Abstract：A series of standard cube concrete of different grades were tested under impact load to study the damage characteristics of concrete. The experiments indicate that concrete of different grades under impact load has different ranges of damage；its interior damage is anisotropic；and its resistance to impact increases with the increasing of its strength. The interpretation of arrival time of head waves is accurate and reasonable by using ultrasonic velocity to describe material interior damage and wavelet transform noise cancellation method to treat ultrasonic signals. Regularities of energy distribution in each wave band have evident changes with the change of damage after the decomposition of ultrasonic signals by wavelet. It also illustrates that energy is more sensitive to damage than ultrasonic velocity is when energy distribution in one wave band is used to describe damage.
