Component additive approach to predict cement paste rheology considering mineral and particle heterogeneity on different scales (CONCERT)

新拌混凝土的流变性主要由所含水泥浆体的性质决定，水泥浆体通常表现出明显的非牛顿流动行为，其特征是屈服应力和明显的触变性。流变性受到水泥水化、系统温度和剪切过程(例如，材料流动或压实引起的振动)的强烈影响。所有因素都会导致颗粒库存和载液组成的变化，因此基本的机理还没有完全了解。所申请项目的目标是根据上述影响参数和所用材料(即水泥、水和高效减水剂)的函数，确定超塑水泥浆体流变性的可预测性。为此，表面络合模型将通过AFM测量水泥及其水化产物的组成矿物，并考虑到高效减水剂的作用。使用所谓的组份方法，这些方法可以在统计上确定由这些矿物的任意部分组成的颗粒之间的相互作用。通过测量颗粒大小和表面粗糙度的变化，考虑了粒度测量的影响。通过广泛的化学和物理调查捕捉到系统的阶段清单和粒度测定的变化，并随后对其进行建模。通过使用放射性示踪剂，可以确定高效减水剂在水泥颗粒表面的吸附行为，或者更确切地说，可以确定高效减水剂在水化产物中的整合情况。这些调查的结果将与水泥浆体流变性的广泛测量相结合。这些流变特性将在常压和各向同性压力升高以及施加附加振动和温度的情况下进行测量。通过结合现场和非现场测量，剪切引起的颗粒和溶液库存中的变化可以与前述组份方法结合使用，以开发流变性预测模型。预期的模型方法有两个特点：它区分胶体和非胶体库存对流变学的贡献，从而允许明显改进对决定性颗粒库存(即胶体成分)的影响的定义，如温度和水合作用。此外，该模型将以概率形式建立，并考虑到水泥的非均质性源于矿物相组成，以及由团聚或剪切条带造成的。手头的人民党提案已经与其他人民党提交者密切协调。对计划中的合作进行了详细描述。

The rheological properties of fresh concrete are mainly determined by the properties of the cement paste contained therein, which generally exhibits pronounced non-Newtonian flow behaviour characterized by a yield stress and pronounced thixotropy. The rheological properties are strongly influenced by the hydration of the cement, by the system temperature and by shearing processes (resulting from e.g. material flow or vibration applied by compaction). All factors lead to a variation in the particle inventory and the carrier fluid composition, whereby the fundamental mechanisms are not yet fully understood. The objective of the requested project is to establish the predictability of the rheological properties of superplasticized cement paste on the basis of the influencing parameters mentioned and as a function of the materials used (i.e. cement, water and superplasticizer). For this, surface complexation models are to be derived by means of AFM-measurements of the constituent minerals of the cement and its hydration products considering the action of superplasticizers. Using the so-called component approach, these then allow statistically firm determinations of the interaction of particles consisting out of arbitrary fractions of these minerals. By conducting measurements with variation in particle size and surface roughness, the effect of granulometry is considered. Changes in phase inventory and granulometry of the system are captured by extensive chemical and physical investigations and subsequently modelled. Through the use of radio-tracers, determinations can be made regarding the adsorption behaviour of superplasticizers to the surface of cement particles or rather the integration of superplasticizer within the hydration products. The results obtained from these investigations will be combined with extensive measurements of the cement paste rheology. These rheological properties will be measured both at atmospheric and elevated isotropic pressure, as well as applying additional vibration and temperature. By combination of in-situ and ex-situ measurements, changes within the particle and solution inventory as a result of shear can then be used, in combination with the aforementioned component approach, to develop a prediction model for rheological properties. The intended model approach is characterized by two characteristics: It distinguishes between the contribution of the colloidal and non-colloidal inventory towards the rheology and allows thereby a distinctly improved definition of the effects such as temperature and hydration upon the decisive particle inventory (meaning the colloidal components). Furthermore, the model will be probabilistically formulated and account for both the heterogeneity of the cement stemming from the mineral phase composition, as well as resulting from agglomeration or shear banding. The PP-proposal at hand has been closely coordinated with other PP-submitters. The planned cooperations are described in detail.