I have designed some new table tops with a local mosaic artist. The artist just sent me the tops (each 200cm / 100cm) that are made out of tiles and on the back side of each there is just a 2-component glue that is slightly flexible which holds the whole thing together. Let s say they are a bit fragile now...
Overall thickness of the tiles is now about 1/2 inch now and my plan is to cast some self consolidating GFRC in the back so that overall thickness would be 1 inch. Basically ill flip the mosaic top upside down on the casting table, cut some melamine around it and cast.
I already did one top and the result is that it started warping. I have also noticed that when my GFRC mix drys it shrinks about 1mm every meter. And i guess that explains the warping. Warping happens on the longer side (200cm) as well as on the smaller side (100cm).
I tried to water the top and added some weight on it to bring it back to flat but it just doesnt seem to work.
These only option i have in mind for the tables to come is the following:
- add some shims under the center of the casting table. The casting surface will have a small camber. So when the concrete dries it would still warp but will be close to flat.
The GFRC mix i use is pretty standard. 50/50 cement and sand , w/c is 0,29 and 3 % fiber and polymer.
Could I change something in the mix to control shrinkage ?
Would love to hear your thoughts on that one !