Corrosion Assessment Methods in Reinforced Cement Concrete

Worldwide huge amount was spent on infrastructure development projects, in which a major part is spent on demolishing deteriorated structures due to their reduction in serviceability due to various external factors. This may be attained by preventing reinforced cement concrete (RC) structures from factors that affect serviceability such as corrosion. The research community is developing various techniques to predict corrosion in RC structures to prevent the structure in the initial stages by carrying out maintenance work instead of going for the reconstruction of deteriorated structures. The corrosion of RC structures was mainly caused by chloride ions penetrating the structure or by carbonation. This coefficient can be used to predict the rate of corrosion in concrete. Electrochemical measurement, Eddy current, Half-cell potential measurement, etc., are the experimental techniques to forecast the corrosion rate in concrete reviewed. Recently various software’s like Life 365, Thermos calc, Concrete Compass, etc., were developed to predict the corrosion rate in RC structures. This research paper reviews the effectiveness of the application of software to predict corrosion rate in RC structures by reviewing previous research works to identify an accurate method to be followed

Investigation of mechanistic deterioration modeling for bridge design and management

2017 Spring.Includes bibliographical references.The ongoing deterioration of highway bridges in Colorado dictates that an effective method for allocating limited management resources be developed. In order to predict bridge deterioration in advance, mechanistic models which analyze the physical processes causing deterioration are capable of supplementing purely statistical models and addressing limitations associated with bridge inspection data and statistical methods. A review of existing analytical models in the literature was conducted. Due to its prevalence throughout the state of Colorado and frequent need for repair, corrosion-induced cracking of reinforced concrete (RC) decks was selected as the mode of deterioration for further study. A mechanistic model was developed to predict corrosion and concrete cracking as a function of material and environmental inputs. The model was modified to include the effects of epoxy-coated rebar, waterproofing membranes, asphalt overlays, joint deterioration, and deck maintenance. Probabilistic inputs were applied to simulate inherent randomness associated with deterioration. Model results showed that mechanistic models may be able to address limitations of statistical models and provide a more accurate and precise prediction of bridge degradation in advance. Preventative maintenance may provide longer bridge deck service life with fewer total maintenance actions than current methods. However, experimental study of specific deterioration processes and additional data collection are needed to validate model predictions. Maintenance histories of existing bridges are necessary to predicting bridge deterioration and improving bridge design and management in the future

Fiber reinforced polymer bar investigation: Long-term in-situ durability and bond strength assessment in conventional and sustainable concrete

Corrosion of steel reinforcement and carbon dioxide emissions are two major global problems. Different methods, techniques, and materials have been implemented to mitigate these problems. Glass fiber-reinforced polymer (GFRP) bar presents itself as a solid alternative to replace conventional steel reinforcement owing to its fantastic features in resisting corrosion. Its demand is progressively increasing. Cement-based concrete, on the other hand, is not eco-friendly due to the excessive amount of carbon dioxide (CO2) emissions yielded from its cement production. One of the alternatives used to mitigate the use of cement in concrete is fly ash. Fly ash is considered a supplementary cementitious material (SCM) and has been only implemented partially to replace cement as a binding material in concrete, however its application has been limited to only limited doses (lower than 30%). In this study, durability and bond-slip investigations were carried out. The durability study was done on GFRP bars extracted from eleven bridges across the United States after being in service from 12 to 20 years. Several tests were conducted on the bar and the surrounding concrete to make the assessment. The tests results showed that there were slight sings for environmental attack but did not show any obvious signs for microstructural deteriorations. In addition, a bond-slip investigation was carried out to evaluate the bond performance of GFRP bars embedded in fly ash-based sustainable concrete. A high-volume fly ash (HVFA) concrete was implemented; 50% and 70% cement replaced with fly ash were used. The results showed that GFRP bars had less bond strength than that resulted from mild steel bars --Abstract, page iv

Corrosion Susceptibility of Internally Reinforced Soil Retaining Structures

DTFH61-83-C-00010The current state of knowledge in the area of metal corrosion in reinforced soil retaining walls has been assessed. It was found that data is missing in several areas including the performance of the metal reinforcement in a highly alkaline environment as well as in the presence of high chloride concentrations. Moreover, no quantitative information was found on the effect of climatological conditions. In order to determine whether there are any corrosion problems in completed Reinforced Earth walls, four such walls were selected for study. All four walls are in relatively severe environments. It was determined that two of the above walls may have corrosion problems which could reduce their design life. It is recommended that further field studies be undertaken in order to assess the magnitude of the problems. It is further recommended that research be conducted to determine the safe limits of the reinforced earth concept

Evaluation of Corrosion Protection Methods for Reinforced Concrete Highway Structures

