You must use rebar to reinforce very large statues.
How to Make Concrete Statues. Concrete statues are usually displayed outdoors, in the garden or on the patio. Creating your own concrete statues can be challenging, but it's a fun and rewarding hobby. When you create a statue from scratch, you can be sure that you have exactly the statue that you want.
Find an object to mold. Brush a layer of shellac over the object to be molded. Once it's dry, mist a layer of mold release medium onto the model. Go over it with a soft brush.
Mix liquid rubber or latex according to the manufacturer's directions. Cover the model completely with the liquid rubber. Allow it to dry until it's tacky.
Add layers of liquid rubber until the mold is thick and sturdy. Let it cure overnight.
Cover the mold with a thick layer of plaster. Let the plaster harden. Remove the plaster in sections. Peel away the rubber mold.
Prepare concrete according to the manufacturer's directions. Mix until smooth. Add oxide colorant if desired.
Reassemble the plaster support piece. Put straps around it to hold it together. Place the latex mold inside of it. Pour concrete into the mold.
Allow the concrete to dry overnight. Remove the plaster. Cut away the rubber mold. Let the statue cure for a few days.