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What are the ultrasonic pulse velocity and the pulse echo tests?

Q. What are the ultrasonic pulse velocity and the pulse echo tests?


A. The ultrasonic pulse velocity test, as described in ASTM C597, consists of measuring the time it takes for a pulse of vibrational energy to travel through a concrete member. The vibrational energy is introduced into the concrete by the transmitting transducer, which is coupled to one surface. The pulse travels through the member and is detected by the receiving transducer, which is coupled to the opposite surface. The direct path length between the transducers is divided by the travel time to obtain the pulse velocity through the concrete. The pulse echo technique also involves measuring the transit time of a pulse of vibrational energy. Unlike the pulse velocity method, in this case the pulse is generated and received on the same surface (ACI 228.2R, ACI 437R). This is made possible because the pulse is reflected by the opposite boundary of the member. If the pulse is generated by impact at a point rather than a pulse from a transducer, it is known as the impact echo method (ACI 228.2R). The impact echo method can be used to measure member thickness (ASTM C1383) or locate internal defects (ACI 228.2R).


References: SP-1(02); ACI 228.2R-13; ACI 437R-19; ASTM C597; ASTM C1383

Topics in Concrete: Nondestructive Testing; Testing of Concrete

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