Plant and Laboratory Scale Studies of High Performance Concrete for Bridge Decks in West Virginia

High-performance concrete (HPC) is increasingly used in bridge decks due to its high strength, superior durability and low maintenance resulting in durable and cost effective bridges. FHWA strongly recommended developing suitable HPC mixtures using local material sources and construction technologies for a specific location or state.;As part of a comprehensive R&D program, a field implementation of laboratory developed HPC mixtures was proposed. From a total of eight mixtures developed in the lab with w/cm=0.40, three HPC mixtures were selected using specific local aggregates, in addition to supplementary cementitious materials and chemical admixtures. From these mixtures, three test slabs were produced at a concrete plant in West Virginia, by simulating typical construction practices. The plant-produced slabs were monitored and evaluated for temperature, weather, fresh, hardened, and durability properties for over 90 days from summer to early winter. Maturity-strength relationships were established. Microscopic determination of air-void parameters were conducted using a proposed new method and compared with standard method. Finally, concrete cores were examined by petrography to determine w/cm ratio, compositional variations, and other possible depositions within hardened slabs. The properties of field-mixed match-cured, field-mixed laboratory-cured and laboratory-mixed specimens were compared to check the performance of concrete designed in the laboratory and used in the field.;The results showed that all combinations performed well, with slag + silica fume combinations being the best in terms of compressive strength, resistance to freezing and thawing, and chloride ions penetration. The proposed new method for estimating the air-void parameters was found to be more representative than standard methods. The petrographic examination revealed that aggregates, w/cm ratio, and cementitious materials contents were consistent with the original mixture design. This study will be used to develop guidelines for full-scale demonstration projects for the state of West Virginia

Album de asombros

Colombia mágica. Diego Samper Martínez. Editerial Colina, Medellín, 1993, 222 págs., ilus

Emprendedores éticos e industriosos

Ética, trabajo y productividad en Antioquia. Alberto Mayor Mora. Ediciones Tercer Mundo. Bogotá. 1984, 537 págs., (ilutrado

¿“Fisuras” o asimilaciones?

Fisuras del arte moderno en Colombia. Carmen María Jaramillo. Imprenta Distrital, Bogotá, 2012, 393 págs., il

Una vida para enseñar y pintar

Rafael Sáenz: profesar la pintura. Luz Análida Aguirre Restrepo. Editorial Universidad de Antioquia, Medellín, 2013, 166 págs., il

Essays in Centralized Market Allocaitons

A long-standing policy concern in many countries is the difficulty of filling medical positions in rural areas. In Colombia, the Ministry of Health requires newly graduated health professionals to work in a rural or marginalized urban area for a year in order to receive professional certification. The decentralized mechanism used until 2013 to allocate graduates to slots was one that health professionals could manipulate to avoid an assignment. In 2014, a single-offer centralized mechanism that cannot be manipulated to avoid an assignment, based on Gale and Shapley’s deferred acceptance algorithm, was adopted. Following a revealed preference approach, I estimate health professionals’ hospital preferences using the 2014 data. Using these estimates and the fact that under the decentralized mechanism health professionals were able to avoid positions that fall below their acceptance threshold, I obtain the average marginal utility a health professional would require to accept a position by simulating the outcome had the decentralized mechanism still been in use. Then, I simulate the outcome of the centralized mechanism in the absence of the requirement that students accept the assignment determined by the mechanism. I find that, given the choice, about 30% of physicians would be left unassigned, im plying that it is important for the policy’s success that assignments be mandatory. I review many algorithms that have been discussed in the literature and find some that result in significant welfare gains. Finally, I show that, in this setting, there is no evidence that manipulable mechanisms can yield a higher welfare gains

Las servidumbres administrativas y sus consecuencias en el régimen de la propiedad privada

Since the beginning of community life, it has been necessary to establish limits to private property in order to meet the social needs that are demanded.Within the scope of the limitations we are going to study administrative or public utility easements whose main foundation is the general interest or public utility that private property represents for society Administrative easements are such an everyday institution that goes unnoticed even for jurists, we take for granted the existence of roads, airports, the light of our houses and even the beaches in which we bathe. However, we do not see the legislative reality that exists behind what is called the public domain and how its establishment affects the owners of the land on which they are constituted. The object of study of this work will analyze the difficulties in conceiving this institution, the most important administrative easements and the problem in reference to economic compensation, encompassed not only from the field of civil legislation, but also administrative and urban planning.Desde el origen de la vida en comunidad ha sido necesario establecer límites a la propiedad privada con el objetivo de satisfacer las necesidades sociales que se demandan. Dentro del ámbito de las limitaciones vamos a estudiar las servidumbres administrativas o de utilidad pública cuyo fundamento principal es el interés general o utilidad pública que la propiedad privada representa para la sociedad. Las servidumbres administrativas son una institución tan cotidiana que pasa desapercibida incluso para los juristas, damos por hecho la existencia de carreteras, aeropuertos, la luz de nuestras e incluso las playas en las que nos bañamos. Sin embargo, no vemos la realidad legislativa que existe detrás de lo que se denomina el dominio público y de cómo su establecimiento afecta a los dueños de los terrenos sobre los que se constituyen. El objeto de estudio de este trabajo analizará las dificultades a la hora de concebir esta institución, las servidumbres administrativas más destacadas y el problema respecto a su compensación económica, abarcada no solo desde el ámbito de la legislación civil, sino también administrativa y urbanística