Recently tore down and rebuilt a 5′ by 5′ front porch roof over a stoop for a customer. the old slab was bad and we broke it up to pour a new one. the brick on the house needed repairs. I asked a mason friend of mine whom I like a lot as a person to do the brick work and pour a new slab. I built the porch first, temp supported it, plumbed down where I wanted the corners of the slab to be, staked them out, showed the mason and left him to do his thing. come back next day and the slab is about 12″ wider than I staked out.
Can a slab (6 – 7″ thick) be cut straight and clean in order to remedy or does it need to be jackhammered out and done again? any suggestions would be much appreciated. Job could have a lead in for an addition in the spring.
“it aint the work I mind,
It’s the feeling of falling further behind.”
Bozini Latini
Replies
Yes. A concrete saw with a diamond blade will cut it. It will take multiple passes because cuts are only made so deep in a single pass. The sooner it's done the softer the concrete will be.
If there is rebar in there that's a different story. Many blades cannot handle rebar too. I'm not that familiar with how it would be done if there was rebar where the cut was to be.
As far as I know, there is only wire mesh in there. how about cutting a straight line w/ a demo saw? are there guides I can rent?Thanks for your responseJason"it aint the work I mind,
It's the feeling of falling further behind."Bozini Latini
I work in manufacturing so my construction experience is mostly in managing contractors doing occasional, sometimes major, work on site. I suppose a demo saw would work, but the only way I've seen union contractors cut a straight line in a slab is to use a wheel-mounted concrete saw. They snap a chalk line then darken it in with a marker. The saw has a guide pin that extends from the saw. The first pass is made carefully by eye along the line. Subsequent passes engage the guide pin in the kerf which helps keep the blade traveling true in the kerf. It is a wet cutting operation, with a water hose attached to the saw.
Hopefully others on the forum with more knowledge will elaborate.
Greetings hv!
FWIW, I've used a 4 1/2" angle grinder with a diamond blade in it to surface the rough edges of a concrete pour I wanted smoothed up. Aside from the noise & dust, it was amazing to me how fast I was able to grind away the concrete with a rim of diamond grit no wider than 1/8". From my own experience with steel, I can grind concrete faster with a diamond blade than a weld with an abrasive wheel. The trick is to use a light touch and keep the face of the blade moving over the surface or you will score grooves in it, sort of like sanding with the grinder fitted with an abrasive disk.
If you can't get access to a large dia. diamond saw, you can probably saw 1/3 the way through the concrete & then give the offcut a few whacks with a sledge to break it off. Snap your saw cut line a little larger than your finished dimension and then surface the rough edge with a small grinder oufitted with a diamond blade if neatness is paramount. It would help if the piece to be removed had no support under it before breaking it off. The deeper you can cut before the sledge comes out, the smoother the resulting edge will be.
The diamond saw blade I used in the 4 1/2" angle grinder was a dry cutting "turbo" style blade bought at a store called Princess Auto for less than $10 CDN. Although of Asian upbringing, that blade was more than adequate for the small job I did (3' of 7- 1/2" thick reinforced concrete, fully cured. When the blade began to lose its cutting ability, I flipped it over to expose the unused face.
When you run into the wire mesh with the diamond blade you'll soon know it by the greatly reduced cutting rate. To preserve the diamond blade, switching over to a steel cutting abrasive cutoff blade will get you through the steel so you can switch back to the diamond when you've cut deeper than the mesh.
As an earlier poster has pointed out, the sooner you do the cutting, the better. Green concrete will cut quite easily, you might even get by with just a masonary abrasive cutting blade instead of the diamond blade in the big saw.
The cutting will take some time, however, I'm certain it will be cheaper than a tear out & re-pour. If the cost of a big dia. saw rental is not in the budget, I'd be willing to try with just the 4 1/2" blade and driving some steel wedges into the resulting sawcut to break off the piece. Even if the rough edge doesn't completely clean up with the mini-grinder, some neat mortar, sack rubbed in, would cover much of the sin.
Its a good bet that your mason friend would have access to all this info. as well as the tools, perhaps it might be prudent to put a little responsibility on him to remedy the situation to your satisfaction.
Have a good one,
STAINLESS
Stainless, Wow, I really appreciate all of your input. sounds like you have been there with some success. I am trying to get in touch with the mason. He is difficult to get a hold of. I am on good terms with him and would prefer he do the work. I think my only fear is that he will not cut it straight since he couldn't follow my layout leading into the whole thing. I am still going to try him first. But if that fails I will certainly rent a saw and try to do it myself. I think a combination of the angle grinder and the demo saw should make it happen. It requires two cuts 65" long. I would imagine it being a days work. The cost of a rental is negligable to the satisafaction of a potential repeat customer. Besides, I like the guy. He works for the phone company with another friend of mine whom I play hockey with. this town is too small to leave someone unhappy. Thanks again"it aint the work I mind,
It's the feeling of falling further behind."Bozini Latini
"...two cuts 65" long ... a days work..."
An hour or two, even if you are dry cutting with a diamond blade in a worm drive saw. With one of the big gas wet saws you will be amazed how fast it goes.
Don't worry so much about HOW to do it. Just refuse to pay for it until he gets it right, sincce you were very cclear about what you wanted
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!