Chris Bacon wrote:
Lobster wrote:
Does anyone know if these things are any good, and if they are still
around? (my guess is "no" and therefore, "no" but just wondered!)

Need a decent area like a driveway to roll them, not easy to roll. Hard
on the back or foot. "Roll for 30 secs". Hm. Translates to at least 5
mins. IRL. I have occasionally used a 10L or 10L paint tub to do the
same thing. Not mad keen on 'em.

If "Roll for 30 secs" was real, you'd see the mechanism in at least some
powered concrete mixers.
Properly incorporating all the stuff with a minimum of water takes a fair
bit of energy.