Set up / hardening time
What hardening times do you get?
How cement ratio affects it?
I usually still leave boot marks after 2 days.
I use aircrete for excavation filling hence I do thick layers of up to half meter.
How to speed the curing up?
I have found covered aircrete to cure harder faster and with less cracking shrinkage. Moisture is your friend when curing concrete :). 2 days of cure and leaving boot prints is typical.. I try to stay off it for a week if I can.