On Jun 3, 11:29�am, hillpc wrote:
So does anybody know what exactly is the purpose of the pyramid
shape? �The round top is to prevent reflective cracking of the asphalt
above.

If you make the bottom wider than the top, you have something of an
anchor to prevent frost heave. It can't push out of the ground. I
was a little confused by the "upside down cone" mentioned earlier. I
believe you want to put it in "right side up" (wider base at the
bottom). That way when the ground shifts, it won't tilt or move.
But, as far as forms are concerned, I agree with the other poster that
they may not be necessary. If you dig a deep enough hole with a wide
base, it should be stable. Leaving forms in place after you pour the
concrete, or even having smooth sides on the concrete from forming,
may actually allow greater movement. Irregularities in the concrete
might help it to grip the earth better. Plus, if you are going to to
remove forms, you would have disturbed soil around it, which is less
stable for the post to anchor.