Research Progress of Cementitious Materials and Related Properties for Building 3D Printing

3D printing is a rapid prototyping process based on mathematical models and mechanical additive production equipment. To date, 3D printing has been developed rapidly in the construction industry. Compared with the traditional molding process, 3D printing building technology has advantages of no template support, convenient construction and high design freedom. Therefore, it has been widely concerned by researchers and scholars all over the world. Recently, ordinary portland cement, fast-hardening and early-strength special cement, composite ordinary cement, alkali-activated cementitious materials and gypsum-based cementing materials have been used in 3D printing. However, it still has many problems. For example, on the one hand, different from traditional pumping concrete, 3D printing concrete needs a faster setting time and strength development rate to meet the pressure of interlayer structure. Thus, the range of initial setting time and final setting time was no later than 45 min and 360 min of ordinary portland cement, respectively, which cannot meet the rapid growth rate of interlayer force of printing components. On the other hand, the ability of inter-layers of cement-based 3D printing cementitious materials is insufficient to resist bending moment and shear force. Alkali-activated materials for 3D printing exists some problems, namely difficulty to control the setting time, large volume shrinkage, and easy cracking. And the poor water resistance is the main issues of gypsum-based cementitious materials. Therefore, the development and regulation of materials is still one of the research focuses of 3D printing architecture for a long time. At the same time, the application of 3D printing technology has some shortcomings on the construction industry;formed process was the layer-by-layer manner without template support. On the one hand, reinforcement cannot be added directly in this way resulting in lower flexural strength. On the other hand, the weak interlayer surfaces and the introduced voids caused by this method become potential defects of the printed structure to a certain extent, resulting in the heterogeneity of the components, weakening the overall bearing capacity and long-term durability of the structure, etc. It hinders wide application of 3D printing concrete. And it also means that its forming process presents a higher challenge on the performance of fresh concrete and its properties in 3D printing. In this paper, the research progress of cementitious materials for building 3D printing and their related properties are summarized. The application research of five types of building 3D printing are introduced, such as ordinary portland cement, fast hardening and early strength special cement, compound ordinary cement, alkali-activated materials, and gypsum-based materials. Setting time and opening time, fluidity, extrusion, buildability, bond strength, anisotropic strength and durability of 3D printing pastes are also introduced. The application of 3D printing cementitious materials structure or component is summarized. The problems faced by 3D printing of buildings are analyzed, and its developments are prospected, which in order to provide reference for the application of 3D printing technology in the construction industry. © 2023 Cailiao Daobaoshe/ Materials Review. All rights reserved.