Reinforced Concrete: Engineering Structure and Mechanical Behavior

Dear Colleagues,

Concrete, sometimes referred to as the stone of the present day, is undoubtedly the most widely used human-made composite material, and second only to water in the entire range of materials used, without which modern construction could not function. It is a material with a great potential to adapt to specific operating conditions—environmental, it is an ecological composite, often made of local raw materials—aggregate, cement, water, admixtures and possibly mineral additives. It is not only a safe product that guarantees the stability and load-bearing capacity of a given structure, but also a sustainable, technologically advanced product used in all reinforced concrete structures.

Building objects, reinforced concrete structures should be designed in accordance with the regulations so that in the expected period of use they meet the basic requirements set for them. In addition, throughout the entire period of operation, they should be maintained in a proper technical condition, preventing excessive deterioration of their technical efficiency and functional properties. Built-in materials—reinforced concrete—are subject to aging processes over time, and their performance properties deteriorate. The level of degradation of performance should therefore be frequently checked, and damaged products should be repaired, overhauled or replaced.

Damage to reinforced concrete structures may be caused by: human errors and conditions occurring during the use of the structure.

 Structural damage caused by human error may result from:

• Improper design of the structure, e.g., in terms of strength, the composition of the concrete mix itself, selection of waterproofing, thermal or other insulation products not adapted to the conditions of use, and simultaneous use of incompatible products;
• Improper execution of the structure, e.g., improper mixing and compaction of the concrete mix, making the concrete cover of the reinforcement too thin, introducing harmful contaminants into the structure with mixing water or aggregate, inadequate concrete care, and leaky insulation.

Damage to reinforced concrete structures resulting from the conditions of use is caused by chemical and physical factors that act simultaneously or separately. The most common causes of damage to the concrete surface and concrete cover of reinforcement caused by the conditions of use, include chemical factors: aggressive substances, soft water, and alkaline aggregate reaction, while the physical factors are: erosion, thermal interactions, salt crystallization, freezing–thawing, and wear.

The harmful effects of chemicals are difficult to detect in the first stages of the reaction. Symptoms of concrete damage do not appear immediately, but only become visible after some time. Chemical substances in the environment that surrounds the structure are mainly chloride and sulphate salts and carbon dioxide. They corrode concrete or reinforcement without damaging the concrete surface and concrete cover of the reinforcement. During the corrosion of the reinforcement, rust forms, which increases the volume of the reinforcing bars and the process of exploding the concrete cover of the reinforcement begins. Cracks, scratches, rusty stains, small detachments appear on the surface of the concrete, and in the next stage, larger fragments of the concrete cover are revealed and the corrosive reinforcement is uncovered. The most common causes of corrosion in reinforcement are:

• Carbonation—caused by: rainfall, temperature, humidity, type and content of cement, and maintenance.
• Corrosive pollutants—caused by: de-icing agents, sea water, and chloride salts introduced during production or from the external environment.

Dr. Gabriela Rutkowska
Dr. Mariusz Żółtowski
Prof. Dr. Martin Krejsa
Guest Editors

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• concrete
• environmental protection
• modification
• structure
• reinforced concrete
• mechanical properties
• damage detection
• evaluation of reinforced
• technical diagnostics of reinforced concrete structures
• circular economy and resource optimization in the context of reinforced concrete structures
• the use of innovative methods of assessing damage to reinforced concrete elements
• reliability measures of reinforced concrete structure
• strength and load-bearing capacity of the reinforced concrete structure
• strengthening and modification of reinforced concrete structures
• steel in a reinforced concrete element