EVALUATION OF SELF HEALING EFFECT IN FLY-ASH CONCRETE BY ULTRASONIC TEST METHOD

Self-healing effect is widely known in concrete. It was reported that concrete with fly ash has self healing effect against freezing and thawing damage. Fly ash is one of the popular admixtures as a waste material from coal fired power plant. In this study, main purpose is to evaluate self healing effect of fly ash concrete by ultrasonic test method. In experiment, fly ash replaced 5 and 15 % of unit sand content. To damage fly ash concrete specimens, one of the freezing and thawing test produced by our laboratory were performed. After the test, the fly-ash concrete specimens are cured by water and performed ultrasonic test. In the ultrasonic test, wave forms are detected and wave velocity and ratio of relative dynamic modulus of elasticity are calculated. It is widely known that wave velocity of damaged concrete is slower than sound concrete and dynamic modulus is used for evaluate of damage. As a result, it is recognized that these fly-ash concrete specimens has self healing effect. In addition, in order to investigate curing effect of concrete against freezing and thawing damage, ultrasonic test method is powerful method of nondestructive test.