IS 516:1959 Part 2 is the Indian Standard (BIS) for methods of tests for strength of concrete - part 2: determination of flexural strength. This code standardizes the testing methods for determining the strength of concrete, specifically detailing the procedure for finding the flexural strength (modulus of rupture) using beam specimens. It is extensively used by QA/QC engineers to verify concrete tensile strength for rigid pavements and flat slabs.
Covers the procedure for determining the flexural strength of hardened concrete by testing beams.
Quick Reference — IS 516 Part 2:1959 Concrete Cores
Core diameter, L/D corrections, capping, soaking, loading rate and IS 456 acceptance link.
| Reference | Value | Clause |
|---|
| Method | Cores cut from hardened concrete for compression test | Cl. 1 |
| Min core diameter | 100 mm (preferable); 50 mm (where unavoidable) | Cl. 4.1 |
| Core diameter — relation to max aggregate | ≥ 3 × max nominal aggregate size | Cl. 4.1 |
| Length-to-diameter (L/D) — preferred | 1.0 (for direct cube-equivalent strength) | Cl. 4.2 |
| L/D — acceptable range | 1.0 to 2.0 (with correction) | Cl. 4.2 (Table 1) |
| L/D correction — 2.00 | 1.00 (no correction) | Cl. 5.2 (Table 1) |
| L/D correction — 1.50 | 0.96 | Cl. 5.2 (Table 1) |
| L/D correction — 1.00 | 0.87 | Cl. 5.2 (Table 1) |
| Capping — required for end planeness | Sulphur capping or HA mortar | Cl. 4.3 |
| Soaking before test | 40 hours in water before crushing | Cl. 5.1 |
| Loading rate | 140 kg/cm²/min (~14 N/mm²/min) | Cl. 5.3 |
| Equivalent cube strength | fc(cube) = (5/4) · fc(core) · L/D correction | Cl. 5.4 |
| Number of cores per location | 3 (mean reported) | Cl. 4.4 / IS 456 Cl. 17.4 |
| Acceptance — IS 456 Cl. 17.4 reference | Mean equivalent cube ≥ 0.85 fck; individual ≥ 0.75 fck | IS 456 Cl. 17.4.3 |
⚠ 1959 publication; many laboratories now also reference ASTM C42 / BS EN 12504-1. Always pair core results with companion cube data when available.
Overview
- Status
- Current
- Usage level
- Frequently Used
- Domain
- Materials Science — Testing Methods and Quality Control
- Type
- Testing Method
- Amendments
- Amendment 1 (1980); Amendment 2 (1989); Amendment 3 (1999)
Also on InfraLens for IS 516
Practical Notes
! Specimens must be tested immediately after removal from water curing while they are still wet; drying out can significantly alter tensile test results.
! Plywood packing strips are mandatory between the specimen and the machine platens to prevent local compressive crushing and ensure a true tensile failure.
! Proper alignment using a jig is critical to ensure the load is applied exactly along the diametral plane.
Frequently referenced clauses
Updates & Amendments3 amendments
1980Amendment 1 (1980)
1989Amendment 2 (1989)
1999Amendment 3 (1999)
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
concreteplain concretecement
International Equivalents
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International Comparison — Coming Soon
We're adding equivalent international standards for this code.
Key Values6
Quick Reference Values
standard specimen diameter150 mm
standard specimen length300 mm
rate of loading1.2 to 2.4 N/mm²/min
plywood strip thickness3 mm
plywood strip width12 mm
plywood strip lengthGreater than the length of the specimen
Key Formulas
fct = 2P / (π × d × l) — Splitting tensile strength (where P is max load, d is diameter, l is length)
Tables & Referenced Sections
Key Clauses
Clause 3 - Apparatus and Test Specimens
Clause 4 - Positioning of the Specimen
Clause 5 - Rate of Loading
Clause 6 - Calculation of Split Tensile Strength
Frequently Asked Questions3
What is the standard specimen size for the splitting tensile test?+
A concrete cylinder of 150 mm diameter and 300 mm length.
What is the specified rate of loading?+
The load must be applied without shock at a constant rate within the range of 1.2 to 2.4 N/mm²/min.
Why do we use plywood strips in the splitting tensile test?+
To distribute the applied load uniformly over the entire length of the cylinder and to prevent local premature compressive failure at the load application points.