Modeling of Concrete Printing Process with Frictional Interface

Three-dimensional (3-D) concrete printing is invariably accompanied by slippage between the printed structure and the platform, which affects the shape of the printed object. This study employs a physics -based friction model in a finite -deformation interfacial kinematic framework to model relative slipping between the bottom layer and the supporting surface. The constitutive model that is specialized for cementitious materials is based on an extension of the Drucker -Prager plasticity model. The evolution of material parameters due to thixotropy and hydration reaction results in increased stiffness that gives rise to the non-physical bounce -back phenomenon. A bounce -back control algorithm is presented and used in conjunction with the plasticity model as well as the interfacial frictional model. The printing process is simulated through an algorithm that controls the kinematics of the nozzle and links the material timescales of curing with the timescales of layered printing. The model and method are validated against experimental data, and several interesting test cases are presented.