In the context of efforts to reduce greenhouse gas emissions in the building sector, the reintegration of traditional earthen construction into modern architectural and renovation practices offers a sustainable alternative. To address the mechanical and water-resistance limitations of adobe bricks, the use of agricultural waste—such as rice husk—is increasingly being explored. This experimental study evaluates the effects of rice husk addition on the mechanical, hygrothermal, and acoustic properties of adobe bricks. Two soil types—one siliceous and one calcareous—were combined with 1, 2, and 3 wt% rice husk to produce bio-based earthen bricks. The influence of rice husk was found to depend strongly on the soils’ mineralogical and granulometric characteristics. The most significant improvements were in hygrothermal performance: at 3 wt%, thermal conductivity was reduced by up to 35% for calcareous soil and 20% for siliceous soil, indicating enhanced insulation. Specific heat capacity also increased with husk content, suggesting better thermal inertia. The moisture buffering capacity, already high in raw soils, is further improved due to increased surface porosity. Mechanically, rice husk incorporation had mixed effects: a modest increase in compressive strength was observed in siliceous soil at 1 wt%, while calcareous soil showed slight improvement at 3 wt%. Acoustic performance remained low across all samples, with minimal gains attributed to limited macro-porosity. These findings highlight the importance of soil composition in optimizing rice husk dosage and suggest promising potential for rice husk-stabilized adobe bricks, especially in thermally demanding environments.

In the context of ongoing efforts to reduce greenhouse gas emissions from the building sector, the reintegration of traditional earthen construction techniques into contemporary architectural and renovation practices presents a promising avenue. To address the inherent limitations of adobe bricks in terms of mechanical strength and water resistance, the incorporation of vegetal waste—such as rice husk—is increasingly explored. This experimental study evaluates the impact of rice husk addition on the mechanical, hygrothermal, and acoustic properties of adobe bricks. Two distinct soil types, one predominantly siliceous and the other rich in limestone, were selected and combined with 1 wt%, 2 wt%, and 3 wt% of rice husk to fabricate bio-based earthen bricks.

This study addresses the lack of data on the acoustic performance of raw earth building materials through a comprehensive multiphysics investigation of unstabilized raw earth and earth–wheat straw composites. Acoustic behavior was analyzed alongside thermal, mechanical, and hydric properties. Four soils from the Champagne-Ardenne region were first examined to evaluate the influence of mineralogical composition, particularly calcium carbonate (CaCO3), on sound absorption. Despite significant compositional variability, all soils exhibited similarly low weighted sound absorption coefficients (αw = 0.12–0.19), mainly governed by their comparable densities. These results indicate that raw earth is a poor sound absorber but has promising sound insulation potential. In a second phase, wheat straw (0–6 wt%) was incorporated into one selected soil to produce lightweight composites. Increasing fiber content reduced bulk density (up to −37%) and significantly improved sound absorption (αw up to 0.34, +162%), due to enhanced porosity and fiber–matrix interactions. Thermal conductivity also decreased markedly, improving insulation performance. However, these gains were accompanied by a transition from brittle to ductile mechanical behavior, with a significant decrease in stiffness redirecting these composites towards infill or self-supporting structures. All formulations maintained good to excellent moisture buffering capacity and satisfactory resistance to water degradation. Overall, earth–straw composites appear as sustainable, locally sourced materials suitable for non-structural applications in low-impact construction.