How to Bind a Concrete Overlay
Concrete may be made to last decades, but even the best laid slab begins to wear down with time. Applying a concrete overlay can make an old worn concrete surface look brand new and add years of life to the slab. It's far less expensive than replacing the entire slab and has your concrete surface out of use for a shorter period of time. Getting the new overlay to bind to the old surface can be a problem, though. You can't simply spread a new surface over the old. You'd have two surfaces in place of the one, and that would quickly lead to your overlay cracking. Preparing the old surface correctly beforehand will allow you to bind the overlay in place, adding strength and durability. Does this Spark an idea?
Things You'll Need
- Power washer
- Broom
- Mop
- Low-pH cleanser
- Concrete degreaser
- Safety goggles
- Work gloves
- Respirator
- Angle grinder
- Crack chaser blade
- Wire brush
- Water
- Putty knife
- Epoxy gel adhesive
- Paintbrush
- Joint repair compound
- Concrete grinder
- Bonding adhesive
- Concrete overlay mix
- Wheelbarrow
- Spade
- Trowel
- Wood float
Instructions
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Clean the existing concrete slab thoroughly. Use a power washer if the slab is located outdoors or a good drainage system is available. Otherwise, sweep and mop the surface using a cleaner with a low-pH rating, removing any dirt and debris that may be present. Remove any oil present on the concrete, using a concrete degreaser, as the oil could interfere with the new overlay or the binding material.
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Put on a pair of safety goggles, gloves and a respirator to repair the surface of the floor. Use a crack chaser blade secured to an angle grinder on any cracks present. Make the edges of the cracks vertical and the depth uniform to up to one inch deep. Remove concrete chips and dust from the cracks using a wire brush, and then wash the cracks out with water. Allow the cracks to dry completely before continuing.
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Line the sides and bottom of the cracks with epoxy gel adhesive, using a paintbrush, and let the adhesive dry for an hour. Fill the cracks completely with joint repair compound, pushing the compound firmly into the cracks with a putty knife and then leveling the compound at the top. Wait for the compound to dry, according to the manufacturer's suggested drying times.
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Create a textured surface for your binding material to adhere to. Use a concrete grinder, available for rent at home improvement stores or equipment rental shops, to go over the surface of the concrete. Create scratches in the floor's surface, covering the entire concrete slab. Sweep up the concrete dust left by the grinding.
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Spread a layer of bonding adhesive across the textured surface of the slab. Use a squeegee to spread a thin layer of the adhesive to serve as a binding agent between the concrete slab and the concrete overlay. By binding the two surfaces you prevent independent movement of the two, which can cause extensive damage to the overlay, or water seepage between the two, which can damage both overlay and slab.
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Mix the concrete overlay material according to the manufacturer's instructions, in a wheelbarrow, and apply it to the adhesive surface, using a spade. Place the overlay material onto the adhesive while it is still tacky, but not wet. Use a trowel to level the overlay and a wood float to settle the aggregate present in the overlay, moving the water in the concrete overlay to the top for better curing. Finish the overlay, tinting it, stenciling or stamping it, and sealing it as desired.
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