ABSTRACT
Chloride presence affects different environments (soil, water, concrete) decreasing their qualities. In order to assess chloride concentration this paper proposes a novel sensor for detecting and measuring it. This sensor is based on electric changes of commercial monocalcium aluminate (CA) when it interacts with chloride aqueous solutions. CA is used as a dielectric material between two coplanar capacitors. The geometry proposed for this sensor allows to assess the chloride content profile, or to make four times the same measurement. Besides, the experimental design gives us the possibility of study not just the chloride effect, but also the time and some geometric effects due to the sensor design. As a result, this sensor shows a limit of detection, sensitivity, and response time: 0.01 wt % Cl- and 0.06 wt % Cl-, and 2 min, respectively, comparable with other non invasive techniques as optical fibre sensors.
ABSTRACT
Exposure assessments are key tools to conduct epidemiological studies. Since 2010, 28 riveters from 18 brake repair shops with different characteristics and workloads were sampled for asbestos exposure in Bogotá, Colombia. Short-term personal samples collected during manipulation activities of brake products, and personal samples collected during non-manipulation activities were used to calculate 103 8-h TWA PCM-equivalent personal asbestos concentrations. The aims of this study are to identify exposure determinant variables associated with the 8-h TWA personal asbestos concentrations among brake mechanics, and propose different models to estimate potential asbestos exposure of brake mechanics in an 8-h work-shift. Longitudinal-based multivariate linear regression models were used to determine the association between personal asbestos concentrations in a work-shift with different variables related to work tasks and workload of the mechanics, and some characteristics of the shops. Monte Carlo simulations were used to estimate the 8-h TWA PCM-Eq personal asbestos concentration in work-shifts that had manipulations of brake products or cleaning activities of the manipulation area, using the results of the sampling campaigns. The simulations proposed could be applied for both current and retrospective studies to determine personal asbestos exposures of brake mechanics, without the need of sampling campaigns or historical data of air asbestos concentrations.
Subject(s)
Air Pollutants, Occupational/analysis , Asbestos/analysis , Environmental Monitoring/methods , Occupational Exposure/analysis , Adult , Automobiles , Colombia , Computer Simulation , Female , Humans , Inhalation Exposure/analysis , Linear Models , Male , Middle Aged , Monte Carlo MethodABSTRACT
Microbiologically induced deterioration (MID) causes corrosion of concrete by producing acids (including organic and inorganic acids) that degrade concrete components and thus compromise the integrity of sewer pipelines and other structures, creating significant problems worldwide. Understanding of the fundamental corrosion process and the causal agents will help us develop an appropriate strategy to minimize the costs in repairs. This review presents how microorganisms induce the deterioration of concrete, including the organisms involved and their colonization and succession on concrete, the microbial deterioration mechanism, the approaches of studying MID and safeguards against concrete biodeterioration. In addition, the uninvestigated research area of MID is also proposed.
Subject(s)
Corrosion , Construction Materials/microbiology , Environmental Microbiology , Acids/metabolismABSTRACT
Microbiologically induced deterioration (MID) causes corrosion of concrete by producing acids (including organic and inorganic acids) that degrade concrete components and thus compromise the integrity of sewer pipelines and other structures, creating significant problems worldwide. Understanding of the fundamental corrosion process and the causal agents will help us develop an appropriate strategy to minimize the costs in repairs. This review presents how microorganisms induce the deterioration of concrete, including the organisms involved and their colonization and succession on concrete, the microbial deterioration mechanism, the approaches of studying MID and safeguards against concrete biodeterioration. In addition, the uninvestigated research area of MID is also proposed.
Subject(s)
Construction Materials/microbiology , Corrosion , Environmental Microbiology , Acids/metabolismABSTRACT
La calidad de los modelos mecánicos que describen el comportamiento estructural es ampliamente reconocida. Sin embargo, existe la percepción generalizada de que las especificaciones de diseño contenidas en los códigos conducen a estructuras que no son óptimas en término de seguridad y economía. Esto se debe principalmente a: (1)la necesidad de establecer requisitos suficientemente amplios para cubrir un gran número de casos; y (2)a la utilización de modelos determinísticos que manejan de manera superficial la incertidumbre de las variables y el proceso. Dentro de la comunidad científica, esta situación ha generado un debate sobre la necesidad de la transición de una forma de pensamiento determinística a una interpretación completamente probabilística. Recientemente, un número importante de publicaciones internacionales indican que los avances computacionales han abierto una ventana muy promisoria para la modelación cualitativa de la confiabilidad y para la elaboración de códigos y reglamentaciones de diseños más eficientes. Para que este cambio sea posible, es necesario el desarrollo de nuevas estrategias fáciles de aplicar en la actividad diaria del diseño. Este artículo llama la atención sobre la importancia del diseño probabilístico, presenta los conceptos básicos y propone la utilización de métodos de simulación (eg. Monte Carlo) en aspectos prácticos de la actividad diaria del diseño(AU)
