The thixotropic behaviour of cementitious materials received widespread attention in recent years. However, structural break-down is often ignored in most research. The role of structural break-down in thixotropy of magneto-responsive cementitious materials should be discussed in order to achieve comprehensive active rheology control of cementitious materials, not only from more liquid-like to more solid-like (set-on-demand), but also from more solid-like to more liquid-like. This research investigates the thixotropy of magneto-responsive cementitious materials in combination with the structural break-down. The magnetorheological response of cement pastes subjected to unipolar and bipolar magnetic fields is experimentally evaluated. The effects of magneto-responsive particle size, magnetic field direction, intervention duration, magnetic flux density and magnetic field frequency on thixotropy of cementitious materials containing carbonyl iron particles (CIPs) are studied. The shear stress of magneto-responsive cementitious materials can be changed in time and on demand by the structural build-up and structural break-down of magneto-responsive particles' alignment and/or movement. With the increase of magnetic flux density, the shear stress of magneto-responsive cement paste reaches a minimum first and afterwards increases dramatically. When the magnetic field frequency increases from 0 Hz to 0.2 Hz, the yield stress of magneto-responsive cement paste decreases dramatically, followed by a slight increase. The origins of thixotropy for fresh magneto-responsive cement paste considering the magneto-responsive particle agitation (e.g. vibration and movement, etc.) are presented.

中文翻译：

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时变磁场干预主动控制磁响应胶凝材料触变性


近年来，胶凝材料的触变行为受到广泛关注。然而，在大多数研究中，结构分解常常被忽视。应讨论结构破坏在磁响应胶凝材料触变性中的作用，以实现胶凝材料的全面活性流变控制，不仅从更像液体到更像固体（按需设置），而且也从更像固体变成更像液体。本研究结合结构破坏研究了磁响应胶凝材料的触变性。通过实验评估了单极和双极磁场下水泥浆的磁流变响应。研究了磁响应粒径、磁场方向、干预时间、磁通密度和磁场频率对含羰基铁颗粒（CIPs）胶凝材料触变性的影响。磁响应胶凝材料的剪切应力可以通过磁响应颗粒的排列和/或运动的结构构建和结构分解而按需要及时改变。随着磁通密度的增加，磁响应水泥浆体的剪切应力先达到最小值，然后急剧增加。当磁场频率从0 Hz增加到0.2 Hz时，磁响应水泥浆体的屈服应力急剧下降，随后略有增加。提出了考虑磁响应颗粒搅拌（例如振动和运动等）的新鲜磁响应水泥浆触变性的起源。