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

由于气候辩论，正在开展可持续水泥的开发工作。这方面的一个重要战略是用适当的复合材料取代水泥中与高二氧化碳排放量有关的熟料含量。世界各地大量供应的煅烧粘土提供了一种替代品。项目第一阶段的目的是评估煅烧粘土作为水泥复合材料的基本适用性，煅烧粘土基于非常不同的主要粘土矿物。该项目第一部分的调查是在纯粘土矿物上进行的。确定了各种粘土在最大火山灰方面的最佳烧制温度，高岭石的最佳烧制温度为约700 °C，伊利石和蒙脱石的最佳烧制温度为约900 °C。煅烧粘土的反应活性按偏高岭土<偏蒙脱石<偏伊利石的顺序降低。在该项目第一阶段的第二部分，充分组成的商业粘土原料，然后研究其活化时，不同的煅烧技术的应用。反应性金属间化合物可以在所有研究的烧制单元中生产，在煅烧炉中需要1小时，在回转窑中需要10分钟，在闪速煅烧炉中仅需要1 - 2秒。在玻璃形成之前形成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（30重量%的变粘土），所有的粘土在水化开始时只显示低反应性。28天后，具有偏高岭土和偏膨润土的混合水泥显示出比下面的CEM I水泥更高的强度。就强度贡献而言，偏伊利石处于良好的硬质粉煤灰的范围内。根据该项目第一部分的结果，以诺模图的形式建立了一个参数模型。在拟议的第二个项目阶段，将研究煅烧粘土混凝土的耐久性。对于调查，将使用项目第一阶段的商业原粘土，以便能够利用第二阶段的现有调查结果。此外，对于试验，将用石英粉进一步稀释这些原粘土，直至达到反应性二氧化硅的标准限值（≥ 25.0 wt.%）。在对粘土进行最佳煅烧和研磨后，生产出混合水泥CEM II/B-S、CEM II/C-M（Q-LL）和CEM VI（Q-LL），然后将其用于对混凝土进行耐久性测试。粘土、熟料基料和硫酸盐载体都是不同的。将研究水泥对混凝土暴露碳化、氯化物渗透和冻融侵蚀的影响。在平行进行的基本调查中，将建立确定混凝土耐久性的解释基础。物理和化学矿物学的影响因素将进行调查。

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.