blend the resurfacing mixture.

  • Garden hose and water supply
  • Power washer
  • Bags of dry concrete resurfacer
  • 5-gallon plastic bucket
  • 1/2-inch drill and mixing paddle.
  • Long-handled squeegee
  • Concrete edger
  • Broom

The major manufacturers of concrete products, including Quickrete and Sakrete, all sell concrete resurfacing products. Usually, these consist of a blend of Portland cement, fine sands, polymer modifying compounds, and other additives that make the surfacer easy to apply and spread over existing concrete surfaces. They are intended to be spread in thin layers from 1/16 to 1/2-inch thick

  • Note: These resurfacing products are intended only for covering the surface of concrete and will serve to repair only the most superficial cracks and pits from spalling. For more substantial repairs, such as wide cracks or those that have slight vertical shifts, you will need to first repair the areas using a product that is specifically for patching, then follow up with a complete resurfacing treatment. One such patching product is Sakrete's Top 'n Bond.

Resurfacing powder is typically sold in 10- or 20-pound pails, or in 40-pound bags. A 40-pound bag will cover about 90 square feet of concrete surface when spread at minimal thickness. At a thicker 1/4-inch layer, coverage is about 17 square feet for each 40-pound bag. With 40-pound bags of resurfacer costing around $50, you can expect to pay about $.50 per square foot to resurface a driveway with a very thin layer, or as much as $3 per square foot if you are laying a thicker layer suitable for filling chips and cracks. You should carefully weigh these costs when determining if it is worthwhile to resurface, especially if the slab is in poor shape and will need replacement in the near future.

Repair the Surface

Concrete resurfacers should be viewed as cosmetic finishes, not repair products. If your concrete surface is not structurally sound, you should not even consider applying a resurfacer until the underlying structural problems have been addressed.

Evidence of structural problems includes symptoms such as heaving, where sections of concrete have sunk or lifted relative to the rest of a slab; large deep cracks that run through the entire thickness of the slab; or concrete surfaces that are beginning to powder or disintegrate. When such symptoms are found, the damaged area of the slab should be removed and replaced if possible, before any resurfacing is attempted. Widespread damage of this type indicates the slab may have reached the end of its useful life and should be replaced entirely. When serious damage is widespread, resurfacing will mask the problems for only a short time.

But if you have only minor cracks or pits in your surface, resurfacing can be effective, provided you first repair the damage with a product specifically formulated for patching.

Clean and Prepare the Surface

It is critical that the concrete surface is cleaned of all loose debris. A strong spray from a garden hose and long-handled scrub brush may suffice, but a good pressure washing will provide a better cleaning. The manufacturers of concrete resurfacers usually recommend power washing with a 3,500 psi washer.

You should also remove any oil stains, paint, or tree sap from the concrete. If your efforts fail to remove the stain entirely, consider applying a sealer over the stain before resurfacing. If left unsealed, the stain will very likely bleed through the resurfacing layer.

It is important that expansion joints be protected when resurfacer is applied. Mask off these control joints with duct tape or weather stripping to prevent the resurfacer from filling them in.

Resurfacer needs to be applied to a moist surface so that it won't draw moisture out of the resurfacer as it cures. Just before mixing and applying the resurfacer, give the slab a cooling spray with the hose and sweep off any standing water from the surface.

Mix the Resurfacer

For best results, mix and apply one bag of resurfacer at a time. You can mix by hand, but the job will be easier if you use a 1/2-inch drill equipped with a paddle mixer. One 40-pound bag will usually require 6 pints of water. Use warm water in cool temperatures, and cold water in warmer temperatures. At 73°F, you will have about 20 minutes of working time

Pour most of the water into a clean 5-gallon plastic bucket, then empty most of the contents of a 40-pound bag of resurfacer into the bucket and mix for several minutes into a smooth, pourable consistency. Let the contents rest for a few minutes, and then mix it again. Add a little more water or resurfacer, if necessary, to create a pourable mix that has the consistency of syrup.

  • If desired, concrete coloring agents can be added to the mixture at this point, just before application. Make sure to use color agents that are compatible with the resurfacer; using products from the same manufacturer is a good idea.

Apply the Resurfacer

The easiest method for applying concrete resurfacer is to pour a small amount on the surface, then immediately begin spreading it evenly with a light, long-handled squeegee. Resurfacer can also be applied with a trowel or brush. Work in segments of no more than about 144 square feet at a time. If possible, segment your work so that you are working to edges of control and expansion joints with each application.

At the edges of the slab, you can create clean, professional-looking edges with a concrete edger, but only if you get to them within the first 10 to 15 minutes of application.

Where a second coat is necessary, let the surface dry for 2 to 3 hours, then apply a second coat following the same procedure. Most manufacturers recommend a second coat, but this is optional, and your decision should be based on how well the first coat has covered small imperfections.

Scuff the Surface

If the resurfacer is allowed to cure without any finishing touches, it will create a smooth surface. That's often what you want in a garage. But the smooth finish can be slippery when wet, which makes it less desirable on a driveway, sidewalk, or patio surface. To add some bite or "tooth" to the finish, use a long-handled broom to make full strokes across the surface. Plan to do this within five minutes of application, while the mix is still wet enough. Make sure all broom strokes are made in the same direction.

Allow the Resurfacer to Cure

As concrete resurfacer cures, it hardens and becomes stronger. Quikrete and Sakrete claim that their resurfacers achieve its maximum compressive strength of 4,500 psi after 28 days. At seven days, it is already at 3,000 to 3,500 psi. But you don't have to wait that long before using the surface. Wait about 8 hours before walking on resurfaced concrete, and at least two days before driving on it.

Resurfacer should be kept slightly moist while curing. Covering with plastic is only necessary to protect the surface from rain immediately after application, but the surface should be lightly misted with water once or twice a day for the first two days.