Flexural Strength Test of Concrete
(Modulus of Rupture — IS 516)

Measurement of the flexural strength (modulus of rupture) of concrete beam specimens under third-point or centre-point loading — the primary design parameter for rigid pavement and industrial floor design.

Overview

What is the Flexural Strength Test of Concrete?

The Flexural Strength Test measures the modulus of rupture (MR) of concrete by loading a 150×150×700mm beam specimen in bending under third-point or centre-point loading. MR directly governs rigid pavement thickness design per IRC 58 — typical target values are MR 4.5 MPa for NH and SH pavements.

Conducted as per IS 516 and ASTM C78 (third-point) or ASTM C293 (centre-point), flexural strength testing is mandatory for PQC mix design validation and routine QC during highway construction. Global Lab casts, cures and tests 150×150×700mm beams in our NABL-accredited flexural testing machine.

MR for Pavement Design

Modulus of rupture directly used in IRC 58 rigid pavement thickness design.

Third-Point Loading

Third-point loading (ASTM C78) provides pure bending zone — more accurate than centre-point.

150×150×700mm Beams

Standard beam size per IS 516 / IRC 44 for PQC and DLC flexural testing.

7 & 28 Day Testing

Flexural strength development tracked to confirm design MR is achieved.

NABL Certified Reports

All results on NABL-accredited letterhead per IS 516 / ASTM C78.

NHAI JMF Compliance

Flexural strength results formatted for NHAI Job Mix Formula acceptance.

Test in Action

Flexural Strength Test of Concrete — Site Images

Concrete

Flexural Testing Machine Setup

Beam Failure at Middle Third

Test Procedure

How the Flexural Strength Test of Concrete is Conducted

1

Beam Casting

150×150×700mm steel moulds cleaned and filled in 2 layers. Each layer compacted with 35 tamping rod strokes per IS 516.
2

Curing

Beams covered 24 hours, demoulded, marked and water-cured at 27±2°C until test age.
3

Beam Positioning

Beam placed in flexural testing machine with two support rollers at 600mm span. Two loading rollers positioned at third-points (200mm from each support).
4

Load Application

Load applied at 0.7 MPa/min per IS 516 until failure. Failure point location (between, within or outside third-points) recorded.
5

MR Calculation

If fracture within middle third: MR = PL/bd². If outside: MR = 3Pa/bd². NABL report issued within 28 days.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
IS 516	Methods of Tests for Strength of Concrete	Flexural Strength	Indian Standard
ASTM C78	Standard Test Method for Flexural Strength of Concrete Using Simple Beam with Third-Point Loading	Third-Point Loading	ASTM
IRC 44	Guidelines for Cement Concrete Mix Design for Pavements	PQC Design	IRC
IRC 58	Guidelines for the Design of Plain Jointed Rigid Pavements for Highways	Pavement Design	IRC

Applications

Where is the CAPO Test Used?

PQC mix design validation for NHAI highway rigid pavement construction

DLC flexural strength verification per IRC 74

Industrial floor slab flexural strength testing for heavy-load applications

Airport runway PQC flexural strength acceptance testing

Precast prestressed concrete element flexural strength characterisation

Research on fibre-reinforced concrete flexural performance and post-crack behaviour

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsNHAI and IRC-accepted flexural strength certificates for pavement projects.

Third-Point Loading AvailableMore accurate ASTM C78 third-point method alongside IS 516 centre-point.

NHAI JMF ExperienceReports formatted directly for NHAI JMF submission and acceptance.

Autovity Digital AccessFlexural load-deflection curves and results accessible digitally.

Combined PQC PackageFlexural + Compressive + Split tensile as a complete PQC characterisation.

Pan-India CoverageBeam testing at all 7 NABL-accredited lab locations.

Flexural Strength Test of Concrete(Modulus of Rupture — IS 516)