16/04/12
The large(r) slab has also been rough cut (50 grit diamond pad). All samples have dried substantially lighter than expected. Not as hard to cut as expected after 4 weeks of curing. Next - slurry!
20/03/12
"Bystanders will need to consult drycleaners" was the motto on Monday night as the wet polisher was fired up for a "green" cut of the freshly de-molded castings. The concrete is amazingly tenacious when trying to release it from the molds. There were some small voids (to be expected - slurry is used to fix these) so a little more vibration would be useful next time around. The 50g of oxide (~0.5% by weight) gave a very dark grey mix. The 50 grit diamond pad made light work of exposing the aggregate / embedded items.
16/03/12
Today we brought down the rest of the gear and got ready for a test pour.
A couple more test molds were made - this time thinner 300 x 300 x 40 frames as well as some "egg ring" 90mm storm pipe circles for doing multiple small batch tests.
A special thanks to the team at Sika Australia who were good enough to donate 2L of Sika® ViscoCrete® PC HRF-2 High Range Water Reducer Retarder (say that quickly 3 times). This special concrete admix gives us a superplastic cement with low water (which means high strength) and quick demolding (for fast fabrication). Normally it comes in 20L minimum quantites which would be enough to make a couple of tons of concrete...
It was amazing how little water was needed to hydrate 15kg of mix (<< 2L)!
First batch used grey cement, river sand, small black river stone and black oxide for a deeper grey mix. The fibres look quiet odd (like there's dog hair in the mix) - we shall see how they look in the final product. Samples included copper wire fragments, brass fasteners and other aggregates.
De-molding is set for Monday night with a "green" concrete cutting to expose the aggregate.
A thanks to for helping with the day's events...
21/02/12
OK so some test 300 x 300 x 50 forms have been built.
I'm currently building some 300mm diameter circular forms out of thin luan plywood as an experiment.
Standby for a pour very soon...
18/09/11
This is a placeholder for factotum's concrete benchtop project page.
The plan is to start with some trial 400 x 400 square forms fabricated from melamine.
Currently we have melamine, cement, oxide, aggregate, sand, poly fibres, mesh and a concrete vibrator.
What we'd really like at some point is a cement mixer for bigger pours.
And a new concrete polisher is on order...