Mortar was used to fill the gap between the stone cap and patio concrete. Obviously that didn’t work well.
I’m afraid non-shrink grout will be too brittle to accomodate differential expansion and contraction between the stone and the concrete.
I need to make a recommendation for an expert witness case. What is an appropriate material for this application?
Got a broadview ?
Like this?
How about Hydraulic cement.
It does not shrink.
Ken,
The application used has been an industry standard based upon what has been available for the time…being that the mortar is porous and therefore susceptible to any freeze thaw affect (if that is applicable) I would simply state that the cracking is to be expected and simply a maintenance issues in this setting. Obviously the larger the joints, the more cracking you are going to have…which is where you may want to focus on.
There are various types of caulkings that can be used however we all know that they will break down themselves well before the 35 - 50 year warranty that many of them advertise.
One other possibility would have been to use cement itself…less porous however I am sure there will eventually be problems with that as well. Again, I would concentrate on the grout width along with any sealers that were (or were not) applied.
regard
Jeff
Ken,
(As Jeff stated above about freeze/thaw)…
Are there other conditions that may be adding to the problem, such as children/adults playing/jumping/sitting on the edge? Given the overhang, wouldn’t the downforce pressure contribute to the cracking over time?
Jeff
I’m with Brian on the poly.
Kenton, Bryan is on the right track.
The mortar needs to be removed and a backer rod installed and then apply a joint with colored one part Poly urethane sealant to match the stone joints.
A one-part does not require primeing of the adjacent surfaces, but a two-part poly urethane sealant does.
Here are a few of the choices available;
http://www.tremcosealants.com/commercial/default.asp
http://www.sikaindustry.com/ipd-transoem-transprod.htm
http://saversystems.com/Product%20Data%20Sheets/crackjoint.pdf
http://www.buildingdiagnostics.com/articles/sealantjoints.html
I have personally used all of these products, and they are excellent for this type of remediation of a cracked mortar joint of differing material as such.
But remember, they have to be installed correctly.
Why sealant joints fail;
http://www.buildingdiagnostics.com/articles/sealantjoints.html
Hope that helps. :)
I am with Brian on the epoxy 
Thanks guys!