SCEBs - University of Colorado Boulder

locks often achieve compressive strengths comparable to ordinary concrete (ASTM
E2392).
Precaution should be taken when comparing testing methods for concrete versus
compressed earth as a building material. Standards for testing concrete specify the
specimens to be cylinders with a height to diameter ratio of 2:1 (ASTM C39). The author
has found no code specifying the actual dimensions of a typical or ideal SCEB test
specimen. The New Mexico Earthen Building Materials Code specifies that compressive
testing is performed on a block in its flat position with the length measuring a minimum
of twice the width (NMAC, 2009). The minimum compressive strength defined by this
code is 300 psi. A major issue preventing the adaptation of the ASTM defined cylinder
test is the preparation method of the cylinder itself. ASTM C192 specifies two methods
for material consolidation (air removal) while preparing concrete test specimens: rodding
and vibration. These two methods are not intended to compact the concrete. In the
context of this report, soils used in SCEB production undergo high levels of compaction
by means of a hydraulic press and ram. Variations in the preparation of test specimens
negate any direct correlation between results achieved from concrete versus compressed
earth.
The durability properties of stabilized compressed earthen blocks remain
relatively un-documented and yet play an important role in the life-time analysis of the
applied technology. The porous nature of earthen blocks allows them to “breathe”, or
absorb and desorb moisture cyclically. While this behavior is beneficial for regulating
indoor humidity levels, it can lead to degrading effects on the blocks themselves. The
hygroscopic nature and high relative specific surface of clay particles present numerous
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