Predicción de la vida útil en servicio de edificios de 50 años expuestos a ambientes marinos

Abstract

Steel reinforcing bars are often coated with rusts formed during service in reinforced concrete (RC) structures. Rust layers growing on steel rebars induce expansive stresses and cause cracking on cover concrete. This study uses steel corrosion rate results measured on reinforced concrete buildings of more than 50 years of age located in marine environments and considers the pressure generated by the volume expansion of corrosion product layers to calculate the service life of the RC structures using a numerical simulation, estimating the time to corrosion cracking of the concrete cover. Akaganeite, goethite, lepidocrocite, hematite, magnetite and maghemite were identified by X-ray diffraction as crystalline phase constituents of the rust layers. RESUMEN: Predicción de la vida útil en servicio de edificios de 50 años expuestos a ambientes marinos.Los refuerzos corrugados de acero embebidos en hormigón, presentan con frecuencia una capa de herrumbre formada durante la vida en servicio de las estructuras de hormigón armado (EHA). Las capas de óxido, productos de corrosión, que crecen en los refuerzos de acero inducen tensiones expansivas y causan el agrietamiento del recubrimiento de hormigón. El presente estudio utiliza los resultados de la velocidad de corrosión del acero corrugado, medidos en edificios de más de 50 años, construidos con hormigón armado, ubicados en ambientes marinos. El estudio considera la presión generada por la expansión de volumen de las capas de productos de corrosión para calcular la vida útil en servicio de las EHA utilizando una simulación numérica, estimando el tiempo hasta la fisuración por corrosión del recubrimiento de hormigón. Akaganeita, goethita, lepidocrocita, hematita, magnetita y maghemita fueron identificadas por difracción de rayos X, como constituyentes de las fases cristalinas de las capas de óxido.

Corrosion Fatigue Numerical Model for Austenitic and Lean-Duplex Stainless-Steel Rebars Exposed to Marine Environments

“…First of all, the specimens were exposed to simulated tidal marine environments for 6 months. The chloride content in a seawater tidal zone was assumed to be 3.5 wt.% NaCl, according to the literature [43,44]. The specimens were equally divided and placed in two polyvinyl chloride (PVC) tubs.…”

Predicción del agrietamiento inducido por corrosión en hormigón armado mediante modelización por elementos finitos

“…The molar volume (V m , cm 3 •mol -1 ) of an iron oxide is defined as the ratio between the molar mass and the density of a given oxide phase. Table 1 presents the a coefficient of oxide molar volume expansion to iron consumed in the corrosion process for a marine environment in the presence of chloride ions (Sánchez-Deza et al, 2017;Sánchez-Deza et al, 2018):…”

“…Each reinforcement has a pipe tubular part Table 1. Molar volume (V m ) and molar volume expansion ratio coefficient (a) (a = V m(oxide) /V m(Fe) ) for oxides of iron generated in a marine environment (Sánchez-Deza et al, 2017;Sánchez-Deza et al, 2018). composed of three regions: two end regions protected with PVC covers and an exposed central region (anodic zone) to measure deformation and to calculate the pressure during an accelerated corrosion process applying a current density of 0.1 mA•cm −2 .…”

“…The reliability of the common thick-walled concrete cylinder approach, under the action of internal pressure originated by the expansion of iron oxide of the corroded steel rebar, is only approximate (Sánchez-Deza et al, 2018). This may be attributed to the boundary conditions, see Fig.…”

“…The spatial gap left by the consumed iron is not enough to accommodate these oxides, which have a higher volume and lower density than iron (Sánchez-Deza et al, 2017), and their growth generates pressure on the surrounding concrete cover. When the expansion stress of the iron oxides surpasses that of the concrete, cracking and spalling can take place (Sánchez-Deza et al, 2018).…”