## 4 Conclusions  
The aim of this paper is to show the scientific possibilities offered by computed tomography for the study of porosity in concrete. For this purpose, six cubic specimens of 40 mm sides made of fiber-reinforced concrete were scanned. The data were then post-processed using digital image processing software. As a result of this stage, all the pores of each specimen were identified and isolated, obtaining their individual properties, such as center of gravity coordinates, volume, length, orientations, etc. Finally, all these data were sorted using different techniques in order to better understand the morphological characteristics of the pores and their spatial distribution. The main utilities provided by each of these techniques are mentioned below:  
* Circumferential test: this allows detection of the presence of the wall effect, which manifests itself through changes in porosity as we approach the limits of the specimens. In addition, in damaged specimens it is very useful to determine crack distribution. * Radial test: similar to the circumferential test, it is able to detect if there is any kind of wall effect. It can also be applied to specimens tested to failure to check whether the distribution of damage is uniform or if there are planes of weakness. * Vertical test: this test is very useful to detect aggregate segregation in concrete, since in these cases it can be clearly observed that the porosity varies along the vertical coordinate. * Neighborhood test: this test evaluates the degree of uniformity in pore distribution and can be very interesting to establish correlations with the macroscopic response of the concrete. * Porosity curves and cumulative pore-volume curves: these curves are used to understand the pore size distribution. They are very useful in drawing comparisons between the porosity of different specimens, as well as in analyzing the influence of components or additives within the concrete matrix. * Histograms of pore distribution and histograms of pore-volume distribution: These types of histograms, which can be plotted in volume or length ranges, can be used in addition to the previous graphs to gain an in-depth understanding of the concrete microstructure. The final objective is to try to explain the dispersion observed in the tests at the macroscopic level. * Sphericity factor and shape factor: these parameters indicate the level of roundness of the pores; that is, how closely they approach a spherical shape. They can be used to determine whether pore shape influences crack initiation and propagation, or to evaluate the impact of components or additives on pore shape. * Pore orientation: as it is shown that pores are not spherical, it is interesting to determine their orientations and check if there are correlations with the macroscopic response of the concrete. This parameter is particularly relevant in fiber-reinforced concrete. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Specimen** & **CUB-01** & **CUB-02** & **CUB-03** & **CUB-04** & **CUB-05** & **CUB-06** & **Average** \\ \hline e\({}_{\text{x}}\) & 0.33 & 0.36 & 0.29 & 0.33 & 0.36 & 0.37 & 0.34 \\ \hline e\({}_{\text{y}}\) & 0.35 & 0.28 & 0.35 & 0.31 & 0.29 & 0.27 & 0.31 \\ \hline e\({}_{\text{z}}\) & 0.33 & 0.37 & 0.36 & 0.37 & 0.36 & 0.36 & 0.36 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Efficiency indexes. All these techniques reveal that computed tomography can provide a great deal of information on the porosity of concrete, much more than that given by conventional procedures. Although the technology has not yet reached a sufficient level of development, it is expected that in the next few years it will be possible to achieve resolutions well below 1 \(\upmu\)m in normal-sized specimens. This will make it possible, by applying the techniques presented in this work, to study the microstructure of concrete at a level never seen before. Conceptualization and methodology, M.A.V., A.M., J.M. and D.C.G. ; development and supervision of the test, M.A.V. and D.C.G.