The ultrasonic pulse velocity (UPV) measurements are taken to obtain information about concrete quality i.e, voids, flaws, cracks, honeycombing etc. in terms of ultrasonic pulse velocity.  The results help in identifying the areas required to be strengthened.

  • The equipment.

The Ultrasonic instrument Pundit Lab+ is manufactured and supplied by Proceq Switzerland is used for taking UPV measurements and below in the fig. C.

Fig. C: Pundit Lab+ (UPV Equipment)

Measurement performance; Optimized pulse shaping, automated transmission settings for optimum performance and a range of new, more powerful transducers ensure accurate, stable measurements.

Integrated waveform display; Allows analysis of the received signal and manual triggering directly on the instrument.

On-line data acquisition; Full remote control of all transmission parameters, data logging function and functionality that turns your PC into an oscilloscope.

USB interface and data analysis software; Data analysis and export to third party programs.

Open interface; Control Pundit Lab using third party software such as LabVIEW

New features in Pundit® Lab+

Integrated gain stage; Removes the need for an external amplifier when using exponential transducers and long cables.

Compressive strength measurement; Conversion curves for strength estimation can be created in the software and uploaded to the instrument to give instant strength estimations on site.

Combined estimates with rebound hammer; SONREB curves may also be uploaded onto the instrument for improved compressive strength estimates in combination with rebound hammer measurements.

Time stamp; A real time clock has been integrated to provide a time stamp to every measurement recorded.

Review list; Saved measurements may be reviewed directly on site without the need for a PC connection.

  • The Principle

The underlying principle of assessing the quality of concrete is that comparatively higher velocities are obtained when the quality of concrete in terms of density, homogeneity and uniformity is good. In case of poor quality, lower velocities are obtained. If there is a crack, void or flaw inside the concrete, which comes in the way of transmission of pulses, the pulse strength is attenuated and it passes around the discontinuity, thereby making the path longer. Consequently, lower velocities are obtained. The actual pulse velocity obtained depends primarily upon the materials and mix proportions of concrete. Density and modulus of elasticity of aggregate also affect the pulse velocity.

There are three ways of measuring pulse velocity through concrete (Fig. D):

a. Direct Transmission or Cross Probing: When both the   probes are kept (at 180o) on opposite faces.

b. Semi-direct Transmission: Both the probes are kept (at 90o) on diagonally opposite faces.

c. Indirect Transmission or *Surface Probing: When both the   probes are kept (at 180o) on the same face.

All these methods have been illustrated in Fig. D.

Fig. D: Methods of UPV Measurement