Role of thixotropy in interlayer microstructure and properties of additively manufactured cementitious materials

This study revealed the relationship among early-age thixotropic behavior, air-phase microstructure, and fracture properties of the interlayer region in additively manufactured (AM) cementitious materials. Cementitious materials were designed and characterized to possess distinctive rheological properties and were additively manufactured into cementitious specimens. The effects of thixotropy and printing time interval on the volume, size and aspect ratios of air-phase clusters and on their statistical distributions were analyzed comprehensively through three-dimensional micro-computed tomography. Also determined were the effects of thixotropy and printing time interval on the fracture properties of the interlayer regions. Based on the experimental evidence, the underlying mechanisms of how the time-dependent thixotropic behavior of AM cementitious materials impacts interlayer microstructure and fracture properties were discussed. The results shed light on material design strategies, through tailoring the fresh-state thixotropy of AM cementitious materials, to mitigate the sensitivity of their hardened-state properties to printing parameters.