An investigation into ancient construction techniques shows that cultures have been combining fired rock dust, plant ashes, sand, clay and earth since prehistory.
Today we have stabilized earthen concrete. A culmination of all humanities attempts at building simply: dwellings which stand the test of time. Advances in the studies of cement mix design and concrete strengths are the forefront of a geopolymer revolution.
Simply put, certain raw earth already contains the right binders and aggregates for a rammed earth or shotcrete structure. Combine that with revolutions in formwork (or form-less) systems, integral insulation and reinforcing, and that makes stabilized earth wall systems some of the most efficient, affordable homes ever built.
From here to Timbuktu, material scientists, ceramicists, masons and craftsman of their trades are re-learning the secrets of how to cast natural sandstone. The precise chemistry depends on the mineral content of the native soil and available admix components.
In firing earth for cement, humans recreate the intense thermal conditions found during a volcano.
Of course, the ideal cementitious material is already fired by a volcano centuries ago, such as the pozzolans of Roman concrete or the kaolinites of Chinese porcelain.
When put in combination with the correct flux and reagent, these materials form bonds which actually gain strength over time, essentially becoming stone again.
The technology lies in an understanding of the soil components and their relationships, and as with cement, is largely the result of experimental artisans throughout the ages. Modern pioneers are bringing to light the fundamentals of geopolymer chemistry.
In cement stabilized earthen structures, the reagglomerated stone matrix is the result of geosynthesis, recreating the minerals of limestone and hydrated feldspar.
“SOLID PHASE SYNTHESIS OF MINERAL BLOCKPOLYMER BY LOW TEMPERATURE POLYCONDENSATION OF ALUMINO-SILICATE POLYMERS.”
Embracing the longevity of this building material is the key to understanding how our homes, public spaces and even societies could grow to benefit nature, at no cost to our future.
The thermal mass and phase change capacity of thick earthen walls are beneficial for humans in so many ways, such as being pest, mold, fire, sound, radiation and tank proof.
Earth building heritage exists around the world, adapting the best construction techniques to the available materials. From primitive ceramics and dwellings, to some of the oldest buildings on earth, impressive beauty springs forth in nearly every civilization throughout humankind.
According to the United Nations, 30% of the world lives in earthen buildings today. And for good reason, since stabilized earth structures remain some of the longest standing in history.
“Earth is nature’s medium of brilliant resilience.”