Concrete is an indispensable construction material of modern age. The properties of concrete are greatly dependant on the constituents, workmanship, water-cement ratio, compaction, curing etc. Direct assessment of the strength of concrete is not possible because direct tests induces destructive stresses and causes failure of the structure. So the concrete strength is tested using standard specimens made with the same mix as that of the structure. But the test specimens can vary from the actual structure in properties due to difference in compaction, size, shape, curing etc. To identify the properties of existing structures, the only possibility is to cut out a standard core and testing it. But this method cannot identify reinforcement corrosion and cracks and can impair with the strength of thin members. Nondestructive testing (NDT) has the ability to determine the strength and durability properties of critical structures without damaging them. The tests can be carried out on site on existing structures as well as on structures under construction. Further NDT does not interfere with the normal performance of the structure.