Myself and a buddy mixed 20 bags of concrete in a single go some years back using a trick I saw on youtube: thick plastic sheeting cut in a large square, concrete placed on it, hole in center for water, each person grabs two corners, and you roll it around. A bag can be mixed in under a minute without any tools.
I'm working on a deck now and I mentioned this to a professional contractor who said he always just mixes with a trowel. So I gave that a shot to see if I was missing something. It's terrible: not only does it take way longer to mix, but it's way messier; scraping the edges, bottom of it, muscling the trowel through all the aggregate. It's crap! In lieu of plastic sheeting this time I just poured my concrete into heavy duty contractor bags, put the water in, 45 seconds of rolling it around on the lawn and it's completely, consistently mixed everywhere throughout. Bonus is now all the concrete is in a bag and can even be carried over to a hole. I found the contractor bags were good for 1-3 60 lb concrete bags before they got a small hole in them
I'm working on a deck now and I mentioned this to a professional contractor who said he always just mixes with a trowel. So I gave that a shot to see if I was missing something. It's terrible: not only does it take way longer to mix, but it's way messier; scraping the edges, bottom of it, muscling the trowel through all the aggregate. It's crap! In lieu of plastic sheeting this time I just poured my concrete into heavy duty contractor bags, put the water in, 45 seconds of rolling it around on the lawn and it's completely, consistently mixed everywhere throughout. Bonus is now all the concrete is in a bag and can even be carried over to a hole. I found the contractor bags were good for 1-3 60 lb concrete bags before they got a small hole in them