Development of Mortars That Use Recycled Aggregates from a Sodium Silicate Process and the Influence of Graphene Oxide as a Nano-Addition.

This research analyses how different cement mortars behave in terms of their physical and mechanical properties. Several components were necessary to make seven mixes of mortars, such as Portland cement, standard sand, and solid waste from a factory of sodium silicate, in addition to graphene oxide. Furthermore, graphene oxide (GO) was selected to reduce the micropores and increase the nanopores in the cement mortar. Hence, some tests were carried out to determine their density, humidity content, water absorption capacity, open void porosity, the alkali-silica reaction, as well as flexural and mechanical strength and acid resistance. Thus, standard-sand-manufactured mortars' mechanical properties were proved to be slightly better than those manufactured with recycled waste; the mortars with this recycled aggregate presented problems of alkali-silica reaction. In addition, GO (in a ratio GO/cement = 0.0003) performed as a filler, improving the mechanical properties (30%), alkali-silica (80%), and acid resistance.

Compact Embedded Wireless Sensor-Based Monitoring of Concrete Curing.

This work presents the design, construction and testing of a new embedded sensor system for monitoring concrete curing. A specific mote has been implemented to withstand the aggressive environment without affecting the measured variables. The system also includes a real-time monitoring application operating from a remote computer placed in a central location. The testing was done in two phases: the first in the laboratory, to validate the functional requirements of the developed devices; and the second on civil works to evaluate the functional features of the devices, such as range, robustness and flexibility. The devices were successfully implemented resulting in a low cost, highly reliable, compact and non-destructive solution.

Mesoscale Characterization of Fracture Properties of Steel Fiber-Reinforced Concrete Using a Lattice-Particle Model.

This work presents a lattice-particle model for the analysis of steel fiber-reinforced concrete (SFRC). In this approach, fibers are explicitly modeled and connected to the concrete matrix lattice via interface elements. The interface behavior was calibrated by means of pullout tests and a range for the bond properties is proposed. The model was validated with analytical and experimental results under uniaxial tension and compression, demonstrating the ability of the model to correctly describe the effect of fiber volume fraction and distribution on fracture properties of SFRC. The lattice-particle model was integrated into a hierarchical homogenization-based scheme in which macroscopic material parameters are obtained from mesoscale simulations. Moreover, a representative volume element (RVE) analysis was carried out and the results shows that such an RVE does exist in the post-peak regime and until localization takes place. Finally, the multiscale upscaling strategy was successfully validated with three-point bending tests.

Probabilistic Flexural Fatigue in Plain and Fiber-Reinforced Concrete.

The objective of this work is two-fold. First, we attempt to fit the experimental data on the flexural fatigue of plain and fiber-reinforced concrete with a probabilistic model (Saucedo, Yu, Medeiros, Zhang and Ruiz, Int. J. Fatigue, 2013, 48, 308-318). This model was validated for compressive fatigue at various loading frequencies, but not for flexural fatigue. Since the model is probabilistic, it is not necessarily related to the specific mechanism of fatigue damage, but rather generically explains the fatigue distribution in concrete (plain or reinforced with fibers) for damage under compression, tension or flexion. In this work, more than 100 series of flexural fatigue tests in the literature are fit with excellent results. Since the distribution of monotonic tests was not available in the majority of cases, a two-step procedure is established to estimate the model parameters based solely on fatigue tests. The coefficient of regression was more than 0.90 except for particular cases where not all tests were strictly performed under the same loading conditions, which confirms the applicability of the model to flexural fatigue data analysis. Moreover, the model parameters are closely related to fatigue performance, which demonstrates the predictive capacity of the model. For instance, the scale parameter is related to flexural strength, which improves with the addition of fibers. Similarly, fiber increases the scattering of fatigue life, which is reflected by the decreasing shape parameter.

Use of co-combustion bottom ash to design an acoustic absorbing material for highway noise barriers.

The present study aims to determine and evaluate the applicability of a new product consisting of coal bottom ash mixed with Portland cement in the application of highway noise barriers. In order to effectively recycle the bottom ash, the influence of the grain particle size of bottom ash, the thickness of the panel and the combination of different layers with various particle sizes have been studied, as well as some environmental properties including leachability (EN-12457-4, NEN-7345) and radioactivity tests. Based on the obtained results, the acoustic properties of the final composite material were similar or even better than those found in porous concrete used for the same application. According to this study, the material produced presented no environmental risk.

Revisión de 85 casos de embarazo ectópico en el Hospital Regional Simón Bolívar en el periodo de 1983-1986 / Review of 85 cases of ectopic pregnancy in Hospital Regional Simon Bolivar in the period 1983-1986

Se realizó un estudio descriptivo retrospectivo, analizando un grupo de pacientes que se presentaron con diagnóstico de embarazo ectópico entre Mayo de 1983 y Mayo de 1986, que comprendió un grupo de 85 mujeres quienes consultaron al Hospital Simón Bolívar y en quienes se resgistró tal diagnósitco definitivo, para revisar sus historias clínicas con el objeto de encontrar las características del grupo de población afectado; las características de la enfermedad y varios aspectos de manejo y conocer las estadísticas y estado de la enfermedad en éste hóspital. Se revisó la literatura respecto de esta patología para comparar las características publicadas y las halladas. Se describe la incidencia relativa, morbilidad, mortalidad, y las características socio-económicas de la población afectada, al igual que los factors de riesgo. Se analizaron aspectos relacionados con el manejo, tales como el tipo de cirugía realizado, tiempo entre la iniciación de los síntomas y el tratamiento, la morbilidad y mortalidad operatoria. Los resultdos del estudio confirman algunos de los hechos y de las características descritas en la literatura médica. El estudio sienta un importante precedente estableciendo claros indicadores de los aspectos más importantes de esta patología en nuestro medio. Se analizaron las historias clínicas siendo sometidas a un cuestionario para evaluar si ellas fueron efectivas en la evaluación y consignación de datos, hallándose que existen claras deficiencias en este aspecto