Browsing by Author "Vera, R."
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- ItemCorrosion products of reinforcement in concrete in marine and industrial environments(ELSEVIER SCIENCE SA, 2009) Vera, R.; Villarroel, M.; Carvajal, A. M.; Vera, E.; Ortiz, C.The corrosion products formed on embedded steel in concrete under simulated marine and industrial conditions and natural marine environment were studied. A 0.50 water/cement ratio concrete was used concrete 3.5% NaCl and 180 g L(-1) of H(2)SO(4) with 70 ppm of chloride ions solutions were used to simulate the synthetic medium. The initial electrochemical variables of the steel and pH, chlorides and sulfates profiles were measured according to the concrete depth. The morphology of the corrosive attack was determined electron microscopy (SEM), and the composition of the corrosion products was determined via scanning zer and an X-ray diffractorneter (XRD). The protective power of the corrosion products was evaluated through anodic polarization curves in a saturated Ca(OH)(2) Solution. The results from XRD and SEM show that all the resulting corrosion products correspond to lepidocrocite, goethite and magnetite mixtures: moreover, akaganeite was also identified under natural and simulated marine environments. Siderite was only detected in samples exposed to a natural marine environment. Concerning the protective nature of the corrosion products, these show lower performance in a simulated industrial environment, where the corrosion rate of the steel is up to 1.48 mu m year(-1). (C) 2008 Elsevier B.V. All rights reserved.
- ItemDiagnosis and rehabilitation of real reinforced concrete structures in coastal areas(MANEY PUBLISHING, 2012) Carvajal, A. M.; Vera, R.; Corvo, F.; Castaneda, A.A diagnosis and rehabilitation study of two reinforced concrete structures located in coastal areas in two different climates is presented. Building 1 was constructed in the north of Chile in 1949, at a distance of 600 m from the coastline, in a seismic zone. Cracks, steel corrosion, loosening of concrete cover and slab deformations have been identified. Building 2 was constructed in Habana City, Cuba, in 1973. It is located at <100 m from the shore. The structure of building 1 shows severe localised damage: loosening of reinforced cover and intense reinforcement bar corrosion due to high deposits of sea salts. High chloride and sulphate content in the concrete mass, low compressive strength in walls and slabs, high level of steel corrosion and zones with the existence of rust instead of steel were reported. A structural rehabilitation project to ensure an increase in service life is not possible. On the contrary, in case of building 2, a possible rehabilitation procedure is recommended. Elimination of chloride contaminated concrete and the use of special mortar is an option, and electrochemical chloride extraction and incorporation of sacrificial anodes is another. An important conclusion is made: the use of chloride and sulphate contaminated aggregates is more dangerous than the penetration of these two contaminants from the external environment for buildings constructed in coastal zones.
- ItemDURACON : Influencia de la acción del medio ambiente en la durabilidad del concreto. Parte 2. Resultados de Chile después de 5 años de exposición(2009) Vera, R.; Villarroel, María; Delgado, Diana; Carvajal Guerra, Ana María; De Barbieri, F.; Troconis, O.
- ItemDURACON: Effect of the Environment on Reinforced Concrete Durability. Results of Chile after 5 years of Exposure(PONTIFICIA UNIV CATOLICA CHILE, ESCUELA CONSTRUCCION CIVIL, 2009) Vera, R.; Villarroel, M.; Delgado, D.; Carvajal, A. M.; De Barbieri, F.; Troconis, O.This study presents the results obtained in Chile under the international project "Influence of Environmental Action in the durability of concrete, DURACON" that joins 11 countries (Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Mexico, Spain, Uruguay, Portugal and Venezuela) that began in 2002. The project considers the exposure of reinforced concrete specimens for at least 5 years at stations located in the marine environment (Valparaiso-PUCV) and urban (PUC-Santiago). The concrete specimens were designed with w/c 0.45 and 0.65 and characterized by determining the compressive strength and tensile strength, elastic modulus, resistivity, capillary absorption, absorption and total porosity. The corrosion of steel was evaluated by corrosion potential and corrosion current and depth of carbonation in the concrete to determine the critical onset corrosion.
- ItemEfecto de la difusión de ión cloruro en el comportamiento de acero galvanizado en estructuras de hormigón armado : resultados preliminares(2013) Vera, R.; Román, J.; Fuentes, M.; Carvajal Guerra, Ana María; Rojas, P.
- ItemMapa de corrosión atmosférica de Chile : resultados después de un año de exposición(2012) Vera, R.; Puentes, M.; Araya, R.; Rojas, P.; Carvajal Guerra, Ana María
- ItemUse of supplements and variation in the stocking rate in cow-calf systems on temperate pastures in Chile: a simulation approach(CSIRO PUBLISHING, 2009) Catrileo, A. R.; Toro, P. M.; Aguilar, C. D.; Vera, R.A simulation model was developed to evaluate the productive and economic effect of the variation in feed practices and stocking rate of a cow-calf system in Chile. Winter supplementation at grazing, stocking rate and economic aspects of the system were analysed. The supplementation of straw v. pasture hay at two different stocking rates was evaluated in the temperate pasture zone in La Araucania, Chile. Data were simulated using a decision support tool to help analyse the system. Simulations with the model involved 20 replicates of a factorial combination of two stocking rates (1.0 and 1.4 cows/ha) with differences in the initial weight ('light' v. 'heavy' with weights of heifers, primiparous and multiparous cows being 340 v. 380, 400 v. 450 and 440 v. 480 kg, respectively), at the same grazing pressure ( kg liveweight/ha), two winter supplements ( oat straw v. pasture hay) and two levels ( 6 v. 8 kg straw, and 5.1 v. 6.8 pasture hay). The model was validated with data collected from an experiment conducted with permanent pastures and a beef cattle cow-calf system from 1984 to 1989. The results indicate that there was a significant (P<0.01) effect of a cow's weight on the calves at 180 days, and on their reproductive performance, with the heavier cows increasing their calving rate by 20% relative to the lighter group. The stocking rate and the type and amount of supplement, however, did not influence (P>0.05) the weight of female and male calves at the time of sale. Finally, supplementation with pasture hay, as opposed to oat straw, incurred a larger (P<0.01) mean cost at an equivalent level of provision of metabolisable energy. Although difficult to analyse under real conditions, the economic and productive benefits of various feed practices and stocking rates were successfully evaluated in the present study using simulation tools.