Novel approach to identify soil compositional factors that control the compressive strength of unstabilized adobes and earth mortars

Because of their low embodied energy, recyclable nature, abundance of raw materials, and limited environmental impact, unstabilized adobes and earth mortars are preferred as earth building materials (EBMs). An ideal range of clay, sand, and Atterberg limits is recommended by earth building standards and references to create strong (≥2 MPa) unstabilized EBMs. But fulfilling these conditions does not guarantee the creation of robust earth materials. Prior research has suggested using surface area and cation exchange capacity to determine whether soils might generate strong EBMs.; they have also recognized the role of friction, particle interlock and bond strength in influencing the compressive strength. Nevertheless, no standard soil compositional parameter has been found in recent research to produce strong unstabilized EBMs (compressive strengths ≥2 MPa). A new soil compositional parameter known as the “C/S ratio”—where C and S stand for the clay and sand contents—was identified through the analysis of data on unstabilized adobes and earth mortars from six different countries. The compressive strengths of earth building materials are controlled by this parameter. The dry density and compressive strength of the unstabilized EBMs were altered by changes in soil structure brought about by variations in C/S ratios. Earth blocks with compressive strengths ≥2 MPa are produced from soils with C/S ratios between 0.35 and 1.6. To classify EBMs into distinct porosity groups, a dry density-based system is suggested.