Pinheads,
Having recently done a project in Denmark, I have had an encounter with a
product that would earn the nickname "popcorn" concrete. The Danes use a
variety of cinder block which uses a very light aggregate that resembles
volcanic pumice. The blocks are very large and light and seem to offer
little in the way of structural integrity. They can be shattered with a
small sledge or a good whack with a piece of dimensional lumber. They do,
however, provide relatively high r-values for masonry. They were used for a
starter course on my project to support walls made of clay slurry and wood
chips. They had the additional benefit of providing a moisture barrier and
venting for the wall system.
David J. Dauerty
To The Line Timber Frames