Residual properties and microstructural evolution of heated 3D printed concrete after exposure to water

The progressive adoption of 3D printed concrete (3DPC) in construction necessitates a comprehensive evaluation of its performance under extreme thermal conditions, especially concerning post-fire residual safety. While previous research has largely focused on material behavior under slow cooling, the effect of rapid water cooling—representative of realistic firefighting operations—on the interlaminar zones of 3DPC remain poorly characterized. This work systematically examines the deterioration of 3DPC after exposure to temperatures reaching 800 °C followed by water quenching. Integrated experimental techniques, including mechanical testing, scanning electron microscopy, X-ray diffraction, thermogravimetry, and nitrogen adsorption analysis, reveal severe coupled damage mechanisms under the combined effect of high temperature and thermal shock. Key observations include a drastic reduction in compressive strength, exceeding 50% after 800 °C treatment, the addition of fibers has made the occurrence of cracks more complicated, and decomposition of hydration products accompanied by CaO rehydration leading to expansive fracture. A critical degradation threshold was identified between 400 °C and 600 °C, where concurrent physicochemical processes result in irreversible loss of integrity. The findings emphasize the vulnerability of printed interfaces to thermal shock and provide a foundational basis for designing damage-resistant 3DPC mixtures and improving fire safety standards in digital fabrication.