A foundation should be between 65°F to 90°F to install grout. Having the right temperature is important to ensure proper flow, adhesion and cure of the grout material.
All concrete should have a minimum compressive strength of 4000 psi at 28 days.
The 30-degree rule is a best practice. If you drop a plumb line down from the center of the rotation shaft and rotate this line 30-degrees in both directions, the line should go through the bottom of the foundation and not the side. This will ensure stability of the foundation.
The purpose of an expansion joint is to engineer a controlled crack in the epoxy grout to reduce the possibility of random cracking, when machinery to grout temperature differentials of 50°F are encountered.