Influence of aspect ratio on the properties of compressed earth cylinders and compressed earth blocks

A large proportion of the human population still resides in earthen structures all over the world. The benefits of earth construction are widely reported, but there is a lack of scientific understanding relating to standard production and test methods which has led to inconsistencies in the reporting of engineering parameters, such as compressive strength. This study investigates the use of small-scale Compressed Earth Cylinders (CECs) to predict the compressive strength of equivalent full-scale Compressed Earth Blocks (CEBs). A full-scale manual CEB machine and a small-scale CEC moulding rig were utilised for the production of test specimens and the results obtained from both production methods were examined. Two soil types with different engineering parameters were utilised in this investigation. It was found that a sample of un-stabilised CEB with an aspect ratio of 0.67 achieved a mean compressive strength of 6.73 N/mm² (Soil A) and 4.60 N/mm² (Soil B). A selection of CECs with an aspect ratio ranging from 0.50 to 2.00 were used to determine a relationship between the aspect ratio and compressive strength for each soil type. The theoretical relationship was used to predict the compressive strength of the equivalent CEBs within ± 3.0%. The theoretical relationship was also used to predict the unconfined compressive strength of the samples and enabled the determination of aspect ratio correction factors of Soil A and Soil B. Findings from this study reveal that the conversion factors between cylinders and blocks are dependent on numerous variables including compaction pressure, aspect ratio, soil type and density.