Tuff-clay synergy for high-performance compressed earth blocks: multiscale optimization of physico-mechanical properties and durability

This study valorises calcareous tuff and clay to develop high-performance; low-cement stabilised compressed earth blocks (CEBs). The materials were characterised mineralogically and geotechnically. The formulation was optimised by varying the clay content (0–30%) and the cement dosage (1–5%). Performance was assessed through compressive strength (dry and wet), capillary absorption, and resistance to 24 wetting-drying cycles. The results show that the optimal composition (77% tuff, 18% clay, and 5% cement) achieved exceptional performances, with a dry compressive strength of 11.94 MPa and only 1.29% mass loss after wetting–drying cycles. A mix with 3% cement provided an efficient eco-friendly compromise, achieving 7.92 MPa dry strength and 77% strength retention after ageing. The synergy between tuff and clay enables the production of structural and durable stabilised CEBs with minimal cement content, providing a sustainable and scientifically-grounded construction solution.