Select the correct option regarding the Ultrasonic Pulse Velocity (UPV) test: 1. Used to measure strength of wet concrete. 2. Used to estimate strength of finished concrete elements. 3. It is a non-destructive test.

Detailed Explanation: UPV Test — Statements 2 and 3 Are Correct

Why B (2 and 3) is correct: The UPV (Ultrasonic Pulse Velocity) test is an established NDT (non-destructive testing) method governed by IS 13311 Part 1: 1992. It sends an ultrasonic pulse through hardened concrete and measures transit time to assess quality, detect cracks, and estimate compressive strength. Statement 1 is false because the test is not applicable to wet/fresh concrete.

Analysis of Each Statement

Statement	Correct?	Explanation
1. Measures strength of WET concrete	✗ FALSE	UPV requires a solid, homogeneous medium. Fresh/wet concrete is a slurry; there is no defined solid matrix for the pulse to travel through. Only applicable to hardened concrete.
2. Estimates strength of finished elements	✓ TRUE	In-situ UPV measurements on hardened structures correlate with compressive strength via established curves. Widely used for assessing existing structures without sampling.
3. Non-destructive test	✓ TRUE	No drilling, coring, or sampling needed. Transducers placed on the surface; concrete is undamaged. Classified as NDT per IS 13311.

UPV Quality Classification (IS 13311 Part 1: 1992)

Pulse Velocity (km/s or m/s)	Concrete Quality
>4.5 km/s (>4500 m/s)	Excellent
3.5–4.5 km/s	Good
3.0–3.5 km/s	Medium / Questionable
<3.0 km/s (<3000 m/s)	Poor (investigate further)

UPV Test Procedure

Step	Detail
Equipment	UPV meter; transmitter and receiver transducers (54 kHz); couplant gel
Transmission modes	Direct (opposite faces); semi-direct (adjacent faces); indirect/surface (same face)
Measurement	Transit time T (µs); path length L (mm); UPV (m/s) = L/T × 1000
Higher velocity means	Denser, more homogeneous, better-quality concrete

• UPV test: non-destructive; used on hardened concrete only; NOT applicable to wet/fresh concrete.
• IS 13311 Part 1: 1992 governs; often combined with Rebound Hammer test for better accuracy.
• UPV > 4.5 km/s = Excellent; 3.5–4.5 = Good; 3.0–3.5 = Medium; <3.0 = Poor.