Study on the Composition of Mortars Based on Forest Biomass Fly Ash for Sustainable 3D Printing (2025-07)¶

This study investigates the feasibility of incorporating forest-based biomass fly ash (BMFA) in its natural form for sustainable three-dimensional (3D) printing. The fresh and hardened properties of mortar incorporating BMFA were evaluated through the rheological and mechanical performance of the mortar. The relationship between yield stress and plastic viscosity with buildability was systematically investigated. Heat release was monitored through isothermal calorimetry. Increasing BMFA content was found to reduce plastic viscosity and the heat of hydration but increase static yield stress in the cement–BMFA binder. A comparison of 28-day compressive and flexural strength between prismatic and 3D-printed specimens indicated that the application of BMFA improved both properties, with results comparable up to 20% replacement of cement with BMFA. However, 3D-printed specimens exhibited lower compressive and flexural strength compared to prismatic specimens. Variations in BMFA content directly influenced the rheological and mechanical performance, as well as buildability. The application of 10% BMFA showed the highest buildability, comparable to the control, but buildability decreased with higher replacement levels. Thermogravimetric analysis (TGA) revealed a decrease in mass loss with increased BMFA replacement.