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能主要由其中所含的水泥浆的性能决定，水泥浆通常表现出明显的非牛顿流动行为，其特征在于屈服应力和明显的触变性。流变性能受水泥水化、系统温度和剪切过程（例如由压实施加的材料流动或振动引起）的强烈影响。所有因素导致颗粒存量和载液组成的变化，其中基本机制尚未完全理解。所请求项目的目的是根据所述影响参数并根据所用材料（即水泥、水和高效减水剂）确定超塑水泥浆体流变特性的可预测性。为此，表面络合模型是通过AFM测量的水泥和其水化产物的组成矿物考虑超塑化剂的作用。使用所谓的成分方法，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。通过在颗粒尺寸和表面粗糙度的变化进行测量，考虑了粒度测定的影响。相库存和粒度的系统的变化被捕获广泛的化学和物理调查，随后建模。通过使用放射性示踪剂，可以确定高效减水剂对水泥颗粒表面的吸附行为，或者更确切地说，确定高效减水剂在水化产物中的整合。从这些调查中获得的结果将与水泥浆流变学的广泛测量相结合。这些流变性能将在大气和升高的各向同性压力以及施加额外的振动和温度下测量。通过原位和非原位测量的组合，由于剪切而导致的颗粒和溶液存量内的变化然后可以与上述组分方法组合使用，以开发流变性质的预测模型。预期的模型方法的特征在于两个特征：它区分胶体和非胶体存量对流变学的贡献，从而允许明显改善对决定性颗粒存量（即胶体组分）的影响（如温度和水合作用）的定义。此外，该模型将概率公式化，并考虑到源于矿物相组成的水泥的不均匀性，以及由团聚或剪切带产生的不均匀性。手头的PP提案已与其他PP提交者密切协调。计划中的合作进行了详细说明。

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.