In this investigation concrete of different compressive strength is exposed to fire for various duration similar to natural fire occurring in buildings. A total of 72 Concrete cubes have been cast from three different concrete mixes then exposed to fire up to 10000C for three different durations (15,30 and 60 minutes) then tested using non- destructive methods like hammer rebound test and Ultra-Sonic Pulse velocity test. Then  the cubes were tested to destruction to measure their compressive strength. The results have shown that the unit weight, compressive strength and actual residual strength decreases with the increase of firing exposure duration similar to concrete exposed to steadily rising temperature. The correlation between the cube compressive strength and RN of the hammer test is very close, however the correlation coefficient of the cube strength with the UPV results is less. Using the combined method of the NDT, the relation between the cube strength and the NDT improves. Equations of relation betweencompressive strength and NDT tests are proposed for use in practice.

Near surface- mounted fibre reinforced polymer is a new technique for strengthening structural members beside externally applied fibre reinforced polymer (FRP) technology. In NSM technique, the FRP material is applied to the tension region of the member inside pre-prepared grooves. In externally applied FRP the debonding of the fibres is a major issue thus, the full utilisation of FRP material can not be achieved, and the fibres are more susceptible to environmental effects. With NSM FRP, these issues can be controlled more effectively. ACI Committee 440 [1] has presented guidelines for design and construction of externally FRP method for strengthening of concrete structures. Although many experiments have been conducted on NSM FRP in flexure strengthening of RC beams, no code is introduced yet. Theoretical studies to derive equations for calculating moment capacity of strengthened beams have been introduced but mostly require several trial procedures to reach the required effective strain for FRP. In this study, a moment capacity chart is introduced based on several assumptions in the derivation of flexure capacity equation. To avoid the brittle behaviour of FRP, it is suggested that the utilization of FRP to be limited to 70% of its ultimate capacity for CFRP, and an equivalent area of reinforcement is adopted for simplicity. Experimental results of other researchers have been verified with the proposed charts, and a good comparison of results have being achieved.

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