landscapingretaining-wallstone
There are a lot of stones on my property of the kind shown in the picture. They are hard and heavy, but extremely brittle. The pictures shows half of a stone that I dropped from about 2' high on another stone and it broke cleanly in half. What species of stone is it and could it be used in a 3'-high retaining wall?
I don't know of a residential use.
It is more a class of stone than a type.
For roadways, high friction aggregates (calcined bauxite is the most common component) is applied (bonded would be a better description) in areas where skids frequently occur, to improve traction.
I would use a grout bag:
Your technique will be similar to that used when "tuck pointing" brick (look it up). Because your grout lines appear to be too narrow, instead of a brick mortar jointer (see pic below) I would customize a finishing tool or maybe use a narrow grout float.
You will definitely need sanded grout (make sure the joint width and depth does not exceed that recommended by the grout manufacturer), or maybe even a coarser aggregate mortar (check with a decorative stone supplier or good tile shop in your area). Use several sponge buckets (dirty, clean, cleaner) and wring often when sponging, changing water frequently.
Do not fear a mild acid wash to remove residual grout haze, muriatic is what we generally use on stone and brick (test on a leftover stone sample prior to using to ensure no dramatic reaction/discoloration).
My Sequence:
1) Do the whole top section first, including finish sponging. If you must stop, at least finish a wall and stop at a corner.
2) Do the whole stone section second, including finish sponging. If you must stop, at least finish a wall and stop at a corner.
3) Do the whole bottom section last, including finish sponging. If you must stop, at least finish a wall and stop at a corner.
4) Wash and/or acid wash haze in one operation after the grout has set (refer to grout maker's recommendation for appropriate time prior to washing).
I dig your design, it is going to be beautiful.
P.S.- You're gonna need a lot of grout.
Best Answer
When you say brittle is it flaky?
It looks like shale if you hit it or drop it on a hard surface it breaks up that would be shale, I have used it because my grampa had a hill that was shale and we used pry bars to break chunks out it works good for walls because it breaks and you can chip high spots off so they fit better if you don’t get parallel top and bottoms most of ours was like layers but different thickness. But it made a nice wall over a couple of summers (I think grampa was just keeping me and my brother busy.