How is ultrasonic pulse velocity (UPV) test used for concrete quality assessment?

UPV test measures the velocity of ultrasonic pulses through concrete: V = distance/time. Higher velocity indicates better quality, denser concrete. Direct transmission gives best results; indirect/semi-direct for inaccessible surfaces. Typical values: >4.5 km/s = excellent, 3.5-4.5 = good, <3.0 = poor/doubtful. UPV detects internal defects, honeycombing, cracks, and uniformity. Combined with rebound hammer (SonReb method), it provides better strength correlation. Limitations include sensitivity to moisture, reinforcement, and aggregate type.