THE EFFECT OF HEAT ON THE CONCRETE STRENGTH

الملخص

This research studies the effect of fire on the compressive strength of concrete. In this study Concrete mix was designed to give a compressive strength of 40 MPa. after that the concrete mixture was spilt into cubes 150 mm³ cubic.  The concrete cubes were then exposed to fire at 240c° temperatures for different times for 1,2,3 and 4 hours . Cubes also heated in electrical furnace at temperatures of 240c°and 300c. The change in the characteristic of the concrete after exposed to fire was then checked by Schmidt hammer, Ultra-Sonic tests and crashing test respectively to measure the compressive strength. The results showed that the concrete compressive strength decreases with the increase in exposure time. The total reduction in compressive strength after four hours of burning at 240c° was 45 % for 28days  age cubes ;this reduction was38 % when using electrical furnace at 240c° whereas the reduction at 300c° was 46%.separation in outer shell of specimens occurred much higher under the influence of direct flame compared to furnace heating. 

KEYWORDS : Concrete , compression, fire, UPV, temperature, flame