This paper shows the scientific possibilities of computed tomography for the study of concrete porosity. The enormous technological advances in computed tomography equipment used in materials research, with increasingly higher energy, better resolution and smaller pixel size will allow, in the near future, viewing pore sizes that are currently unthinkable, competing in resolution with the traditional techniques of mercury porosimetry and nitrogen adsorption. The challenge at that time (and to a lesser extent today) will be how to extract as much information as possible from the large amount of data provided by computed tomography equipment. In this article, through the study of six cubic specimens of 40 mm sides, different techniques of extraction and presentation of the information are shown, which help us to better understand the characterization of the morphology and distribution of the pores inside the concrete matrix. This information is essential to understand some of the macroscopic responses of the concrete.

This paper proposes a reliable and comprehensive procedure for the assessment of steel fibre distribution in fibre reinforced concrete. Two techniques have been used: computed tomography (CT) scanning and inductive testing. Both techniques have been applied to study the distribution of steel fibres in specimens extracted from structural elements, carrying out a comparative analysis of the results. Firstly, the data from the CT-scanning and the inductive method have been processed to obtain the density of steel fibres and their orientation in all the specimens, before comparing the results. Then, a complementary study was carried out to validate the inductive method, using hand-made cylinders with a previously known fibre dosage and orientation. Finally, the dual energy CT technique was applied and some conclusions about its potential were discussed. Both methods exhibited comparable accuracy and precision in measuring fibre density and orientation. Considering that CT-scanning is the reference technique, this mutual agreement reinforces the reliability of the inductive method. Additionally, the authors employed the dual energy CT aiming to explore the potential of this novel technique within the domain of fibre reinforced concrete research.

This research develops a new low-cost energy dissipation system, capable of being implemented in residential structures in developing countries with high seismic activity, in which the current solutions are not economically viable. These residential structures are entirely made of precast concrete elements (foundations, walls, and slabs). A solution is developed that consists of a new connection between a precast foundation and a structural wall, which is capable of dissipating almost all the seismic energy, and therfore protecting the rest of the building from structural damage. To validate the solution, a testing campaign is carried out, including a first set of “pushover” tests on isolated structural walls, a second set of “pushover” tests on structural frames, and a final set of seismic tests on a real-scale three-storey building. For the first and second set of tests, ductility is analyzed in accordance with ACI 374.2R-13, while for the third one, the dynamic response to a reference earthquake is evaluated. The results reveal that the solution developed shows great ductility and no relevant damage is observed in the rest of the building, except in the low-cost energy dissipation system. Once an earthquake has finished, a precast building implemented with this low-cost energy dissipation system is capable of showing a structural performance level of “immediate occupancy” according to ACI 374.2R-13.

Steel fiber-reinforced concrete (SFRC) is a composite material, consisting of conventional concrete with the addition of short, randomly distributed steel fibers. Fibers modify the mechanical behavior of concrete, improving some of its properties: they increase its ductility, enhance its residual tensile strength, and under certain conditions, increase its ultimate flexural strength. All these advantages make this material competitive with conventional reinforced concrete. However, the psychological barriers of the construction sector and the technical challenges that remain to be solved are slowing down the consolidation of this building material. One of these challenges is the improvement of the understanding of fatigue, which not only affects SFRC, but concrete in general. In this regard, work to date suggests that fibers, given certain circumstances, increase the fatigue life of concrete. This would result in SFRC being very effective in structures where fatigue is a critical action, such as wind turbine concrete towers.