Wastewater sludge are characterized by complex rheological properties, strongly dependent on solids concentration and temperature. These properties are required for process hydrodynamic modelling but their correct measurement is often challenging at high solids concentrations. This is especially true to model the hydrodynamic of dewatered sludge during drying process where solids content (TS) increases with residence time. Indeed, until now, the literature mostly focused on the rheological characterization of sludge at low and moderate TS (between 4 and 8 %). Limited attention was paid to pasty and highly concentrated sludge mainly because of the difficulties to carry out the measurements. Results reproducibility appeared to be poor and thus may not be always fully representative of the effective material properties. This work demonstrates that reproducible results can be obtained by controlling cracks and fractures which always take place in classical rotational rheometry. In that purpose, a well-controlled experimental procedure has been developed, allowing the exact determination of the surface effectively sheared. This surface is calculated by scattering a classical stress sweep with measurements at a reference strain value. The implementation of this procedure allows the correct determination of solid-like characteristics from 20 to 45% TS but also shows that pasty and highly concentrated sludge highlight normal forces caused by dilatancy. Moreover the surface correction appears to be independent of TS in the studied range.

废水污泥的特征是复杂的流变特性，在很大程度上取决于固体浓度和温度。这些属性是过程流体力学建模所必需的，但是在高固体浓度下，它们的正确测量通常具有挑战性。在干燥过程中模拟脱水污泥的流体动力学时尤其如此，其中固含量（TS）随着停留时间的增加而增加。的确，直到现在，文献大多集中在低TS和中等TS（介于4％和8％之间）下的污泥的流变特性。对糊状和高浓度污泥的关注很少，主要是因为难以进行测量。结果的再现性似乎很差，因此可能无法始终完全代表有效的材料性能。这项工作表明，通过控制传统旋转流变仪中经常发生的裂纹和断裂，可以获得可重复的结果。为此目的，已经开发了一种控制良好的实验程序，可以准确确定有效剪切的表面。通过散射经典应力扫描并在参考应变值下进行测量来计算该表面。该程序的实施允许正确测定20％至45％TS的固体状特征，而且还显示出糊状和高度浓缩的污泥突出了由膨胀引起的法向力。此外，在所研究的范围内，表面校正似乎与TS无关。为此目的，已经开发了一种控制良好的实验程序，可以准确确定有效剪切的表面。通过散射经典应力扫描并在参考应变值下进行测量来计算该表面。该程序的实施允许正确测定20％至45％TS的固体状特征，而且还显示出糊状和高度浓缩的污泥突出了由膨胀引起的法向力。此外，在所研究的范围内，表面校正似乎与TS无关。为此目的，已经开发了一种控制良好的实验程序，可以准确确定有效剪切的表面。通过散射经典应力扫描并在参考应变值下进行测量来计算该表面。该程序的实施允许正确测定20％至45％TS的固体状特征，而且还显示出糊状和高度浓缩的污泥突出了由膨胀引起的法向力。此外，在所研究的范围内，表面校正似乎与TS无关。该程序的实施允许正确测定20％至45％TS的固体状特征，而且还显示出糊状和高度浓缩的污泥突出了由膨胀引起的法向力。此外，在所研究的范围内，表面校正似乎与TS无关。该程序的实施允许正确测定20％至45％TS的固体状特征，而且还显示出糊状和高度浓缩的污泥突出了由膨胀引起的法向力。此外，在所研究的范围内，表面校正似乎与TS无关。