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sedimentation (jar) test, ball drop test, cohesion (ribbon) test, etc. The results from these
tests need to be interpreted carefully and are often difficult to quantify. The most
efficient way to determine the suitability of a soil for blocks is to make and evaluate
several sample blocks from an available source (McHenry, 1984). It is for this reason
that the author has chosen to only mention these soil evaluation methods and not devote
significant research time to verifying their legitimacy.
In particular, the “jar” test is often suggested to provide the proportions of sand,
silt, and clay. While the test may be accurate for certain soils, it is not always correct to
interpret the results directly. Statistical analysis performed at Texas A&M has shown
wide variability in “jar” test results suggesting that many tests may be needed to be
performed before a high level of confidence can be achieved (Graham and Burt, 2001).
The interpretation of the jar “test” assumes that the strata layer heights correspond to the
proportions of the soil‟s constituents. This assumption is not exact, as one can only
distinguish between successive strata at sudden changes of grain-size distribution, which
may not coincide with the actual defined limits between sand, silt and clay (Minke,
2006).
A proposed standard of care must involve a rigorous understanding of the
mechanical properties of the construction materials intended for structural design (Craig,
2000). Material properties such as strength, stiffness, and ductility assist with design
decisions determining load capacity, settlement, and deformation. An earthen block‟s
primary function in a building application is to provide structural support for the walls
themselves, as well as any expected dead and live loads. The block‟s strength in
compression is of particular interest. Mechanically compacted cement-stabilized earthen
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