Effects of Initial Surface Treatment Timing on Chloride Concentrations in Concrete Bridge Decks (original) (raw)
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Scarification and overlay (SO) procedures are often performed on concrete bridge decks to minimize the corrosion of reinforcing steel due to chloride ingress. Given the need to develop guidelines for the initial timing of SO treatments, the objectives of this research were to collect information from state department of transportation (DOT) personnel about their SO procedures and, subsequently, to recommend timing of initial SO procedures on concrete bridge decks for preventing the accumulation of corrosion-inducing levels of chlorides and extending deck service life. A questionnaire survey of state DOTs was conducted, and numerical modeling of SO treatments was performed for decks with and for decks without stay-in-place metal forms (SIPMFs). Full-factorial numerical modeling was performed through a service life of 50 years to determine the recommended initial timing of SO treatment in each case. The research results show that, overall, bridge decks without SIPMFs can endure longer delays in SO treatment timing than those with SIPMFs; the allowable delay in SO timing ranged from 2 years to 6 years for decks with SIPMFs, while the allowable delay ranged from 6 years to 18 years for decks without SIPMFs. In addition, the results show that the allowable delay also depends on the original cover depth (OCD). On average, for each additional 0.5 in (12.7 mm) of OCD, the period of additional allowable delay for decks with SIPMFs was 2 years; however, for decks without SIPMFs, the additional allowable delay was 5 years with each additional 0.5 in (12.7 mm) of OCD.
Impact of specification changes on chloride-induced corrosion service life of bridge decks
Cement and Concrete Research, 2002
A model to determine the time to first repair and subsequent rehabilitation of concrete bridge decks exposed to chloride deicer salts that recognizes and incorporates the statistical nature of factors affecting the corrosion process is developed. The model expands on an existing deterministic model using statistical computing techniques, including resampling techniques such as the parametric and simple bootstrap. Emphasis was placed on the diffusion portion of the diffusion-cracking model, but advances can be readily included for the time for corrosion deterioration after corrosion initiation.
Chloride Ion Transport in Bridge Deck Concrete under Different Curing Durations
During freezing temperatures, ice accumulates on exposed concrete slabs such as bridge decks. Deicing salts such as calcium chloride are applied to control this ice formation. These salts migrate down to the reinforcing steel, and they can break down the passivation layer on steel, causing it to corrode. This paper is part of a broader research study to explore the possibility of opening the bridge decks earlier than the 10-12 days as practiced now, by decreasing the number of wet-mat curing days. Seven concrete mixtures typically used in Texas bridge decks were evaluated for chloride permeability using the ponding test ͑AASHTO T259͒. The primary experimental variables were the curing duration, type and percentage of supplemental cementitious materials, type of coarse aggregate, duration of ponding, and the surface preparation of ponded concrete specimens. Results of the investigation indicated that curing duration may be decreased for some concrete mixtures as no apparent improvement was shown after a specific curing duration, which ranged from 2 to 8 days depending on the mix.
Long-term chloride profiles in bridge decks treated with penetrating sealer or corrosion inhibitors
Construction and Building Materials, 2015
h i g h l i g h t s Sealers applied at the time of construction alone are not effective in reducing chloride penetration over the long term. Sealers should be first applied right after construction, and then periodically reapplied. Corrosion inhibitors reduce the apparent diffusion coefficient, while penetrating sealers reduce the apparent surface concentration. The relative effect of inhibitors in reducing the diffusion coefficient would be less pronounced in higher quality concretes. The average surface C o and D for untreated Wisconsin decks are 0.574% (22.49 lb/yd 3) and 0.087 in 2 /yr (0.56 cm 2 /yr), respectively.
Development of a Chloride Concentration Sampling Protocol for Concrete Bridge Decks
2014
Development of a Chloride Concentration Sampling Protocol for Concrete Bridge Decks Sharlan Renae Montgomery Department of Civil and Environmental Engineering, BYU Master of Science As the primary cause of concrete bridge deck deterioration in the United States is corrosion of the steel reinforcement as a result of the application of chloride-based deicing salts, chloride concentration testing is among the most common techniques for evaluating the condition of a concrete bridge deck. The objectives of this research were to 1) compare concrete drilling and powder collection techniques to develop a sampling protocol for accurately measuring chloride concentrations and 2) determine the number of chloride concentration test locations necessary for adequately characterizing the chloride concentration of a given bridge deck. Laboratory experiments on concrete drilling and powder collection were conducted to compare current concrete powder sampling techniques, including constant and stepwi...
