We have always seen vermiculite concrete mixed in a rotating-paddle mixer. Can it be mixed in a rotating drum truck mixer?
It can. The water and cement are placed in the mixer first. Then the drum is rotated while adding vermiculite. Rotation continues for about a minute after all the aggregate has been added but is discontinued while the truck proceeds to the job site. There the drum is turned at the fastest speed until the concrete is uniform and flows freely from the mixer.