I am new here, and I have done alot of searches and read many forum posts looking for my answer, but I did not find the answer to this question.... so here goes:
My situation is that I am in the process of replacing an 18' above ground pool. On the upside, the area is already very level. On the downside original pool was not installed on patio blocks, so I need to install them. A deck abuts the pool on one side (deck spans a little over 2 pool rails).
While attempting to install the pool block to be at ground level I have found that the ground on the deck side is very loose. The patio blocks I am installing are about 2" thick, and while digging down I noticed that the ground gets alot firmer at about a 4.5" depth (packed rock). Anyway, what I want to know is what can I use to pack beneath the patio block that will avoid it settling over time, (I should mention that the main pool area is very solid (apparently mechanically packed) *large* crushed stone, so lowering the entire grade of the pool would be very, very difficult).
Originally, I tried dirt, but the dirt I have is either topsoil or very clay-like. Even after alot of hand tamping down (using a 6x6 post) the dirt mix seemed pretty "flexible". (I can't use a mechanical tamper because the patio block hole is only 16x8x2) and I would prefer not to compound the issue by making an even bigger hole.
My second attempt was try layering the dirt mix with a layer of crushed stone ("Vista Red" which I purchased from Home Depot). Basically I put a 1" layer of the dirt mix (then tamped it down alot) then a layer of the crush stone and tamped/pounded into the dirt mix, then another layer of dirt, tamp, crushed stone, tamp, etc. This way seem to make a firmer sub-layer but is still not as rock-solid as I would hope. I am also concerned that using crushed stone (even pounded into a dirt mix) might cause problems down the line. (I have read gravel is not a good base, but I am not sure if this crushed stone/dirt mix is better or not?).
Sorry for the long post, but I want to give some details regarding what I am working with.
So I guess my question is: When you need to firm-up or re-build a patio block hole that is slightly deeper than desired, what is the best material to use? (Assuming hand tamping is the compression method).