Characterization of thixotropic properties of fresh cement‐based materials.

Accurate evaluation of the thixotropy of mixtures is crucial for the design and production of self‐compacting concrete, pumped concrete, and 3D printed concrete. However, there is no uniform standard for the assessment of the thixotropy of fresh cement‐based materials. In this paper, four widely used test procedures (thixotropic index, static yield stress growth curve, thixotropic hysteresis loop area, and three‐stage curve) are compared to determine the relationships between them. The results show that the test procedures based on the break‐down (destruction) process (thixotropic index, thixotropic hysteresis loop area, and degree of breakdown) are difficult to distinguish between reversible and irreversible thixotropic structures and to accurately assess the thixotropy of mixtures. The short‐term structural build‐up rate Rthix is more suitable for characterizing the thixotropic properties. The three‐stage curve can characterize both the degree of structural damage and the reconstruction ability of the paste, nano‐attapulgite clay can significantly improve the structural recovery degree of the mixture at the early hydration stage. This study will provide guidance and a theoretical framework for choosing the thixotropic characterization method of cement‐based materials in practical engineering applications. [ABSTRACT FROM AUTHOR]