Flattening A Seam In A Concrete Patio

[cabinetman]

I've got a concrete patio that's about 45 years old. It was done in two halves at different times. There was no attempt to create a smooth edge on the first pour or the second pour, creating a clean seam. One is just butted up to the other.

Well after all the years, surface edges have feathered back (about 3/4" on each side) from the joint, and one side is about 1/2" higher than the other. I would like to level out the joint which is about 18' long. If there was something like a masonry belt for a belt sander, that would be great.

I had a few thoughts. I could just grind a slot and install some sort of joint track, like for expansion/contraction. I really prefer to have just a clean seam if possible.

Any thoughts?
.

[Uncle Cracker]

You can rent a concrete grinder... looks like a floor buffer on steroids...

[smorris]

You can rent a concrete grinder... looks like a floor buffer on steroids...

+1.
Let us know how it works...LOML mentioned that she wants me to take up the tile floor and replace it with wood. 1100 sq ft is a lot of tile to chip up and leveling the mortar is a job for something like that.

[gjat]

I've actually done an extensive amount of this. For your application, i'd use a diamond grinding bit on a side grinder. I rented one from someplace like Sunbelt or National, and got the blade from them. You can buy a diamond bit from Harbor Frt, but I don't know the quality.

[cgallery]

Right now in my neighborhood they're grinding sidewalk tile joints to make them even (fixing trip hazards). It exposes the aggregate on the high tile. A 4" (approx.) wide joint takes 10-15 minutes for the guy, depending on how uneven the tiles are.

It is being done with a side grinder w/ some sort of diamond blade.

It looks like some sort of franchise is doing the work. They have a truck with a catchy (but not catchy enough I guess because I can't remember it right now) name.

They did one tile in front of our house. The cost to us for the work was $30. Perhaps we're benefiting from a quantity discount, perhaps not.

[pelligrini]

They did one tile in front of our house. The cost to us for the work was $30. Perhaps we're benefiting from a quantity discount, perhaps not.

Probably, and they were already in the area and set up.

If they were like the contractors that redid the curbs on our street you may have paid for it twice. Once outright, and again when they billed the city. That's the only way I can figure out how my neighbors got their new driveways at such a low cost.

[cabinetman]

You can rent a concrete grinder... looks like a floor buffer on steroids...

That's probably the wisest thing to do, but I was trying to come up with some method so I don't have to rent a machine.
.

[Uncle Cracker]

That's probably the wisest thing to do, but I was trying to come up with some method so I don't have to rent a machine.
.

They make hand "sanders" for concrete (has a pumice block with grooves cut in it), but I'll bet on this job one of those would be a PITA...

[cabinetman]

They make hand "sanders" for concrete (has a pumice block with grooves cut in it), but I'll bet on this job one of those would be a PITA...

I hate H&K projects. The only ones worse are OMB.
.

[gjat]

That's probably the wisest thing to do, but I was trying to come up with some method so I don't have to rent a machine.
.

No, you don't want that. Tried it and it failed. It's too wide of a swath, too rough, hard to control depth. The side grinder with a diamond cup on it is what you want. We had to take up to an inch off about 6 to 8 pads in an area about 3' by 12'.
My first choice was this scarifier: http://www.kutritemfg.com/kr13_scarifier.php

After consulting with a couple of conrete contractors, we went with this grinder set up with this: http://www.harborfreight.com/cpi/cta...emnumber=66353

The grinder worked much better. If you're going to re-float the seam, make sure you use a product that will feather out. I believe it has to be a latex product, I'll check on it if you're interested.

[cabinetman]

After consulting with a couple of conrete contractors, we went with this grinder set up with this: http://www.harborfreight.com/cpi/cta...emnumber=66353

The grinder worked much better. If you're going to re-float the seam, make sure you use a product that will feather out. I believe it has to be a latex product, I'll check on it if you're interested.

I looked at that diamond HF grinder. I wonder how long it's good for. I will be feathering it out away from the seam. Maybe no seam if the product is any good.
.

[gjat]

That would be my concern as well. We paid about $80 for ours and we never wore it out and did a **** of a lot of grinding. I think you would be fine because chances are you're grinding 2500 psi concrete, not 4000 psi (which we were doing). You also want to sweep away the grindings as you go. I'll think you'll be surprised at how quick it goes.

[cabinetman]

That would be my concern as well. We paid about $80 for ours and we never wore it out and did a **** of a lot of grinding. I think you would be fine because chances are you're grinding 2500 psi concrete, not 4000 psi (which we were doing). You also want to sweep away the grindings as you go. I'll think you'll be surprised at how quick it goes.

Thanks for the info. How can you tell the PSI? This concrete is very light gray with small aggregate. I formed a ramp out of the utility room and used sand mix because there wasn't much thickness. That stuff dried a deeper gray. A much darker color.

I'm thinking that no matter what I use, the feathered edge will look raggety. Maybe cut a straight line on both sides of the seam, and step it down for a fill, and that way have a straight edged repair (like 6"-8" wide). Does that sound reasonable?
.

[Mr__Bill]

I'm thinking that no matter what I use, the feathered edge will look raggety. Maybe cut a straight line on both sides of the seam, and step it down for a fill, and that way have a straight edged repair (like 6"-8" wide). Does that sound reasonable?
.

There is a product called concrete topper, or something like that. The borg carries it and it's made to be used as a skim coat over rough concrete. You may be able to do the whole patio, make it all look the same and if you like add some color to to too.

I'm getting ready to do some repairs to my patio with this stuff so if anyone knows the pitfalls using it please advise.

Bill
it's rained so much the concrete is soggy and the aluminum is rusting.....

[pelligrini]

Thanks for the info. How can you tell the PSI? This concrete is very light gray with small aggregate. I formed a ramp out of the utility room and used sand mix because there wasn't much thickness. That stuff dried a deeper gray. A much darker color.

I don't know of ways to tell other than lab-work. More than likely, a lower PSI concrete is used for flatwork.