Effects of Fly Ash and Bottom Ash on Rebound Number, Ultrasonic Pulse Velocity and Compressive Strength of Concrete Exposed to Fire

Abstract

This research was aimed to study the rebound number, ultrasonic pulse velocity and compressive strength of fly ash concrete and internally cured concrete, which using bottom ash as cured material after exposed to fire. The normal concrete and high-strength concrete were investigated in this study. And to study the relationship between rebound number and ultrasonic pulse velocity with compressive strength of concrete, before and after exposed to fire. The water to binder ratio of concrete were 0.35 and 0.55. The weight percentages of replacement of cement by fly ash were 10 and 30%. The volume percentages of replacement of fine aggregate by the bottom ash were 10 and 30%. The test temperatures were 300, 500 and 700 °C for one hour. The results indicated that the compressive strength decreases with higher test temperature. The use of fly ash in concrete tends to improve fire resistance of concrete while the use of bottom ash tends to reduce fire resistance of concrete. The rebound number and ultrasonic pulse velocity decrease with the increases of test temperature.