About the research
Three-dimensional (3D) printing concrete technology has already been adopted for structural applications. Many houses and pedestrian bridges have been 3D printed in the US and other countries. In spite of exploratory applications, 3D concrete printing technology remains fragmentary, and its full-scale uses in transportation infrastructure are still rarely seen. In order to bring the full benefits of this technology to the construction industry, it still requires a much better understanding of the relationships among digital design, operation/processing, mechanisms of building materials, formulation of printing materials, and performance of printed products. The present study aimed at exploring the feasibility of developing 3D printable concrete mixtures and evaluating their potential uses for transportation infrastructure.
In this project, a commercial 3D clay printer was used to print small-scale clay, paste, and mortar objects. The effects of printing parameters and procedures, printable materials, and mix proportions on printing properties, such as flowability, extrudability, printability, buildability as well as on mechanical properties (compressive and tensile strength) of printed objects, were investigated. The methods for characterizing the quality of 3D printed objects were examined.
The results indicate that paste and mortar mixtures made with cement, silica fume, a rapid-set grout powder, viscosity modifying agents (VMAs), and superplasticizer can be engineered to have desirable flowability, extrudability, printability, and buildability for 3D printing. Samples that were 3D printed with different printing paths and tested under different loading direction showed clear anisotropic behavior in their mechanical properties. Printing qualities, such as geometric accuracy, distortion, surface roughness, etc., of printed objects can be well evaluated using image analysis. In addition, a qualitative ranking system was also developed for evaluation of the printing qualities of 3D concrete printing.