Thanks cbucner, that is a great help!!
When I look at the instructions for Hydraulic cement they say:
"only mix what you can use in about 3 minutes"
Should I be able to fill a 12' x12" square 1"deep in 3 minutes??

Also Shoud I use a bonding agent between old and new?

In the past I have used the bonding agent instead of water to mix the cement...