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Discussion Starter · #1 ·
So I have a problem that's really baffling me.. I completed a set of steps about 3 weeks ago.. no problems and everything looked great. I got a call today that the limestone stair treads have hairline fractures around some of the railings.. 3 out of 9 railing core holes have hairline fractures shooting out from it.. so far...

I used weldcrete on the back of the treads and layed them in mortar.. so they should be stuck good.. to install railings I core drilled a 2" hole and set the railings in exterior non-shrink grout. Made sure water cannot pool at those locations..

What could be the issue? We got our first major freeze this week so could it be water freezing somewhere?? This never happend to me before.. could the non-shrink of held water and froze?

I think the best method to repair is an epoxy crack injection method since its only really cosmetic... Thoughts?

I haven seen it for myself yet since I'm on vacation.. so no pics yet.

Baffled since I haven't had the problem and there isant anywhere water could pool...

Thoughts?
 

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contraction of the steel allowing water to get in? Who knows? What type of limestone? really dense or fairly soft? The HO is saying hairline cracks. Maybe they were there before and his eyesight is better than yours? maybe the stone cracked when you drilled it and now the cracks are expanding due to freezing

Until you see it yourself it's all conjecture
 

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Some "non-shrink" grout expands slightly and the expansion could cause cracking radiating out from a weak point( drilled hole).

Have seen non-shrink grout packed under column base plates and bearing plates since the expansion guarantees full contact and bearing.

It takes very little expansion to cause shear or tensile cracks in a weak, brittle material like limestone. I think the brand name of what I saw US Steel/American Bridge used was something like embeco(spelling?).

The AIR temperature may have been below 32F on an evening or two, but not likely the stone or grout really got down enough for freezing expansion of the absorbed moisture.
 

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Discussion Starter · #4 ·
Some "non-shrink" grout expands slightly and the expansion could cause cracking radiating out from a weak point( drilled hole).

Have seen non-shrink grout packed under column base plates and bearing plates since the expansion guarantees full contact and bearing.

It takes very little expansion to cause shear or tensile cracks in a weak, brittle material like limestone. I think the brand name of what I saw US Steel/American Bridge used was something like embeco(spelling?).

The AIR temperature may have been below 32F on an evening or two, but not likely the stone or grout really got down enough for freezing expansion of the absorbed moisture.
I was thinking that could be the case. But it took weeks to occur.. I used I think quickcrete pourable nonshrink because the bag of sika I had was definitely not pourable but more like packable..

Looks like ill be doing some crack injection in the spring.. unless anyone has a better option
 

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Rich - You are right. The "pourable" grouts are OK for grouting masonry walls because it is intended that the extra water (8" to 11" slump)is sucked out by the masonry to create density and bond without any consolidation.

A confined space needs to be packed full for your use and the excess water is bad. Unfortunately, the are many different types and companies like Quikrete do not fully explain the uses since they may not have the proper materials in their product line.
 

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Discussion Starter · #8 ·
I was actually very pleased with quickcretes product.. highly pourable, set fast and is weather resistant unlike others.

What I was thinking was maybe a pocket of water was trapped but I highly doubt it plus the masonry would of had a chance to absorb it in 2-3 weeks it had before any possible freeze.

Either someone pulled/shook the rails excessively until cracking occurred or the nonshrink grout truly did expand for the limestone to show its fractures in the freeze thaw cycle we had.

I don't have many options for a fix besides epoxy injection.. This way its only a cosmetic issue... thoughts?

I wish I was like all the rest of the hacks that run from there problems. But by fixing them just make me a better contractor people can rely on. May cost me some $$$ to fix so no further problems occur but oh well...
 

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Whatever was used to fill the holes. I've seen that happen a bunch of times, and the best thing to do is match the filler hardness as close to, but softer than the stone. I don't know what kind of limestone you have, but it's obvious that the grout is causing the problem.
 

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I read that the Super Por-Rok I use will expand 1%. Never realized this. I have seen anchoring cement blow out very strong, freshly cured concrete. Not sure what they used, but the contractor had to pull about 30' of handicap railing, hammer out the crete, re-pour and remount the railing. It wasn't pretty.
 

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Discussion Starter · #16 ·
But why is it cracking 3 weeks later? the nonshrink should have done all it's expanding long ago
Exactly what I'm thinking...
 

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Discussion Starter · #17 ·
People use Hydraulics because they're fast and that's good thing when doing railings. Not necessarily a good thing in Limestone IMO though. How far into the slab is the railing? concrete base I assume?
I'd say the holes go 8 inches down..

So count 2" for the limestone and the rest is in a solid base.
 
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