The paper presents the assessment of concrete strength for three buildings with different ages situated on the east coast at various distances from the sea. Rebound hammer and ultrasonic pulse velocity are used for the assessment of concrete strength, and half cell potential tester to detect the probability of corrosion. It is quite interesting to note that the results also reveal the quality of concrete in various portions of the structural element. It is found that the buildings closer to the sea environment are deteriorating due to weathering action, resulting in spalling of concrete and corrosion of steel reinforcement.

Damage assessment of civil engineering structures and their health monitoring have become one of the most important and recently emerging fields in civil engineering so as to utilize the existing structures to its full extent and to design the structures more effectively in situations exposed to severe environment conditions. The deterioration of concrete structure depends on its exposure conditions and the age of the structure. The influence of age and severe environment conditions can be understood by quantitatively assessing the strength of existing structures having different ages and exposed to different environment conditions (Limaye and Limaye, 2003). Assessment of existing strength of concrete structure helps to find its suitability for use at present and in forecasting the residual life of the structure. The assessment of concrete strength in a number of structures leads to the proper understanding of the influence of age and exposure condition on concrete strength.

Concrete gains its strength over time from a chemical reaction between cement and water. Typically, concrete gains its design strength in 28 days (IS: 8900, (1978); BS 1881 Part 202, (1986); and IS 13311, (1992)). Afterwards the strength continues to increase due to chemical reaction, but at a very lower pace. This increment is expected to continue up to about two to three years from the time of construction. On the other hand, external factors such as environment conditions acting on the structure contribute to the deterioration of the strength of concrete. The deterioration is slow during the first two to three years and gains momentum depending upon the type or exposure, materials used, mix proportions, admixtures, workmanship, maintenance, accidents, abuses, natural calamities and risk level incorporated in the design (Raikar et al., 2003).

Reinforced concrete structures are expected to serve for a long period of time, i.e., for about 50-100 years. A number of RCC structures have been reported in the literature with deterioration of concrete and steel strengths and extensive damage to the structure at a very early age ranging from 12-34 years. The authors themselves observed a severe damage to the concrete structure adjoining the sea in a span of 12 years. Corrosion of reinforcement is found to be more profound in structures located in marine environment. In all the three buildings, the grade of concrete is M20. Non-destructive testing methods offer reliable and quick results (IS: 8900, (1978); BS 1881 Part 202, (1986); IS 13311, (1992); and Chandrakant, 2002)).

Structural Engineering Journal, Non-Destructive Testing, Health Monitoring, Steel Reinforcement, Civil Engineering Structures, Reinforced Concrete Structures, Non Destructive Testing Methods, Ultrasonic Pulse Velocity, Normal Distributions, Ultrasonic Pulse Velocity, Compression Testing Machines.