The effect of elevated temperature on the performance of pozzolanic cement mortar

The current study focuses on the mechanical behavior of fly ash (FA) and wood ash (WA) as cement replacements at increased temperatures. Mortars containing 5, 10, 15, and 20% FA and WA as cement replacement were made and then exposed to temperatures of 200 ℃, 400 ℃, 600 ℃, and 800 ℃, with chosen samples being air-cooled or water-cooled. Curing times for the specimens were 28, 56, 150, and 365 days, respectively. For each age, compressive and tensile strength tests, weight loss at increased temperatures, and scanning electron microscopic examinations were performed. The control sample and FA at 10% replacement without temperature exposure showed a maximum compressive strength of 18 MPa and 1.4 MPa tensile strength at 28 days. Significant moisture was lost at high temperatures, decreasing strength performance. The control sample had a compressive strength of 23.3 MPa after 28 days of exposure to high temperatures under 600 ℃ air-cooled conditions. FA had the maximum value of 18.30 MPa at 15% replacement for 365 days air-cooled at 200 ℃, while WA had the highest strength of 16.40 MPa observed at 200 ℃ for 365 days. The cooling method had a considerable effect on the strength performance, with air-cooled being the better alternative. The study’s findings demonstrate the potential of FA and WA as environmentally friendly cement substitutes that can improve mortars’ durability and heat resistance at elevated temperature. This has significant implications for the building sector, particularly in regions prone to high thermal stress. It encourages the use of environmentally friendly materials without sacrificing structural integrity.