This first picture is of the welded framework inside the mold prior to casting. There is also a block of styrofoam in place to make it hollow. This reduces the weight and concrete consumption, making it easier to work with. In the bottom you will find a few pieces of steel that will be machined after casting, to get precision surfaces for the rails and the ballscrew mounts

The mold is placed on a cast iron fixture table and clamped down by screws to make sure it is as flat as possible. This was not necessary when casting the base since the base is adjustable, but the tower will have rails bolted directly onto it so it is important to have a precise mold.

 After pouring the concrete, the mold top was covered with plastic to keep it from drying too quickly. It was allowed to cure for 48 hours at room temperature, before going into an oven at 60 degrees for 96 hours (still covered in plastic). This should help it cure faster.

After curing, the concrete was taken out of the mold and placed back in the oven at 40 degrees for 72 hours to allow it to dry out properly. At the time of writing, 24 hours have passed. On Monday it will be taken out of the oven and, after cooling and some light finishing, be coated with a thick layer of epoxy.

Final machining of the steel inserts will take place a few days after the epoxy coating, to allow the concrete to set fully. The accelerated curing and drying, along with a thick coating, should greatly improve the dimensional stability of the concrete. Concrete shrinks considerably over time, but with this heat treatment most of the shrinkage should be over and done with, and should prevent the tower from warping. Only time will tell how well it worked, but I'm certain that it will be an improvement over not heat treating it.