Mitigating Plastic Shrinkage and Cracking in 3D Printed Concrete Through Surface Rewetting (2024-09)¶

Rewetting 3D-printed elements is an active mitigation approach aimed at preventing rapid increases in capillary pressure. The method lowers the capillary pressure in freshly placed concrete layers, reducing internal stresses and minimizing the risk of cracking. In the present study, the concrete surface was rewetted at a constant application rate at different times following specimen production. The results demonstrate that rewetting can significantly reduce shrinkage and the tendency of printed elements to crack. However, inline spreading of water during extrusion, such as attaching water jets directly to the printing nozzle, proves ineffective. The study results confirm that rewetting the concrete surface efficiently prevents shrinkage when performed during the phase of decreasing evaporation in the concrete element, i.e., shortly after extrusion.