Jackhammer help

[sweathog]

I just finished excavating the plumbing area in my basement to move the locations of the lines. I was on the fence about whether or not to try to jackhammer up my basement or not and couldn't find much info on the web from people that had gone though it. I know it's not rocket science, but the little I did find mentioned cracks in the concrete (where they didn't want them) and other mishaps. So to say the least I was a little hesitant. Well, it turned out great. I figured I'd share the process in case someone else is in the same boat. I've gained lots of info from sites like these and it's nice to have a chance to give a bit back.

http://web.mac.com/lfraser/iWeb/jackhammer

cheers,

lf

 

[Mikey]

That's the easy part. The real trick is replacing the broken-up slab. You've got to tie the new slab into the old to maintain integrity. Usually dowels or re-bar pieces are epoxy-grouted into the old slab to provide continuous reinforcement across the interface. My friendly PE gave me this advice:

The right thing to do would be to scarify the face of the cut, drill the dowels in 6" deep at 6" centers across from each other, tie-wire them together, epoxy them in place, allow to set (24 hours) then pre-soak the ground and existing concrete for 24 hours before pouring back. After pouring either apply either curing compound or lay and keep wet rags/burlap over the new concrete for 7 days.

http://www.michigan.gov/documents/MDOT-Material_Source_Guide_Qualified_Products_84764_7.pdf

As for the epoxy,

The company that we use is Sika Dur. You just mix the 2 parts, fill the hole and rotate the bar. The consistency is such that it does not sag/run out.

Hilti has a glass "capsule" that has another glass capsule inside of it with the two parts of the epoxy and aggregate. You put the capsule in the hole the insert the bar in breaking the capsules to mix the components. The draw back to this system is that you have to have a drill adapter to drive the chisel point of the rebar into the capsule to rotate and mix the components.

 

[Sponsor]

 

[Prashster]

I was in the same boat. Funny how little info there is on this subj, huh?
Anyway, this forum had a LOT of awesome info on it. Namely, Cass and BobNH gave me a lot of advice on how to do it right.

A couple of things for future reference:

1) Not sure you needed to demo THAT much concrete. If you just limited yr demo to the trenches and the pit, the slab integrity wouldn't have been as much of an issue, and you could just patch the lines.

2) Overbreak and slab cracking is an issue with a hammer like that. To minimize that possibility, it's best to cut the outline with an electric cutoff saw. It's dusty as all get-out, but worth it for the protection (and the neat look).

3) Before you patch your hole, put down gravel and a vapor barrier.

4) If you're ever just doing a sump hole, I recommend an SDS Max Rotary Hammer. You drill holes around the perimeter in 2" intervals with it, flip a switch, and then chip out the center. The holes provide stress relief points to prevent overbreak. Dustless and clean.

All that being said, as a fellow diyer, I appreciate what you must be feeling. Isn't it awesome ?!

 

[Mikey]

"dusty as all get-out" has to be the understatement of the century. I used a dry saw, and we're still discovering dust around the house in spite of extraordinary precautions to avoid it. I would without question spend the extra bucks to rent a diamond-blade wet saw the next time.

 

[sweathog]

Dusty is the truth. I briefly considered the diamond blade saw but figured I'd try the smaller route first. It did a nice job, but was pretty slow going. I positioned a wet/dry vac just to the side and it caught a small amount, but windows and doors being opened helped more.

That's great advice for the re-pouring. I have a friend that works for a builder and he's going to give me a hand with that. Instead of mixing it myself, I'm going to have it delivered. It'll be mixed better and won't set up as fast. I like the rebar/epoxy route, that should really keep it grabbed. What does the wet burlap do over the course of the 7 days, just allow it to set slower? Maybe I'll do the same type of site when I fill it back in.

Prashter, I was going to stop after the first day but thought having the extra would give me more optioins and I didn't want to have to go rent the thing again. The cracking and overbreaking seemed to be minimized by drilling the pilot holes. Even though I stopped scoring, I did drill the holes every 6 or so inches first, then broke from there. The first hole was the toughes. I wasn't quite as worried about the neat edge as I was told by several people that a rough edge is not as good for repouring stability. And yes, I plan on putting down the gravel and vapor barrier. I also plan on putting a mesh over the finished piece that straddles the border before putting down tile. Not sure what the product is called, but it's supposed to help keep it from cracking along the edges.

You're right too, when the dust has settled, it feels much better to have done it yourself.

 

[Prashster]

I built a plastic bubble in which to contain the dust. There was a - not kidding - quarter-sized hole out of which enough dust escaped to lightly fog the entire basement.

The problem with the wet saws is that they don't make big ones that are electric powered. I don't think it's safe to use a gas powered one indoors unless you can open enough windows.

 

[Lakee911]

Any reason why you can not use a little water for your dry saw to contain the dust? I saw somewhere a little gizmo that attached to your circular saw--looked kind of like a waterbottle for hampsters--that would provide some water to minamize dust. Could even get a helped to spray a little water from a sprayer (like from a hand pump chemical sprayer). Obviously you wouldn't want to over do it, and you would want a GFCI recepticle.

 

[Mikey]

I built the plastic bubble, used fans to create negative pressure while evacuating to outside air, set up the ShopVac to try to capture the dust, etc. The dust leaked out under the sill of one of the walls and piled up 1/8" deep all over the adjoining room. From there, of course, it was easy for it to cover the whole house. I still don't know how it happened. The neighbors complained the dust was settling on their flower beds, and the lawn and outside of the house around the window where the dust was coming out were covered. One neighbor almost called the fire department, thinking it was smoke. It hasn't washed off yet (it's been over a a year), but this year's hurricane season may do the job.

Science fiction fans will remember Arthur C. Clarke's "A Fall of Moondust". I had that kind of dust.

As for water, it would take a LOT of water. I think the combination of a diamond wet saw to establish a clean breakline, with the rotary hammer to do the serious work, might be the way to go.

 

[Prashster]

"I still don't know how it happened"

I think concrete dust is actually a living organism, with a very bad temper. It reminds me of that Stephen King story, "The Mist" that ate all the people coming out of a supermarket.

I just sawed right in the bubble and didn't exhaust anything. Stupid me. I'd only be able to cut in 6" intervals before the dust was so bad, I couldn't even see the line I was cutting.