Durabilidad del Concreto en Ambiente Urbanos y Urnbano/Marinos de México y España

Trabajo presentado en el III Congreso Nacional ALCONPAT (Asociación Latinoamericana de Control de Calidad, Patología y Recuperación de la Construcción), celebrado en Caracas (Venezuela), en noviembre de 200

Weathering Effects of an Historic Building in San Francisco de Campeche, México

Este trabajo presenta una descripción cualitativa del fenómeno de degradación que ha ocurrido en los muros externos del bastión de San Carlos, una estructura militar construida con material calcáreo entre los siglos XVI y XVII en la ciudad colonial de San Francisco de Campeche, México. Se identificaron varias estructuras debidas al intemperismo en los morteros y las piedras calizas. Se realizaron análisis mediante microscopía electrónica de barrido (sem/eds), difracción de rayos X (xrd) y microscopía óptica (om) para determinar la naturaleza de los compuestos formados. Los resultados indican que el clima tropical provoca efectos físicos, químicos y biológicos en los materiales de construcción, principalmente debidos a la disponibilidad de agua. La influencia de esta disponibilidad de agua parece ser la causa fundamental de los daños observados en el edificio, por encima de la acción de las sales marinas o los contaminantes atmosféricos. Se observó la formación de costras ricas en carbonato de calcio, debidas al proceso de disolución y recristalización acrecentado por la abundante presencia de agua. También se identificaron neominerales como whewellita y wheddelita, relacionadas con la actividad microbiana. La presencia de elementos como cloro, sodio y azufre indican que la degradación del edificio ocurrió mediante procesis sinérgicos durante su larga exposición al ambiente tropical de San Francisco de Campeche

Concrete Carbonation in Mexico and Spain: DURACON Project, Four Year Evaluation

This work is part of the DURACON Ibero-American project, which seeks to characterize concrete durability under environmental conditions, based on reinforced concrete sample exposure in at least two different atmospheres (marine and urban), for each of the 11 countries in the project. Specimens were exposed to the environmental conditions of 13 Mexican sites (8 urban and 5 marine atmospheres). Concrete specimens were 15 x 15 x 30 cm, with 6 rebars each, and three concrete covers (15, 20 and 30 cm). Two concrete mixtures were used with water/cement ratios of 0.45 and 0.65, respectively. Six reinforced and six plain concrete specimens were placed on each exposure site. Environmental data was collected on each exposure site, including rainfall, relative humidity, time of wetness, temperature, wind velocity, and carbon dioxide/chloride concentrations. Corrosion rates and potentials, as well as concrete resistivity were measured in the reinforced samples. Carbonation depths were measured on the plain ones. The present work focused on the measurements of environmental parameters during the first two years of exposure to analyze the potentiality and the probability of carbonation-induced corrosion, and the evaluation of the corrosion initiation period for the reinforcing steel on the 13 Mexican exposure sites

Effect of the marine environment on reinforced concrete durability in Iberoamerican countries: DURACON project/CYTED

[EN] This work presents some of the results from the project: “Effect of the environment on reinforcement durability” (DURACON) in its first two-years period, which investigates the influence of urban and marine meteorochemical parameters on the performance of reinforced concrete structures. The results presented in this investigation are from 21 marine test sites only (no urban environments are included), distributed among 11 countries (Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Mexico, Spain, Uruguay, Portugal and Venezuela). The environment was evaluated using ISO Standard 9223 and the concrete was characterized by measuring compressive strength, elastic modulus, total and effective porosity, chloride permeability according to ASTM standards, as well as the effective porosity and resistance to water absorption using the Fagerlund method. To that effect, concrete specimens (with and without reinforcement) were prepared for electrochemical and physical/mechanical/chemical tests using the existing materials in each participating country, following strict procedures which enabled the preparation of similar concrete samples. Two water/cement (w/c) ratios (0.45 and 0.65) were selected, where the concrete with 0.45 w/c ratio had to have a minimum cement content of 400 kg/m3 and the one with 0.65 w/c ratio a compressive strength of 210 kg/cm2. Type I Portland cement, siliceous sand, and crushed rock as coarse aggregates (13-mm maximum nominal size) were used. After a one-year exposure, the results of the corrosion potentiality and probability analysis of the reinforcement in the different test stations showed that, for marine atmospheres, the most aggressive environment to induce steel corrosion was at Portugal’s Cabo Raso station, and the least aggressive one was at Chile’s Valparaíso station. These results are comparable with the ones found using electrochemical measurements, after a two-year exposure.Peer reviewe