Adsorption of superplasticizers in alkali-activated materials - Fluorescence microscopic in-situ investigations

碱激活材料中高效减水剂的吸附 - 荧光显微镜原位研究

• 批准号: 460294323
• 负责人: Dr. Alexander Wetzel
• 金额: --
• 依托单位: Fachgebiet Werkstoffe des Bauwesens und Bauchemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/460294323?language=en
• 关键词: Adsorption; superplasticizers; alkali; activated; materials

Alkali-Activated Materials (AAM) have advantages compared to Ordinary Portland Cement (OPC) in terms of CO2 balance and in many cases in terms of durability. This increase in durability is due to the formation of strength-forming phases, which differ from the C-S-H phases in concrete made of OPC. The raw materials used are mineral materials rich in silicon and aluminium, which are ideally present as fine particles and in reactive form. Mainly used precursors are ground granulated blast furnace slag, fly ash or calcined clays. Since these materials belong to the group of latent hydraulic or pozzolanic materials, a stimulation of the chemical reaction is necessary. Alkali activators can be used for this purpose; alkali hydroxide or water glasses are mostly used, but, alkali sulfate or carbonate solutions can also be used. Despite the variety of possible combinations of the precursors and alkali activators, there are still no effective superplasticizers known for these systems, if one wants to compare the effectiveness with that of OPC. Most available superplasticizers lose their effectiveness, especially at higher concentrations of the alkali activators. A complex matrix of possible interactions results from the combination of precursors, types and concentrations of alkali activators as well as the types of superplasticizers, which require a high empirical effort in fresh and hardened concrete investigations. In the recently finalised DFG-funded project 389127734 the adsorption behaviour of superplasticizers on mineral particles was investigated in-situ by fluorescence microscopy. This method of analysis was established within the project and results on the adsorption behaviour of superplasticizers could already be directly correlated with rheological properties and the setting behaviour in cementitious systems. The influence of cation concentrations on the adsorption behaviour and thus on the effectiveness of superplasticizers could be proven. Thus, this method is suitable for time-resolved investigations of the adsorption behaviour of superplasticizers on various precursors and in different alkaline activator solutions. The aim of this project is the systematic investigation of AAM under variation of the precursors, the activator solutions and the used superplasticizers. Microscopic investigations will be correlated with investigations on fresh and hardened concrete in which the same parameters are varied. In addition to the further development of in-situ fluorescence microscopy for the investigation of the adsorption behaviour of superplasticizers, the correlation of the results of the various investigations will provide general insights into the mechanisms of action of superplasticizers in AAM. This will facilitate the use of alkali-activated binders and improve the performance of these systems. Especially with regard to the increasing importance of the use of OPC-free or -reduced systems, this objective is of interdisciplinary importance.

与普通波特兰水泥（OPC）相比，碱活化材料（AAM）在CO2平衡方面以及在许多情况下在耐久性方面具有优势。这种耐久性的增加是由于形成了强度形成相，其不同于由OPC制成的混凝土中的C-S-H相。所使用的原材料是富含硅和铝的矿物材料，理想情况下，它们以细颗粒和反应形式存在。主要使用的前体是磨碎的粒状高炉矿渣、粉煤灰或煅烧粘土。由于这些材料属于潜在的水硬性或火山灰材料，因此需要刺激化学反应。碱活化剂可用于此目的;主要使用碱金属氢氧化物或水玻璃，但也可使用碱金属硫酸盐或碳酸盐溶液。尽管前体和碱性活化剂的各种可能的组合，但如果想要将有效性与OPC的有效性进行比较，则仍然没有已知用于这些系统的有效的超增塑剂。大多数可用的超增塑剂失去其有效性，特别是在较高浓度的碱性活化剂下。 一个复杂的矩阵可能的相互作用的结果从前体的组合，类型和浓度的碱性活化剂以及超塑化剂的类型，这需要在新鲜和硬化混凝土的调查高度经验的努力。在最近完成的DFG资助的项目389127734中，通过荧光显微镜原位研究了超增塑剂在矿物颗粒上的吸附行为。这种分析方法是在项目中建立的，高效减水剂的吸附行为的结果已经可以直接与水泥体系的流变性能和凝固行为相关。可以证明阳离子浓度对吸附行为的影响，从而对高效减水剂的有效性。因此，该方法适用于时间分辨的调查的各种前体和不同的碱性活化剂溶液中的超增塑剂的吸附行为。本项目的目的是系统地研究AAM在前体、活化剂溶液和所用高效减水剂的变化下的反应。微观调查将与新拌混凝土和硬化混凝土的调查相关联，其中相同的参数是不同的。除了进一步发展的原位荧光显微镜的超增塑剂的吸附行为的调查，各种调查的结果的相关性将提供一般的见解超增塑剂在AAM的作用机制。这将促进碱活化粘合剂的使用并改善这些系统的性能。特别是对于使用无OPC或OPC减少的系统的日益重要性，这一目标具有跨学科的重要性。