---
title: "Ultrasonic pulse velocity test"
subject: "Concrete Technology and Masonry Structure"
chapter: 5
key: "semester_5/concrete_technology_and_masonry_structure:upv-test-interpretation"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/upv-test-interpretation
site: BCT Engineering
---

# Ultrasonic pulse velocity test

Concrete Technology and Masonry Structure · Chapter 5: Testing of concrete and quality control

- Asked in: 2074 Ashwin, 4+2 marks; 2071 Shrawan, 6 marks (asked 2 times)
- Video: [Ultrasonic pulse velocity test of Concrete](https://www.youtube.com/watch?v=XFhsFoewejo) — R B Singh Civil Engineering Academy
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/upv-test-interpretation
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-5

## Question

How is the Ultrasonic Pulse Velocity test carried out? How do you determine the compressive strength / interpret the results with the quality of concrete?

## Short answer

In UPV test, pulse velocity V = L/T is computed from measured transit time and path length. Direct transmission gives best results. IS 13311 classifies quality: V > 4.5 km/s excellent, 3.5-4.5 good, 3.0-3.5 medium, <3.0 doubtful. Strength is estimated from a calibration curve with about +/-20% accuracy.

## Answer

#### Ultrasonic pulse velocity (UPV) test (IS 13311 Part 1)
**Principle:** the velocity of an ultrasonic pulse through concrete depends on its density and elastic properties. Sound, dense concrete transmits the pulse faster than porous or cracked concrete.

**Apparatus:** pulse generator and receiver with two transducers (usually 54 kHz), a timer reading to 0.1 microsecond, a coupling gel, and a reference calibration bar.

**Procedure**
1. Calibrate the instrument on the reference bar.
2. Clean the surface and apply grease or gel to ensure good acoustic contact.
3. Put the transducers on the concrete, either **directly** (opposite faces, most reliable), **semi-directly** (adjacent faces) or **indirectly** (same face, least reliable).
4. Measure the path length $L$ and the transit time $T$.
5. Calculate the velocity:

$$
V = \frac{L}{T}
$$

Take several readings and average them. Avoid paths parallel to reinforcement, as steel carries the pulse faster.

**Quality of concrete (IS 13311 Part 1)**

| Pulse velocity (km/s) | Quality |
|---|---|
| Above 4.5 | Excellent |
| 3.5 to 4.5 | Good |
| 3.0 to 3.5 | Medium |
| Below 3.0 | Doubtful (poor) |

**Strength estimation:** a correlation curve between $V$ and the compressive strength of cubes of the same mix (made and tested in the laboratory) is used. The accuracy is about ±20% only, because moisture, aggregate type, age and reinforcement also change $V$. Better accuracy is obtained by combining it with the rebound number (SONREB method).

**Uses:** uniformity of concrete, locating voids and cracks, depth of surface cracks, deterioration by fire, frost or chemical attack, and dynamic modulus.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Pulse velocity is higher in:
   A. Sound dense concrete
   B. Cracked concrete
   C. Porous concrete
   D. Voided concrete
   Answer: A. Dense concrete transmits pulses faster. (Key point: Principle)

2. Why avoid paths parallel to reinforcement?
   A. Steel absorbs pulse
   B. Steel carries the pulse faster, giving false velocity
   C. It reduces frequency
   D. It damages transducers
   Answer: B. Steel gives higher velocity readings. (Key point: Steel)

3. Velocity below 3.0 km/s indicates:
   A. Excellent
   B. Good
   C. Poor (doubtful) quality
   D. Medium
   Answer: C. Below 3.0 is poor. (Key point: Interpretation)

4. Strength is estimated from UPV by:
   A. Correlation curve with cubes of same mix; accuracy about +-20%
   B. A single universal formula
   C. Rebound only
   D. Exact formula with 1% error
   Answer: A. Moisture, aggregate, age and steel affect V; combine with rebound (SONREB). (Key point: Strength estimation)

## Related in Concrete Technology and Masonry Structure

- [NDT circumstances; ultrasonic pulse velocity test](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Andt-circumstances-upv) — Concrete Technology and Masonry Structure, chapter 5
- [Characteristic strength from test results](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Acharacteristic-strength-30-28) — Concrete Technology and Masonry Structure, chapter 5
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