Prediction of durability and service life of concrete structures and their designs have gained great importance in the recent years. This has resulted from the unsatisfactory durability performance of a number of structures built with reinforced concrete over the last few decades that puts great burden on construction budgets the world over. Corrosion in the reinforcement is the primary cause of poor durability performance of concrete structures. Other major factors that cause deterioration in reinforced concrete structures are alkali-induced reactions, chemical attack, abrasion and erosion, freezing and thawing, and shrinkage and settlement among others. Traditional approaches to durability design have mostly been based on prescribed limiting values for specified parameters of a mix design. It has been seen that subsequent development of specifications based on performance gets hampered by the lack of standardized, consistent and reliable test procedures and protocols with which performance of concrete can be evaluated.
Deterioration on reinforced concrete structures has been shown to be related to their defective construction and interaction with aggressive external substances. Hence, durability assessment of concrete structures can be made in terms of permeation properties that can be measured. Measuring the permeation properties of concrete provides a relatively accurate estimate of the durability of reinforced concrete structures. Ideally, the techniques of durability assessment and performance testing should be able to provide comprehensive information on the integrated quality of a cover made of concrete as a function of time. Before conducting the assessment, the assessor should understand that even though the quality of concrete cover can be assessed by applying performance parameters such as rate and depth of water penetration, and transport resistance to gases and ions, its durability depends on few other factors including:
- Characteristics of exposure and material that lead to micro-cracking.
- Residual moisture profile or loss of moisture.
- Seasonal and cyclic effects.
- Hydration effects.
- Electrical and conductivity properties of concrete.