Table of Contents
In this article, we will discuss Ultrasonic Pulse Velocity Test.
Concrete is a composite material that is composed of a mixture of fine and coarse aggregates bonded together with biding material which hardens over time. The binding material mostly includes fluid cement paste, lime putty, lime, etc.
In other words, when water is added to a mixture of cement, and fine and coarse aggregates, a workable paste is formed which hardens with time. The such paste is known as concrete.
The binding material such as cement reacts with the water and other constituents to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. Concrete is a type of construction material employed all over the world. It is often said that the present age is a concrete age.
Concrete is extensively used for the construction of columns, beams, foundations, slabs, and other load-bearing elements of buildings, roads, dams, bridges, etc.
The growing popularity of concrete in civil engineering works is due to its distinctive characteristics like strength, durability, low maintenance, energy efficiency, and sustainability.
The major application areas of concrete include the following:
b. Residential and Commercial Buildings
c. Roads and Driveways
d. Foundations
e. Culverts and Sewers
f. Fences
g. Concrete Bridges
h. Marine Constructions
Concrete is commonly used in all types of construction so, it is necessary to test existing concrete in the field.
1. Ultrasonic Pulse Velocity Test
The UPV Test calculates the time of travel of an ultrasonic pulse moving through the concrete. The high UPV Test and lower time of travel demonstrate good quality of concrete in terms of density, uniformity, homogeneity, etc.
Ultrasonic Pulse Velocity Test is conducted on concrete to evaluate the quality of concrete by handing ultrasonic pulse velocity through it as per IS: 13311 (Part 1) – 1992.
2. Objectives of UPV Test
The ultrasonic pulse velocity test is employed to calculate the following factors. The concrete homogeneity, The availability of cracks, voids, and other imperfections, and Structural modifications of concrete that may happen with time, To set concrete quality, To compare the quality of one member of concrete with another, To calculate the value of the dynamic modulus of elasticity.
3. Principle of UPV Test
In this test, an ultrasonic pulse is produced by an electro-acoustical transducer. When the pulse is induced into the concrete from a transducer, it experiences multiple reflections at the borders of the various material phases within the concrete.
A series of waves are generated in concrete which contains longitudinal (compression), shear (transverse), and surface (Rayleigh) waves. The transducer positioned on another side catches fasted longitudinal waves.
The velocity of the ultrasonic pulse primly relies on the shape, size, and geometry of the concrete material through which they pass and depends only on its elastic properties. This method is appropriate for evaluating the structural belongings of concrete.
according to the ultrasonic pulse velocity principle when the concrete grade is good in terms of density, homogeneity, and uniformity, it comparably gets higher velocity in concrete. In another case, if the concrete quality is poor, the velocity got is descending.
In case, if the concrete has cracked, and voids inside it, the strength of pulse velocity is reduced and it moves around discontinuity, thereby following the more extended path for travel. Therefore, lower velocities are accepted.
The velocity of the pulse relies on the concrete material or mix proportion. Aggregate density and modulus of elasticity also had an effective effect on the velocity of the pulse.
a. Apparatus
The Instruments and devices used for the ultrasonic pulse velocity test:
a. Electrical pulse generator
b. Transducer – one pair
c. Amplifier
d. Electronic timing device.
Any appropriate type of transducer working within the frequency range of 20 kHz to 150 kHz may be employed. Piezoelectric and magnetostrictive types of transducers may be employed, the last being more appropriate for the lower part of the frequency range. UPV test is conducted on concrete as per IS: 13311 (Part 1) – 1992.
| Path Length (mm) | Natural Frequency of Transducer (kHz) | Minimum Transverse Dimension of Members (mm) |
| Up to 500 | 150 | 25 |
| 500 – 700 | > 60 | 70 |
| 700 – 1500 | > 40 | 150 |
| Above 1500 | > 20 | 300 |
1. Electronic Timing Device
The electronic timing device is qualified of calculating the time travel of the pulse at the transmitting transducer and the onset of its arrival at the obtaining transducer.
2. Performance of the Assembly of Apparatus
The Ultrasonic pulse velocity apparatus employed test is qualified for calculating pulse velocity to the accuracy of +1 % over a span of 20 microseconds to 10 milliseconds. For this, it is vital to review the accuracy of the apparatus by completing calculations on two standard reference specimens in which the pulse transit times are known accurately.
The review should be done on two steel specimens and should have the lowest transit times of about 25 microseconds to 100 microseconds respectively. Generally, this transit time is specified by the supplier of the apparatus to an accuracy of 0.2 microseconds.
It is suggested that more straightforward steel specimens should be employed to set zero for equipment and longer steel should be employed to review the accuracy of transit time measurement of the apparatus.
During the test, the transducer kept in contact with one surface of concrete and traverse a known path length Q in the concrete, and then an electrical signal was transmitted to the second transducer kept in contact with another surface of the concrete member and the transit time (T) of the pulse to be calculated.
The pulse velocity (V) is provided by:
V = L/T
Once the path is located by the transducer the pulse velocity is transmitted at a right angle to the surface of the concrete to get the best outcome.
4. 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 characterizing the quality of concrete in structures in terms of the ultrasonic pulse velocity.
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