Hi. Does anybody have experience of using insulating materials in their lime plaster mix? I have seen expanded glass beads for sale that could be mixed instead of sharp sand. There are some pre mixed products on the market too, one for instance with bits of Cork mixed in...
Are these expanded glass beads smooth and shiny? If so, they would tend to weaken the bond of the lime, or at least reduce the grain interlocking, and make a more fragile surface. That's why mason's sand is sharp and rough.
posted 3 years ago
Yes I believe they would be smooth. I thought about adding hair into the mix to counter that,or maybe 50 50 beads and sand?
Can you describe the application a bit more? Could you have an inusulative layer and then lime plaster? Have you heard of expanded polystyrene concrete? Waste styrofoam is used as a insulating material, I know it is not natural and may not be right for your application but it is an interesting use of this waste product.
Hey Mike, sorry about to late reply.
I've used lots of lightweight Crete mixes, Scoriacrete, Pumice Crete, air Crete, EPS Crete. Those lightweights are all best suited for cement binders in my opinion.
Now on to lime. I plastered the inside on my Scoria bag dome with a very lime rich papercrete and it was wonderful, no real cracking or shrinking, not a hint of mold, easily workable, trowelable, sticks overhead like glue. When I brown sponge floated my second coat, There was a local shortage of masonry sand, so I hauled in a trailer of local Pumice , I screened it to 1/4 or 3/16" minus. My lime guru said that mine has a composition that is close to ideal pozzolons. That was a nice lightweight workable mix too that I floated everything out with. My final coat was a skim coat in thickness. It was quickrete brand bags of fine (I forget but maybe 100 grit) silica sand, and Pumice fines (maybe 32nd ths big...??), And lime. That polished out hard with no cracking. I lime washed with pigment and silica and mica flakes. Only cracked a little at floor to wall juncture, and i blame my big dogs for playing to rough on that.
All my lime was type s bagged hydrated, soaked in a barrel, sometimes a week, sometimes 6+ months. Although i think a week is fine. I mixed all in a mortar mixer, except the papercrete was towed.
The paper is a great aggregate for the flexible strength of the lime binder. It also provides a great symbiotic moist cure for the lime. The pozzolana, well I didn't know what to expect, but after experiencing other non pozzolana or non hydraulic lime plasters, the pozzolana if you can get some is worth it, much more durable final product, at least in my high atmospheric pressure, dry, high elevation climate which is too hard for regular hydrated lime plasters. Low elevation humid climates probably differ, probably OK without the Pumice, no Pumice local, and wouldn't paper.
Don't expect to gain much insulation out of these, however it's nice to touch a plastered wall in winter and it not be cool. Just one more technique in thermal comfort for my place, because my sunroom brick floor and brick trombe directly catch all the real solar. Cement stucco or my sunroom brick gets hot and cold. My internal Earthen plaster feels warm and cool. My Pumice lime stuff doesn't feel like it has a temperature.