Identification of mechanisms of action of conventional superplasticizers and novel bio-based flow agents in calcium-free geopolymer model systems

识别无钙地质聚合物模型系统中传统高效减水剂和新型生物基流动剂的作用机制

• 批准号: 471259463
• 负责人: Professorin Dr.-Ing. Andrea Osburg
• 金额: --
• 依托单位: Lehrstuhl Bauchemie und Polymere Werkstoffe
• 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/471259463?language=en
• 关键词: Identification; mechanisms; action; conventional; superplasticizers

In recent years, the focus in construction industry has transitioned towards innovative technologies and materials. It is well known that the production of cement has a significant impact on the environment; by manufacturing around 4 Gt of cement annually, the carbon emissions created during the production process are accounted to 1.5 Gt. Hence, the search for alternative binders, that are preferably independent from other industrial sectors, is essential. One such binder is calcined clays, which are available worldwide but vary widely in their chemical and mineralogical composition. Furthermore, no suitable admixtures currently exist for calcium-free geopolymer systems. The objective of this research project is to identify suitable superplasticizers for calcium-free geopolymers and to determine the mechanism of action using geopolymer model systems. As model systems, metakaolin- and metaton-like base materials are synthesized via a sol-gel process and mixed with water glass solutions. This allows the use of calcium-free systems. Commercially available polycondensate superplasticizers (melamine sulfonic acid and β-naphthalenesulfonic acid formaldehyde polycondensates) and PCE superplasticizers with variation of the backbone (MPEG, APEG, HPEG and IPEG) are utilized to disperse the geopolymer model systems. Initially, the flow effect and chemical stability in the highly alkaline environment is determined due to structural investigations. In addition, starch superplasticizers that exhibit high stability in the highly alkaline environment of calcium-free geopolymers are synthesized. Starch superplasticizers are synthesized by varying the molecular parameters of charge type, charge amount, and molecular mass (<100 kDa and >100 kDa), and key parameters, that induce high dispersion performance in the calcium-free model geopolymers, are identified. Rheological experiments are conducted to characterize the flow behavior of the model geopolymer systems with addition of the effective superplasticizers. The change in viscosity and yield point as well as the time dependence of the rheological properties are recorded and compared to a reference geopolymer glue. Investigations on the change of the zeta potential due to the addition of effective superplasticizers provide insight whether the flow effect is caused by surface interactions. Moreover, degrees of adsorption during the early geopolymer reaction are determined. The results can be associated with the structural parameters of the effective superplasticizers. Microstructural investigations can provide information if the effective superplasticizers change the contents of air, capillary, and gel pores in hardened geopolymer glues. Then, the findings on the effectiveness of superplasticizers in the geopolymer model systems can be evaluated and the results can be converted into a generally valid mechanism of action (empirical model).

近年来，建筑行业的重点已转向创新技术和材料。众所周知，水泥的生产对环境有重大影响。通过每年制造约4 GT的水泥，生产过程中产生的碳排放量被占1.5 gt。因此，对替代粘合剂的搜索优选独立于其他工业部门至关重要。一种这样的粘合剂是钙化的粘土，它们在全球范围内可用，但其化学和矿物质组成差异很大。此外，目前没有适用于无钙地质聚合物系统的合适混合物。该研究项目的目的是确定适合无钙地质聚合物的合适的超塑料，并使用地球聚合物模型系统确定作用机理。作为模型系统，Metakaolin和Metaton样的基本材料通过溶胶 - 凝胶工艺合成，并与水玻璃溶液混合。这允许使用无钙的系统。市售的多根敏化质量（三聚氰胺磺酸和β-萘甲磺酸甲醛多根二敏酸盐）和PCE超塑料具有骨架变化（MPEG，APEG，HPEG和IPEG）的变化，以分散地球popolymer模型系统。最初，由于结构研究，确定了高度酒精环境中的流动效应和化学稳定性。此外，合成了在无钙地球聚合物的高度合金环境中暴露高稳定性的淀粉超塑料。通过改变电荷类型，电荷量和分子质量的分子参数（<100 kDa和> 100 kDa）的分子参数以及诱导无钙模型地球聚合物中较高分散性能的关键参数来合成淀粉超塑剂。进行流变学实验，以表征模型地球聚合物系统的流动行为，并添加有效的超塑料。记录粘度和产量点的变化以及流变特性的时间依赖性，并将其与参考地聚合物胶进行比较。由于添加有效的超塑剂而导致的ZETA电位变化的研究提供了洞察力是否由表面相互作用引起的流动效应。此外，确定早期地球聚合物反应期间的增加程度。结果可以与有效超塑剂的结构参数有关。如果有效的质量化器在硬化聚合物Glyces中改变空气，毛细管和凝胶孔的内容，则微观结构研究可以提供信息。然后，可以评估地球聚合物模型系统中质量增生器的有效性的发现，并可以将结果转换为通常有效的作用机理（经验模型）。