The effect of high temperatures on the compressive strength of fly ash Pozzolanic concrete

The mechanical property of compressive strength in concrete is an essential factor that is indicative of structural stability, which cannot be denied. Recently, the utilization of pozzolanic material, namely fly ash, has attracted considerable attention due to its numerous advantages in tackling environmental and economic phenomena. Consequently, the implementation of this approach has the potential to reduce CO₂ emissions and conserve raw materials for sustainable construction. The goal of this study is to find out how adding different amounts of fly ash to cement (0%, 20%, and 30%) affects the compressive strength of concrete when it is heated to high temperatures (from 20 C° to 1200 C°). The present investigation employed non-destructive compressive strength tests using ultrasonic testing based on determining the wave propagation velocity and direct compressive strength. The specimens were designed to detect compressive strength under different levels of temperature with a constant water-bender ratio of W/B = 0.452. The study involved a total of 63 concrete cubes, each with dimensions of 150 * 150* 150 mm, divided into different categories. The average compressive strength of three cubes at each temperature level has been measured after 28 days of concrete casting. The results exhibited a significant increase in compressive strength with the addition of fly ash up to 400 C°, accompanied by cracks. This indicates an increase in the durability of construction exposed to high temperatures.