Ternary Gypsum-Cement-Pozzolan Composites for 3D Printing with Reduced Environmental Impact

The objective of this study is to develop a sustainable gypsum-cement-pozzolanic (GCP) ternary binder composite using both commercially available and waste gypsum, such as construction demolition waste gypsum (CDG) and industrial by-product phosphogypsum (PG). The GCP ternary composite combines the quick setting time of gypsum, high final strength of Portland cement (PC), with a crucial pozzolanic component that ensures chemical stability. Within the framework of this research, fresh state properties, mechanical properties, and durability was tested and compared among the developed GCP composites. The obtained results showed that the open printing time and consistency is suitable for 3D printing for all mixtures. The compressive strength results indicated that the developed composites possessed a compressive strength comparable to that of ordinary concrete (>35MPa). The water absorption was less than 20% and the softening coefficient remained above 0.70 for all mixtures. The results showed poor frost durability for composites containing PG, however both mixtures containing CDG showed satisfactory frost resistance. The GCP mixture used for the trial 3D printing to assess its buildability and print quality showed satisfactory results, indicating its suitability for 3D printing.