BUILDING WITH RAMMED EARTH: MATERIALS INSIGHTS FROM “CASA DEL THÈ” PAVILION CASE STUDY

Over the last few years, the building sector has witnessed a rediscovery of raw earth as a sustainable alternative to traditional building materials. This study investigates the potential of rammed earth (RE) as a sustainable building material by examining the mechanical properties of an earth-based mixture from the "Casa del Thè" pavilion (Monticello d’Alba, CN, Italy). This installation utilised a specific rammed earth mixture (Pavilion mix) composed of waste soil from a Botticino marble extraction site (Tb), a vineyard soil (Tv), and an aggregate material (St). Comprehensive geotechnical (Atterberg Limits, Specific Gravity, Granulometry), chemical, and mineralogical characterisations (XRF, XRD, ATR-FTIR, TGA) were performed on the constituent materials. Unconfined Compressive Strength (UCS) test on cylindrical samples prepared at the construction site yielded 1.06 MPa for pure Tb samples and 1.67 MPa for the Pavilion mix. Subsequently, the mixtures were replicated in the laboratory, and cylindrical samples, dimensionally identical to those from the construction site, were prepared using the Proctor compaction apparatus. A comparative analysis between the construction site and laboratory-prepared samples revealed a notable influence of the preparation methodology on mechanical performance, with laboratory-prepared Tb and Pavilion mix samples achieving mean UCS values of 1.44 MPa and 1.24 MPa, respectively. Consequently, an attempt was made to optimise the soil mixture composition for improved mechanical properties. This involved establishing a rammed earth suitability criterion based on particle size distribution and Fuller’s equation. Concurrently, a digital tool called Granulometry Builder was developed to predict the granulometric distribution of hypothetical raw earth mixtures. This allowed the formulation of an optimised mixture (Optimal mix) comprising Tb, St and a clayey soil designated as ABS, whose granulometric curve closely approximated the empirically derived ideal distribution. However, despite this compositional optimisation, the Optimal mix yielded a mean UCS value of 0.99 MPa, reflecting the complex interplay between mechanical properties, particle size distribution, the intrinsic nature of constituent materials, and residual water content. Nevertheless, this study provides foundational insights for future advancements in soil mix design and compaction techniques, thereby contributing to the broader application of rammed earth as a sustainable and structurally viable construction material.