Ana María Carvajal

Reinforced Concrete Durability in Marine Environments DURACON Project: Long-Term Exposure

This paper presents the results, after a long-term evaluation in marine environments, from an Ibero-American project called “Effect of the environment on reinforcement durability” (DURACON). This p...

Concrete Carbonation in Ibero-American Countries DURACON Project: Six-Year Evaluation

Concrete carbonation data from 16 test sites in 9 countries (Bolivia, Chile, Colombia, Costa Rica, Mexico, Spain, Uruguay, Portugal, and Venezuela) were compared to identify concrete performance du...

Estudio del efecto del ambiente marino-industrial en estructuras de hormigón armado que poseen protección superficial de mortero con acrílico incorporado

Resumen es: Esta investigacion presenta analisis y resultados experimentales del comportamiento de recubrimientos superficiales tipo mortero, en probetas de hormigon...

Effect of Last Generation Additives on the Concrete Durability

The influence of carbonation on corrosion of reinforcement depends on the degree of ease of diffusion of CO2 through the concrete from its surface, also on environmental conditions, on the pore structure of concrete (cement, aggregates, and water (without additives)) and on the W / C, where a high ratio generates porous and permeable mortar and concrete (Duran C., 2003; Troconis O. et al., 2006). Permeability is not necessarily related to porosity, but depends on the geometry of the pores and the distribution of pore sizes: two porous bodies can have similar porosities but different permeability, so it is important to consider the penetration of CO2 into the concrete. If the concrete is not permeable, the attack will be relatively superficial and limited to the surface. The attack in concrete is governed by molecular diffusion, which is much slower than convection processes. The use of concrete with low permeability is the primary means to prevent or minimize the effects of external attack (Morin et al., 2001; Papadakis et al., 1992). A well-proportioned mix of aggregate, which follows a continuous grading curve will produce concrete of good workability, high cohesion and a reduced tendency to segregation. At the same time it will be slightly porous and therefore possess a prolonged durability. Superplasticizer additives added to the mix, filling the interstitial space between large particles, which can cause a high density, high strength and resilient material, with a smaller amount of mixing water (Erdogdu S., 2000; Morin et al., 2001). The main mechanism for CO2 transport in concrete is difusion, and with moisture, carbonation leads, a phenomenon to be considered from the viewpoint of durability of reinforced concrete (Carvajal et al., 2006). There are expressions that relate the diffusion coefficient of concrete with compressive strength, where increase of resistance, decrease of diffusion coefficient. Because the phenomenon of diffusion of gases is of long-term, resistance in ancient age must to be taken into account and not the resistance usually specified at 28 days.

Metodología de Obtención de Muestras de Hormigón en Polvo para Análisis de Cloruro y Correlación entre el Contenido de Cloruros en Ambiente Marino Real por Cinco Años y Ambiente Acelerado de Muestras de Hormigón

La contaminacion de obras de hormigon armado por agentes quimicos agresivos ha sido y sigue siendo un problema grave y de gran relevancia en lo que respecta a la durabilidad y funcionalidad de estas, lo que genera gran preocupacion debido a la poca informacion existente sobre su efecto real y la forma en que se puede afrontar con el fin de otorgar seguridad a obras afectadas por los grandes enemigos del hormigon armado, como lo son los iones cloruro. Se consultaron normas extranjeras para obtener una metodologia de obtencion de muestra de hormigon para el posterior analisis del contenido de iones cloruro, ya que las normas chilenas no lo indican. Las normas ASTM C 42/C 42M – 04 “Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete” ASTM C 1218/C 1218M – 99 “Standard Test Method for Water-Soluble Chloride in Mortar and Concrete” y ASTM C 1152/C 1152M – 04 “Standard Test Method for Acid-Soluble Chloride in Mortar fueron de utilidad para la obtencion de una muestra representativa de hormigon para ser empleada en los analisis cuantitativos de iones cloruro Debido a la importancia de encontrar una metodologia para el analisis cuantitativo de este tipo de iones, se analizaron distintas normas que tienen relacion con el analisis de iones cloruro, tanto nacionales como extranjeras, y se ha podido comprobar que las formulas de calculo no son consecuentes pues no dan los mismos resultados (ASTM C-114 con NCh 1444 Of 80 y NCh1498 Of 82). Se ha analizado el contenido de cloruros de probetas de hormigon armado que fueron expuestas durante cinco anos al agua de mar, en condicion de semiinmersion, en San Antonio, Puertecito, V Region de Valparaiso, como tambien de probetas gemelas sometidas a ciclos de semiinmersion secado en laboratorio en camara acelerada, con el fin de comparar ambas situaciones, encontrandose una relacion entre estos. Palabras clave: Determinacion de cloruros, ambiente acelerado, ambiente real.

The Use of Polarization Resistance to Evaluate the Environmental Impact on Reinforced Concrete Structures in the Iberoamerican Region

This work presents the three-year results of the project: Effect of the environment on reinforcement durability (DURACON), which is investigating the influence of the meteorochemical parameters of marine and coastal-marine environments on concrete durability performance, by measuring the electrochemical parameters (corrosion rate and corrosion potential) of the embedded reinforcing steel. To that effect, concrete specimens were exposed to the marine environments making a total of 21 test stations distributed among ten countries (Argentina, Bolivia, Chile, Colombia, Costa Rica, Mexico, Spain, Uruguay, Portugal and Venezuela). This paper presents the reinforcement electrochemical evaluation, which allows identifying its corrosion activation. The chloride ions concentration which induces the reinforcement corrosion is also presented, depending on the environment to which the concrete specimens were exposed.