Assessing Static and Dynamic Yield-Stress of 3D Printing Mortar with Recycled Sand (2025-01)¶

his study investigates the printability of mortar containing recycled sand for 3D printing applications, addressing the increasing demand for sustainable construction materials. The main objective is to understand how the morphology and fineness modulus of sand, along with the water-to-binder (w/b) ratio, influence the rheological properties of the mortar. 30 different mixtures were analyzed to assess their impact on static and dynamic yield stresses, offering insights into the key factors necessary for optimizing mixture designs in successful 3D printing processes. The analysis shows that the static yield stress is significantly influenced by the mixture’s water-to-binder ratio, as well as the fineness modulus and morphology of the sand particles. However, for the dynamic yield stress, only the water-to-binder ratio in the mixture and the fineness modulus of the recycled sand have a significant impact, while the morphology has negligible influence. Multiple linear regression analyses reveal that higher fineness modulus and water-to-binder ratios generally lead to lower static and dynamic yield stresses, as well as a reduced degree of shear thinning. These findings suggest that incorporating recycled sand enhances shear thinning in 3D printing mortar, potentially improving the buildability of the mixtures.