Rammed earth (RE) construction has gained increasing interest in recent years owing to sustainability demands in the construction industry and the advancement of digital fabrication techniques. However, the domination of the cement-stabilized RE material in the RE industry poses environmental concerns due to the substantial carbon emissions associated with cement production. In this study, bio-based alternatives to cement-stabilized RE are investigated through evaluating xanthan gum (XG) and animal glue (AG) as bio-binders for RE stabilization. Unconfined compressive strength tests are conducted on XG and AG-stabilized specimens for mechanical performance evaluation, and unstabilized RE samples as baseline for comparison. Results show that AG-stabilized specimens demonstrate a 294% strength improvement over unstabilized RE, reaching 6.86 MPa at 28 days, while XG-stabilized specimens achieve a 221% improvement. XG-stabilized specimens, however, exhibit susceptibility to microbial proliferation. The findings from this research demonstrate that XG and AG have the potential to be viable alternatives to mainstream RE construction methods, paving the way for advancing environmentally friendly RE construction.

Conventional practices in earth construction, such as cement stabilization and the energyintensive firing of bricks, contribute significantly to carbon emissions due to the processes involved in cement production and kiln operation. Additionally, concerns over the low strength of earth-based materials have limited their broader applications. This research addresses these challenges by implementing ultra-high pressures (200 MPa and 400 MPa) and bio-binders (animal glue and xanthan gum) to enhance earth materials for construction. Unstabilized earth mixture and normal pressure case (20 MPa) are also included in this study for comparison. A customdesigned mold and a specialized production process are developed to fabricate cylindrical earth samples for testing. After undergoing three hours of consolidation and 28 days of curing, unconfined compressive strengths are measured. Scanning electron microscopy is used to investigate the influence of ultra-high pressures and bio-binders on the microstructures of compressed earth blocks. The experimental results demonstrate that animal-glue- and xanthan-gumstabilized samples under ultra-high pressure achieve compressive strengths comparable to traditional fired bricks, while unstabilized samples exhibit the strength of cement-stabilized rammed earth. This research demonstrates that ultra-compression combined with bio-binder stabilization presents a viable strategy for reducing the carbon footprint of earth construction while significantly enhancing the mechanical properties.

Among the sectors influencing the environment, the building sector is known to be very energy consuming and to use large granular materials. Face to these problems, the development of materials based on renewable and biodegradable resources represents amajor scientific challenge to produce high-performance materials and materials that can be used as an alternative to synthetic materials. Several materials have been studied and proposed, in particular for the thermal insulation of buildings [1]. However, these materials based on vegetable aggregates remain, in most cases cement or lime-based [2], which are energy consumers and emit carbon dioxide [3, 4]. This work aims to propose a bio-composite with both vegetable aggregates and binders with thermal performances that are competitive with materials based on mineral binders. Vegetable glues were extracted using wheat straw fines that cannot be used as aggregates. The straw fines were soaked in a solution containing 6% NaOH at 90 degrees C for 2 h. Then, the extracted liquid was concentrated by adding sunflower pith powder and/or gelatin. The bio-binder was mixed with the straw aggregates to prepare biocomposite samples using the protocol developed in the PEPITE research program funded by the Region Centre. Experimental results in thermal conductivity allowed us to examine the influence of each bio-binder and compare the performance of straw aggregate-based bio-composites developed [5, 6].