Additive manufacturing of Portland cement pastes with additions of kaolin, superplastificant and calcium carbonate

The aim of this investigation is to develop inexpensive formulations of Portland cement pastes for use in additive manufacturing with the direct ink writing technique. Kaolin, a superplastificant based on cellulose, and calcium carbonate were used as additives and modifiers of printing quality. A total of 15 formulations were created for the printing process, of which 3 were able to produce printed parts with the right shape, stability and finish. Cylindrical samples of 17 mm in diameter and 26 mm in height were created for compression testing. Parts with complex geometries were also printed in order to evaluate the versatility of the formulations in the process. The microstructure was characterized with scanning electron microscopy and X-ray diffraction. Mass flow through the nozzle and density were measured and Weibull distribution graphs were plotted. The results showed that the best formulation was mainly associated to an optimal kaolin content, which functioned as a rheology regulator. Water absorption tests showed that the printed samples were porous materials, which would make them suitable for use in many applications. (C) 2020 Elsevier Ltd. All rights reserved.