https://hdl.handle.net/10259/4810 2026-04-17T11:58:52Z 2026-04-17T11:58:52Z Vicente Cabrera, Miguel Ángel Mena Alonso, Álvaro González Cabrera, Dorys Carmen Ruiz, Gonzalo Cifuentes, Héctor Leiva, Carlos Yu, Rena C. Mínguez Algarra, Jesús https://hdl.handle.net/10259/11386 2026-02-18T01:05:51Z 2025-03-01T00:00:00Z

Numerical and experimental study of the optimal specimen geometry for direct tension strength tests in high tensile strength fiber reinforced concrete Vicente Cabrera, Miguel Ángel; Mena Alonso, Álvaro; González Cabrera, Dorys Carmen; Ruiz, Gonzalo; Cifuentes, Héctor; Leiva, Carlos; Yu, Rena C.; Mínguez Algarra, Jesús The accurate determination of the tensile strength of concrete is a topic of growing interest, especially driven by the new ultra-high tensile strength fiber-reinforced concretes. However, this is a complex task, as traditional methods provide inconsistent results (both splitting tensile test and 3-point bending test). The most robust method is the direct tensile test. However, in concrete, it poses a technical challenge that has not yet been satisfactorily solved. The aim of this study is the design of a test specimen that maximizes the percentage of successful failure and also allows a viable anchorage solution to the load application equipment, especially for high and ultra-high tensile strength concretes. An optimized geometry of a bone-shaped specimen that maximizes the probability of collapse occurring at the central neck is presented. First, a mathematical function of the generatrix of the bone-shape specimen is presented. The behavior of the solution is also analyzed numerically and statistically, comparing it with other commonly used solutions for direct tensile tests. Additionally, the design, fabrication, and calibration of a tailored cardan joint for load centering, thus minimizing its eccentricity and the dispersion of the results. Finally, the results of a static test campaign carried out on six carbon-fiber reinforced high tensile strength concrete specimens. The proposed bone-shaped specimen shows a much higher percentage of successful failures than the other specimen geometries commonly used for tensile testing, which improves the quality of tensile characterization test campaigns for high and ultra-high tensile strength concretes.

2025-03-01T00:00:00Z Rojas, Guillem Mena Alonso, Álvaro Muñoz, Álvaro Kanstad, Terje Vicente Cabrera, Miguel Ángel https://hdl.handle.net/10259/11385 2026-02-18T01:05:50Z 2025-09-01T00:00:00Z

Experimental study of the fibre distribution in SFRC: a comparison between CT-scanning techniques and the inductive method Rojas, Guillem; Mena Alonso, Álvaro; Muñoz, Álvaro; Kanstad, Terje; Vicente Cabrera, Miguel Ángel 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.

2025-09-01T00:00:00Z Ríos, José D. Mínguez Algarra, Jesús Martínez de la Concha, Antonio Vicente Cabrera, Miguel Ángel Cifuentes, Héctor https://hdl.handle.net/10259/10127 2025-02-01T01:05:38Z 2020-11-01T00:00:00Z

Microstructural analyses of the addition of PP fibres on the fracture properties of high-strength self-compacting concrete by X-ray computed tomography Ríos, José D.; Mínguez Algarra, Jesús; Martínez de la Concha, Antonio; Vicente Cabrera, Miguel Ángel; Cifuentes, Héctor This paper analyses the influence of the presence of polypropylene fibres in the microstructure of a high-strength self-compacting concrete by X-ray computed tomography and its consequences on the mechanical and fracture properties. The addition of PP fibres alters the pore structure of the concrete matrix, and this affects the macroscopic response (i.e., mechanical and fracture behaviour). A microstructural analysis of an unreinforced concrete, used as reference mix, and two polypropylene fibre-reinforced mixes with two fibre length (6 and 24 mm) were experimentally carried out. Complementary, a comprehensive experimental study of the mechanical and fracture properties of each concrete were performed. Finally, it was established a correlation between the microscopic response (pore morphology and pore distribution) and the macroscopic behaviour of high-strength self-compacting concrete.

2020-11-01T00:00:00Z Vicente Cabrera, Miguel Ángel Ruiz, Gonzalo González Cabrera, Dorys Carmen Mínguez Algarra, Jesús Tarifa, Manuel . Zhang, Xiaoxin . https://hdl.handle.net/10259/10085 2025-01-30T01:05:35Z 2019-11-01T00:00:00Z

Effects of fiber orientation and content on the static and fatigue behavior of SFRC by using CT-Scan technology Vicente Cabrera, Miguel Ángel; Ruiz, Gonzalo; González Cabrera, Dorys Carmen; Mínguez Algarra, Jesús; Tarifa, Manuel .; Zhang, Xiaoxin . The effects of the fiber orientation and content on the behavior of steel fiber-reinforced concrete (SFRC) under static and cyclic compressive loads are studied using the computed tomography (CT) technique, and the resistance mechanisms of the fibers are carefully observed. The results suggest that the intrinsic scatter in the fatigue life could be partially explained by the essential scatter in the fiber orientation and content. On the contrary, no relationship is observed between the intrinsic scatter in compressive strength and fiber orientation and content, which suggests that the compressive strength of the specimens is mainly due to their concrete matrix.

2019-11-01T00:00:00Z