A model to determine the time to first repair and subsequent rehabilitation of concrete bridge decks exposed to chloride deicer salts that recognizes and incorporates the statistical nature of factors affecting the corrosion process is developed. The model expands on an existing deterministic model by using statistical computing techniques, including resampling techniques such as the parametric and simple bootstrap. Emphasis was placed on the diffusion portion of the diffusion-cracking model, but advances can be readily included for the time for corrosion deterioration after corrosion initiation.
Surface Chloride Levels in Colorado Structural Concrete
2018
This project focused on the chloride-induced corrosion of reinforcing steel in structural concrete. The primary goal of this project is to analyze the surface chloride concentration level of the concrete bridge decks throughout Colorado. The study indicates three factors that can affect chloride concentration levels in bridge decks: age of the concrete, traffic, and weather. Samples were collected from decks and curbs of bridges in different climate regions with various concrete ages and traffic levels. Water-soluble chloride concentrations were tested for all samples. Chloride concentration profiles for all the locations were listed and plotted. The deepest concrete powder was collected at a depth of 2 inches. The rebar level of the bridge was usually at or below this depth. The chloride concentrations of most bridge decks were below the critical values at the rebar level. The chloride concentrations of bridge decks are usually greater than that of bridge curbs. However, these bridge curbs showed deeper chloride penetration than the bridge decks. Younger bridges had much lower chloride concentrations, which is expected. Heavier traffic resulted in higher chloride concentrations. The bridges built in colder regions had a higher chloride concentration up to 2" depth (the rebar level). Climate may be the most significant influential factor among age, traffic, and climate when considering chloride concentration of bridge decks in Colorado. Corrosion protection should focus on the bridges decks who locate in the cold climate zone and with high traffic volume.
Life-Cycle Performance of Deteriorating Structures, 2003
This paper presents a probabilistic approach for predicting the chloride contamination of concrete and reinforcing steel corrosion, which takes into account the uncertainty associated with the analytical models of chloride transport, corrosion initiation, as well as damage accumulation, material properties, structural dimensions, and applied environmental and mechanical loads. The proposed approach is illustrated on an aging reinforced concrete bridge deck that has been exposed to chlorides from deicing salts for forty years. An extensive non-destructive and destructive evaluation of the corrosion-damaged deck was undertaken. The field survey data showed a considerable level of variability in all parameters measured with coefficients of variation ranging from 34% for the concrete cover depth to 86% for the diffusion coefficient. The distributions of the chloride concentration at the level of the top reinforcement mat and the time for its corrosion initiation were generated using Monte Carlo Simulation. The simulated results were very close to the field data, which illustrates the prediction capabilities of probabilistic methods as opposed to deterministic methods.
Evaluation of Time-dependent Chloride Parameters for Assessing Reinforced Concrete Bridges
proceedings of the 6th International Conference on Bridge Maintenance, Safety and Management (IABMAS), 2012
Chloride diffusivity of concrete is an important input parameter in service life prediction models. Diffusion coefficient is influenced by mix proportions, curing, compaction, pore size distribution, time, relative humidity and temperature, and decreases over time. However, many life time prediction models still consider this parameter as a constant, resulting in overly conservative durability designs, especially when GGBS or Fly ash are present in concrete mix. Some of the models proposed so far for estimating this parameter are time-dependent, while others are based on mix proportions. A laboratory program is reported, and a novel numerical model is sought for to estimate the degree of hydration as determined from the heat of hydration of concrete. Diffusion coefficients are measured using Nordtest rapid migration test; and a correlation is sought for, between the two. Tests are performed at regular intervals to allow for characterization of the influence of the aforementioned parameters.
2015
Kentucky's bridges continue to age and experience distress. The intrusion of chlorides into concrete remains the primary mechanism for deterioration. It leads to reinforcing steel corrosion that damages the adjoining concrete structure. This study found problematic chloride concentrations in Kentucky concrete bridge elements (decks, pier caps, abutments). Chloride levels have been found at concentrations sufficient to initiate reinforcing steel corrosion. In some cases, chloride concentrations were sufficient to cause accelerated corrosion and produce major section loss of reinforcing steel. Advanced stages of corrosion such as these typically require costly repairs and maintenance to extend the service life of bridges. Field inspections and laboratory analyses conducted during this study verified the ongoing problem of concrete deterioration across bridges within Kentucky's transportation network.