Elevated Temperature Response and Fire Resistance Considerations of 3D-Printed Concrete (2025-09)¶

3D printing introduces unique challenges in construction, particularly regarding fire safety. The layer-by-layer deposition leads to potential weaknesses such as interlayer debonding, spalling, and cracking when exposed to elevated temperatures and thermal gradients. Despite growing interest, large-scale fire performance of 3D-printed concrete (3DPC) remains underexplored. This study investigates the thermal and fire behaviour of 3DPC, both material wise and of printed full scale. Laboratory tests on small specimens (160 × 40 × 40 mm) assessed the mechanical performance of 3D-printed concrete exposed to temperatures up to 800 °C. The results show that over 80% of compressive strength was retained after heating the samples to 450 °C. Full-scale wall segments (500 mm × 180 mm × 500 mm) with three different internal topologies (hollow, triangular, and sinusoidal) were subjected to standard fire resistance tests. Elements with attached thermocouples were fixed in the oven without a load and exposed to ISO 834 temperature–time profile. The occurring damage on the exposed and unexposed surface was evaluated using optical measurements. Results has shown that the elements maintained integrity (E) and insulation (I) criteria up to 450 °C at 1 cm depth for 19–25 min, and at 2 cm for 45–65 min. Tests revealed extensive surface cracking in all samples, with the most significant damage observed in hollow-core elements. In contrast, samples with triangular and sinusoidal infill exhibited lower thermal penetration and reduced structural degradation. The findings indicate promising thermal insulating performance of 3DPC and highlight the critical role of internal geometry in fire response. However, further research is required to assess fire behaviour under mechanical loading and to validate performance across a wider range of infill designs and real-scale conditions.