Experimental and Numerical Investigation of Plastic Shrinkage Control in 3D-Printed Concrete Using Natural Zeolite (2026-04)¶

Plastic shrinkage cracking is a major durability concern in 3D-printed concrete (3DPC), primarily due to its large exposed surface area, high paste content, and the absence of formwork, which accelerate moisture evaporation. This study systematically investigates the efficacy of natural zeolite as a partial Portland cement replacement for controlling plastic shrinkage in 3D-printed concrete. The key innovation of this research lies in the integration of advanced real-time monitoring and microstructural analysis to decipher the underlying mechanisms. Through quantitative analysis of sequential images, five critical cracking parameters (length, width, area, growth rate, and density) were meticulously evaluated across different layers. The results demonstrate that a 10% replacement of cement with natural zeolite induces a substantial reduction in all cracking parameters, with the most pronounced effect observed in the top layer, where crack density was curtailed by up to 46.6%. Microstructural examinations via XRD, TGA, and SEM revealed that the porous structure of natural zeolite enhances water retention, promotes pozzolanic reactions, and facilitates the formation of additional C-S-H gel, leading to a denser matrix and more uniform stress distribution. Furthermore, a pioneering numerical model was developed using the time-hardening creep model in ABAQUS, showing a significant reduction in interlayer shear stresses (approximately 0.07 MPa) and plastic shrinkage strain (about 30%) in zeolite-modified specimens. This research definitively positions natural zeolite as an effective supplementary cementitious material for enhancing early-age cohesion, improving strain distribution, and increasing the durability of 3D-printed concrete, thereby advancing robust and sustainable digital construction.