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，水泥生产对环境产生重大影响，每年生产约 4 吨水泥，生产过程中产生碳排放。因此，寻找最好独立于其他工业部门的替代粘合剂是至关重要的，煅烧粘土是世界各地都有的，但其化学和矿物成分差异很大。不目前存在用于无钙地质聚合物体系的外加剂，该研究项目的目的是确定适用于无钙地质聚合物的超增塑剂，并使用地质聚合物模型系统、偏高岭土和类聚石基质材料来确定其作用机制。通过溶胶-凝胶工艺合成并与水玻璃溶液混合，这允许使用市售的缩聚超增塑剂（三聚氰胺磺酸和）。利用β-萘磺酸甲醛缩聚物和主链变化的PCE高效减水剂（MPEG、APEG、HPEG和IPEG）来分散地质聚合物模型体系。首先，确定了高碱性环境中的流动效应和化学稳定性。此外，还合成了在无钙地质聚合物的高碱性环境中表现出高稳定性的淀粉高效减水剂。通过改变电荷类型、电荷量和分子量（<100 kDa 和 >100 kDa）的分子参数来合成，并确定了在无钙模型地质聚合物中诱导高分散性能的关键参数。通过添加有效超增塑剂来表征模型地质聚合物体系的流动行为，记录粘度和屈服点的变化以及流变特性的时间依赖性，并与参考值进行比较。对由于添加有效超增塑剂而引起的 zeta 电位变化的研究可以了解流动效应是否是由表面相互作用引起的。此外，可以确定早期地质聚合物反应期间的吸附程度。有效减水剂的结构参数。如果有效减水剂改变硬化地质聚合物胶中的空气、毛细管和凝胶孔的含量，则微观结构研究可以提供信息。可以评估地质聚合物模型系统中超增塑剂的有效性，并将结果转换为普遍有效的作用机制（经验模型）。