The steel reinforced concrete structures perform well in various environmental conditions, but structures may undergo premature damage in aggressive environments such as marine or acidic, primarily due to steel corrosion, and substantial reduction in service life occurs. This also causes huge economical loss and create safety and environmental problems. The repair and maintenance of steel reinforced concrete structures for their safety needs effective monitoring and inspection systems for evaluating the corrosion condition of steel. Since the corrosion of steel reinforcement occurs through electrochemical reactions, electrochemical methods are suitable to study the corrosion processes. In this chapter, some commonly used electrochemical techniques have been comprehensively explained. In addition, there is a critical requirement to develop effective and long-lasting techniques to control the corrosion of steel. Hence, some of the commonly used corrosion control methods have been comprehensively described in this chapter.
Top1. Introduction
Prior to the invention of cement, mortars were made by mixing water, sand and slaked lime (Lazell, 1915). John Smeaton discovered hydraulic lime mortars in 1754 (Searle, 1935). A British mason named Joseph discovered the cement in 1824 and filed the first patent on Portland cement (Gagg, 2014). However, the objects prepared with the use of Portland cement were extremely brittle and incapable to tolerate shocks. Joseph Monier, a French gardener in 1867 made flowerpots with embedded iron nails and consequently observed a remarkable enhancement in the durability of his pots. Afterward, efficient scientific developments in concrete manufacture took place. In 1911, American Society for Testing and Materials (ASTM) formulated a detailed specification for the utilization of steel in concrete (Singh & Venugopalan, 2013). Subsequently, various developments ensued in designing the steel reinforcement bars in order to produce stronger and durable concrete structures. Consequently, the steel-reinforced concrete became the most widely used structural material in the world because of its economical, strength and durability properties. Steel-reinforced concrete structures were viewed as maintenance-free and unlimited service life until the mid-1970s. Conversely, since then, several durability related problems have emerged, such as alkali-silica reactions, sulphate attacks and corrosion of steel reinforcement. Among all durability related problems in steel-reinforced concrete structures, corrosion of steel reinforcement has been recognized as the main source of deterioration (Zhao & Jin, 2016).
Generally, the corrosion affects our daily lives directly as well as indirectly. In direct, it shortens the useful service life of our goods. In indirect, the manufacturer and provider of goods and services incur costs of corrosion from the clients. In particular, the corrosion of reinforcing steel bar in concrete results the collapse of bridges, failure of a part of highways, damage to buildings, and parking structures, etc. consequently endangers public safety and requires considerable repair costs. For instance, the unexpected collapse of the Silver Bridge over the Ohio River at Point Pleasant due to corrosion fatigue in 1967 resulted in deaths of 46 people and cost millions of dollars (“The Effects and Economic Impact of Corrosion,” 2000). Therefore, in order to estimate the cost of corrosion in the United States (US), a study entitled “Corrosion Costs and Preventive Strategies in the United States” was conducted with the help of Federal Highway Administration (FHWA) and National Association of Corrosion Engineers (NACE) International, from 1999 to 2001 by CC Technologies Laboratories. This investigation estimated the average direct cost of corrosion of $8.3 billion per year for highway bridges alone and the total corrosion cost of US industries was estimated to $276 billion annually, which is approximately equal to 3.1% of the US Gross Domestic Product (GDP) (G. H. Koch, Brongers, Thompson, Virmani, & Payer, 2002). In 2014, a study entitled “International Measures of Prevention, Application, and Economic of Corrosion Technologies (IMPACT)” was initiated by NACE International and conducted by Det Norske Veritas (DNV), Germanischer Lloyd (GL), and American Productivity and Quality Center (APQC) and its industry and technology partners worldwide. From this study, the cost of corrosion at the global level is estimated to be $2.5 trillion per year, which is about 3.4% of the global GDP in 2013 (G. Koch et al., 2016). Hence, from the safety and economical perspective, the corrosion of steel reinforcement is very serious problem that can affect the sustainability of the steel-reinforced concrete structures directly. Numerous studies have been conducted worldwide in order to extend service life of steel reinforced concrete structures; regardless of this, several aspects are still not well known, and there is the requirement to incorporate present facts into practical field.
This chapter is organized in two major thematic sections. In the first section, an overview of various corrosion monitoring techniques for steel reinforced concrete has been undertaken. The second section includes studies related to the different corrosion control methods for steel reinforced concrete.