“水泥-减水剂-水”悬浮分散体系微结构与流变性

Recently, high performance concrete (HPC) and ultra-high performance concrete (UHPC) with higher workability have been intensively needed due to the production of architectural construction of increasing bulk, intricacy and various functions. Superplasticizer has played a key role in significantly increasing the workability by means of modifying microstructure and rheological properties of concrete. However, the characterization of microstructure and the relationship of microstructure and rheological properties as well as the working mechanism of superplasticizer on them fail to be fully revealed, which has largely impeded the further development of workability of HPC and UHPC. This research aims at systematically investigating the effects of superplasticizers with varied molecular structures on the microstructures and the rheological properties of fresh cement paste as well as their working mechanisms. By directly observing and quantitatively characterizing the microstructure of paste, the correlation of microstructure with rheological properties is established and corresponding models are also proposed to describe this correlation. Combined with the influences of superplasticizers with varied molecular structures on the microstructure and rheological properties, the working mechanisms of superplasticizers are elucidated, which develops and improves the molecular structure design of superplasticizers in theory. Based on the correlation of molecular structure of superplasticizer with microstructure and rheological properties of paste, the microstructure induction of fresh cement paste and the artificial control over the functions of superplasticizers could be achieved. This research will provide theoretical guidance to the development of new superplasticizers, HPC and UHPC with higher performance as well as the effective control over practical construction.

近年来，我国建筑结构的不断大型化、复杂化和功能化对高性能与超高性能混凝土的工作性提出了更高要求。高效减水剂因可有效改善新拌浆体微结构进而优化流变性，已成为工程实践中大幅提高混凝土工作性的关键。然而，目前对于微结构与流变性的本质关联、减水剂改变微结构优化流变性的机理等基础问题尚未被完全解决，严重制约了高性能与超高性能混凝土工作性的进一步提升。为此，本课题旨在系统研究不同分子结构的减水剂对新拌水泥浆早期微结构与流变性的影响规律与作用机制。通过对微结构进行直接观测与定量表征，揭示微结构与流变性的本质关联并加以量化与模型化；结合不同分子结构减水剂对微结构与流变性的影响规律，明确其改变微结构与流变性的机理，发展并完善减水剂结构设计理论；建立减水剂分子结构、浆体微结构与流变性的关联，从而实现浆体微结构诱导与减水剂功能的可控性，为新型减水剂的研发、高性能与超高性能混凝土的性能优化提供理论指导与技术支撑。

高效减水剂因可有效改善新拌浆体微结构与流变性，已成为工程实践中大幅提高混凝土工作性的关键。然而，目前对于减水剂改变微结构优化流变性的机理、水泥基材料的微结构与流变性的本质关联等基础问题尚未被完全解决，严重制约了高性能与超高性能混凝土工作性的进一步提升。项目针对“水泥-减水剂-水”悬浮分散体系，系统研究了不同分子结构的减水剂对新拌水泥浆早期微结构与流变性的影响规律与作用机制。通过调整小单体比例分别合成了羧基-磺酸基，羧基-胺基，羧基-硅烷三类具有相同主链电荷密度与分子量的梳状减水剂；采用旋转流变仪与光学微流变仪分别测定了不同类型与掺量的减水剂对新拌浆体的塑性粘度、屈服应力与粘弹性参数的影响以及各参数随时间、温度的变化规律；采用Morphologi G3显微镜观测了不同减水剂对新拌水泥浆悬浮液显微结构的影响，提取了平均粒径、频谱平台峰值、平台宽度、形状因子、分形维数等参数对微结构进行了定量表征，并与流变参数建立了关联；采用SEM观测了不同类型减水剂对水化产物的形貌、组成与分布的影响；通过TOC与水化量热分析了不同减水剂在水泥颗粒表面的吸附行为及其对水泥水化的影响规律，阐明了减水剂的吸附机制与影响水泥水化的作用机理；基于新拌浆体微结构与减水剂的作用机理，推导了流变参数模型；最终从微结构角度建立了吸附-水化-流变的内在关联，从本质上揭示了不同主链官能团改变新拌浆体微结构与流变性的作用机制。