Soil Characterization

Compressed and stabilized earth blocks (CSEBs) are typically manufactured through one-side compaction. The resulting soil matrix-hydrated cement microstructure is heterogeneous, posing the question of whether CSEB materials can be considered homogeneous and isotropic for the purpose of analysis of CSEB structures, similar to rammed earth. As earth masonry emerges as a sustainable material for affordable and high-quality dwellings, addressing this question becomes relevant to define constitutive models for analysis and design, and interpret material test data for quality assurance and control.
This paper reports on a study of a representative CSEB material made of a lean clay and 6% of ordinary Portland cement by weight of soil. Cube specimens were saw-cut from different locations of CSEBs (i.e., corners, middle third), which were manufactured using a hydraulic press. Scanning electron microscopy images were used to gain visual evidence of the microscale and mesoscale heterogeneity. Energy-dispersive X-ray spectroscopy data were used to gain quantitative information on the chemical composition and its spatial distribution. Eighty-four cube specimens were tested under uniaxial compressive loads, either parallel or perpendicular to the compaction direction. One-way analysis of variance was enlisted to characterize the statistical significance of the difference between the mean compressive strength for different specimen groups. These groups were intended to assess the influence of location of the saw-cut cube in the source block to investigate homogeneity, and load direction to investigate isotropy. It is concluded that the representative CSEB material can be regarded as homogeneous and isotropic in terms of mechanical properties.