Digital fabrication of concrete elements requires a better understanding of the rheological behaviour of the cementitious material used. Fresh concrete is known to be a thixotropic material having time-dependent characteristics. Moreover, fresh mortars used in three-dimensional (3D) printing should maintain a sufficient shear stress to avoid any deformation or failure during printing. This paper concentrates on the experimental investigation of the buildability properties of different printable materials, on the basis of shear stress, measured using the Fall cone test. The effect of different constituents such as high-range water reducer, viscosity-modifying agent, limestone filler and water content on the evolution of the yield stress in mortars, derived from the shear stress, are studied experimentally and discussed in detail. Accordingly, the change of variables induces a quasi-linear relationship with the growth of the structuration rate and structural build-up (A_thix) of mortars, which corresponds to the variation of the yield stress with time. These findings enable the use of the A_thix concept and the proposed curves for designing new printable mixes that better suit the buildability properties of large-scale 3D printed structures.

中文翻译：

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混合成分对 3D 打印砂浆触变性的影响

混凝土构件的数字化制造需要更好地了解所用水泥材料的流变行为。已知新拌混凝土是具有随时间变化的特性的触变材料。此外，用于三维 (3D) 打印的新鲜砂浆应保持足够的剪切应力，以避免在打印过程中发生任何变形或失效。本文专注于对不同可印刷材料的可建造性特性的实验研究，基于剪切应力，使用 Fall cone 测试测量。通过实验研究并详细讨论了高效减水剂、粘度调节剂、石灰石填料和含水量等不同成分对砂浆屈服应力演化的影响，该演化源于剪切应力。因此，A _thix ) 的砂浆，对应于屈服应力随时间的变化。这些发现使得能够使用A _thix概念和提议的曲线来设计新的可打印混合物，以更好地适应大型 3D 打印结构的可建造性。