ULTRASONIC PULSE VELOCITY TEST ON CONCRETE

Ultrasonic Pulse Velocity (IS 13311 (PART 1) : 1992) testing of concrete is based on the pulse velocity method to provide information on the uniformity of concrete, cavities, cracks and defects. Presence of voids, honeycombing or other discontinuities.

•  The pulse velocity in a material depends on its density and its elastic properties which in turn are related to the quality and the compressive strength of the concrete. 

Based on this technique, the velocity of sound in a concrete is related to the concrete modulus of elasticity.

V=√E/ρ

where,

E = modulus of elasticity,

Ρ =density of the concrete

• Ultrasonic waves are very similar to light waves in that they can be reflected, refracted, and focused.

• Reflection and refraction occurs when sound waves interact with interfaces of differing acoustic properties. 

• An ultrasonic reflection from the presence of discontinuities or geometric features enables detection and location.

• This test method is applicable to assess the uniformity and relative quality of concrete, to indicate the presence of voids and cracks, and to evaluate the effectiveness of crack repairs.

•  It is also applicable to indicate changes in the properties of concrete, and in the survey of structures, to estimate the severity of deterioration or cracking.

• The UPV equipment includes a transducer, a receiver and an indicator for showing the time of travel from the transducer to the receivers.

• Ultrasonic pulse uses fast potential changes to create vibration that leads to its basic frequency.

•  The transducer is firmly attached to concrete surface to vibrate the concrete. The pulses go through the concrete and reach the receiver. The pulse velocity can be determined from the following equation.

V=L/T

V= wave velocity.

L= length of specimen

T= time taken to travel through length

UPV equipment PUNDIT Manual 1992

• The equipment consists of two transducers, usually in the form of metal cylindrical heads, one of which is used to transmit an ultrasonic pulse and the other is a receiver.

•  They are brought into contact with the concrete surface (‘coupled’) using a gel or grease.

•  They are connected by cable to a control box which contains a pulse generator, timing circuit and digital display.

• The digital display indicates the time for the ultrasonic pulse to travel between the transmitting and receiving transducers.

• It is possible to develop an empirical relationship between pulse velocity and strength but this relationship is influenced by type of cement, type and size of aggregate, presence of reinforcement, moisture condition, compaction and age of concrete. 
  
  
  

  S.No	Pulse velocity in cross probing (km/sec)	Concrete Quality Grading
  1.	Above 4.5	Excellent
  2.	3.5 to 4.5	Good
  3.	3.0 to 3.5	Medium
  4.	Below 3.0	Doubtful

  
  

  
  

   

S.No	Pulse velocity in cross probing (km/sec)	Concrete Quality Grading