How Do You Clean Concrete Before Sealing It?
How Do You Clean Concrete Before Sealing It?
You have decided that sealing your concrete slab is a good investment of your time and money. You may have even chosen and purchased your sealer. Before you begin sealing, however, it is very important that you properly clean your concrete.
Unless your concrete is brand new, it has inevitably accumulated dirt, oil, and other grime. If the sealer is applied over these items, it will bind to the contaminants instead of the concrete and will therefore not work as well or last as long as it should (in addition to sealing in any unsightly blemishes in the concrete!).
If you have any stains that have soaked deeply into the concrete, these should be removed first. Use the appropriate product for the type of stain to be removed - rust stains should be treated with rust remover, and oil stains should be treated with a degreaser. Follow the manufacturer’s instructions for using the product to remove stains. Stubborn stains or blemishes (such as spray paint) may require a two step removal process.
Once any deep stains have been removed, a simple pressure washing should be sufficient to remove the remaining dirt and surface stains. Use a pressure washer that is rated at at least 3000 psi and has a flow rate of at least 4 gallons per minute. A higher pressure rating may be required to remove skid marks or surface level paint stains. A mild detergent may be added to the water if needed, but is generally not necessary for surfaces with normal dirt accumulation.
If you are cleaning a driveway or other surface that is not perfectly level, begin pressure washing at the highest point of the concrete to allow the contaminants that are washed away to flow down over concrete that you have not yet washed. Hold the nozzle of the pressure washer approximately 1 foot from the concrete and move it across the concrete in a wide sweeping motion. Do not hold the nozzle too close to the concrete or linger in one place for longer than necessary - doing so could damage the concrete!
Once clean, allow it to dry for at least 24 hours before applying
concrete sealing. Weather conditions can greatly affect the time it takes a slab to dry - if necessary, use fans or dehumidifiers to accelerate the process. Do not drive on or otherwise use the clean slab any more than absolutely necessary until the sealer has been applied. Any moisture that is still in the slab or dirt that is introduced between cleaning and sealing may interfere with the sealer’s ability to bond with the concrete.
Once your concrete slab is clean and completely dry, you are ready to apply sealer. Once sealed, cleaning dirt and spills off of your concrete should require nothing more than a broom and cleaning rag. Your concrete will be protected from stains and heavy wear and tear for many years to come!
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