Fluid intrusion in powder beds for selective cement activation – An experimental and analytical study

The presented work addresses particle bed binding by selective cement activation as an additive manufacturing process for the construction industry. Its focus is the fluid intrusion behavior in powder beds since this is of merely importance for the shape accuracy and the mechanical performance of printed objects. Therefore, an analytical approach taking into account the particle-bed properties as well as the particle-fluid interaction is developed to model time-depending fluid intrusion from bottom to top into non-reactive particle beds. The approach is further developed to meet the boundary conditions in the printer, i.e. limited amount of fluid, fluid flow from top to bottom and reactive components. For all adoption steps, the measured and modeled values are compared and a good alignment is obtained. Finally, the model is applied to 3D-printing experiments and mechanical performance and shape accuracy of printed specimens could be explained with the help of the developed model.