Upscaling the printing ink from cement paste to mortar level is the path people must take to apply active rheology control to smart and advanced digital fabrication, which will decrease the content of binder and reduce carbon footprint. This study investigates the rheological response of cement mortars with carbonyl iron particles (CIPs) by using penetration tests and vane tests. A customized magnetorheological test setup, making use of a pipe/nozzle-like inline magnetic intervention, was developed to modify the rheological properties of responsive mortars within a few seconds. The alignment of magneto-responsive particles and the hindrance of sand on magneto-responsive particles in the mortars were visualized and determined by scanning electron microscopy (SEM). With an inline magnetic field, the yield stress determined by the slow penetration test and the torque measured by the vane test increased by a significant factor. The magneto-responsive effect and the response speed rate of the mortar can be adjusted on demand and in time. The effect of cement-to-sand (c/s) ratios and sand gradations on the magnetorheological response of cement mortars was studied. With the increase of sand content (decrease of c/s ratio), the percent increase of yield stress and torque decreased and the magneto-response speed reduced, which indicates a reduction in response efficiency. The magneto-responsive particles could more easily move in the mortar when the particle size of sand increased. Experimental proofs of concept to apply active rheology control to a 3D printing nozzle or pumping line were conducted.

中文翻译：

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通过在线磁场的干预，升级对水泥砂浆的主动流变控制

将印刷油墨从水泥浆升级到砂浆级别是人们将主动流变控制应用于智能和先进数字制造的必经之路，这将减少粘合剂的含量并减少碳足迹。本研究通过渗透试验和叶片试验研究了含羰基铁颗粒 (CIP) 的水泥砂浆的流变响应。开发了一种定制的磁流变测试装置，利用类似管道/喷嘴的内联磁力干预，可以在几秒钟内改变响应砂浆的流变特性。通过扫描电子显微镜（SEM）可视化并确定砂浆中磁响应颗粒的排列和砂对磁响应颗粒的阻碍。在串联磁场的情况下，由慢速渗透测试确定的屈服应力和由叶片测试测量的扭矩增加了一个显着的系数。砂浆的磁响应效应和响应速率可按需、及时调整。研究了水泥砂比和砂级配对水泥砂浆磁流变响应的影响。随着砂含量的增加（c/s比降低），屈服应力和扭矩的增加百分比降低，磁响应速度降低，表明响应效率降低。当沙子粒径增大时，磁响应颗粒更容易在砂浆中移动。进行了将主动流变控制应用于 3D 打印喷嘴或泵送线的概念实验验证。