ULTRASONIC PULSE VELOCITY TEST
The ultrasonic pulse velocity method is used to establish
· The homogeneity of concrete.
· The presence of voids, cracks, and other imperfections.
· Changes in structure of concrete which may occur with the time.
· The mass integrity of the concrete in relation to standard requirement.
· The mass integrity of one element of concrete in relation to the other.
The ultrasonic pulse is generated by an electro acoustical transducer. When the pulse is transmitted through the concrete, it undergoes multiple reflections at the boundaries of the different material phases within the concrete. A complex system of stress waves is developed which includes longitudinal shear and surface waves. The receiving transducer detects the onset of the longitudinal waves, which is the fastest. The velocity of the pulses is almost independent of the geometry of the material through which they pass and depends only on its elastic properties. Ultrasonic pulse velocity is a very desirable technique for investigating structural concrete in the field.
Pulse velocity method is a convenient technique for investigating structural concrete. Comparatively higher velocities are obtained when the quality of concrete in terms of density, homogeneity and uniformity is good. If there is crack, void or flaw inside the concrete which comes in the way of transmission of the pulses, the pulse strength is attenuated and it passes around the discontinuity thereby making the path length longer and lower velocities are obtained. The UPV method involves measuring the travel time over a known path length of pulse.
