Dynamic and Static Yield-Stress Determination of Cementitious Paste with Admixtures (2020-07)¶

The 3D printing of cementitious material requires an understanding of the printing material’s rheological properties, especially yield stress and viscosity. The ability to adjust and control these properties in the 3-D printing process represents a breakthrough for the construction sector. The aim of this paper is to experimentally determine the dynamic yield stress and static yield stress of cementitious materials with admixtures. Unlike conventional rheometer geometries, the National Institute of Standard and Technology (NIST) spindle geometry is used in this work for the measurement of both yield stresses. While dynamic yield stress was measured by increasing and decreasing the rotational velocity, the static yield stress was characterized by two methods: the torque increase method and the constant rotational speed method. For both yield stresses, a total of 16 mixtures were studied in a factorial experimental design of the chemical admixtures. The impact of each admixture has been highlighted. The structural build up was assessed through the structuration rates. The temperature effect on the early age properties was studied for the most promising formulations.