碱激发矿渣胶凝材料水化反应特性研究

Alkali activated cementing materials are obtained by mixing vitreous granulated blast furnace slag with highly basic solutions such as waterglass, sodium hydroxide, sodium carbonate, etc. The development of alkali-activated slag cementing materials has been one of the hottest topic in recent years because of the energy and environmental advantages of its production over ordinary Portland cement manufacture. Specifically, the development and application of these materials can play an important role in the reduction of energy consumption and decline in greenhouse gas emissions of cements production. However, some scientific issues in the design and application of these materials still need to be resolved. Firstly, the quantitative measurement of the hydration phase is a basic problem for researchers to evaluate the relations between the hydration products and the cementing properties, because the hydration products of this kind material are poorly crystalline, fine and intimately intergrown. Secondly, the relationship between the type and quantity of hydration products and the type and quantity of activators is not clearly understood. Therefore, it is not possible to provide theoretic guidance for the formula design and property control of the material. Thirdly, the major factors governing the hydration of the slag and the correlation between the hydration degree of the slag and cementing properties of the material need to be further investigated. Focusing on the above mentioned issues, the project will develop a new method for the quantitative characterization of the hydration product by the synthesis and characterization of the typical hydration phases, formulate a model to expound the relationship between the type of hydration product and the cementing property of the material by detailed investigations on the hydration products and cementing properties under the activation of different activators, and unveil the effect of the hydration degree of the slag on the cementing properties of the material by investigations on the correlations between the hydration process and degree of the slag and the properties of the material.

碱激发矿渣是以碱性激发剂和粒化高炉矿渣为主要原料所制备的一种新型胶凝材料，不仅胶凝性能优良，而且具有良好的节能环保特性，发展潜力巨大。然而，该材料的设计和应用仍存在一些共性科学问题亟待解决。首先，由于碱激发矿渣水化产物的结晶程度低、粒度细、共生紧密，水化产物的定量表征问题尚未解决，难以判断水化产物的种类、数量与宏观胶凝性能间的联系；其次，不同激发剂对水化产物种类和生产速度的影响规律缺乏明确认识，其配方设计和性能控制缺乏理论指导；第三，矿渣水化程度与胶凝性能间的相关性研究缺乏充分研究。针对上述科学问题，本研究拟从典型水化产物的合成和表征入手，为碱激发矿渣水化产物的定量表征提供一种新方法；通过典型碱激发剂作用下材料的水化产物和宏观性能的系统研究，构建碱激发矿渣水化产物与宏观性能相关性模型；通过对矿渣水化程度、结构变化与胶凝性能的相关性研究，揭示矿渣性质和水化程度对胶凝性能的影响规律。

本研究从典型水化产物的合成入手，提出了碱激发矿渣胶凝材料典型水化产物的合成方法，明确了典型水化产物的理化特性和定量分析手段。通过对一价碱金属离子、二价碱土金属离子以及两者复合激发体系的研究，阐明了不同激发体系条件下碱激发矿渣胶凝材料水化产物种类、生成量、微观结构与宏观性能之间的相关性。另外，通过水化反应动力学研究，揭示了不同激发体系条件下矿渣的水化反应过程，阐明了影响矿渣水化反应程度和反应速率的关键因素。. 研究表明，采用化学合成法，通过调整原料配比，可制备不同结构式的水化硅酸钙凝胶和高纯度钙矾石。借助热重分析、X-射线衍射定量分析和化学分析，可实现对水化硅酸钙凝胶和钙矾石的准确定量。激发剂种类和用量是影响碱激发矿渣胶凝材料力学性能、水化产物种类和生成量、水化产物微观结构的关键因素。CaO作为激发剂时的最佳用量为胶凝材料总质量的5%，主要水化产物为水化硅酸钙凝胶和类水滑石相。CaSO4的加入，促进了钙矾石的生成，能够在一定程度上弥补单一CaO激发时胶凝材料早期抗压强度低的问题。采用强碱性的NaOH和水玻璃作激发剂时，碱激发矿渣胶凝材料表现出优异的力学性能，其最佳用量分别为矿渣质量的6%和15%。激发剂用量的增加能够提高矿渣的水化反应程度，但激发剂过量会降低水化硅酸钙凝胶的聚合程度，对试样抗压强度产生不利影响。水化反应动力学研究表明，碱激发矿渣胶凝材料水化特性符合Krstulovic-Dabic动力学模型，其水化反应速率常数随激发剂碱性的增强而提高。不同水玻璃模数条件下，矿渣的水化过程均先后经历了结晶成核与晶体生长NG、相边界反应I和扩散过程D，各阶段水化反应速率常数均随水玻璃模数增加逐渐降低，且会导致碱激发矿渣胶凝材料水化过程中NG→I以及I→D转变点后移，并延长了I控制过程的时间。