On 7/29/2011 10:40 AM, bjshov8 at tx.rr.com wrote:
> Thinset sounds like a good idea for easy installation, as long as it is rated
> for exterior use. Professionals use epoxy for concrete repair and there are
> a lot of different types and ways to use them. What I see most often is a
> clear liquid epoxy that is injected under pressure into cracks, but
> preparation for this work involves applying injection ports and plugging the
> outsides of cracks using a more opaque epoxy that is probably more of a
> paste. I think epoxy would really be a pain for the type of repair mentioned
> here.
>
> That loctite product mentioned earlier might be an easy solution too. It
> looks like you put it in a caulking gun and have at it. The loctite page
> also mentions a polyurethane sealer that could probably be used. Urethanes
> are typically not sold for home use because of the additional precautions
> that they require but they really arent hard to use, just harder to clean up.
> For that matter you might be able to stick the pieces back together with
> common silicon caulk. I've even bonded to concrete with normal wood glue, so
> of course YMMV. And yes if water gets in the crack and freezes it will
> separate the pieces.
>
> Some years ago my wife had a concrete bird bath that broke. This is the kind
> with a concrete column that varies about 4" to 6" in diameter, plus a
> concrete bowl that sets on top. Somehow it fell over and the column broke in
> half. I used masking tape around the ends of each piece to protect the
> surface, following the joint edge carefully. I bought a package of normal
> epoxy at the store, the kind where the epoxy mixes and comes out of one hole.
> I coated one surface with the epoxy, placed the other piece on top of it,
> and wiped off what epoxy squeezed out. When it cured a little bit I peeled
> off the tape. There is a thin line visible where the joint was but it
> doesn't detract from the appearance of the thing.
If I understand the original question it was about flakes that need to
be reattached to concrete exposed to the sun and elements. Any adhesive
would have different thermal expansion rates the concrete. The chips
would heat up in the sun faster than the rest of the concrete. So you
need a thick layer of flexible adhesive. Thin set mortar on the other
hand is basically concrete without the aggregate and with some lime.
Mortar has the same expasion rate as concrete and only varies by the
aggregate. Buttering both surfaces and squeezing out most of the the
mortar would have a thin gap that would blend into the concrete over
time. Since mortar and the concrete are basically the same material,
the chips would be reintegrated rather than attached.
Just some thoughts.
Peter T
>
>
>
>>> A while back my wife had (more or less) decorative curbing installed
>>> around the driveway, shrubbery beds and the back yard. A couple of
>>> weeks ago we had a contractor in to do some dirt work and he drove a
>>> rubber tracked mini excavator across part of the curbing and some of
>>> the face spalled off. I still have all the pieces, but what do I use
>>> to bond it all back together?
>> Thinset mortar, like used to install tile. Coat both surfaces and let it
>> ooze out. Come back a couple of hours later with a stiff brush and
>> clean off the excess.
>>
>> What ever you use, make sure the gap is completely filled or frost will
>> separate it.
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