Post and Pier Wood Foundation Backfill?

[Mrs_DIY]

We are building a 12 x 12 cabin and are doing 6 x 6 PT wood piers.  The "An Easy to Build Post and Pier Foundation" article on countryplans.com mentions backfilling the holes with a "soil cement mix" or "crushed rock."  We are thinking of using the crushed rock at the bottom of the 42" hole (for 8") then placing the 6x6 down then backfilling with more crushed rock?
My husband is concerned that there is no cement involved.
Any comments?  Would "crushed rock" be enough to do the trick?
Thank you in advance.

[jraabe]

That is the best way to set a PT pier. The gravel footing spreads the weight out over the soil and the gravel backfill will drain the water rather than hold it next to the pole as concrete does.

If you do want to do some concrete it is best to set the top of the concrete about 8" below the surface and finish the top off with gravel. Posts do not rot easily below about 6" of the surface.