Recyclability of vernacular adobes with high chalk content in the context of sustainable construction

The contemporary construction industry faces significant challenges, necessitating a response to multiple issues: reducing material resource consumption, minimizing construction waste, transitioning to carbon-neutral building methods, and fostering a circular, local, and inclusive economy. The recycling of raw earth adobes, an ancient architectural practice still employed today, appears to meet all these criteria. This study addresses the potential alterations in the physical properties of high chalk content adobes undergoing multiple cycles of reconstitution. The investigated primary adobes were collected from a recently demolished 19th century barn near Épernay, in the Champagne region located in northeastern France. During the recycling process, the bricks underwent dry crushing, wetting, mixing, molding, and drying. Careful attention was given to reproducibility through controlled water content and manual compaction techniques. Next, physical, mechanical, and thermal tests were performed. The findings indicate that the mechanical and thermal properties remain consistent over several recycling cycles. For example, mechanical tests across three recycling cycles demonstrated that the normalized peak compressive stress is barely affected. In complement, thermal conductivity and diffusivity measurements showed minimal variation across cycles, confirming that recycling did not impact these thermal parameters. The substitutability of raw earth, defined as the ability of the recycled material to reach levels of performance comparable to the original, is evidently robust. In view of these promising results, future research works should explore the possibility of combining raw earth from recycled adobes with additives such as plant-based ash, with the potential goal of improving its durability, mechanical strength, and moisture resistance. • Vernacular chalky earth bricks undergo destruction-wet remolding cycles. • Molding of the bricks is made as reproducible as possible through pressure monitoring. • Physical, mechanical and thermal characteristics are not affected by the recycling cycles. • Cohesion of the chalky earth is reversible by wetting, which is highly energy efficient. • The material holds great potential for meeting the challenges of the circular economy.