Bonding Agent

ApgarNJ

hey guys, i'm a carpenter/builder, not a mason, but at my personal house here, its a 50s ranch house, to be built onto in the near future but for now, I need to pour a 2" slab over my existing concrete floor in the basement, i plan on putting a 2x4 around the perimeter and then removing it to allow a channel for water, and drilling some weepholes. i just can't justify the cost of having the basement waterproofed by a basement company. plus, i have a monolithic slab/footing(at least that's what it looks like near the gravity drain pit) and that makes jackhammering the perimeter impossible. (the basement people wanted to come in several feet away from the wall and cut in a drain. not sure I want to do that just yet.
I cleared everything out of the basement this afternoon and pressure washed it really good with a tight nozzle and got a lot of dirt off the old concrete.
what is a good bonding agent to use and any more prep work involved before the bonding agent is applied.
i've never done this before I will get someone to finish it for me as we pour the thin slab, but I want to make sure it's going to bond together. Quickcrete makes a bonding agent but because i'm not in the masonry business I don't know if there are major differences between brands.

let me know what you guys use.

CJKarl

I would say you're NEVER going to actually bond a skim/leveling pour over an existing slab. You could never hold the cure/shrinkage pressures.
I would pour the best concrete I could get, and plan on covering it with something. Sounds like you have a water problem, so maybe think about painting or staining it instead or carpet or wood.
There's always tile too.

__________________
There's Always A Market For Quality
http://www.kaufmannmasonry.com/

ApgarNJ

i'm not looking for perfection.
most of the basement will be unfinished. i'm framing a small room down there for my office, until we add onto our house. we have a baby coming soon and need to turn my current office into a bedroom.
i plan on putting carpeting or some floor covering in the room i frame out in the basement. the rest of the slab will be left alone.

do you think it won't adhere to it? i figured 2 inches would be enough to level everything nice and clean looking. plus allow the water to channel when it rains to the gravity drain in the corner.

i don't have the head room to pour a thicker slab.

CJKarl

I feel you pain. and understand what you are trying to do. My opinion is skip the bonding agent for a stronger concrete mix. I see you have cleaned the slab, good. I would just dampen it before you pour the skim coat.

__________________
There's Always A Market For Quality
http://www.kaufmannmasonry.com/

artisanstone

The other thing you can do is increase your mechanical bond. Use a sandblaster on the old slab or go to your local rental store and get a machine that basically takes ball bearings and bounces them off the slab, pulverizing the surface. This will do two things. First you will remove the "cream from the old slab, exposing aggregate for your new slab to mechanically cling to. Second, on a microscopic level, there will be more accessible pores for the portland crystals to infiltrate.

__________________
Bill Baddorf
Bill@artisanstoneworks.net
www.artisanstoneworks.net
www.stonefoundation.org

Tscarborough

If the purpose is just to get a clean, level floor, you can get either trowel grade or self leveling products to skim it. If you want to raise the level for the drains, either acid etch or scarify it, then use a paintable bonding agent and fiber mesh in a high strength concrete mix. Make sure if it is from a plant that they do not use normal aggregate, as it will be too large for a 2" slab.

Any cracks or joints will mirror through the new slab too, unless other measures are taken.

__________________
It ain't Rocket Science unless you are building rockets.

neolitic

Can't add anything intellegent
to the bonding question, but
when you put the 2X on the
perimeter, rip it in two on
the diagonal so that it will slip
out easier without busting the
edges of your pour.
Also, three things....
form oil,
form oil,
and form oil.

__________________
Put your location in your profile!
(Sorry....it seems there really are dumb questions)

ApgarNJ

thanks for the replies guys. the main thing is getting the floor to be dry and allowing water to channel around to my drain. the floor there now is not super smooth, so maybe an acid wash will help things.

where could i get fiber mesh out? is that a fabric that you lay down before the pour or push it down into the mud as you are finishing it off?

maybe i'm confused but is the bonding agent added to the mix? or is it painted on the floor prior to the pour and it dries, then you pour?

sorry for all the questions but i have to do this job myself with some help finishing because i can't afford right now to have a mason come and do it. i know it wouldn't be super expensive but work has been slow lately, so i'm trying to get it done myself.

on the 2x tapering, i should rip it on the 3 1/2" side on a taper so one side is 1 1/2" and the bottom side is maybe 1 1/4" still 3 1/2 high though. i planned on tacking it with a few screws into the block wall, and then pulling them out before it is fully hardened.

what is the best way to keep the cracks that are there from carrying through to the new slab? there aren't major cracks but a few that are very old and have been patched by previous owners. back in the 50s they never made the slabs look perfect anyways.

neolitic

Rip it so that when the top
piece (net to the wall)is pulled
the bottom piece is loose
(less than the full 1½").

Order fiber glass reinforcing
mixed in the concrete.
Costs less than a roll of mesh
and will go a long way to help
keep old cracks from telegraphing.

Bonding agent goes on existing
slab.

__________________
Put your location in your profile!
(Sorry....it seems there really are dumb questions)

ApgarNJ

any brand of bonding agent?

Tscarborough

Bonding agents are somewhat localized, just make sure that is paintable. That is, it can be applied to the surface as opposed to added to the concrete. Fiber mesh is chopped fibers that you add to the concrete.

If the cracks are old and dead, I wouldn't go through the trouble of isolating them.

__________________
It ain't Rocket Science unless you are building rockets.