The accessibility to rheological parameters for concrete is becoming more and more relevant. This is mainly related to the constantly emerging challenges, such as not only the development of high-strength concretes is progressing very fast but also the simulation of the flow behaviour is of high importance. The main problem, however, is that the rheological characterisation of fresh concrete is not possible via commercial rheometers. The so-called concrete rheometers provide valuable relative values for comparing different concretes, but they cannot measure absolute values. Therefore, we developed an adaptive coaxial concrete rheometer (ACCR) that allows the measurement of fresh concrete with particles up to d max = 5.5 mm {d}_{{\rm{\max }}}=5.5\hspace{.5em}{\rm{mm}} . The comparison of the ACCR with a commercial rheometer showed very good agreement for selected test materials (Newtonian fluid, shear thinning fluid, suspension, and yield stress fluid), so that self-compacting concrete was subsequently measured. Since these measurements showed a very high reproducibility, the rheological properties of the fresh concrete could be determined with high accuracy. The common flow models (Bingham (B), Herschel–Bulkley, modified Bingham (MB) models) were also tested for their applicability, with the Bingham and the modified Bingham model proving to be the best suitable ones.

中文翻译：

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自适应同轴混凝土流变仪的开发和新拌混凝土的流变特性

混凝土流变参数的可及性变得越来越重要。这主要与不断出现的挑战有关，例如不仅高强混凝土的发展进展非常快，而且流动行为的模拟也非常重要。然而，主要问题是新拌混凝土的流变特性无法通过商用流变仪进行。所谓的混凝土流变仪为比较不同的混凝土提供了有价值的相对值，但它们不能测量绝对值。因此，我们开发了一种自适应同轴混凝土流变仪 (ACCR)，可以测量颗粒高达 d 最大限度 = 5.5 毫米 {d}_{{\rm{\max }}}=5.5\hspace{.5em}{\rm{mm}} . ACCR 与商用流变仪的比较表明，所选测试材料（牛顿流体、剪切稀化流体、悬浮液和屈服应力流体）非常吻合，因此随后可以测量自密实混凝土。由于这些测量显示出非常高的重现性，因此可以高精度地确定新拌混凝土的流变特性。还测试了常见的流动模型（Bingham (B)、Herschel–Bulkley、改进的 Bingham (MB) 模型）的适用性，Bingham 和改进的 Bingham 模型被证明是最合适的模型。