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This study aims to check the compatibility of a selection of waste and recycled biopolymers for rammed earth applications in order to replace the more common cement-based stabilization. Five formulations of stabilized rammed earth were prepared with different biopolymers: lignin sulfonate, tannin, sheep wool fibers, citrus pomace and grape-seed flour. The microstructure of the different formulations was characterized by investigating the interactions between earth and stabilizers through mercury intrusion porosimetry (MIP), nitrogen soprtion isotherm, powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The unconfined compressive strength (UCS) was also evaluated for all stabilized specimens. Three out of five biopolymers were considered suitable as rammed earth stabilizers. The use of wool increased the UCS by 6%, probably thanks to the combined effect of the length of the fibers and the roughness of their surfaces, which gives a contribution in binding clay particles higher than citrus and grape-seed flour. Lignin sulfonate and tannin increased the UCS by 38% and 13%, respectively, suggesting the additives' ability to fill pores, coat soil grains and form aggregates; this capability is confirmed by the reduction in the specific surface area and the pore volume in the nano- and micropore zones. [ABSTRACT FROM AUTHOR]

Three biopolymers were tested as rammed earth (RE) stabilizers, evaluating their impact on the hygrothermal behavior from material to building scale. Hygrothermal characterization included the determination of sorption isotherm, water vapor permeability, thermal conductivity at different moisture content, and specific heat capacity. The hygrothermal data were used as input for the simulation at whole-building scale considering combined heat and moisture transfer. The results were evaluated by comparing heating demand, thermal comfort during summer, and the contribution of walls for passively controlling indoor humidity. The results show that hygric properties were only slightly affected by the use of stabilizers, while the thermal conductivity was 33% higher for RE stabilized with lignin, consequently increasing the heating demand at whole-building scale. All RE walls were effective in reducing temperature oscillations in summer. In the particular case of a canicular event, the indoor temperature was reduced by up to 10° compared with the outdoor value. The indoor humidity also benefited from the passive regulation by RE walls, regardless of whether a stablizer was used. • Stabilization of RE with lignin sulfonate increases thermal conductivity by up to 30%. • RE can reduce indoor temperature by up to 10° during canicular events. • The use of paint on RE walls decreases their contribution to controlling indoor humidity. • Uninsulated RE walls represent approximately 50% of the total sensible heat losses. [ABSTRACT FROM AUTHOR]