链烷醇胺作用下水泥水化调控和混凝土微观结构演变

Alkanolamines have been widely used as the special construction chemicals, not only to enhance the efficiency of cement comminution, but also to impact the hydration of both clinker and supplementary cementitious materials (SCMs) so as to alter the performance of cement and concrete. This study, which is guided by kinetics of chemical reactions firstly, investigates the impact of rapid (ferro-)aluminate reaction on early hydration of cement, which is resulted from C3A/C4AF hydration and SCMs Al3+/Fe3+ dissolution in the presence of alkanolamines. By applying dissolution-precipitation theory, the external addition of gypsum is introduced to control the rate of (ferro-)aluminate reaction to guarantee the normal hydration of C3S further improving the performance of cement and concrete. In addition, the influence of the rate of (ferro-)aluminate reaction on hydration assemblages is also studied to explain the development of microstructures of hardened cement paste and the interfacial transition zone, and then the relationship among hydrates composition, concrete microstructure and macro-properties development is expected. The outcomes of this investigation will provide theoretical and practical guidance to performance optimization of cement and concrete with alkanolamines.

链烷醇胺作为特种化学建材应用于水泥制备中，在提高水泥粉磨效率同时，还参与水泥熟料和矿物辅料的水化反应，从而影响水泥混凝土的性能。本项目首先从化学反应动力学角度出发，研究链烷醇胺作用下C3A/C4AF水化和矿物辅料溶解释放Al3+/Fe3+所引起的快速（铁）铝酸盐反应对水泥早期水化的影响机理，并依据“溶解-沉淀”理论提出外掺石膏的方法，调控（铁）铝酸盐反应速率，保证C3S正常水化，使水泥混凝土具有合理的性能发展。此外，本项目将深入研究（铁）铝酸盐反应速率对水化产物形成的作用机制，揭示链烷醇胺作用下混凝土硬化水泥浆体和界面过渡区的结构演变规律，以此建立水化产物组成、混凝土微观结构特征与宏观性能发展的对应关系。项目成果将为掺链烷醇胺水泥混凝土的性能优化提供理论基础和技术支持。

链烷醇胺作为水泥助磨剂中的核心组分，被广泛应用于现代水泥生产，在具有减小粉磨能耗功效的同时，还可参与水泥熟料和矿物辅料水化，从而影响水泥混凝土性能。链烷醇胺首先对水泥胶砂流动性有一定影响，表现为链烷醇胺增大水泥胶砂的经时流动度损失。此外，链烷醇胺对水泥水化动力学有较大影响，可显著促进铝酸盐反应，从而推动熟料和矿物辅料的整体水化速率。三乙醇胺（TEA）和二乙醇单异丙醇胺（DEIPA）显著促进二次钙矾石形成，而三异丙醇胺（TIPA）可加快钙矾石（AFt）向低硫型水化硫铝酸钙（AFm）的转变，这归咎于不同的链烷醇胺对熟料中间相C3A和C4AF有不同的促溶作用。被加速的铝酸盐反应作用于水泥水化产物和硬化水泥浆体微观结构，表现为水化富Fe的低硫型水化硫铝钙大量形成，可与C-S-H形成明显混杂，使其Si/Ca减小、Fe/Ca增加。此外。水化硫铝酸钙可取代内部C-S-H，沉淀于未水化熟料颗粒表面，这是现有文献从而报道过的现象。被加速的铝酸盐反应还可干扰C3S正常水化，影响水泥1d强度。提高水泥SO3含量可调控铝酸盐反应速率，增加水化硫铝酸钙的形成量，提高AFt/AFm比例，减小孔隙率。合理的SO3含量可使水泥早期强度达到最优。TEA和TIPA均可促进粉煤灰-石灰石、煅烧粘土-石灰石水泥体系中矿物辅料反应，且后者作用更强。其机理是，与TEA相比，TIPA在促进C3A水化的同时，能持续促进C4AF反应，释放出额外Ca2+、Al3+参与火山灰反应和石灰石反应。增加复合水泥体系中的SO3含量，不但可提高水化硫铝酸钙的形成量，还可提高其中AFt比例。由于水化硫铝酸钙具有填孔作用，因此调硫后体系中毛细孔的临界和特征孔径均减小且总孔隙率减小，从而贡献于复合水泥强度发展。