Comparative Life Cycle Assessment of Rammed Earth Stabilized with Different Biopolymers

Rammed Earth (RE) is a traditional technique based on the compaction of local soil, avoiding long-distance transportation and carbon emissions processes typical of concrete production. Nevertheless, RE presents limited mechanical performances and low resistance against water. Cement is usually added to improve RE properties to comply with the construction standards. Consequently, the environmental impacts increase and the recyclability of the soil at the end of life is lost. In the present study, some biopolymers were considered for RE stabilization: lignin sulfonate, tannins, and sheep wool fibers. These additives were found to be effective to improve the unconfined compressive strength of the RE in a previous study by Losini et al. [1]. In this study, the analysis focuses on the environmental impacts of the production phase of a stabilized rammed earth (RE) wall via Life Cycle Assessment (LCA). Through a comparative LCA from cradle to gate, the environmental impacts generated by the construction phase of the RE wall stabilized with three natural additives, is performed on a functional unit equal to 1m2 wall with a thickness of 30 cm. The unstabilized RE is then compared with the stabilized materials, both in terms of improvements of compressive strength and LCA environmental indicators. As a result, lignin and sheep wool fibers stabilized walls show almost negligible differences in terms of environmental impact while improving the mechanical properties up to +38% and +6% respectively. Despite the relatively high enhancement of the mechanical strength by +13%, the tannins stabilizer performs around +95% rise in all environmental indicators compared to the unstabilized material.