E. Reyes

Experiencias Docentes en Innovación Educativa como Mejora de una Enseñanza Tradicional de los Materiales de Construcción

This paper presents the results of a teaching experience in the subject Construction and Building Materials after incorporating active methodologies as suggested by the European Higher Education Area (EHEA). From the academic year 2006-07 traditional teaching methods were improved, based on the use of cooperative learning, continuous assessment and new technologies. In the last three courses there has been a marked increase in the number of students passing the course, 32% increase over students enrolled in the subject, in comparison with previous academic years. Based on these results it can be concluded that the use of active teaching techniques to complement traditional teaching improves learning of students and enhance student’s motivation. However, the use of these techniques requires greater dedication of teachers and greater involvement of students in their learning process.

Study of the brickwork masonry cracking with a cohesive fracture model

Este articulo presenta un modelo de calculo que permite simular el comportamiento en rotura de la fabrica de ladrillo bajo solicitaciones de traccion y cortante. El modelo extiende el modelo cohesivo formulado por los autores para hormigon, considerando la anisotropia del material. El procedimiento de calculo consta de dos fases: 1) obtencion de la trayectoria de grieta mediante un calculo elastico lineal; 2) incorporacion del modelo cohesivo en la misma mediante elementos de intercara. El modelo se ha implementado en un programa de elementos finitos comercial con una subrutina de usuario y se ha contrastado con los resultados experimentales de los ensayos a escala. Las propiedades mecanicas de la fabrica, en especial las de fractura, se miden con ensayos de caracterizacion en dos direcciones. Estas se incorporan al modelo de calculo para simular los ensayos de fractura en modo mixto, prediciendo los resultados adecuadamente para distintas orientaciones de los tendeles

Viability Study of a Safe Method for Health to Prepare Cement Pastes with Simultaneous Nanometric Functional Additions

The use of a mixing method based on a novel dry dispersion procedure that enables a proper mixing of simultaneous nanometric functional additions while avoiding the health risks derived from the exposure to nanoparticles is reported and compared with a common manual mixing in this work. Such a dry dispersion method allows a greater workability by avoiding problems associated with the dispersion of the particles. The two mixing methods have been used to prepare Portland cement CEM I 52.5R pastes with additions of nano-ZnO with bactericide properties and micro- or nanopozzolanic SiO2. The hydration process performed by both mixing methods is compared in order to determine the efficiency of using the method. The hydration analysis of these cement pastes is carried out at different ages (from one to twenty-eight days) by means of differential thermal analysis and thermogravimetry (DTA-TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) analyses. Regardless of composition, all the mixtures of cement pastes obtained by the novel dispersion method showed a higher retardation of cement hydration at intermediate ages which did not occur at higher ages. In agreement with the resulting hydration behaviour, the use of this new dispersion method makes it possible to prepare homogeneous cement pastes with simultaneous functional nanoparticles which are physically supported on the larger particles of cement, avoiding exposure to the nanoparticles and therefore minimizing health risks. Manual mixing of cement-based materials with simultaneous nanometric functional nanoparticles on a large scale would make it difficult to obtain a homogenous material together with the health risks derived from the handling of nanoparticles.

Mixed Mode Fracture of Brickwork Masonry

The brickwork masonry, especially walls, often shows cracking ought to differential settlements and excessive deflections of the slabs. In these circumstances the cracks are induced by a combination of tensile and shear stresses, under static loading. Until now the study of the brickwork masonry failure under static loading has been focussed on the compression and compression/shear failure mechanisms, and minor effort has been devoted to study the tensile/ shear failure (mixed mode I/II fracture) [1],[2]. This is the reason because there are not enough experimental data for a good knowledge of the mixed mode fracture of the brickwork masonry. The experimental results are needed for a better knowledge of the failure mechanisms of the brickwork masonry under tensile/shear loading and to supply a benchmark to validate the analytical and numerical models for the mixed mode fracture of the brickwork masonry.

Simulation of the Mixed Mode Fracture of Concrete with Cohesive Models

Considerable effort has been devoted to developing numerical models to simulate the mixed mode fracture of quasi-brittle materials. Traditionally, the numerical methods based on the Finite Element Method were classified into two groups [1]: smeared crack approach and discrete crack approach.