Influence of metal oxides and particle size on earthen mortar built with tropical soils

Abstract

French Guiana heavily relies on high-cost imported materials to sustain its strong population growth and construction demand. Local alternatives such as earth concrete are needed to reduce the use of conventional concrete. It is currently unknown if tropical soils are suitable for non-cement stabilized earth construction and especially what are the characteristics of these soils.  In this study, 14 soils were characterized (particle size, EDS-SEM, FTIR, color) and evaluated as building materials on earth mortar prismatic specimens. For each soil, physical and mechanical mortar properties were evaluated based on two formulations of equivalent plastic consistency, with or without dispersant (0.5% of dry mass). The results show that hardened mortar properties were driven by water content at fresh state, particle size, and Fe and Al-oxide content. Water content directly correlated with fine-grains content and negatively impacted all mortar properties. The use of dispersant reduced water content and considerably improved compressive strengths, reaching up to 4 MPa. Compressive strength positively correlated with Fe and Al content and could be predicted by soil color. Overall, the characterized soils demonstrated good mechanical aptitude when mixed with a low level of dispersant, indicating a high potential for construction, particularly for metal oxide-rich soils.