Stability of concrete subjected to vibration – Analysis of the nano- and microscopic structural build-up and structural breakdown behavior of cementitious suspensions

振动下混凝土的稳定性 â 分析水泥悬浮液的纳米和微观结构构建和结构破坏行为

• 批准号: 411375374
• 负责人: Professor Dr.-Ing. Ludger Lohaus
• 金额: --
• 依托单位: Institut für Physikalische Chemie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/411375374?language=en
• 关键词: Stability; concrete; subjected; vibration; Analysis

Trends in modern concrete construction are moving towards slimmer, lighter, more complex shaped and more closely reinforced components. For such components comparatively soft and flowable concretes are required, which have to subject under vibration additionally for full filling the whole formwork. But also in conventional concrete construction more flowable concretes are used to achieve more favorable processability properties of the concrete, a faster construction progress or even to an advanced mechanization and automatization of the concrete installation progress. Modern construction chemistry has contributed significantly to the further development of fresh concrete properties, in particular by providing highly effective superplasticizers. At the same time, however, this increases the complexity of the building material system. The development of self-compacting concrete (SCC) is the culmination of these trends so far. Nevertheless, SCC, which must not subjected to vibration because of the risk of segregation, has rarely been used in Germany until now. This is due to the increased sensitivity of SCC in the application. For very narrow reinforcement layouts and complex concreting situations, even the high flowability of SCC is not always sufficient, since not all cavities can be safely filled without additional vibration energy. Also in the field of normal concrete increases with increasingly softer or flowable consistency the risk of segregation. In any case, current case of damage show that problems with the stability of concrete can occur with increasing flowability and complexity of the building material system as well as under difficult and narrow concreting conditions. Although there are well-founded approaches in the field of SCC ensuring a sufficient stability of concrete, comparable approaches for soft to flowable concretes under vibration are lacking. Therefore the segregation stability of flowable concretes subject to vibration is to be described on the basis of engineering model approaches. The model approaches are based on the description of structural build-up and structural breakdown processes in the cementitious suspension. The influence of early hydration products on the shear- and time-dependent behavior of the suspension should be recorded. By taking account of the composition of the concrete, optimization strategies for increasing the segregation stability of flowable concrete under vibration can be derived simultaneously.

现代混凝土结构的趋势是向更薄、更轻、形状更复杂和更紧密加固的部件发展。对于这样的部件，需要相对柔软和可流动的混凝土，其必须经受额外的振动以完全填充整个模板。而且在常规混凝土施工中，使用更易流动的混凝土以实现混凝土的更有利的加工性能、更快的施工进度或甚至混凝土安装进度的先进机械化和自动化。现代建筑化学对新拌混凝土性能的进一步发展做出了重大贡献，特别是通过提供高效的超塑化剂。然而，这同时增加了建筑材料系统的复杂性。自密实混凝土（SCC）的发展是迄今为止这些趋势的顶点。然而，由于存在离析的风险，SCC不得受到振动，因此直到现在为止，在德国很少使用SCC。这是由于SCC在应用中的敏感性增加。对于非常狭窄的钢筋布局和复杂的混凝土浇筑情况，即使SCC的高流动性也不总是足够的，因为并非所有空腔都可以在没有额外振动能量的情况下安全填充。此外，在普通混凝土领域中，随着越来越软或可流动的一致性，隔离的风险增加。无论如何，目前的损坏情况表明，随着建筑材料系统的流动性和复杂性的增加，以及在困难和狭窄的混凝土浇筑条件下，混凝土的稳定性可能会出现问题。虽然在SCC领域有充分的方法来确保混凝土的足够稳定性，但缺乏在振动下用于软到可流动混凝土的类似方法。因此，振动作用下流动性混凝土的离析稳定性应基于工程模型方法来描述。该模型的方法是基于结构的建立和结构的破坏过程中的水泥悬浮液的描述。应记录早期水化产物对悬浮液的剪切和时间依赖性行为的影响。通过考虑混凝土的组成，优化策略，提高振动下的流动性混凝土的离析稳定性，可以同时得出。