I intend to add on to an existing concrete patio that was installed about 20 years ago and is still in great shape. No cracks and very little heaving. I am going to use 1'x1'x2" patio blocks for the extention. My original plan was to dig out about 6 inches and back fill it with about several inches of compacted "sand". I asked my lawn guy for some help with labor and he told me he had access to "stone dust" which I intened to use "instead" of sand. What he delivered is more like "crushed concrete and stone" it has some fine material but is is very coarse with fairly large pieces. So I modified my plan and plan to still dig out 6" only now I will pack in about 2" of this "crushed stone material" (by the way this is NOT "stone dust" is it?) and 2"s of sand and the last 2" will be the patio block. I also intend to separate the layers with this fabric material I got at Home Depot (it is specificly used to separate layering materials).

By the way the ground if hard packed clay. I layed a brick walkway about 15 years ago with just a few inches of sand on top of the clay and it has not sagged or buckled in all this time. So I feel pretty confident about the patio not shifting too much. I am extending the patio to put in an "outside kitchen" using "stone" blocks. which will be pretty heavy. Or maybe I will build it out of wood and keep the weight down.

I hope narration is not too disjointed or overstated.

Anyway I am looking for comments on the layering of the "crushed stone" and "sand" as well as an explanation of what "stone dust" is. I presume it is NOT what I have?

Thanks a lot

Charlie