Enhancing Mechanical Properties of Three-Dimensional Concrete at Elevated Temperatures Through Recycled Ceramic-Powder Treatment Methods (2024-06)¶

To promote the construction industry and establish a green environment, the integration of sustainable building materials is urgently required. This study presents the influences of three materials (silica fume, fly ash, and recycled ceramic powder (RCP)) and different RCP dosages (0%, 10%, 20%, and 30%) on the mechanical properties and microstructure of concrete at different temperatures. The study presents the results of comprehensive flow tests, printability assessments, mechanical evaluations under different loading directions, high-temperature analyses, digital image correlation, X-ray powder diffraction and scanning electron microscopy. The experimental findings indicate the successful printing of all samples, with wall structure failure occurring only at a height of 730 mm. Furthermore, compared to those of other materials, the RCP displays a superior heat resistance, with a significant increase in compressive strength (28.9%) to 53.9 MPa at 300 °C. Additionally, the introduction of the RCP into 3D-printed concrete results in an anisotropic behaviour, with an initial enhancement in the mechanical strength, followed by attenuation as the RCP content increases. Microstructural analysis reveals enhanced interfacial adhesion with RCP addition, albeit accompanied by the emergence of numerous pores. The optimal mixture, which is designated as RCP-2-0-1 with 20% of the cement replaced by RCP, exhibits a significant anisotropic compressive strength (55.9 MPa) and an adequate anisotropic flexural strength (12.49 MPa) and impressive heat resistance (11.7% increase in compressive strength at 300 °C). This renders it a suitable sustainable impact-resistant thermal material for use in structural applications.