How to Repaint Coal Fly Ash Concrete

Scrape off as much of the existing paint coat using a stiff wire brush and a putty knife. There may be several layers of paint present; use the putty knife to break through them.

Sand the exposed spots of the multiple layers of paint using a belt sander. This smooths the area out and keeps the remaining paint from chipping away even more

Fill in any cracks, holes or uneven spots on the concrete. Use a latex-based patching compound applied with a putty knife to fill large cracks and depressions while using elastomeric caulk and a caulking gun to fill smaller cracks.

Sand the entire surface that you want to paint using a belt sander.

Remove dust, paint flakes and dirt using a shop vacuum.

Paint the concrete with a water-based concrete primer. Use a brush to paint the primer on, "feathering" it in with short side-to-side brushstrokes wherever you need to even out the surface of the concrete.

Sand down any rough or high spot using your belt sander once the primer dries, then dab on a thin layer of primer where you sanded it away. Let the touch-up primer dry before painting on top of it.

Apply concrete or patio paint available from any home-improvement store using a roller to deliver an even finish. If necessary, allow the paint to dry overnight and apply a second or third coat.