A video I saw of people hosing down piled bags of quikcrete (bagged concrete mix) really interested me. I calculated it would cost less than $1000 for a 10ft long, 8ft high wall.
Just lay down the bags, stick some rebar through them as you go, than hose them down and you got a solid wall a single man could build little by little.
How well does the concrete end up mixed? I'd be really concerned that it would be a big pile of hollow concrete shells around powder that never came in contact with water.
If you buy bags of pre-mixed concrete then it's already mixed.
What we normally refer to as concrete is a mix of Portland cement, Lyme, and aggregate (pebbles and/or sand). Pre mixed concrete comes as that already mixed and you just need to add water. You don't really need to mix the water in unless your looking to float the concrete to make a nice finished flat surface like a road or sidewalk. Anyone who has accidentally left a bag of pre mix out in the rain knows it hardens up fine.
My friend got a satellite dish put in years ago. The installer could only get a clear view in the corner of his yard, and had to ground-mount the antenna on a pole.
He dug a hole, put the pole into it and emptied a bag of concrete in with it.
He explained to my friend that it would suck the moisture out of the ground and become a solid plug. And it did.
Just lay down the bags, stick some rebar through them as you go, than hose them down and you got a solid wall a single man could build little by little.