pouring concrete...

[Hamilton Audio]

I've got to redo a concrete trough drain in front of my garage door. My ashphalt driveway stops about 12" short of the pad, allowing room for a 6" wide trough and another 6" or so of finished concrete.

The way I've figured it (and for how its going to cure), the form will need to stay in place forever. This is because the rails of the grate system will sit on top, and once cured, the form becomes a functional part of the design :) As this is a "test" (not sure why the existing pour disintegrated so badly, so I don't wanna spend huge bucks to have it happen again....), I'm going to use wood for the form...

My question is this....what can I do to the wood form to further preserve it from moisture damage? I'm going to use pressure treated stock, and considered coating it in tar and letting it harden before pouring. The form will be completely invisible, under plate steel, so aesthetics make no difference. Also, any recommendations for enhancing the strength and longevity of the pour? I've considered getting 3.5" screws and driving them from the inside of the form out, all along the length of each side to provide "fingers" for the concrete to grab...I've got the following on my list:

- using 1/8" hardboard strips to keep the garage pad and the new concrete pour separate

- using a concrete "adhesive additive" adding to both the new concrete mix and brushed onto the very hard underlying existing concrete

I've read about an acrylic fortifier? is it worth looking for? any other advice? sorry for the long winded post....I'm tackling this project this weekend...

thks! b

[SQLit]

Why do you want to preserve the wood? Forms are removed when the concrete is set. Still green but hard. Talk to some locals about a monolithic pour. Set the sides with metal stakes, pour the bottom and then the sides. As it sets start removing the stakes from the bottom and filling the holes. In a few hours the sides can be stripped. My parents drive way was done this way, they used expanded metal for the grating. Using tar or anything else on the wood will only create problems as your working. Most concrete folks use releaser so the concrete will not adhere as well. Rebar run horizontally would be better. Maybe wire mesh formed into a trough that you like. Do not for get to slope it so it drains. That was what they did not do for the parents. Theirs tends to fill up with snow and ice when the conditions are right for that sort of thing. Mom has a garden hose on the hot water from the laundry and that cleans it up pretty quick.

[Hamilton Audio]

again, I'd want to preserve the wood because the way the railings/grating goes, there will be no possible way to remove the form once it is set in place :) You've got some good ideas there...I'll see what I end up working with...

thanks! b