ABSTRACT
This study investigates the effect of elevated temperatures on the mechanical properties of Grade 30 concrete, including compressive strength, tensile strength, and flexural strength. A total of 132 specimens (44 specimens per test) were prepared, with 12 control specimens and 120 specimens exposed to various heating durations at 300 and 500 degrees Celsius. The specimens were cured for 7 and 28 days and then subjected to uniaxial compressive loading, flexural, and split tensile tests. The concrete mix followed the Department of Environment Method with a ratio of 1:1.69:3.58 (cement: fine aggregates: coarse aggregates) and a water content ratio of 0.45. Specimens underwent heat treatment for 0, 30, 60, 90, and 120 minutes at 300 and 500 degrees Celsius. The result at 28 days showed that the 39.5Mpa Compressive strength with a decrease of 9.49%, 12.66%, 17.72%, 20.89%, and 24.68% at 300 degrees Celsius and 31.01%, 35.44%, 39.87%, 48.10%, and 51.27% at 500 degrees Celsius after heating for 0, 30, 60, 90, and 120 minutes respectively. The Flexural strength had a value of 1.32Mpa for 28 days and after introduced to heat at 300 degrees Celsius, it decreased by 18.18%, 25.76%, 28.79%, 34.85%, and 37.88% after heating for the same heating durations. At 500 degrees Celsius, the decrease was 43.94%, 46.97%, 53.03%, 56.06%, and 63.64%. Tensile strength exhibited a similar trend, having a tensile strength of 3.38Mpa with reductions of 11.31%, 16.09%, 22.42%, 25.12%, and 27.65% at 300 degrees Celsius and 30.28%, 33.05%, 37.54%, 41.05%, and 47.24% at 500 degrees Celsius. The study reveals a significant reduction in the mechanical properties of Grade 30 concrete as a result of elevated temperatures. The decrease in strength is influenced by both temperature and heating duration. At 500 degrees Celsius and 120 minutes duration, the most substantial reductions in flexural, compressive, and tensile strengths were observed, highlighting the sensitivity of concrete to prolonged exposure to high temperatures.
