Completed form : 24" x 14" x 12" Shaped out of GFRC. Hand packed and troweled.
Weight: 70 #
Color: Black Oxide
Materials for mold:
- 4x8x3/4" sheet of melamine
- half sheet of bender ply
- 1 5/8 drywall screws
- 1 tube black silicone
- 2" ridged foam
- 75 # of GFRC and activator
Step 1: Melamine Mold and Pour
The sides are fairly straight forward..Cut and assemble.
The center dividers and bottom piece were copied from a shaped template by using a laminate trimmer with a bearing bit.
The shaped inner walls were bent into place using bender ply, screws, clamps and a lot of patience.
Insert the the shaped dividers to keep it all together and add a little hot glue
All corners were sealed with silicone.
Sorry no pics as I was elbow deep in black GFRC.
Once you have properly blended said mixture [ it should be the consistency of clay ] its off to the races.Hand packing the bottom first and then up the sides.. I had made shaped 2" foam to be stacked and placed inside the GFRC sides. These were needed to support the last layer as we topped out . We tried for 1/2" to 3/4" wall thickness everywhere. Troweling the top layer flat. This mixture gets hot so when you have a closed form like this you need to provide a way to vent the internal pressure. I tried pin holes ..not enough and ended with a somewhat distorted top surface.
Step 2: Demolding
- Next day I carefully removed the sides
- Pulled out the shaped dividers and voila!
Step 3: WET POLISHING
Not sure if the time was well spent here. Wrestling around with a wet 70 pound piece was a challenge. Went thru the grits with a wet polisher to mellow out the lumps created by the expanding trapped air.The inner surfaces were worked with diamond hand pads and abraded knuckles ..Kept flipping it around until I had enough.. The vertical sides were hard to keep clean as the slurry would run down and leave a stain on the polished surface. Next time!
Runner Up in the
Concrete and Casting Contest