Efficiency and influence of calcined phyllosilicates during the early hydration of cement

煅烧粘土是一种具有巨大潜力的有前途的材料。这些材料可以弥补未来对水泥替代品日益增长的需求，以及现有辅助胶凝材料(如飞灰或高炉矿渣)可用性的下降。煅烧粘土通过对层状硅酸盐在550℃至850℃的温度范围内进行热处理来发展其化学火山灰反应能力。粘土混合物在混凝土工业中的广泛应用尤其令人感兴趣，它表现出非常复杂的矿物学。它们由不同数量的层状硅酸盐(高岭石、伊利石、云母、蒙脱石)组成。粘土混合物的组成不仅因地区不同而不同，而且在一个粘土坑内也会有所不同。对不同结构的煅烧层状硅酸盐的机理以及它们在水泥早期水化过程中与水泥熟料相的相互作用的基本知识，对于煅烧粘土混合物在砂浆和混凝土中的预期用途至关重要。在项目的第一阶段，有必要调查不同煅烧的层状硅酸盐的反应性，这取决于它们的矿物学结构和早期化学-火山灰反应的影响。在早期水化过程中(加水后的第一个48小时内)与模型水泥的相互作用将在水化系统上进行研究和定量分析。为了进行实验研究，合成了Alit和C3A两种熟料相，并在添加硫酸盐载体的情况下研制了一种还原胶凝模型体系。通过调整熟料相的粒度和添加硫酸盐载体，可以使水泥水化过程中的硅酸盐与铝酸盐反应分离。通过添加不同的煅烧层状硅酸盐，首次可以分别考虑两种熟料相的反应机理。结合粘结剂化学中已建立的方法(原位X射线衍射法、热重法、量热法)，可以建立单个煅烧层状硅酸盐的反应动力学模型。研究结果为进一步了解煅烧粘土混合物的反应机理提供了基础信息。基于该模型，可以评估煅烧粘土混合物对水泥水化动力学的影响，以及评估天然粘土混合物在复合水泥中充分使用或作为混凝土外加剂的适宜性，而无需进行广泛的经验测试。

Calcined clays represent a promising material with great potential. These materials may compensate the increasing demand for cement substitutes in future and the decreasing availability of established supplementary cementitious materials such as fly ash or blast furnace slag. Calcined clays develop their chemical-pozzolanic reactivity by thermal treatment of the phyllosilicates in the temperature range between 550 and 850 °C. Clay mixtures, which are especially interesting for a broad application in concrete industry, exhibit a very complex mineralogy. They consist of different phyllosilicates (kaolinite, illite, mica, montmorillonite) at varying quantities. The composition of clay mixtures can vary not only from region to region but also within one single clay-pit. Basic knowledge on the mechanism of structurally different calcined phyllosilicates and their interaction with the cement clinker phases during early cement hydration is essential for the intended use of calcined clay mixtures in mortar and concrete. During the first phase of the project, it is necessary to investigate the reactivity of different calcined phyllosilicates depending on their mineralogical structures and the impact of chemical-pozzolanic reaction at early age. The interaction during early hydration (within the first 48 hours after water addition) with a model cement will be investigated and quantitatively analyzed on hydrating systems. For the experimental investigations, the two clinker phases Alit and C3A are synthesized and a reduced cementitious model system is developed with the addition of sulfate carrier. Adjusting the granulometry of clinker phases and the addition of the sulfate carrier it is possible to separate the silicate from the aluminate reaction in the cement hydration. It will be possible for the first time to consider the reaction mechanisms of the two clinker phase separately with the addition of different calcined phyllosilicates. The combination of established methods from binder chemistry (in situ X-ray diffraction, thermogravimetry, calorimetry) enables a model for the reaction kinetics of individual calcined phyllosilicates. The results provide basic information for a fundamental understanding of the reaction mechanisms of calcined clay mixtures. Based on this model, it is possible to evaluate the influence of calcined clay mixtures on the hydration kinetics of cements and to assess the suitability of naturally occurring clay mixtures sufficiently for their use in composite cements or as concrete additives without extensive empirical tests.