Release for wood "waffle" inserts for lighter weight pavers 2

[containerwall]

I'm using 2 x 12 boards cut with a table saw at a 20 degree bevel so I can decrease the interior thickness of pavers from two inches to 3/4" in order to benefit from less material and lighter weight. The 1-1/2" thickness is pressed 1-1/4" into the concrete. I seal the cut boards with two coats of elastomeric roofing material. I have tried many releases and have decided to use corn oil as it is least toxic to handle and breathe around. I'm using a seven sack mix with pea gravel and concrete sand, 60% pea gravel and 40% sand and a 0.4 water cement ratio. I embed the waffle insert during vibration for ease of insertion.

The problem is I can't get the waffle insert out. I can't understand why not. The remedies I see are to use a rasp and round the corners some, rub grease over the surface, keep spraying with oil before use to encourage maximum absorption, and pull out early with concrete very green.

The more I endure, the performance gradually becomes better as I guess the alkali reaction finally stabilizes. The first six or seven times is so difficult and the paver usually breaks.

Is there a good trick for prepping wood to get a good release from concrete the first time it's used? I believee the wood is fir.

Thanks for any suggestions

 

[dik]

If you let your concrete set for a few days, it will adhere to the wood form, even with form release oil. Most contractors will loosen the formwork the day following the pour, even if they don't remove it.

Can you cut your form panels in two, you may have a 'joint line', but it will be on the underside. If you cut your form pieces in the middle using a 20 degree cut, you could have placed the 90 degree edges together giving you the 20 degree edge with a single cut. Often done for keyways. Can also cut a bit of a notch on the 90 degree edges to get a screwdriver, tire iron, or whatever into to pry the two halves up.

I can send you a cad sketch of the above cut if you want.

Dik

 

[dik]

Paver Insert FYI

Dik

 

[dhengr]

Sand the edges and end grain as smooth as possible, and increase the draft angle, then use several coats of a glossy epoxy paint, and a few more coats on the ends and edges. Drill a few .25" holes through/in the face of the boards. When you are ready to pull the forms which should have handles on them, give each of the holes a shot of compresses are or water under pressure. This will push the form away from the conc. Maybe use a 9x9" cake pan, because its smooth, and the bottom will flex, and will take form oil well. Use the compressed are idea here to. You have to solder an air stem on the inside of the pan. You may blow a hole in too thin a conc. face. Maybe make your void/lightener out of the lest expensive 1" foam board and leave it in place. If you are making pavers and you make them too thin, and then have trouble getting them perfectly, and fully, bedded in sand, they will likely crack and break up in the middle. The foam board left in place should improve this support picture.