Development of P-3DP (Powder-based 3D Printing) technologies for the production of cement-based materials

This thesis represents an effort to optimally investigate the processes involved in binder jetting 3D printing of cementitious materials by systematically studying the effects some key processing variables have on structural and dimensional performance variation of the printed components. Binder jetting has the potential for complex geometries with high precision, along with minimum material waste, which is yet to be transformed into consistent mechanical strength and dimensional accuracy, especially when scaling from the laboratory to industrial applications. This paper presents the printing of quick-setting cement-based materials using a binary cement system composed of ordinary Portland cement and quick-setting cement. The critical parameters that received most of the research effort included the water-to-cement ratio, the particle size of the siliceous sand aggregates-namely, coarse versus fine OPC: QSC mix proportion, and the layer thickness used during printing. The experiments were conducted by fabricating specimens under different conditions using blended dry powders and deionized water. The printed products were then tested in terms of dimensional accuracy, compressive strength, and flexural strength. It follows that changes in the w/c ratio and aggregate size have a direct impact both on mix flowability and bond formation at the interlayer surface, and consequently on the mechanical performance and print fidelity of the final product. Additionally, the investigation on the binary cement mix goes on to reveal that OPC content plays a vital role in strength development and the optimum mechanical properties emerge at certain OPC:QSC ratios, especially with coupled reduced layer thickness. Further research based on these findings now examines the mutual relationships between these variables in an integrated framework that relates process parameters to performance attributes. Lastly, this research investigates how scaling of the optimized parameters, obtained under controlled conditions in the laboratory, can be done to industrial production with the view to identify modifications that are necessary to realize enhanced structural integrity and precise dimensional control under actual construction conditions. The integrated approach presented in this paper will provide an advanced understanding of BJ3DP for cementitious construction and open up opportunities for more reliable, cost-effective, and scalable additive manufacturing in the construction industry.