Reducing the Cement Content in 3D Concrete Printing Mixtures Through Porcelain Polishing Residue Incorporation (2026-01)¶

The fresh-state requirements of 3D concrete printing (3DCP) often lead to high cement consumption. Polishing porcelain residue (PPR) is a fine material with pozzolanic activity, being a potential candidate for replacing cement in 3DCP. In this work, we produced 3DCP formulations with 0-40% replacement of cement with PPR; a commercially available 3DCP mixture was also assessed for comparison. Paste rheological tests demonstrated that PPR incorporation led to higher structural build-up rates (Astruct), with the flocculation contribution (Athix) being dominant over the chemical contribution (Achem) for the highest PPR content. 3D printing tests showed that replacing cement with PPR did not affect the yield stress and buildability of the mixtures, while it progressively increased the Astruct, allowing for a 135% higher layer deposition time. Replacing cement with PPR reduced the 28-day compressive strength of the 3D-printed elements by 11.4% (20% PPR) and 21.1% (40% PPR). Nonetheless, the CO2 intensity index decreased from 15.4 kg CO2-eq/m3.MPa (0% PPR) to 12.7 kg CO2-eq/m3.MPa (40% PPR), matched values reported in the literature for conventional concrete. The 28-day flexural tests conducted in printed elements yielded strengths of 6.8-9.4 MPa, and SEM-EDS revealed a homogeneous distribution of the chemical elements across the bulk layer and joint region.