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正朝着更薄，更轻，更复杂的形状和更紧密的组件朝着迈进。对于此类组件，需要相对柔软且可流动的混凝土，必须在振动下进行全面填充整个模板。但是，在常规混凝土结构中，更多可流动的混凝土可用于实现混凝土的更有利的加工性能，更快的构造进度，甚至是高级机械化和混凝土安装进度的自动化。现代建筑化学为新鲜混凝土特性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剂。但是，同时，这增加了建筑物材料系统的复杂性。迄今为止这些趋势的结晶是自我压缩混凝土（SCC）的发展。然而，直到现在，在德国很少使用SCC，由于存在隔离的风险，因此不得遭受振动。这是由于SCC在应用中的灵敏度的提高所致。对于非常狭窄的增强布局和复杂的混凝土情况，即使是SCC的高流动性也不总是足够，因为如果没有额外的振动能量，并非所有腔都可以安全地填充。同样在正常混凝土领域，随着越来越柔软或可流动的一致性的隔离风险增加。在任何情况下，当前的损坏情况表明，由于建筑物材料系统的流动性和复杂性以及在困难和狭窄的混凝土条件下的流动性和复杂性，可能会出现混凝土稳定性的问题。尽管在SCC领域中有充分的方法，可确保具体的足够稳定性，但在振动下的柔软至可流动混凝土的可比较方法。因此，应在工程模型方法的基础上描述可流动混凝土的隔离稳定性。该模型方法基于对水泥悬浮液中结构堆积和结构分解过程的描述。应记录早期水合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，可以同时得出振动下可流动混凝土的隔离稳定性的优化策略。