This paper aims to model the extrusion-based 3D printing process of a plain ordinary Portland cement (OPC) paste using the discrete element method (DEM), and outlines the methodology adopted to evaluate the linkage between particle scale processes and extrusion process. A mini slump test is used to define the rheological model to be used in DEM, and extract the relevant parameters. They are then implemented in a scaled-down extrusion printing model to determine the influence of particle-scale effects on extrusion force. The DEM model is able to capture the differences in extrusion load-displacement responses similar to the experiments. Refinements to the model based on extracted parameters are also discussed.