SCEBs - University of Colorado Boulder

3.10. Durability Testing
The durability of the blocks has been assessed at the University of Colorado by
determining the effect of repeated wetting and drying on their unconfined compressive
strength values. Repeated wetting and drying of the blocks can alter the soil structure and
create concentrated weaknesses through cracking and the infiltration of water.
Typically, at least six blocks are tested for durability. A curing period of 28 days
is allowed before testing. SCEBs are cured in a controlled environment (~92.5% relative
humidity, ~72º F). The blocks are submerged in water for approximately 24 hours
immediately prior to UCS testing. The procedure involves saturating all of the blocks,
and subjecting a desired number of them to UCS testing. The remaining blocks are then
allowed to lose moisture content over a minimum of two days. The saturation process is
repeated for all of the blocks and the next set of blocks is subjected to UCS testing. This
process is repeated for the remaining blocks. A minimum value of 300 psi block‟s UCS is
required. During the saturation and drying cycles, each block is carefully examined for
any observable cracking or degradation effects. Figure 3.16 shows mini-blocks soaking
in water and Figure 3.17 shows the detrimental effects of several saturation cycles.
Despite the fact that Section I 14.7.4.23 of the New Mexico Earthen Building Materials
Code allows for shrinkage cracks provided that “these cracks do not jeopardize the
structural integrity of the blocks”, any observable cracking at this level of testing should
cause concern and warrant amending the soil mixture used.
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