Why did the limestone crack and can it be repaired (glued)?


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Old 10-14-06, 04:47 PM
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Question Why did the limestone crack and can it be repaired (glued)?

This is regarding front porch steps. 10" wide limestone treads with 1 1/2" dia wet core drilled hole at center line and 4" in from end with aluminum railing set in expanding grout.

One hole has hairline crack through hole but not completely across limestone. Can this be glued? With what product?

The other limestone is completely cracked through hole with end of limestone, separate additional hole on this stone has hairline crack through hole.

My theory on this is, stone is not anchored securely to block wall and as grout expanded and/or water seeped between grout and limestone froze and expanded the only resistance to movement was the limestone which was not strong enough not to crack.

Any help to understand this and more importantly to fix it is appreciated.

Thanks guys!
 
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Old 10-14-06, 10:31 PM
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Limestone is great in compressive strength, but not in tensile. By using an expansive grouting material for an application where there will certainly be movement, you have created a situation where the brittle limestone will almost certainly crack. Properly done, the hole in the limestone would be slightly larger than the handrail, and the grout would stop below the limestone. The joint between the limestone and the railing upright should be filled with a flexible sealant.

To repair it, the grout should be removed to the level of whatever is supporting the limestone, and that joint should then be sealed with a flexible sealant. If this is done, the cracks will be cosmetic only.
 
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Old 10-15-06, 09:42 AM
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Can you reccomend a flexible sealant or describe it in more detail?

Thanks.
 
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Old 10-15-06, 10:19 AM
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I have had good luck with NP1 by Sonneborne.
 
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Old 10-15-06, 07:31 PM
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Thanks I'll give it a try!
 
 

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