IS 516:2021 Part 5/Sec 1 is the Indian Standard (BIS) for methods of tests for strength of concrete - part 5: non-destructive testing of concrete - section 1: ultrasonic pulse velocity. This code covers the non-destructive testing procedure for assessing the quality of concrete using the Ultrasonic Pulse Velocity (UPV) method. Engineers use it to evaluate concrete homogeneity, detect internal voids or cracks, and estimate the dynamic modulus of elasticity in existing structures without causing damage.
Specifies the method for determining the ultrasonic pulse velocity in concrete.
Test setup, rejection criteria, quality grades (R-value bands), calibration frequency and direction corrections.
| Reference | Value | Clause |
|---|---|---|
| Hammer type | Schmidt rebound hammer (Type N — standard impact) | Cl. 4 / IS 13311 Pt 2 ref |
| Test surface preparation | Smooth, ground if rough; remove laitance | Cl. 6.2 |
| Test grid — points per location | Min 9 (typically 12) | Cl. 6.4 |
| Spacing between points | ≥ 25 mm (and ≥ 25 mm from edge) | Cl. 6.4 |
| Discard outlier rule | Reading differing > ±6 from mean rejected | Cl. 7.1 |
| Quality grade — R ≥ 40 (horizontal) | Very good / hard layer | Cl. 8 (Table) |
| Quality grade — R 30–40 | Good | Cl. 8 (Table) |
| Quality grade — R 20–30 | Fair | Cl. 8 (Table) |
| Quality grade — R < 20 | Poor / doubtful | Cl. 8 (Table) |
| Direction correction — vertical (downward) | + correction (refer hammer chart) | Cl. 7.2 |
| Calibration — frequency | Before/after each project (anvil block) | Cl. 5.2 |
| Calibration anvil — required reading | 80 ± 2 (typical N-type) | Cl. 5.2 |
| Min concrete age | 14 days (for trustable correlation) | Cl. 6.1 |
| Member thickness — min | 100 mm | Cl. 6.1 |
| Use — strength estimate ONLY with site correlation | Direct strength from R is unreliable; use cube correlation | Cl. 8.1 |
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Standard Compressive Strength Specimen Type (Primary) | Cube | Cylinder | ASTM C39/C39M |
| Compressive Strength Loading Rate (Stress/time) | 14 N/mm²/minute | 0.25 ± 0.05 MPa/s (approx. 15 ± 3 N/mm²/min) | ASTM C39/C39M |
| Curing Temperature for Standard Specimens (Water/Moist Curing) | 27 ± 2 °C | 23 ± 2 °C | ASTM C31/C31M (referenced by C39/C39M) |
| Flexural Strength Test - Span-to-Depth Ratio (Third-Point Loading) | 4 (e.g., 600 mm span for 150 mm depth) | 3 (e.g., 450 mm span for 150 mm depth) | ASTM C78/C78M, EN 12390-5 |
| Number of Layers for Compaction of 300mm High Cylinders (by rodding) | 6 layers (approx. 5 cm deep each) | 3 layers (approx. 10 cm deep each) | ASTM C31/C31M |
| Maximum Time from Curing to Compressive Test | Within 30 minutes | Within 15 minutes | EN 12390-3 |