Message text written by Mark Rabinowitz
> 
I was wondering when someone would point out the questionable logic of
composite patching on cracked limestone steps.

Mike E., do you approve your material for wearing surfaces?

I found that even dutchmen repairs were problematic as they often seemed to
encourage further losses in the original stock adjacent to the edges of the
repair if located at the nosing.  Also, if the limestone is cracked it's
likely due to settling and foundation problems which neither repair
addresses.  I think unit replacements on cracked treads is the way to go.
You have to lift the broken ones and fix what's going on underneath.
<

Bravo, Mark. As one of my engineering professors used to say,
"Understanding the problem is 90% of the solution". If there are cracks and
they are "working" and you make a rigid repair (stone, composite patch,
epoxy or parrot guano) something's going to be the weaker component and
suffer for it.

But that doesn't preclude composite patching of wearing surfaces. With
proper detailing (no feathered edges, minimum depths maintained throughout,
proper surface prep), composite repairs to stairway surfaces can perform
very well. The concrete industry has a generally positive 40-year history
using latex-modified concrete toppings on bridge decks taking thousands of
cars per day, snow-plows and 70,000-pound tractor-trailers going 65 mph. We
have seen patched stone stairs remaining in good condition 10 years after
repair. I've also seen a few fail in a matter of days. If the latter should
happen to you, refer to paragraph #1, above.

Mike E.