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

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 . . . .
DanG (remove the sevens)




"bill" wrote in message
...
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

On Sun, 22 Nov 2009 13:41:39 -0600, DanG wrote:

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.


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.

bill wrote:
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


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.

--
aem sends...

On Nov 22, 5:39�pm, aemeijers wrote:
bill wrote:
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

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.

--
aem sends...

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

On Mon, 23 Nov 2009 09:52:18 -0500, Jeff The Drunk wrote:

On Sun, 22 Nov 2009 15:09:23 -0600, Michael Dobony
wrote:

On Sun, 22 Nov 2009 13:41:39 -0600, DanG wrote:

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.


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.

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.

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.

Jeff The Drunk wrote:
....
... 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).

--

On Nov 23, 11:40�am, dpb wrote:
Jeff The Drunk wrote:

...

... 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).

--

highway grade concrete is far different than whats in your typical
garage

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

"aemeijers" wrote in message
...
bill wrote:
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
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.

--
aem sends...

"Jeff The Drunk" wrote:

On Mon, 23 Nov 2009 09:01:32 -0600, Michael Dobony
wrote:
-snip-

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.

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

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

On Mon, 23 Nov 2009 12:42:00 -0600, bill wrote:

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

"aemeijers" wrote in message
...
bill wrote:
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
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.

--
aem sends...

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.

On Mon, 23 Nov 2009 15:10:30 -0500, Jeff The Drunk wrote:

On Mon, 23 Nov 2009 13:44:03 -0500, Jim Elbrecht
wrote:

"Jeff The Drunk" wrote:

On Mon, 23 Nov 2009 09:01:32 -0600, Michael Dobony
wrote:
-snip-

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.

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

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

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.

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.


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.

??? 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.