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
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?
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 . . . .
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
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.
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).
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
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.
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.
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.
IMHO, this is one of those things it is better the pay the money to a
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.
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.
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