Since the 1970s, research projects and field studies have been conducted on different methods for protecting reinforced concrete bridges from corrosion damage. The methods include alternative reinforcement and slab design, barrier methods, electrochemical methods, and corrosion inhibitors. Each method and its underlying principles are described, performance results of laboratory and/or field trials are reviewed, and systems are evaluated based on the results of the trials. Using performance results from the studies and costs obtained from transportation agencies, an economic analysis is used to estimate the cost of each system over a 75 year economic life using discount rates of 2, 4, and 6%. Epoxy-coated reinforcing steel is the most common corrosion protection method used in the United States today. Although controversial in many areas, epoxy-coated reinforcement has performed well in many states, including Kansas, since it was introduced in the early 1970s and is a low-cost backup to many other corrosion protection options. Research on stainless steel reinforcement indicates that it may remain free of corrosion in chloride contaminated concrete for more than 75 years. At a low discount rate (2%), solid stainless steel reinforcement is a cost-effective option compared to other options, but at higher discount rates (4%+), the present value cost of a deck with solid stainless steel is significantly higher than that of an unprotected deck. Stainless steel clad reinforcement is much less expensive than solid stainless steel reinforcement. The performance of stainless steel-clad reinforcement will be similar to that of solid stainless steel bars if the stainless steel coating is continuous and if the black steel core, exposed at the bar ends, is protected so that it does not come into contact with concrete pore solution. The present value of the cost of a bridge deck built with stainless steel-clad reinforcement is significantly lower than the present value for the cost of any other corrosion protection system. This method should be considered for experimental use. Solid stainless steel should be considered, as well, if a low discount rate (around 2%) is used. Hot rubberized asphalt membranes are the least expensive option, other than stainless steel-clad reinforcement. Hot rubberized asphalt and spray-applied liquid membranes should be considered for use on future projects. In laboratory tests, corrosion inhibitors have been shown to provide protection to steel in chloride contaminated concrete, but information on their performance in the field is limited. Both calcium nitrite and organic corrosion inhibitors have the potential to be cost-effective, if they perform as well in the field as they have in the laboratory, and should be considered for experimental use

Comprehensive Bridge Deck Deterioration Mapping of Nine Bridges by Nondestructive Evaluation Technologies Final Report, January 2011

The primary objective of this research was to demonstrate the benefits of NDT technologies for effectively detecting and characterizing deterioration in bridge decks. In particular, the objectives were to demonstrate the capabilities of ground-penetrating radar (GPR) and impact echo (IE), and to evaluate and describe the condition of nine bridge decks proposed by Iowa DOT. The first part of the report provides a detailed review of the most important deterioration processes in concrete decks, followed by a discussion of the five NDT technologies utilized in this project. In addition to GPR and IE methods, three other technologies were utilized, namely: half-cell (HC) potential, electrical resistivity (ER), and ultrasonic surface waves (USW) method. The review includes a description of the principles of operation, field implementation, data analysis, and interpretation; information regarding their advantages and limitations in bridge deck evaluations and condition monitoring are also implicitly provided.. The second part of the report provides descriptions and bridge deck evaluation results from the nine bridges. The results of the NDT surveys are described in terms of condition assessment maps and are compared with the observations obtained from the recovered cores or conducted bridge deck rehabilitation. Results from this study confirm that the used technologies can provide detailed and accurate information about a certain type of deterioration, electrochemical environment, or defect. However, they also show that a comprehensive condition assessment of bridge decks can be achieved only through a complementary use of multiple technologies at this stage,. Recommendations are provided for the optimum implementation of NDT technologies for the condition assessment and monitoring of bridge decks

Development of Deterioration Models for Bridge Decks Using System Reliability Analysis

Generally, in the existing Bridge Management Systems(BMS) deterioration is modeled based on the visual inspections where the corresponding condition states are assigned to individual elements. In this case, the limited attention is given to the correlation between bridge elements from structural perspective. In this process, the impact of the history of deterioration on the reliability of a structure is disregarded which may lead to inappropriate conclusions. The Improved estimate of service life of a bridge deck may help decision makers enhance the intervention planning and optimize the bridge life cycle costs. A reliability-based deterioration model can potentially be an appropriate replacement for the existing procedures. The objective of this thesis is to evaluate the system reliability of conventional bridges designed based on the existing codes. According to the methodology developed in this thesis, the predicted element-level structural conditions for different time intervals are applied in the non-linear Finite Element model of a bridge superstructure and the system reliability indices are estimated for different time intervals. The resulting degradation curve could be calibrated and updated based on the outcomes of the visual inspections. Also, the reliability of innovative bridges that use non-conventional materials or structural forms such as Steel-Free Deck System has been evaluated by applying the newly developed method. The available deterioration models for conventional superstructuresare not applicable for the innovative bridge systems. Since there is no established deterioration model available for these innovative structures, it is difficult to predict the reliability of such bridges at different time intervals. The method developedhere adopts the reliability theory and establishes deterioration models for conventional and innovative bridges based on their failure mechanisms. This method has been applied in simply-supported traditional reinforced-concrete bridge superstructures designed according to the Canadian Highway Bridge Design Code (CHBDC-S6), and in an innovative structure with a Steel-Free Deck System, namely the Crowchild Bridge, in Calgary, Canada, as case studies. As an example to show the application of such developed deterioration curve, the developed model has been adopted in an old superstructure in Montreal. The results obtained from the newly developed model and bridge engineering groups’ estimations are found to be in accordance. Based on the reliability estimates, the conventional bridges designed based on the new code are found to be in a good condition during the initial stages of their service life,but their condition degrades faster once corrosion in steel reinforcements is initiated and spalling of concrete becomes evident. In case of the Steel-Free Deck, there is a low probability of failure at the end of the 75 years of its service life. It is found that the element-level assessment of a concrete deck is a conservative approach, since the interaction between the structural elements results in considerably higher reliability index and lower probability of failure. This thesis demonstrates how the proposed system reliability-based evaluation method can be adopted in determining the structural condition of a bridge which represents an important step forward in Bridge Management Systems. The system reliability deterioration model can be easily integrated to the existing Bridge Management Systems (BMS) by replacing the existing condition index by the reliability index or adding it to the assessing process as an additional parameter