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IS 9399:1979 is the Indian Standard (BIS) for apparatus for flexural testing of concrete. This standard specifies the requirements for the apparatus used to conduct flexural strength tests on concrete beams. It details the machine frame, load application methods (two-point and central), dimensions and material of rollers, and the accuracy of the load indicating system.
Specification for apparatus for flexural testing of concrete
Overview
Status
Current
Usage level
Specialized
Domain
Materials Science — Cement, Concrete, Aggregates and RCC
! This code is for the apparatus itself; the testing procedure and calculation of flexural strength (modulus of rupture) are covered in IS 516.
! The code allows for two loading methods: two-point (third-point) loading and central loading. The former is more common as it subjects a larger portion of the beam to maximum bending moment.
! Ensure rollers are clean, free to rotate, and properly aligned to prevent inducing torsion or stress concentrations during the test.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
concretesteel
International Equivalents
Similar International Standards
ASTM C78 / C78M-22ASTM International, USA
HighCurrent
Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)
Specifies both the test method and apparatus for third-point loading flexural tests on concrete.
EN 12390-5:2019CEN (European Committee for Standardization), Europe
HighCurrent
Testing hardened concrete - Part 5: Flexural strength of test specimens
Covers the method for determining flexural strength and details the required testing apparatus.
ISO 1920-5:2018ISO (International Organization for Standardization), International
HighCurrent
Testing of concrete — Part 5: Flexural strength of test specimens
Provides the international standard method and apparatus specifications for concrete flexural strength.
BS 1881-118:1983BSI (British Standards Institution), UK
MediumWithdrawn
Testing concrete. Method for determination of flexural strength
Was the former British standard for the flexural strength test, including apparatus requirements.
Key Differences
≠IS 9399 is a dedicated standard for the apparatus, while the test procedure is in IS 516. In contrast, ASTM C78 and EN 12390-5 integrate both apparatus specifications and test method into a single document.
≠The support span for a standard 150 mm deep beam is 600 mm per IS 516 (for which the IS 9399 apparatus is designed), whereas both ASTM C78 and EN 12390-5 specify a span of three times the specimen depth (450 mm).
≠The rate of loading in the associated Indian method (IS 516) is specified as a rate of load application (e.g., 400 kg/min), while ASTM C78 and EN 12390-5 specify it as a rate of stress increase (e.g., 0.86-1.21 MPa/min or 0.05 MPa/s).
≠IS 9399 specifies a fixed roller diameter of 38 mm, while EN 12390-5 allows a range of roller diameters from 20 mm to 40 mm.
Key Similarities
≈All standards are based on the same fundamental test principle: determining flexural strength using a simple beam with third-point loading.
≈All require the apparatus to have two supporting rollers and two load-applying rollers, with the load rollers equidistant from the supports.
≈The apparatus in all standards must be articulated, with specific rollers designed to swivel or move slightly to ensure uniform load application and accommodate minor specimen irregularities.
≈The specified roller diameter of 38 mm in IS 9399 is identical to the 1.5 in (38 mm) requirement in the widely used ASTM C78 standard.
Parameter Comparison
Parameter
IS Value
International
Source
Standard Structure
Separate standard for apparatus (method in IS 516)
Apparatus and method in a single document
ASTM C78 / C78M-22
Support Span (for 150x150x700 mm beam)
600 mm
450 mm (3 x specimen depth)
EN 12390-5:2019
Roller Diameter
38 mm
20 mm to 40 mm
EN 12390-5:2019
Loading Rate Unit
Rate of loading (kg/min)
Rate of stress (MPa/s)
EN 12390-5:2019
Testing Machine Accuracy
±1% of load above 10% of full scale
±1.0% of indicated load for upper 80% of range (Class 1)
EN 12390-4:2019
Roller Material Hardness
Hardened steel (not quantified)
Rockwell hardness of not less than 55 HRC
ASTM C78 / C78M-22
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Loading Machine Accuracy±2% of indicated load
Standard Roller Diameter38 mm
Roller and Bearing Plate Hardness> 550 HV
Roller LengthAt least 10 mm greater than the width of the test specimen
Distance between two-point loads200 mm for 150mm specimen, 133 mm for 100mm specimen