I know that there are many factors that affect the distance that shotcrete can be pumped. For a dry-mix process, is there a rule of thumb for a maximum recommended horizontal pumping distance?

The best information on this subject can be found in ACI 506R-05, “Guide to Shotcrete,” and likely in past articles in Shotcrete magazine. The distance that can be pumped is a function of too many parameters to fit a rule of thumb. The distance that can be pumped is influenced by the equipment being used, the vertical lift, the available compressed air, and other factors. We would suggest that you consult with one of our corporate members (www.shotcrete.org/BuyersGuide) in the area of the project and get their input.