SCEBs - University of Colorado Boulder

This rate was maintained until failure occurred, as evidenced by the stress-strain curve
output from the Instron machine. Failure was defined as the ultimate stress achieved by
compressed earth blocks behaving in a brittle manner.
4.1.3. Results
Displayed below are the results of the Unconfined Compression Strength
durability tests. Figures 4.3 - 4.5 show the UCS values of the blocks taken at one week
intervals during the initial four week curing phase. One can see that after seven days the
SCEBs have reached nearly full strength. Figures 4.6 – 4.8 show the UCS values of the
blocks after each saturation cycle. These results did not show an obvious trend of
decreasing strength with repeated saturation cycles. To address the issue of scale effects,
a corrected unconfined compressive strength was calculated based on the analysis
performed in Chapter 5, Section 5.2.2.1. The mini-blocks tested had an aspect ratio of
approximately 0.4. The UCS values are corrected for a specimen with an aspect ratio of
2. In nearly every case, the soil mix with a higher proportion of clayey soil was superior.
Figure 4.9 shows a typical example of deterioration of a SCEB made from 25% Amsden
clay by mass after five wetting/drying cycles.
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