Abstract: “Experimental investigations were carried out for assessing the influence of thermal loading on the cube and cylinder compressive strength of normal and high strength concrete with and without polypropylene fibers. The tests were carried out under two phases of heating and cooling. In the first phase of heating, the specimens were subjected to single heating-cooling cycle with a hold period of 3 hours at 2000C and were cooled in the furnace before testing the specimens for the residual compressive strength. Similar treatment was carried out on the specimens at 4000C, 6000C and 8000C and their residual strength’s were determined. In the second phase of heating and cooling, the specimens were subjected to successive cyclic heating-cooling regime from 2000C to 8000C, with an increment of 2000C and a hold period of 3hrs. After subjecting the specimens to successive cycles of heating-cooling, the specimens were cooled in the furnace and tested for compressive strength. Specimens were also pr”

Keywords: Elevated temperature; normal strength concrete; high strength concrete; polypropylene fibers; compressive strength; tensile strengths; strength ratio