Impact of Early Particle Characteristics on Rheology and Buildability in 3D-Printed Magnesium Silicon Potassium Phosphate Cement Incorporating Fly Ash (2025-12)¶

Early particle evolution including particle size distribution, specific surface area and zeta potential, critically regulates the rheological properties of cement by governing interparticle interaction forces. Existing researches focuse on the influence of FA incorporation on rheological and mechanical properties. This study investigated FA-induced particle evolution and its relationship with rheological properties. FA triggered rapid particle agglomeration within 30 min (increasing median diameter by 366.5 % at 15 % FA compared to the control group), concurrently reducing specific surface area and redistributing surface charge through accelerated hydration product nucleation. This particle restructuring enhanced interparticle attraction, substantially elevating static yield stress from 559.19 Pa to 2998.36 Pa, and increasing thixotropic area to 3.13 × 104 Pa/s at 15 % FA content. The transition of Lissajous-Bowditch curve from elliptical to linear profile confirmed the enhancement of viscoelasticity. Furthermore, FA promoted K-struvite crystallization and M-S-H gel formation, while FA-released Al3+ generated AlPO4 as a distinct crystalline phase through independent hydration reaction. These findings expand the understanding of driving forces for the early rheological properties of 3D-printed MSPPC and provide an effective reference for regulating the rheological properties through the basic parameters of admixtures.