Techshore QA/QC : Civil Engineering [Ultra Sonic Pulse velocity testing ]

Ultra Sonic Pulse velocity testing 

Application  : 
To find interior hardness of concreate surface.
Ulta Sonic Pulse velocity testing method is mainly used for crack filling by epoxy injection

Instrument description :
The device consists of

1. A concrete tester which displays the time in micro seconds.
2. A transducer which consist of a transmitter probe and reciever probe.
3. A calibration rod to calibration the instrument periodically.

Working Principles :

1. Ultrasonic waves when passed through subjects will be affected by change in density , presence of voids, cracks and moisture.
2. A transducer is a device that can convert one form of energy to another.Longitudinal sound waves are propagated through the concrete subject using the transducer probes. UT sound waves are Transmitted and received using the transmitter and receiver probes respectively. 

Inspection Procedure :

1. Initially the instrument is calibrated on intact and uncracked surface of the concrete, then readings are taken from cracked surface.
2. Time taken by the sound wave to travel through the subject is obtained from the concrete tester in micro seconds.
3. Velocity of wave is then calculated using the equation V= D/T.
4. Reasons for change in velocity :
   UT waves cannot propagate through air , they always needs solid medium to travel.
   UT waves transmission will be affected by density of material , presence of aggrigates , presence of reinforcement bard , presence of crack , moisture contents , vacuum etc.
5. Experiment is repeated and measurements are made multiple time and the average of all the readings are considered to uncrease the accurancy of result.
6. Cracks ploted are then filled using epoxy injection procedures.
   Experiment is recoducted again after detection and filling the cracks to revalidate the succesfull filling of  crack detected. 

Methods  : 
Different experiment menthods used are Direct Method , Indirect method and semi direct method

1. Direct method Trasmitter and reciever are placed on oppisite surface/sides of the concrete surfaces  
2. Indirect methodTrasmitter and reciever are placed on same side/surface of the concrete surfaces.
3. Semidirect methodTrasmitter and reciever are placed on adjacent side/surface (right angle to each other) of the concrete surfaces. 

Note : In all three methods velocity is calculated by equation V=D/T