Evaluation and Optimization of Corrosion Performance of Reinforced Concrete

Dear Colleagues,

Corrosion of steel reinforcement is one of the main causes of deterioration of reinforced concrete structures around the world. In the Gulf Region, corrosion of reinforcement is a very serious threat to RC structures due to the severe conditions of marine environments and high temperature, especially in the coastal areas along the Arabian Gulf. Research has been in progress for several decades to address this corrosion and improve the sustainability of RC structures. However, past research has not been able to find an ultimate solution to the problem of corrosion of steel bars in concrete. This issue still remains a vital area of research and a major point of concern at present.

This Special Issue will focus on the investigation of corrosion for steel-reinforced concrete including modeling, experimentation, corrosion processes, mechanisms, theories involved therein, methods and materials. It will also focus on the development of corrosion inhibitors, rust converters, coatings, films, passive layers, additives, etc. The investigations will be carried out in a multi-scale environment focusing on macro, micro and nano scales. Both structure and material perspectives will be included for a thorough and comprehensive investigation. Various environmental conditions will be incorporated, especially pertaining to the hot and humid weather of the Gulf Region responsible for corrosion of steel-reinforced concrete infrastructure. The outcome of this Special Issue will be a better understanding of corrosion phenomena in concrete structures, corrosion protection and maintenance and development of new methods and materials for sustainable rust-proof steel-reinforced concrete infrastructure.

Steel reinforcement in concrete is protected initially by a thin layer formed on the surface of rebars called the passive layer. However, if this passive layer is destroyed due to the attack of chloride ions, chloride-induced corrosion of the reinforcement will be initiated. This corrosion will continue as long as a supply of both moisture and oxygen is available. The amount of chlorides on the surface of the rebar embedded in concrete that can break the passive layer and hence initiate corrosion is called the “chloride threshold value”. Many factors influence the chloride threshold value for corrosion initiation of steel rebar embedded in concrete. Temperature is known to be one of the major factors that have significant effects on corrosion. However, only limited studies have addressed the effect of temperature on the chloride threshold value, with contradictory outcomes. Therefore, the current Special Issue will investigate the effect of high exposure temperatures on the chloride threshold value. It is speculated that free chloride maximum limits specified in various building codes may not be sufficient at high exposure temperatures. The chloride limits specified in the codes for various exposure conditions may need to be assessed/modified considering exposure class and the effect of high temperature.

This Special Issue will also focus on the influence of rebar elemental composition, alloying, microstructure and methods of manufacture on the corrosion of RC structures. The corrosion resistance performance of concrete rebars rolled from fine-grained microalloyed steels will be evaluated vis à vis rebars rolled from steel having similar chemistry but subjected to thermomechanical treatment after hot rolling. Three test environments, namely, simulated concrete pore solution, mortars and an industrial atmosphere, will be used to assess the performance of these rebars. Mass loss, electrochemical impedance spectroscopy and Raman spectroscopy measurements may be used to acquire quantitative data and explain the observed results. Another area of research for this Special Issue is the development of economical, eco-friendly and easy to apply rust-stabilizing surface treatments for steel reinforcement bars in concrete exposed to harsh environments of the Gulf Region. Development of new classes of corrosion inhibitors and coatings for rust protection of concrete rebars will also be included. The influence of natural pozzolan, silica fume, fly ash and several other chemical/natural admixtures on the development of a passive layer for corrosion protection of steel rebars under concrete environments will also be covered. Steel reinforcement bars attain a very stable state of passivity in the presence of high-alkaline concrete. However, the passivity is lost and corrosion starts once chlorides, sulphates and other aggressive ions reach the steel–concrete interface. The rate of corrosion increases drastically under conditions of hot weather and marine environments. Soil, water and climatic conditions of the region are highly favorable to cause depassivation of rebars, resulting in severe corrosion of reinforced concrete structures. Use of proper corrosion inhibitors in concrete is reported to increase the chloride threshold value; prevent chlorides from reaching the steel bar; deposit and develop a protective layer; strengthen the passive layer; stabilize the corrosion products; and react with the rebar surface to form a stable non-corrosive layer under normal conditions. All these key areas will be focused on in this Special Issue of Applied Sciences.

Prof. Dr. Raja Rizwan Hussain
Guest Editor

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