Ecological and energetic optimization of concretes: Challenges in the processing of calcined illitic and smectitic clays - solution approaches using tailor-made superplasticizer structures

在前期研究中发现，偏白云母和偏高岭土可以很好地流化，而常规聚羧酸类高效减水剂不能很好地分散偏伊利石，为此，本文重点研究了煅烧后伊利石的化学矿物学性质及其表面结构。除了物理表征外，还计划进行全面的矿物学研究（粒度和形态、吸水能力、阳离子交换能力、zeta电位），以获取其表面特性（层电荷）。最大的注意力将给予水泥体系中的表面电荷的发展。为此，特别是在孔隙溶液中进行ζ电位测量，其中煅烧粘土所吸收的离子将立即补充。这样，可以在平衡条件下（饱和吸附）评估水泥中存在的实际表面电荷。基于这些数据，可以计算吸附在煅烧粘土表面上的Ca 2+离子之间的空间距离。与此相关的是，计划与KIT的“应用矿物学/粘土科学”研究所（Emmerich博士）合作，将该研究小组在伊利石粘土方面的知名专业知识纳入该项目。由于伊利石通常以与蒙皂石粘土间层的矿物形式出现，因此计划研究这种混合层粘土和纯蒙皂石。这个从变伊利石→变蒙脱石→变蒙脱石的系列应该允许开发一个模型来描述这个序列中的特定矿物学变化。该项目的第二部分讨论了煅烧粘土的流变特性以及它们与高效减水剂的相互作用。基于对表面结构和电荷的发现，应合成定制的超增塑剂，根据其官能团的分子几何结构的空间分析，其可以与吸附在煅烧粘土表面上的Ca 2+离子形成络合物。为了这个目的，MPEG-，APEG-和HPEG-基的聚羧酸酯与不同的空间距离之间的羧酸基团，两性以及磺化和磷酸化梳状聚合物将被合成和测试。为了实现某些结构，全新的合成路线，包括。可能需要开发RAFT/ATR聚合。通过这种方式，可以深入了解为什么常规高效减水剂不能使偏伊利石流化，以及实现这种流化效果所需的特定分子参数。优化的高效减水剂的流化效果将通过旋转粘度法进一步评估。最后，为了深入了解超塑化剂-水泥-煅烧粘土的相互作用，将通过压滤研究聚合物是否优先吸附在水泥上或煅烧粘土上。

In the preceding project, it was found that while metamuscovite and metakaoline can be fluidized well, it was however impossible to disperse metaillite with conventional polycarboxylate superplasticizers.For this reason, in the present submission the focus is on the behavior of calcined illite with respect to its chemical-mineralogical properties and its surface structure after calcination. Apart from a physical characterization, comprehensive mineralogical investigations (particle size & morphology, water sorption capacity, cation exchange capacity, zeta potential) are planned to capture its surface properties (layer charge). Utmost attention will be given to the development of the surface charge in the cementitious system. For this purpose, zeta potential measurements will be carried out especially in a pore solution in which ions taken up by the calcined clay will be replenished immediately. This way, the actual surface charge existing in cement can be assessed under equilibrium conditions (saturated adsorption). Based on these data, the spatial distance between Ca2+ ions adsorbed on the surface of the calcined clay can be calculated. Relative to this subject, a cooperation with the institute for “Applied mineralogy/Clay science” at KIT (Dr. Emmerich) is planned to incorporate the well-known expertise of this research group on illitic clays into this project.Because illite often occurs as mineral interstratified with smectite clay it is planned to study such mixed layer clay and pure smectite as well. This series from metaillite → metaillite-smectite → metasmectite should allow to develop a model describing the specific mineralogical changes within this sequence.The second part of the project addresses the rheological properties of the calcined clays as well as their interaction with superplasticizers. Based on the findings on the surface structure and charge, tailor-made superplasticizers shall be synthesized which according to a steric analysis of the molecular geometry of their functional groups can form a complex with Ca2+ ions sorbed on the surface of the calcined clay. For this purpose, MPEG-, APEG- and HPEG-based polycarboxylates with varied spatial distance between the carboxylate groups, an amphoteric as well as sulfonated and phosphated comb polymers will be synthesized and tested. To achieve certain structures, entirely new synthesis routes incl. RAFT/ATR polymerization may need to be developed. This way, a profound understanding of why conventional superplasticizers cannot fluidize metaillite, and which specific molecular parameters are required to achieve such fluidizing effects shall be achieved.The fluidizing effect of the optimized superplasticizers shall be evaluated further via rotational viscosimetry. Finally, for an in-depth understanding of the interaction superplasticizer-cement-calcined clay it will be investigated via pressure filtration whether the polymers adsorb preferentially on cement or on the calcined clay.