Superposing particle interactions and hydration effects on the rheology of cementitious systems in the presence of different ions in the aqueous phase – (SPHERE DOS)

水相中存在不同离子时，叠加颗粒相互作用和水化作用对胶结体系流变学的影响 â (SPHERE DOS)

• 批准号: 387092747
• 负责人: Professorin Dr. Regine von Klitzing
• 金额: --
• 依托单位: Fachbereich 7.4: Baustofftechnologie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/387092747?language=en
• 关键词: Superposing; particle; interactions; hydration; effects

The future challenges of concrete technology demand for tailored rheological properties during the casting and early hardening process. The individual adjustment of slump retention and setting time plays a major role for technologies such as just-in-time manufacturing, target slump delivery of ready-mixed concrete, sprayed concrete, dry-mixed mortar and 3D-printing. While superplasticizers affect the rheology due to adsorption, accelerators are used to influence the hydration reaction. The employed admixtures beyond superplasticizers complicate the already complex superplasticizer effects by affecting the pore solution chemistry, as well as the morphology and interactions of the particles; depending upon the chemistry and dosage all happening within minutes. Since the effect of superplasticizers strongly depends upon the cement hydration reaction, rapid hydration causes significant rheology changes already during the casting process. A false estimation of the time dependent viscosity change can result macroscopically in improper filling, varied air pore content, poor bond, cold joint problems, inhomogeneous fibre distribution and other aspects. However, the root cause can be found on the microscopic scale in rapid changes of the ionic concentration, particle interactions, changes of the morphology and the solid volume fraction, which furthermore affect the dispersing forces between particles and the effectiveness of superplasticizers.The SPHERE project aims at understanding the rheological effects on different dimensional scales; from mesoscopic to macroscopic. The general objective is to understand the rheology of accelerated cementitious systems during the critical steps of processing from casting until setting. In order to understand the fundamental mechanisms underlying the rheological changes, the system needs to be studied from the perspective of particle interactions as well as from hydration effects that mutually interact. Eventually, the observed effects need to be understood and evaluated on their relevance for the application level, which means an upscaling from the particle interface to the large scale concrete application has to be conducted.Direct particle interactions will mainly be studied using atomic force microscopy in various conditions on simplified model systems. The results will support understanding changes of rheological phenomena induced by changes in the pore solution chemistry as well as by adsorption of ions and polymers on particle surfaces. Effects of changed morphology and phase evolutions will be studied using XRD techniques, SEM, AFM, US, DTA, etc. The rheological response will be examined on various scales from solution level up to paste, mortar and concrete rheometry as well as by using applied technologies such as spraying, large scale casting and standard fresh concrete technologies.

混凝土技术未来的挑战要求在浇注和早期硬化过程中定制流变性能。坍落度保持率和凝结时间的单独调整对于即时制造、预拌混凝土、喷射混凝土、干混砂浆和3D打印的目标坍落度交付等技术起着重要作用。虽然超增塑剂由于吸附而影响流变学，但使用促进剂来影响水合反应。所采用的除超塑化剂之外的掺合物通过影响孔溶液化学以及颗粒的形态和相互作用而使已经复杂的超塑化剂效果复杂化;这取决于化学和剂量，所有这些都在几分钟内发生。由于高效减水剂的效果强烈依赖于水泥水化反应，因此快速水化已经在铸造过程中引起显著的流变学变化。对时间依赖性粘度变化的错误估计可在宏观上导致不适当的填充、变化的空气孔隙含量、差的粘结、冷接合问题、不均匀的纤维分布和其它方面。然而，根本原因可以在微观尺度上发现，离子浓度的快速变化，颗粒相互作用，形态和固体体积分数的变化，进而影响颗粒之间的分散力和高效减水剂的有效性。SPHERE项目旨在了解从介观到宏观的不同尺度上的流变效应。总的目标是了解从浇注到凝固的关键加工步骤中加速水泥体系的流变性。为了理解流变学变化的基本机制，需要从颗粒相互作用以及相互作用的水合作用的角度来研究该系统。最后，需要理解和评估所观察到的效应与应用水平的相关性，这意味着必须进行从颗粒界面到大规模混凝土应用的升级。直接颗粒相互作用将主要使用原子力显微镜在各种条件下在简化的模型系统上进行研究。结果将支持理解的流变现象的变化引起的孔溶液化学的变化，以及通过吸附的离子和聚合物在颗粒表面上。改变形态和相演变的影响将研究使用XRD技术，SEM，AFM，US，DTA等的流变响应将在各种规模上从溶液水平到膏体，砂浆和混凝土流变学以及通过使用应用技术，如喷涂，大规模铸造和标准的新鲜混凝土技术进行检查。