Drying Process in a 3D-Printed Multilayer Wall System (2026-03)¶

The long-term durability of thick multilayer 3D-printed walls is limited by poorly understood drying behaviour, which affects moisture management and performance. This study investigates the drying dynamics of a multilayer 3D-printed wall composed of two concrete layers enclosing a lightweight thermal mortar core, using simultaneous extrusion of structural and insulating mortars to streamline construction, reduce labour, and ensure continuous insulation. Gravimetric monitoring of small- and medium-scale specimens was combined with a validated numerical model (maximum deviation 3%) to analyse long-term moisture evolution. Sensitivity analyses evaluated the influence of temperature, relative humidity (RH), material properties, geometry, and configuration. Under constant reference conditions (20°C, 50% RH), the concrete layers acted as diffusion barriers, delaying core drying to nearly 20 years to reach 80% RH. Increasing temperature from 10°C to 50°C reduced drying time from 45 to 5 years, while decreasing RH from 90% to 10% shortened drying from over 50 years to approximately 12 years. Increasing capillary absorption and reducing vapour diffusion resistance accelerated drying by up to 70–74%. Exterior insulation configurations reduced drying time by 65% compared to the reference geometry. Unsteady-state simulations for Lisbon, Brussels, and Warsaw revealed significant climatic influence. In Mediterranean conditions, south-facing walls reached equilibrium in under four years, while north- and west-facing walls in oceanic climates retained the highest moisture levels. Seasonal moisture peaks occurred during winter. These findings highlight the critical role of material compatibility, façade orientation, and climate-responsive design in ensuring moisture control and durability of multilayer 3D-printed wall systems.