Additive Manufacturing of Cementitious Materials by Selective Paste Intrusion: Numerical Modeling of the Flow Using a...

The construction industry is undergoing a transformation with the advent of 3D printing technologies. While traditional methods remain dominant, emerging techniques like selective paste intrusion offer new possibilities for fabricating precise structures. Prior research has established that cement-based 3D printing involves embedding a fluid cement paste into a dry particulate matrix. However, a key challenge remains in controlling the paste distribution to ensure structural integrity and shape accuracy. Existing studies have explored the rheological behavior of cementitious materials but have not fully addressed the penetration dynamics in granular beds. This gap motivated researchers to develop numerical models that simulate paste intrusion. The uncertainty around how paste flows through particle beds has driven the need for predictive modeling tools. No prior work has combined phase-field methods with visco-plastic models to study this phenomenon. The lack of reliable simulation frameworks has limited progress in optimizing printing parameters. This study addresses these limitations by introducing a new numerical approach.

The primary aim of this study is to enhance the understanding of cement paste flow during selective paste intrusion in 3D printing. The specific problem involves predicting how paste distributes within a dry particle bed to achieve desired shape accuracy and mechanical performance. The motivation stems from the need to improve the reliability of 3D-printed concrete components. By simulating the flow dynamics, the researchers aim to identify key factors influencing penetration depth. The study seeks to validate numerical models against experimental data from 3D and 1D systems. A secondary goal is to compare the numerical results with analytical predictions. The focus is on developing a predictive framework that can guide future printing processes. This approach is intended to support the design of high-performance cementitious structures.

The researchers employed a two-dimensional axisymmetric phase field method to model the flow of cement paste into a granular bed. The simulation was conducted using Comsol software, which allowed for the integration of a visco-plastic model. The phase field approach enabled the tracking of the paste-particle interface during intrusion. The model accounted for variations in average grain diameter, contact angle, and paste rheology. The numerical framework was designed to replicate the physical conditions of selective paste intrusion. The simulations were structured to capture the progressive penetration of the paste into the particle matrix. The model incorporated boundary conditions based on experimental setups. The results were compared with existing 3D and 1D experimental data to assess accuracy.

The numerical simulations revealed that the penetration depth of cement paste is strongly influenced by the average grain diameter and contact angle. The model predicted a decrease in penetration with increasing particle size, consistent with experimental observations. The contact angle was found to significantly affect the paste's ability to infiltrate the particle bed. The visco-plastic model accurately captured the non-Newtonian behavior of the cement paste. The simulations showed good agreement with both 3D and 1D experimental results. The phase field method successfully captured the interface dynamics during intrusion. The model's predictions were validated against analytical solutions from one-dimensional systems. The study demonstrated that the numerical approach is reliable for predicting paste penetration in granular beds.

The authors conclude that the proposed numerical model is a reliable tool for predicting the penetration of cement paste during selective paste intrusion. The study highlights the importance of grain diameter and contact angle in determining the depth of paste infiltration. The phase field method, combined with a visco-plastic model, effectively captures the flow dynamics of cementitious materials. The results align with experimental data from both 3D and 1D systems. The model's ability to simulate real-world conditions supports its use in optimizing printing parameters. The findings suggest that numerical simulations can guide the design of high-accuracy 3D-printed concrete structures. The study does not propose new materials or experimental setups but validates an existing modeling framework. The authors emphasize the need for further validation with additional experimental data.