How clay particulates affect flow cessation and the coiling stability of yield stress-matched cementing suspensions
How clay particulates affect flow cessation and the coiling stability of yield stress-matched cementing suspensions
复制标题
粘土颗粒如何影响屈服应力匹配固井悬浮液的流动停止和卷绕稳定性
DOI：
10.1039/c9sm02414j
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发表时间：
2020
期刊：
影响因子：
3.4
通讯作者：
Sant, Gaurav
中科院分区：
文献类型：
--
作者：
Mehdipour, Iman;Atahan, Hakan;Neithalath, Narayanan;Bauchy, Mathieu;Garboczi, Edward;Sant, Gaurav
由于挤出机中的流动停止以及沉积后的长丝脆性/断裂，致密悬浮液的流动阻力的显著增加可能会阻碍3D打印过程。了解发生的流变变化的性质对于操纵流动条件或为3D打印添加流动改性剂至关重要。因此，本文阐明了粘土颗粒对控制流动停止和通常印刷性较差的致密水泥悬浮液形状稳定性的影响。绳索盘绕方法实施与不同的间距，以探测屈曲稳定性和倾向于在沉积过程中经历拉伸和弯曲的致密悬浮液的断裂。絮凝和短期渗流的贡献，由于结构形成的动力学变形速率使用阶梯式等应力方法解卷积。结果表明，当颗粒体积分数接近堵塞极限时，剪切应力指示具有幂律标度的发散;剪切应力的这种幂律发散随粘土用量的增加而减小10倍。在含粘土悬浮液中的这种行为产生于相对填充分数（λ/λ max）的降低和具有更强颗粒间相互作用的分形结构聚集体的形成，其均匀排列控制挤出机中的流动停止和悬浮液均匀性，从而赋予更大的屈曲稳定性。这些结果为评估/改善基于浆料的3D打印过程中的可挤出性和可打印性行为提供了新的见解。
The remarkable increase in the flow resistance of dense suspensions can hinder 3D-printing processes on account of flow cessation in the extruder, and filament fragility/rupture following deposition. Understanding the nature of rheological changes that occur is critical to manipulate flow conditions or to dose flow modifiers for 3D-printing. Therefore, this paper elucidates the influences of clay particulates on controlling flow cessation and the shape stability of dense cementing suspensions that typically feature poor printability. A rope coiling method was implemented with varying stand-off distances to probe the buckling stability and tendency to fracture of dense suspensions that undergo stretching and bending during deposition. The contributions of flocculation and short-term percolation due to the kinetics of structure formation to deformation rate were deconvoluted using a stepped isostress method. It is shown that the shear stress indicates a divergence with a power-law scaling when the particle volume fraction approaches the jamming limit; ϕ → ϕj ≈ ϕmax. Such a power-law divergence of the shear stress decreases by a factor of 10 with increasing clay dosage. Such behavior in clay-containing suspensions arises from a decrease in the relative packing fraction (ϕ/ϕmax) and the formation of fractally-architected aggregates with stronger interparticle interactions, whose uniform arrangement controls flow cessation in the extruder and suspension homogeneity, thereby imparting greater buckling stability. The outcomes offer new insights for assessing/improving the extrudability and printability behavior during slurry-based 3D-printing process.