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The results are based on data1. Figure 3 displays temperatures of the tank wall and of the gas phase over testing time. It can be seen that a complete coating strongly delayed the heating of tank wall and gas phase, whereas the partly coated tanks only had a minor influence on temperature development. There was no significant difference between a half coated and a thirdly coated tank measurable. Figure 4 shows the internal pressure of tanks over testing time. Only the fully coated tank enabled a low pressure over 90 min testing time. Hence, a complete coating is necessary to guarantee the fire safety of hazmat tanks and a partly coating is not sufficient.
Although concrete itself is not a combustible material, concrete mixtures with high density, such has high-performance concretes (HPCs), are susceptible to significant damage during fires due to explosive spalling. Past research has shown that the inclusion of polymer fibers in high density concrete can significantly mitigate fire damage due to the contribution of the fibers to increased permeability levels at high temperature. This allows vapor pressures caused by the evaporation of internal water during fire to escape from the material without causing significant spalling. Recent microscopic investigations have also shown that the addition of polypropylene (PP) fibers to high-density HPC with a high amount of fine-aggregate has a considerable influence on the nature and character of crack formation due to autogenous shrinkage. Initial cracks, which originate from the fiber beds, undergo further expansion and propagation when concrete is subjected to thermal exposure in excess of 170 °C. It is thus of interest to determine whether the resulting cracks join the adjacent fiber beds and therefore contribute to a significant increase in the permeability of the concrete, which is directly correlated to lower pore pressures and reduced spalling during fire.
In this study, X-ray Computed Tomography (CT) was applied to provide a clear demonstration of the interaction between polymer fibers and cracking during thermal exposure. For this purpose, two concrete samples containing different polymer fiber types were subjected to incremental application of a defined thermal exposure. CT images were acquired before and after each thermal exposure and powerful image processing tools were used to segment the various material components, such as polymer fibers, cracks, aggregates and cement matrix, in each image. This enabled a detailed analysis of crack formation and propagation as well as the visualization and quantification of polymer fiber characteristics within the concrete. This paper will provide a description of the distribution and orientation characteristics of the polymer fibers within each sample obtained through the CT-based analysis. Using these results, the impact of fiber distribution and orientation characteristics on actual cracking geometries have been measured and visualized. This paper will also provide recommendations for further optimization of the selected materials and propose improved methods for future CT-based analysis techniques.