ULTRASONIC PULSE VELOCITY

Updated: May 1, 2020

AIM

To assess the quality of concrete by ultrasonic pulse velocity

method as per IS: 13311 (Part 1) - 1992.

PRINCIPLE

The method consists of measuring the time of travel of an

ultrasonic pulse passing through the concrete being tested.

Comparatively higher velocity is obtained when concrete quality

is good in terms of density, uniformity, homogeneity etc.

APPARATUS


ULTRASONIC PULSE VELOCITY METER

PROCEDURE

i) Preparing for use: Before switching on the 'V' meter, the

transducers should be connected to the sockets marked

"TRAN" and " REC".

The 'V' meter may be operated with either:

a) the internal battery,

b) an external battery or

c) the A.C line.

ii) Set reference: A reference bar is provided to check the

instrument zero. The pulse time for the bar is engraved on it.

Apply a smear of grease to the transducer faces before

placing it on the opposite ends of the bar. Adjust the 'SET

REF' control until the reference bar transit time is obtained

on the instrument read-out.

iii) Range selection: For maximum accuracy, it is

recommended that the 0.1 microsecond range be selected

for path length upto 400mm.

iv) Pulse velocity: Having determined the most suitable test

points on the material to be tested, make careful

measurement of the path length ‘L’. Apply couplant to the

surfaces of the transducers and press it hard onto the

surface of the material. Do not move the transducers while a

reading is being taken, as this can generate noise signals

and errors in measurements. Continue holding the

transducers onto the surface of the material until a

consistent reading appears on the display, which is the time

in microsecond for the ultrasonic pulse to travel the distance

'L'.

The mean value of the display readings should be taken

when the units digit hunts between two values.

Pulse velocity = Path length/Travel time

v) Separation of transducer leads: It is advisable to prevent the

two transducer leads from coming into close contact with

each other when the transit time measurements are being

taken. If this is not done, the receiver lead might pick-up

unwanted signals from the transmitter lead and this would

result in an incorrect display of the transit time.

INTERPRETATION OF RESULTS

The quality of concrete in terms of uniformity, incidence or

absence of internal flaws, cracks and segregation, etc.,

indicative of the level of workmanship employed, can thus be

assessed using the guidelines given below, which have been

evolved for characterising the quality of concrete in structures in

terms of the ultrasonic pulse velocity



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