Theoretical and experimental investigations to extend the calculation basis of different types of concretes exposed to natural fire

在本研究项目中，将通过理论和实验研究，探索和描述在自然火灾条件下，在升高和降低温度下，正常强度（CC）、高性能（HPC）和超高性能（UHPC）混凝土中不同类型高温行为的原因。由于混凝土的胶凝相和骨料相的刚度和热应变的差异，机械和/或热载荷导致材料内的裂缝，特别是在结构中的不连续点处，例如水泥-骨料-粘结区域和孔。这些裂缝在冷却阶段是部分可逆的（例如，通过水泥的再水化），从而对混凝土的机械和热特性产生影响。首先，为了了解这些特性的变化，本研究项目包括物理和化学过程的实验研究。此后，建立小规模的实验室测试，以确定热和热机械性能，这是为模拟和计算的具体值的定义的基础。下一步将进行全尺寸试验。结果进行了比较，以证明以前确定的具体值是否也可以应用到真实的规模的结构元素。所有的实验都伴随着数值模拟，以检查理论上的具体值，运行参数研究和验证值作为进一步计算的基础。

In this research project, the reasons for different types of high-temperature behaviour in normal-strength (CC), high-performance (HPC) and ultra-high-performance (UHPC) concrete will be explored and described at both increasing and decreasing temperatures under natural fire conditions by conducting theoretical and experimental investigations. Due to the difference in stiffness and thermal strain of concrete's cementitious and aggregate phases, mechanical and/or thermal loads cause cracks within the material, especially at points of discontinuity in the structure such as cement-aggregate-bond areas and pores. These cracks are partly reversible (e.g. by re-hydration of cement) during the cooling phase and thereby have an influence on the mechanical as well as the thermal characteristics of concrete. Firstly, to understand these changes in characteristics, this research project consists of experimental investigations into both physical and chemical processes. Thereafter small scale laboratory tests are set up to determine the thermal and thermomechanical properties which are the basis for the definition of specific values for simulations and calculations. In the next step, full scale tests are conducted. The results are compared to the small scale findings to prove whether the formerly determined specific values can also be applied to real scale structural elements. All experiments are accompanied by numerical simulations to check the specific values theoretically, run parameter studies and validate the values as basis of further calculations.