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，人们正在开展可持续水泥的开发工作。这里的一个重要策略是用合适的复合材料取代水泥中的熟料含量，这与高二氧化碳排放有关。在世界范围内大量可用的煅烧粘土提供了另一种选择。项目第一阶段的目的是评估基于不同主要粘土矿物的煅烧粘土作为水泥复合材料的基本适用性。项目第一部分的调查是对纯粘土矿物进行的。确定了各种粘土的最佳烧成温度，其中高岭石约为700℃，伊利石和蒙脱石约为900℃。煅烧粘土的反应性依次为偏高岭土<偏蒙脱土>偏钛土。在该项目第一阶段的第二部分，研究了不同煅烧技术下适当组成的商业粘土原料的活化性。在所研究的所有燃烧单元中都可以产生反应性的甲基丙酮，在马弗炉中需要1小时，在回转窑中需要10分钟，在闪蒸炉中只需要1 - 2秒。在玻璃形成之前，非晶相的形成导致了所有粘土中火山灰反应性的显著增加。在混合胶结物中（含30 wt%的元粘土），所有粘土在水化开始时都表现出较低的反应性。28天后，偏高岭土和变质膨润土混合的水泥强度高于下垫层的CEM I水泥。在强度贡献方面，该尾矿在良好的硬煤粉煤灰范围内。根据项目第一部分的结果，建立了以nomogram形式表示的参数模型。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。在调查中，将使用第一阶段的商业原料粘土，以便能够在第二阶段利用已经获得的调查结果。此外，在试验中，这些原料粘土将用石英粉进一步稀释，直到达到活性二氧化硅的标准限值（≥25.0 wt.%）。对粘土进行最佳煅烧和研磨后，制备出CEM II/B-S、CEM II/C-M （Q-LL）和CEM VI （Q-LL）混合水泥，用于混凝土耐久性试验。粘土、熟料基料和硫酸盐载体都是多种多样的。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。在并行进行的基础调查中，将建立确定混凝土耐久性的解释基础。研究了物理和化学矿物学影响因素。

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.