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

煅烧层状硅酸盐在水泥早期水化过程中的效率和影响

• 批准号: 438621761
• 负责人: Dr.-Ing. Nancy Beuntner
• 金额: --
• 依托单位: Institut für Werkstoffe des Bauwesens
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/438621761?language=en
• 关键词: Efficiency; influence; calcined; phyllosilicates; during

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.

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，以及已建立的辅助胶凝材料（如粉煤灰或高炉矿渣）的可用性下降。煅烧粘土通过在550至850 °C之间的温度范围内对层状硅酸盐进行热处理来发展其化学火山灰反应性。粘土混合物具有非常复杂的矿物学性质，在混凝土工业中具有广泛的应用前景。它们由不同数量的不同层状硅酸盐（高岭石、伊利石、云母、蒙脱石）组成。粘土混合物的组成不仅在不同地区之间有所不同，而且在同一个粘土坑内也有所不同。对于煅烧粘土混合物在砂浆和混凝土中的预期用途而言，关于结构不同的煅烧层状硅酸盐的机理及其在早期水泥水化期间与水泥熟料相的相互作用的基本知识是必不可少的。在该项目的第一阶段，有必要研究不同煅烧层状硅酸盐的反应性，这取决于它们的矿物结构和早期化学火山灰反应的影响。将研究早期水化过程中（加水后的前48小时内）与模型水泥的相互作用，并对水化系统进行定量分析。在实验研究中，合成了Alit和C3 A两种熟料相，并通过添加硫酸盐载体开发了一种简化的胶凝模型体系。通过调整熟料相的粒度和硫酸盐载体的添加，可以将水泥水化过程中的硅酸盐与铝酸盐反应分离出来。这将是第一次考虑的反应机理的两个熟料相分别添加不同的煅烧层状硅酸盐。从粘合剂化学（原位X-射线衍射，热重，量热法）建立的方法的组合，使个别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。基于这个模型，它是可能的，以评估煅烧粘土混合物对水泥的水化动力学的影响，并评估其用于复合水泥或作为混凝土添加剂，而无需广泛的经验测试的天然存在的粘土混合物的适用性。