Looks like they got cracked and water got in and froze???
If you can find a stone that is a close match that can be cut to fit
I'd chip the old one out and replace it. (using thin-set) If not,
clean out the hole, etch with acid, and fill the hole with hydraulic
cement to seal it up and stabilize it.
On Thu, 19 Jan 2012 07:01:06 +0000, Chuck Banshee wrote:
Hydraulic Water-Stop Cement:
QUIKRETE® Hydraulic Water-Stop Cement (no. 1126) is a rapid setting, high
strength repair material designed to plug leaks instantly in concrete and
masonry. Sets in 3-5 minutes and can be used above and below grade.
Designed to block running water or leaks in cracked masonry or concrete
Use For: Swimming pools, Foundations, Sealing around concrete pipe
I'm going to first build the walkway, and, in doing so ... I'll get good
at cutting the flagstone to shape.
Then, I'll start to repair the three bad areas. I'm not sure 'freezing'
is the problem if only because it doesn't freeze where I live ... but I
would still need to repair the holes.
I'll see if I can chip them out and cut a flagstone to fit.
Guess you can cross off freezing/thawing then :)
Two other possibilities come to mind...
1. An inherent weakness in the rock
2. IIRC, the new ones you are planning to do are 1" thick but the existing
are only 1/2" and are on mortar. Were they laid on a separate slab. If so,
I would point to lack of support, even if they were laid in a new, grooved
troweled of mortar. Remember, the rocks are not smooth either on the face
or the back. If the entire piece isn't supported the piece can break.
I have used a lot of Saltillo tile in my house. Like your rock, it is soft
and the surface - particularly the back - is irregular; sometimes the back
is as much as 1/2" or more out of plane. I comb out my thinset with a 1/2"
x 1/2" notched trowel which is fine most of the time but for the more
irregular ones I butter the back so it is plane. With the tile, I can tell
if it is totally supported by rapping it with my knuckles...a hollow sound
means it needs mortar.
If you are sand laying them, you need to make sure the sand is well
compacted before laying and compact the stone well after laying.
I would agree with that (rather astute since you're not here looking at
them like I am) assessment.
Unfortunately, I do not know. The concrete (under the broken stone)
'appears' to follow the roughness of the underside of the stone - so I
would think they were laid on top of wet concrete. But I am only guessing
at that since I bought the house with the flagstones in place.
I would agree with that now that you've pointed it out. So maybe they're
wearing like this due to lack of proper support. It's not wear and tear
because they're just not in heavily traveled areas (two are in walkways,
one is in the driveway).
Thanks for the wonderful advice!
UPDATE: Thanks for all your help & advice!
Here's what I bought from Home Depot to cut the sandstone flagstone for
For the sprinkler head holes, I bought the following:
* Milwaukee PN 49-56-7250 Large Quick Change Arbor (for 1 1/4" to 6 7/8"
* Milwaukee 49-56-0444 Carbide Grit Hole Saw (2")
* Milwaukee 49-56-0456 Carbide Grit Hole Saw (2 1/2")
The reason for the two hole saws is I'm not sure how wide to make the
hole in the flagstone for the Rainman 1800 sprinkler head to fit up.
For the cutting of the flagstone to shape it, I picked up these 7"
circular saw blades:
* Hilti PN 00087803 7" Concrete Abrasive Blade (7"x1/8"x5/8"-dm)
* AvantiPro (PN PD070T) & Husky (PN 139-268) 7" Diamond Turbo Blade
I'm running into a problem with pipes under the flagstone at the moment
so I'll let you know how well these two types of circular saw blades work
out on the inch-thick concrete.
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