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

Modeling Steel Corrosion Failure in Reinforced Concrete by Cover Crack Width 3D FEM Analysis

A new predictive 3D FEM model is proposed using the corrosion damage function by measuring the concrete cover crack width, which is a function of the free concrete cover depth, the steel rebar diameter, the mechanical properties of the concrete, and the length of the anodic zone. A significant aspect to evaluate service lifetime conditions in corroded reinforced concrete structures (RCSs) is the concrete cover crack width. Surface cracks originate due to the pressure exerted by the volume expansion of the corrosion products and oxide layer formed on the rebars. In this work, concrete cover crack width on corroded RCS is analyzed by means of finite element method allowing a corrosion damage model to be proposed. The model obtained was used to find a theoretical relationship between the dissolved steel (corrosion process) and the concrete cover crack width. The results were validated using three experimental data sets from the literature: two corrosion case studies in natural environments and one work covering accelerated corrosion in laboratory test conditions. All the beams were exposed to the simultaneous action of flexural stresses and corrosion. A good correlation was observed between the model and the experimental results, thus supporting reliability of the analytical process and validation of the proposed corrosion damage model.The authors express their gratitude to the PROMEP Program of the Autonomous University of Sinaloa and the CECYT of Sinaloa State, Mexico, for financial support. UM and DB acknowledge funding from The University of Akron, Fellowship Program FRC-207367

Finite element modelling to predict reinforced concrete corrosion-induced cracking

A finite element (FE) method was proposed to calculate the corrosion penetration depth (r) on steel reinforcement necessary for the first visible crack to appear on the concrete cover. The FE analysis was carried out using the commercial software from ANSYS. The obtained FE method is a function of free concrete cover depth (C), reinforcement diameter (D), length of the anodic zone (L), and concrete type. The results show a strong influence of localized corrosion (small-size anode versus large-size cathode) on the prediction of the r value. This influence can only be analysed three-dimensionally. The proposed FE method is validated with experimental results from literature. This approach is a novelty in considering the longitudinal direction in the analysis to account for the extension of the anodic cell. Corrosion type strongly depends on the C/L ratio, this leads to uniform corrosion for values between 0.02<C/L<0.1 and localized corrosion for values between 0.5<C/L<4.0.The authors wish to express their gratitude to the National System of Researchers of CONACYT-Mexico (SNI) for financial support. D.M. Bastidas acknowledges funding from The University of Akron

Corrosion behavior of steel embedded in ternary concrete mixtures

The main reason for the premature failure of reinforced concrete structures is corrosion of the reinforcements. The use of new mortars based on ternary mixtures, an alternative to ordinary Portland cement (OPC), requires extensive research in order to check its passivating properties for reinforcements and the instability or permanence of the passive state achieved. Pozzolans and slag extend the market for concrete by improving specific properties of concrete products, allowing them to be constructed with other materials or placed in environments that would have precluded the use of Portland cement alone. In properly formulated concrete mixtures, pozzolans and slag have been shown to enhance long-term strength, decrease permeability, increase durability, and reduce thermal cracking of bulk concrete. Steel reinforcements have been exposed for 13 months in mortars immersed in a 3.5% NaCl solution. The effect of mortar composition using ternary mixtures of fly-ash (FA), micro-silica (MS), and granulated blast furnace slag (GBFS) was tested. OPC was also tested as a reference. Electrochemical characterization was performed, measuring corrosion potential, linear polarization resistance, and electrochemical noise resistance. The best passivating properties were shown by the mixture of 10% FA and 10% GBFS. © 2011 by ESG.Peer Reviewe

Effect of cathodic protection on steel-concrete bond strength using ion migration measurements

Impressed current cathodic protection (ICCP) is a widely used method to protect steel reinforcements against corrosion. Bond degradation between concrete and steel at protection and overprotection levels was studied. Two types of materials were tested: an ordinary Portland cement (OPC) and a mixture of 85% OPC and 15% fly ash (OPC/FA). Concrete specimens were immersed in a 3.5% sodium chloride (NaCl) solution. Chemical analysis of sodium, potassium and hydrogen ions was performed using atomic absorption spectrophotometry (AAS). Hydrogen ion content was monitored using electrochemical impedance spectroscopy (EIS). Mechanical behaviour was analysed by means of pullout tests, and microstructure characterisation was carried out using scanning electron microscopy (SEM). Sodium, potassium and hydrogen ions were found at the concrete-steel interface. The mechanical properties of the specimens were poorer at overprotection level than at protection level. © 2011 Elsevier Ltd. All rights reserved.Peer Reviewe

Corrosion behavior of Zn-TiO2 and Zn-ZnO Electrodeposited coatings in 3.5% NaCl solution

Electrodeposition is a widely used method to protect metallic materials from corrosion. Electrodeposited coatings provide the metal substrate with both cathodic protection and a barrier effect. The corrosion resistance achieved with this type of zinc-electroplating process in increased by adding nanometric materials to the electrolytic bath. In the present research, coatings were obtained by electrodeposition of pure zinc, Zn-TiO and Zn-ZnO nanoparticles. The coatings were generated by immersion in a chloride acid bath applying a current density of 0.05 and 0.10 A/cm for 1 min and adding 2 g/l of TiO or ZnO nanoparticles. Corrosion behaviour was evaluated with potentiodynamic polarization curves and the electrochemical impedance spectroscopy (EIS) technique using a 3.5% NaCl test solution. After electrochemical testing, the coating surface morphology was analysed by scanning electron microscopy (SEM) and the atomic composition by energy dispersive X-ray spectroscopy (EDS). The electrodeposited coating thickness was measured using the ultrasound technique. The coating thickness was less than 2.5 μm and its corrosion resistance increased with the addition of nanoparticles.The authors would like to acknowledge the work group UANL-CA-316, and P.O. Samaniego G. D.M. Bastidas gratefully acknowledges funding from The University of Akron. Paper in memoriam of Dr. Alberto Martinez-Villafañe (†).Peer Reviewe

Effect of silica fume and fly ash admixtures on the corrosion behavior of AISI 304 embedded in concrete exposed in 3.5% NaCl solution

The use of supplementary cementitious materials such as fly ash, slag, and silica fume improve reinforced concrete corrosion performance, while decreasing cost and reducing environmental impact compared to ordinary Portland cement. In this study, the corrosion behavior of AISI 1018 carbon steel (CS) and AISI 304 stainless steel (SS) reinforcements was studied for 365 days. Three different concrete mixtures were tested: 100% CPC (composite Portland cement), 80% CPC and 20% silica fume (SF), and 80% CPC and 20% fly ash (FA). The concrete mixtures were designed according to the ACI 211.1 standard. The reinforced concrete specimens were immersed in a 3.5 wt. % NaCl test solution to simulate a marine environment. Corrosion monitoring was evaluated using the corrosion potential (E) according to ASTM C876 and the linear polarization resistance (LPR) according to ASTM G59. The results show that AISI 304 SS reinforcements yielded the best corrosion behavior, with E values mainly pertaining to the region of 10% probability of corrosion, and corrosion current density (i) values indicating passivity after 105 days of experimentation and low probability of corrosion for the remainder of the test period.This research was funded by PRODEP for the support granted by the SEP, to the Academic Body UV-CA-458 “Sustainability and Durability of Materials for Civil Infrastructure”, within the framework of the 2018 Call for the Strengthening of Academic Bodies with IDCA 28593. Funding support from The University of Akron, Fellowship Program FRC–207367

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