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

在之前的项目中发现，虽然偏长云母和偏高岭土可以很好地流化，但常规的聚羧酸类高效减水剂无法分散偏长云母。因此，本报告的重点是煅烧伊利石的化学矿物学性质及其煅烧后的表面结构。除了物理表征外，还计划进行全面的矿物学研究（粒度和形貌、吸水能力、阳离子交换能力、zeta电位），以捕获其表面特性（层电荷）。胶结体系中表面电荷的发展将受到最大的关注。为此目的，zeta电位的测量将在孔溶液中进行，其中被煅烧粘土吸收的离子将立即得到补充。这样，就可以在平衡条件下（饱和吸附）评估水泥中存在的实际表面电荷。根据这些数据，可以计算出Ca2+离子在煅烧粘土表面吸附的空间距离。关于这个问题，计划同KIT的“应用矿物学/粘土科学”研究所（Emmerich博士）合作，将这个研究小组在伊利石粘土方面的著名专门知识纳入这个项目。由于伊利石常与蒙脱石粘土互层，故拟对这种混合层粘土和纯蒙脱石进行研究。这一系列从复辉石→复辉石→复辉石→复辉石应该可以建立一个描述该序列中特定矿物变化的模型。该项目的第二部分解决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。根据对表面结构和电荷的研究结果，根据其官能团的分子几何结构进行立体分析，可以合成量身定制的高效减水剂，并与煅烧粘土表面吸附的Ca2+离子形成配合物。为此，将合成和测试基于MPEG、APEG和hpeg的聚羧酸盐，这些聚羧酸盐基团之间具有不同的空间距离，两性以及磺化和磷酸盐梳状聚合物。为了实现某些结构，可能需要开发全新的合成路线，包括RAFT/ATR聚合。通过这种方式，我们将深刻理解为什么传统的高效减水剂不能流化金属矿，以及需要哪些特定的分子参数来实现这种流化效果。优化后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，为了深入了解高效减水剂-水泥-煅烧粘土的相互作用，将通过压力过滤研究聚合物是优先吸附在水泥上还是优先吸附在煅烧粘土上。

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.