Effect of Heat Intensity and Duration on the Compressive Strength of Concrete

The objective of this paper is to evaluate the effect of high temperatures and durations on the strength of concrete using concrete specimens produced from two mix ratios of 1:2:4 and 1:3:6 and exposing them to different heat conditions. In the first condition the specimens are subjected to one hour heat intensities of 100 ^OC, 200 ^OC, 300 ^OC & 400^OC and in the second condition they are subjected to heat periods of 30, 60, 90 and 120 minutes under a constant 600^OC temperature. The 1:2:4 concrete mix specimens lost 85.96% of its strength after 2 hours of heating at 600^OC and also lost 16.04% of its strength after 1 hour duration of 400^OC. The 1:3:6 concrete mix specimens recorded a 73.61% maximum strength reduction after 2 hours of 600^OC heat and a 19.63% strength loss under heat from ambient temperature to 400^OC. Though the results showed an overall reduction in concrete strength it however did not establish a clear cut relationship between concrete strength and heat intensity or heat duration.