# Impact of Fiber Type on Chloride Ingers in Concrete: A MacroXRF Imaging Analysis
## 3 Results
### XRF Analysis  
As mentioned, the raw data from MacroXRF consists of the number of photons generated by a specific element after being excited by X-rays. A higher number of emitted photons indicates the presence of more chlorine elements excited, signifying its presence in the sample at various levels. For capturing XRF images with two-dimensional maps of the elements, the analyzed samples were concrete cores with diameters of 100 mm and a height of 50 mm. The matrix used consisted of 40 \(\times\) 25 pixels with 1000 XRF spectra. In the resulting maps, the color scale represents the intensities of the K-lines of the elements in the XRF spectra: red indicates higher intensity (greater contribution), and dark blue indicates lower intensity (lesser contribution--background). These color variations directly correspond to the number of chlorine photons excited and detected in each region of the sample, allowing for a visual representation of chloride distribution. The vertical axis Y represents the height of the samples in mm, while the horizontal axis X represents the 30 mm width scanned. In these XRF maps, the readings on the Y axis indicate the height of the sample at which the chlorine element has penetrated. Upon cutting the samples, it was also possible to visually verify the proportions of cement paste and aggregates. By comparing the central region with the two-dimensional maps, it was possible to identify some of these aggregates and their influence on the presence or absence of the evaluated elements. Referring to the chloride penetration that occurred through the pores, points in darker blue had fewer pores or were aggregates, while points in red are regions with more pores. Figure 10 shows the intensity of the chlorine element by depth in the concrete samples with polypropylene fiber (PF) compared to the reference sample (RC). Figure 11 shows a comparison between the measurements obtained on these samples on the same scale. Analyzing the graphs in Figure 11 and fitting a trend line, it is evident that there was a general decrease in the presence of chlorine in the samples as the depth/reading position increased. However, the reference sample exhibited the highest chlorine presence at the initial depths of the scan, maintaining high levels of this count. This observation was confirmed by the two-dimensional maps, where chlorine was found throughout the depth of the reference concrete sample in a uniform manner, with similar intensity/concentration. This suggests that the voids in the reference sample were predominantly interconnected, allowing the chloride from the accelerated test to travel freely. A similar behavior can be observed for the concrete reinforced with glass fibers. Figure 12 presents the chloride count by depth for the concrete samples reinforced with glass fibers at different percentages, along with the two-dimensional maps identifying chlorine. Figure 13 presents a comparison of the measurements obtained for the glass fiber samples on the same scale. Figure 11: Results of MacroXRF measurements for chlorine in PF samples. Figure 10: Chloride count for polypropylene fiber and reference samples. Figure 12: Chlorine count in glass fiber and reference samples. Figure 13: MacroXRF results for chlorine in GF samples. For the concrete with glass fibers (GFs), it became more challenging to establish a standard analysis, particularly for the 0.5% GF sample, which exhibited chlorine peaks at unexpected depths. Therefore, it was necessary to consider the baseline patterns adjusted in the graphs in Figure 12 to the right. The photon counts for this sample were also higher than those for the GF25 samples, as confirmed by the map images. This suggests that the fiber content in this sample might have resulted in more interconnected voids with more permeable pathways compared to the other samples. The chlorine peaks in the line analysis and the intensity points on the map could be associated with contamination or the presence of aggregates.