Building Artificial Rock Forms - Part Two
How will the concrete stick to the sides of the form?
Adding layers of steel mesh to your artificial rock styrofoam form will allow the concrete to have something to cling to on vertical surfaces. This will also serve for a multitude of other purposes. The steel mesh layers will add overall cohesive strength to your artificial rock as well as minimize any hairline cracking in the concrete as it cures.
Applying steel mesh to the artificial rock form
As illustrated below you will want to apply the steel mesh first and then the chicken wire last. It is absolutely critical that you apply the steel mesh to the styrofoam being sure to leave a gap between the foam and the wire. You can do this with small chunks of styrofoam as spacers as shown below. This will allow the concrete to fully encompass the steel mesh. You will attach the steel mesh to the form by using the same wire pins idea used when building the styrofoam form. You will also be able to bend the wire mesh itself to have pins that will puncture into the styrofoam form as shown below. This is especially important along the bottom edge as you do not want sharp steel protruding downward from the bottom of the rock.
Also be sure to "sew" all the seams and overlaps in steel together to ensure the form itself is solid and will not excessively shake or move when you are applying the concrete. If the steel is too loosely attached or moves during concrete application you will find yourself sculpting concrete on one side of the rock while big chunks of concrete are shaken loose on the opposite side. Basically you should be able to pick up your entire form by grasping any single piece of wire.
Step two: Applying the chicken wire to the artificial rock form
The steel mesh is stiff and difficult to conform to the shape of your artificial rock form. The chicken wire is a thinner gauge steel and is much easier to conform to the shape of your rock. You will wrap the chicken wire around the form a few times being sure to wrap it nice and tight. Next you will be attaching the chicken wire using pliers to cut, bend and tie the chicken wire directly to the steel mesh.
NOTE: Be sure to add a concentration of chicken wire in all places where the concrete will need to climb a vertical side. It is much easier to add wire at this stage as opposed to during the concrete sculpting should you realize that you haven't enough mesh for the concrete to cling to.
Now you have a finished form for your artificial rock and you are ready to proceed to learning the secrets to mixing and curing a batch of concrete. Mixing concrete is one of the most important stages in making artificial rocks.