Calcined clays as pozzolanic man constituent for composite cementsPart 2: Concrete investigations with special consideration of durability

由于气候问题的争论，目前正在开展可持续水泥的开发工作。这里的一个重要战略是用合适的复合材料取代水泥中与高二氧化碳排放相关的熟料含量。在全球范围内大量供应的煅烧粘土提供了另一种选择。第一个项目阶段的目的是评估基于非常不同的主要粘土矿物的煅烧粘土作为水泥复合材料的基本适宜性。项目第一部分的调查是对纯粘土矿物进行的。根据最大火山灰密度确定了各种粘土的最佳烧成温度，高岭石为700℃左右，伊利石和蒙脱石为900℃左右。焙烧粘土的活性按变高岭土&变蒙脱石&变沸石的顺序递减。在该项目第一阶段的第二部分，然后研究了充分组成的商业粘土原材料在不同焙烧技术下的活化性能。在所研究的所有烧成单元中都可以生产活性金属粉，在马弗炉中需要1小时，在回转窑中需要10分钟，在闪速焙烧炉中只需要1-2秒。在玻璃形成之前形成的无定形相导致所有粘土中火山灰反应性的显著增加。在混合水泥中(含30wt%的偏硅酸盐)，所有粘土在水化开始时只表现出较低的反应活性。28天后，掺偏高岭土和变膨润土的水泥表现出比基础CEM I水泥更高的强度。就强度贡献而言，变质岩处于良好的硬煤飞灰范围内。在项目第一部分成果的基础上，建立了诺模图形式的参数模型。在拟议的第二阶段工程中，将研究含有煅烧粘土的混凝土的耐久性能。在勘测方面，将使用第一阶段工程的商业原始粘土，以便能够将已有的勘测结果用于第二阶段。此外，在测试中，这些原始粘土将进一步用石英粉稀释，直到达到关于活性二氧化硅的标准限制(≥25.0wt.%)。通过优化粘土的煅烧和粉磨，制备出CEM II/B-S、CEM II/C-M(Q-LL)和CEM VI(Q-LL)的混合水泥，并对其进行了耐久性试验。粘土、熟料基质和硫酸盐载体都是不同的。将研究水泥对混凝土的碳化、氯离子渗透和冻融侵蚀的影响。在平行进行的基础调查中，应为确定的混凝土耐久性建立一个解释基础。将对物理和化学矿物学影响因素进行调查。

Due to the climate debate, work is being carried out on the development of sustainable cements. One important strategy here is to replace the clinker content in cement, which is associated with high CO2 emissions, with suitable composite materials. Calcined clays, which are available worldwide in large quantities offer an alternative. The aim of the first project phase was to evaluate the basic suitability of calcined clays based on very different main clay minerals as composite materials in cement. The investigations in the first part of the project were carried out on pure clay minerals. Optimum firing temperatures were determined for the various clays with respect to maximum pozzolanity, which are about 700 °C for kaolinite and about 900 °C for illite and montmorillonite. The reactivity of the calcined clays decreases in the order metakaolin < metamontmorillonite < metaillite. In the second part of the first phase of the project, adequately composed commercial clay raw materials were then investigated for their activatability when different calcination techniques were applied. Reactive metatones can be produced in all the firing units investigated, requiring one hour in the muffle furnace, 10 minutes in the rotary kiln and only 1 - 2 seconds in the flash calciner. The formation of amorphous phases prior to glass formation leads to a significant increase in pozzolanic reactivity in all clays. In blended cements (with 30 wt% metaclay), all clays show only low reactivity at the beginning of hydration. After 28 days, the blended cements with metakaolin and metabentonite show higher strengths than the underlying CEM I cement. In terms of strength contributions, the metaillite is in the range of good hard coal fly ashes. Based on the results of the first part of the project, a parameter model was developed in nomogram form. In the proposed second project phase, the durability properties of concretes with calcined clays will be investigated. For the investigations, the commercial raw clays of the first project phase will be used in order to be able to utilize the already available investigation results for the second phase. Furthermore, for the tests, these raw clays will be further diluted with quartz powder until the normative limit regarding reactive silica is reached (≥ 25.0 wt.%). After optimal calcination and grinding of the clays, mixed cements CEM II/B-S, CEM II/C-M (Q-LL) and CEM VI (Q-LL) are produced, which are then used to carry out the durability tests on the concrete. Both the clay, the clinker base and the sulphate carrier are varied. The impact of cement will be investigated on concretes for the exposures carbonation, chloride penetration and freeze/thaw attack. In fundamental investigations carried out in parallel, an interpretation basis for the determined concrete durability is to be established. Both physical and chemical-mineralogical influencing factors will be investigated.