Concrete is a mixture of clay, lime, sand, gravel and water. Some concrete contains small amounts of metal and is referred to as reinforced concrete. The idea of adding metal to the concrete was pondered by a French gardener named Joseph Monier in 1840. Since then, reinforced concrete has been used to create garden statues, fountains and birdbaths. A concrete birdbath can add charm to a garden and is highly durable. It is not indestructible, however, and can be subject to breaking, cracking and chipping, especially in the winter. You can repair a broken concrete birdbath and render it good as new.
Empty the concrete birdbath of any water. Lift off the basin carefully and dump out the water.
Move the birdbath into a garage, basement, work shed or anywhere else out of the elements where you can repair it and let it cure.
Fill a bucket with warm water and a few squirts of dish detergent. Agitate the water to make it sudsy. Clean loose dirt and residue from the birdbath by scrubbing it with the solution and a scrub brush.
Empty the bucket of dirty water. Refill it with clean water. Dip a clean sponge into the water to rinse dirt and soap from the birdbath. Allow it to dry thoroughly -- ideally overnight.
Mix the two-part epoxy's two parts -- a resin and a hardener -- together on a piece of cardboard, using a wooden craft stick. Mix the two parts gently; vigorous mixing will cause air bubbles.
Apply the epoxy mixture to any cracks with the wooden stick. For a broken area, apply epoxy with the wooden stick where the broken pieces meet. Join the two pieces and hold them together, applying pressure until the bond is made. Remove any excess epoxy with a clean rag.
Let the epoxy cure for at least 24 hours before returning the birdbath to its outdoor location.
You can purchase two-part epoxy from a hardware or home improvement store. You can use masonry adhesive instead, which you apply with a caulk gun. Use a quick-setting concrete product such to repair fractures in a concrete birdbath.
Work on the birdbath where it lies if it is too heavy to move indoors. However, you should not subject the two-part epoxy to the elements while it is curing. If rain or snow is in the forecast, cover the concrete birdbath with a plastic tarp.