The deterioration of concrete structures in the last few decades calls for effective methods for condition evaluation and maintenance. This resulted in development of several nondestructive testing (NDT) techniques for monitoring civil infrastructures. NDT methods have been used for more than three decades for monitoring concrete structures; now it has been recognized that NDT plays an important role in the condition monitoring of existing RC structures. NDT methods are known to be better to assess and evaluate the condition of RC structures practically. This paper reviewed several available NDT methods developed and used in the last few decades. 1. Introduction Testing and quality checkup are important at different stages during the life of a structure. To properly maintain the civil infrastructures, engineers required new methods of inspection. Better inspection techniques are needed for deteriorating infrastructure (Rens et al., 1997) . The traditional method of evaluating the quality of concrete in civil structures is to test specimens casted simultaneously for compressive, flexural, and tensile strengths; these methods have several disadvantages such as results are not predicted immediately, concrete in specimens may differ from actual structure, and strength properties of a concrete specimens depend on its size and shape; therefore to overcome above limitations several NDT methods have been developed. NDT methods depend on the fact that certain physical and chemical properties of concrete can be related to strength and durability of structures. These methods have been used for more than three decades for evaluating the condition of a structure; now in the present century NDT has become more sophisticated, as it has developed from a hammer to Impact Echo and Impulse response (Lim and Cao, 2013) . NDT has been defined as comprising methods used to examine objects, materials, or systems without impairing their future usefulness, that is, inspect or measure without harm. NDT methods are now considered as powerful tools for evaluating existing concrete structures with regard to their strength and durability. NDT methods have been drawing more and more attention, in the sense of reliability and effectiveness. The importance of being able to test in situ has been recognized, and this trend is increasing as compared to traditional random sampling of concrete for material analysis (Shaw and Xu, 1998) . NDT methods may be categorized as: penetration tests, rebound tests, pull out tests, dynamic tests, and radioactive methods. According to McCann
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