Rheology of low clinker concretes with tailored superplasticizer polymers - Control and modelling of viscosity and thixotropic structural build-up

具有定制超塑化剂聚合物的低熟料混凝土的流变学 - 粘度和触变结构构建的控制和建模

• 批准号: 387118319
• 负责人: Dr. Daniel Jansen
• 金额: --
• 依托单位: Lehrstuhl für Mineralogie
• 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/387118319?language=en
• 关键词: Rheology; low; clinker; concretes; tailored

To understand the fundamental mechanisms of properties of fresh cementitious materials, systematic research is required on the relationship between microstructure and the rheological properties of fresh cement paste. The aim of this research is to examine the effect of superplasticizer / particle interactions on the microstructure, viscosity and thixotropic structural build-up of cementitious suspensions.Understanding the internal structure of cementitious suspensions is not an easy task due to polydispersity, opaqueness, high solid fraction and hydration reactions. Thus, there is a lack of fundamental understanding of the intrinsic structure of fresh cement paste which is of great importance for the workability of concrete. Furthermore, the initial fresh state microstructure affects the microstructure of the hardened paste and consequently strength and durability [1]. The microstructure of a cementitious suspension is determined by the interparticle interactions. In simple terms, particles agglomerate when attractive interactions exceed repulsive interactions. Therefore, understanding the effect of superplasticizer on microstructure and obtaining a reliable estimate of the interparticle interactions in cementitious suspensions is a crucial step towards understanding the rheological properties.In this research, pastes and mortars will be prepared using specifically polymerized superplasticizers with either phosphonate or polycarboxylate functional groups and variations in backbone length, side chain length and side chain density. Viscosity and thixotropic build-up will be determined using rotational rheometry. Simultaneously, the evolution of microstructure is observed with an in situ laser backscattering measurement device (Dynamical Optical Reflectance Measurement with Selective Multi Depth Focus). Whereas, the kinetics of structural break-down in dependence of shear load is not addressed in this research. Finally, the effect of superplasticizer technology on microstructure as well as viscosity and thixotropic structural build-up will be discussed on the basis of colloidal surface interactions, hydration kinetics and a microstructural model.

为了了解新拌胶凝材料性能的基本机理，需要系统地研究新拌水泥浆体的微观结构与流变性之间的关系。本研究的目的是考察高效减水剂/颗粒相互作用对水泥悬浮液的微观结构、粘度和触变结构建立的影响。由于水泥悬浮液的多分散性、不透明度、高固相分数和水化反应，了解水泥悬浮液的内部结构并非易事。因此，对新拌水泥浆体的内在结构缺乏基本的了解，这对混凝土的工作性是非常重要的。此外，初始新鲜状态的微观结构影响硬化浆体的微观结构，从而影响强度和耐久性[1]。胶凝悬浮液的微观结构由颗粒间相互作用决定。简单地说，当吸引相互作用超过排斥相互作用时，粒子就会聚集。因此，了解高效减水剂对微观结构的影响以及对胶凝悬浮液中颗粒间相互作用的可靠估计是了解水泥浆流变性的关键一步。在本研究中，将使用特殊聚合的高效减水剂来制备浆体和砂浆，这些高效减水剂的官能团可以是磷酸盐，也可以是聚羧酸盐。粘度和触变堆积将使用旋转流变仪进行测定。同时，用激光背散射原位测量装置(选择性多深度聚焦动态光学反射测量)观察了微结构的演变。然而，结构破坏与剪切载荷相关的动力学在本研究中并未涉及。最后，从胶体表面相互作用、水化动力学和微观结构模型出发，讨论了高效减水剂技术对微细结构、粘度和触变结构的影响。