Feasibility study of developing cementless blended materials as 3D printable materials

In recent years, 3D printing of structural components and elements has become a popular method of construction automation. The key to the development of 3D printing was its diversity of printable spraying materials, which offered fast construction, material savings, and stable quality. A cementless blended material was made from three industrial by-products (fly ash, ultra-fine fly ash and ground-granulated blast furnace slag) without adding an alkaline activator. Various tests were conducted to compile the results, including viscosity, setting time, spray, and flow tests. The test results showed that viscoelastic solid pastes with viscosities of more than 6000 cP could be used as spraying materials for 3D printers. 3D printing can be accomplished with a ternary cementless blend consisting of 10 % ground-granulated blast furnace slag, 40 % ultra-fine fly ash and 50 % fly ash at a water to cementitious ratio of 0.25. Furthermore, the printer's spray flow rate should be set at 40 % to achieve the best aesthetic integrity. The compressive strength test verified that the 3D printed specimens had similar compressive strengths to conventional molded specimens and it confirmed that the source of strength of cementless materials was C-A-S-H colloids. According to the study, the cementless blended material developed can be used in 3D printing as a spraying material and is consistent with promoting high-value industrial by-product technology.