Material composition influenced damage development in high-strength concrete under cyclic loading

与普通强度混凝土相比，高强混凝土具有更致密和更好的微观结构。高强度混凝土在单调增加的外部载荷下的材料行为与普通强度混凝土的材料行为相比是显著不同的。它主要受水泥或粘结剂的优化性能和界面过渡区的影响。关于高强混凝土和普通强度混凝土的疲劳性能，目前还不清楚它们的不同微观结构导致的损伤过程的差异，因此，在本项目中，将对高强混凝土在循环荷载下的退化机理进行研究、描述和建模。特别是，成核和传播的裂纹内的不同阶段的降解将进行调查。本文采用逐步分析的方法，系统地分析了生产高强混凝土的工艺措施对典型混凝土疲劳性能的影响。将使用不同的损害指标确定退化机制。差异将详细说明和量化，而在实验虚拟实验室的损害指标的应用将进行调查和评估。此外，高分辨率的成像过程将被应用于观察不同的裂纹状态，并将它们与疲劳过程中的损伤指标的发展。在这个联合项目中，计划了一个实验/建筑材料子项目和一个理论/计算子项目。这两个分项目将在内容和方法上密切合作。发生在非常小尺度上的损伤过程有时只能在大得多的尺度上通过实验观察到。这些损伤过程的知识将获得由实验结果校准的尺度过渡建模，允许得出结论的过程上的罚款规模。为了实现这一点，将使用多尺度投影方法结合XFEM和非局部损伤来模拟多尺度上的裂纹成核和动态裂纹扩展。为了在合理的模拟时间内计算捕获几千个负载循环的进度，将应用基于小波的多时间尺度方法WATMUS。对于微观结构组件的弹性-粘塑性材料模型将被假定。实验和模拟的结合将导致对高强混凝土损伤机理的新的认识，并最终导致新的和改进的混凝土组合物的疲劳性能的可预测性。

Compared to normal-strength concrete, high-strength concrete exhibits a denser and improved microstructure. The material behaviour of high-strength concrete under monotonically increasing external loads is significantly different compared to the material behaviour of normal-strength concrete. It is mainly influenced by optimized properties of the cement or the binder agent and the interfacial transition zone. Concerning fatigue properties of high-strength concrete and normal-strength concrete until now it is unclear how the damage processes differ due to their different microstructures.As a consequence, within this project the degradation mechanisms of high-strength concrete under cyclic loading will be examined, described and modelled. In particular, the nucleation and propagation of cracks within the different phases of degradation will be investigated. Based on a stepwise methodology the influence on the fatigue behaviour of typical concrete technology measures to produce high-strength concrete will be analysed systematically. The degradation mechanisms will be determined using different damage indicators. Differences will be elaborated and quantified while the application of the damage indicators within an experimental-virtual-lab will be investigated and evaluated. In addition, high resolution imaging processes will be applied to observe different crack states and to relate them to the development of the damage indicators within the fatigue process.Within this conjoint project an experimental/building material subproject and a theoretical/computational subproject are planned. The two subprojects will cooperate intensively regarding contents and methodology. Damage processes happening on a very small scale can sometimes be observed experimentally only on a much larger scale. Knowledge about these damage processes will be gained by a scale transitioned modelling calibrated by experimental results which allows for drawing conclusions about processes on the fine scale. To realize this, the multiscale projection method in combination with the XFEM and non-local damage for the simulation of crack nucleation and dynamic crack propagation on multiple scales will be used. To capture the progress computationally for a couple of thousand load cycles within reasonable simulation times, the wavelet based multi timescale method WATMUS will be applied. For the microstructural components an elastic-viscoplastic material model will be assumed. The combination of experiment and simulation will lead to new insight into the damage mechanisms of high strength concrete and eventually it will lead to the predictability of the fatigue properties of new and improved concrete composition.