grinding concrete question


I need to grind an apron or slope area across a garage door opening. The opening originally had storefront glass in it, so the edge of the slab is flat. I'm wanting to go about an inch deep at the slab edge, so the slope will be about 1" in 7 or 8" setback. I figure to rough away a lot of the material first with an electric hammer and a 3" wide bit. I tried cutting grooves, but I think that adds a lot of time & dust, but doesn't speed up the chipping process all that much. Will a concrete grinder, the kind that looks like a floor buffer, be difficult to control on the roughed slope area? thanks, bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You just thought you had dust with a saw blade - you ain't seen nothing yet til you put a grinder on it. The fastest thing to do would be to cut, remove, and repour the lip. The next choice would be to saw lots of slots at the finish grade, bump off the highs with a chipping bit on a rotary hammer (not a hammer drill). Follow with a bushing head on the roto hammer to get the shape you want. Grind and polish only if absolutely necessary - it would be easier to use something like Mapei's Planipatch to smooth the top.
--
______________________________
Keep the whole world singing . . . .
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 22 Nov 2009 13:41:39 -0600, DanG wrote:

I would go with the cut, remove and repour (pinning the sections together with short sections of rebar, like they do on roadways). Use a laser to level it out properly.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 22 Nov 2009 15:09:23 -0600, Michael Dobony

Replacement is the best long term solution. When you grind concrete you grind away the cement exposing the course aggregate below the float. This is not good to expose to rain, snow, ice etc.. for obvious reasons.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 23 Nov 2009 09:52:18 -0500, Jeff The Drunk wrote:

Concrete highways are often grooved after the fact, exposing the course aggregate, but they hold up. Of course, the highway is probably not the same grade of concrete as your building is.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 23 Nov 2009 09:01:32 -0600, Michael Dobony

I've only seen the berm grooved to warn sleepy drivers they're headed off the road. And I don't even know if that was done after the fact. Any other cuts as in those made to install reflectors were always sealed in epoxy. What roads that you know of are grooved down to the aggregate in the driving lanes? I've never seen that here on the east side of the US.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jeff The Drunk wrote: ...

Don't get around much, do we??? :)
There are quite a lot of areas that have been grooved (primarily on curves) to help minimize hydroplaning on I75 and various other places.
The grooves have been indeed been cut after the fact (often long after).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

highway grade concrete is far different than whats in your typical garage
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Depends on how you define "don't get around much."

I drove from NE OH to Tampa FL and back in 2005 and don't recall intentionally grooved surfaces in the actual driving part of the roadway. But I won't argue that they don't exist, just that I've not experienced them.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I've seen bridges grooved in NY, VT & Massachusetts. The NY Thuway also had those damned warning groves across all lanes of traffic to wake you up before you got to the tollbooth.
That said- I imagine it would be easier & better for the OP to remove & replace the apron area.
I've ground some old concrete. It is not easy work.
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 23 Nov 2009 13:44:03 -0500, Jim Elbrecht

Ah ok yep I remember the warning groves in toll booth areas now that you mention it.
I'm sure there are some important differences in roadway concrete that allows this grooving without detriment to the integrity of the entire surface. I've seen driveway concrete that if not sealed and maintained erode to the aggregate and start to pock out after 20 or so years of exposure to the elements and deicing chemicals.
But it's all moot now, the OP has decided to bust out what he has and re pour it which is the best and easiest way.
I probably should have a chat with a friend who owns a concrete supply company for a little closure on the subject. He helped another friend with expert advice when it came time to sue for a badly botched driveway job. She won, the company ripped it up and redid it this time correctly and with better concrete.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 23 Nov 2009 15:10:30 -0500, Jeff The Drunk wrote:

You also missed the second part of my comment. Driveway concrete is not generally highway mix. There are several concrete roads here in southern Missouri that have had the top layer removed to smooth out the roads. Lots of roadway curves are grooved after the fact to remove water, as are many straights that are prone to hydroplaning.

??? Why didn't she go to the friend in the first place to do the work? Driveways are rarely poured with good concrete unless specifically requested. Wish I had specified highway grade and gone to 8" and pinned.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
bill wrote:

concrete company that has the BIG tools, and the truck mounted compressor, who will be able to knock it out in a couple hours. May cost a few hundred, but your back, and the neighbors, will thank you. What you describe doesn't sound much different than how they do curb cuts around here lately. No more cutting out entire sections and repouring a whole fancy apron, just cut off the rounded section and grind it all smooth. Not sure if they seal the cut surface with anything or not.
Just for giggles, I'd also price out what it would cost to cut out a nice square section, and pour a ramp. Concrete may be cheaper than the cost of all the grinding stuff that gets used up. This is especially true if you are doing any concrete work outside to lead up to the door.
-- aem sends...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

grinding will leave the aggregate exposed, may cause prematre failure and certain to look wierd.
the top surface of concrete is the cream of the cement. not the aggregate stones
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I think all the suggestions about cutting out the section and repouring are the way to go. Carrying the slope into the original slab area has to do with drainage. The garage door is set back about 8" and with the flat slab, some water (predictably) creeps in under the door. I'm pouring a new ramp slab next to the door opening regardless, so the cut and repour will work great. Thanks to everyone for the help. Bill

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 23 Nov 2009 12:42:00 -0600, bill wrote:

Make sure the old and new are pinned and you might also consider putting a small lip behind the door in addition to the ramping. I wish I had done that to my garage.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.