Make a sketch of the concrete pylon. Write down all the measurements and lengths. The construction will happen in sections. Keep the heights at 2 or 4 feet. Keep in mind, the bigger it is, the heavier. Divide the total height of the pylon by 2 or 4 feet; this will equal the number of sections that you need to stack to achieve the desired height.
Cut the sheets of flexible plywood to 2- or 4-foot-wide lengths, using the the lengths of the circumference of the inner and outer walls as your measurements.
Attach the sheets end to end (if needed) to create the exact length, using duct tape. Tape down the seam and place some pieces across the seam for strength. The plywood will resemble a cylinder. Place it on a flat, level surface where the concrete will be poured.
Cut a length of wire mesh to surround the inner wall form. Tie the two ends of wire mesh sheet with wire tie wraps. Be sure that the sheet does not touch the inner wall form.
Form a cylinder of plywood to be used for the outer wall form in the same way, attaching ends together with duct tape. Surround it with wire mesh. Create as many forms as you need for your total pylon height.
Support the forms with 2-by-4 inch lumber and screws. Be sure to support the structure all around in order to maintain the circular shape. Do not allow any screws to penetrate into the mold, for they will end up inside the concrete. Create enough forms to stack on top of each other and reach the desired height.
Estimate the amount of concrete needed for all the sections in cubic yards. Order extra in order to have enough to fill all the pylon forms.
Mix the concrete according to the manufacturer's instructions and pour into the forms. Use a hoe to move the concrete around the form. Do not knock the wire against the inside form wall. The wire should lay 3 inches away from the inner walls to prevent rusting.
Pour concrete to the top of the form and trowel the top flat. Trowel the top of the concrete pylon a few times to flatten and strengthen the ends. Do the same with all the forms and wait a month to allow the concrete to fully cure.
Line up the sections with a level. The sections should not lean. If leaning occurs, grind them to level the ends. Apply an adhesive or epoxy between the sections to join them. Depending on the size of the pylon sections, some equipment may be required to move and stack the sections safely.
Insert rebar into the center core of the stacked concrete pylon sections. Tie the pieces of rebar together using wire wrap until the rebar extends from the bottom to the top of the pylon.
Complete the concrete pylon by filling the center cores with a grout or concrete mix. This will fill and tie the pylon sections together including the steel rebar. A concrete pump truck is recommended to deliver concrete to heights over 12 feet.