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STEVE'S INTRODUCTION
TO LIGHT WEIGHT CONCRETE
Concrete
is strong in compression and the best way to take advantage of
this property is by building structures that are inherently self
supporting and don't need a lot of iron reinforcing. Since most
building here in Mexico is with concrete, it is easier to let
your imagination go wild. Local builders have been working with
ferro-cement, styrofoam panels, plastered straw bale, and soil-crete.
I have had the most success with light weight
concrete. Light weight concrete differs from heavy concrete by
it's use of naturally light weight materials (aggregates) such
as pumice (volcanic stone) in place of the sand and gravel used
in ordinary structural concrete mixes. It only weighs half as
much.
Not all
concrete is ugly, hard, cold and difficult to work with. There
exists a whole range of light weight concretes "which have
a density and compressive strength very similar to wood.They are
easy to work with, can be nailed with ordinary nails, cut with
a saw, drilled with woodworking tools, easily repaired . We believe
that ultra-light weight concrete is one of the most fundamental
bulk building materials of the future." A Pattern Language
The stuff I use is right in the middle of the chart.
Light
weight concrete is about one half the weight of hard structural
concrete. It can be mixed from a variety of light weight aggregates
including vermiculite, perlite, scoria, and pumice. Some form
of suitable aggregate is available most everywhere in the world.
Our locally available aggregate here in San Miguel is a type of
pumice (espumilla or arenilla) which we typically mix 8:1 or 10:1
(by volume) with cement for walls, and 5:1 for roofs. Most lightweight
concrete has a good R-value and is a good insulator of heat and
sound. It is used as soundproofing in subway stations. It
has tremendous sculptural possibilities and is ideal for monolithic,
wall-roof construction.
I feel that we need more intelligent building systems. I'm looking
for a home that lasts 200 years, that you can maintain and remodel
easily, and that uses mostly locally available, abundant materials. Light weight
concrete fits the bill here in Mexico.
For more information on light weight concrete see:
US Department
of the Interior Bureau of Reclamation
CONCRETE
MANUAL
