Printability and Mechanical Performance of Algae-Based Geopolymer Materials for Additive Manufacturing in Construction

The rapid development of additive manufacturing technologies in construction creates a demand for sustainable and environmentally responsible printing materials. Simultaneously, the increasing occurrence of freshwater algal blooms generates significant quantities of biomass waste that require effective management strategies. The incorporation of algal biomass into geopolymer formulations offers a promising approach for implementing circular economy principles in the construction sector.

This study investigates the use of freshwater algal biomass (Cladophora glomerata) as a bio-based additive in 3D-printable metakaolin-based geopolymer composites. The materials were produced through alkali activation of metakaolin using sodium hydroxide and sodium silicate solutions. Algal biomass was incorporated at 5 vol.% to evaluate its influence on rheological behavior, printability, shape stability, mechanical properties, and microstructure. The composites were fabricated using extrusion-based 3D printing technology and characterized through mechanical testing and microscopic observations.

The results demonstrate that the addition of algal biomass enables successful 3D printing while maintaining high mechanical performance. The compressive strength of the algae-modified composites reached 21.46 MPa compared with 22.69 MPa for the reference material, corresponding to a decrease of only 5.4%. Similarly, the flexural strength decreased from 7.02 MPa to 6.34 MPa (9.7%). The density of the composites remained comparable, ranging from 1.82 to 1.85 g/cm³. Moreover, the incorporation of algal biomass improved buildability and shape retention during printing. Microstructural observations confirmed good integration of algal particles within the geopolymer matrix, contributing to the formation of a stable composite structure.

The findings confirm that Cladophora glomerata biomass can be effectively utilized as a sustainable bio-based additive in 3D-printable geopolymer composites. The combination of low-carbon geopolymer technology, algal biomass valorization, and additive manufacturing provides a viable route toward environmentally friendly construction materials and supports the implementation of circular economy strategies in the building sector.