Information on the most widely used ASTM standards within the materials testing industry
EN 12390‑5 Hardened Concrete Flexural Strength Test
EN 12390‑5 is the European standard test method for measuring the flexural strength of hardened concrete using prism test specimens. Flexural strength, also known as bending strength, gives indirect evaluation of concrete’s tensile performance, since unreinforced concrete typically suffers tensile failure when subjected to bending loads.
Widely adopted by construction laboratories, concrete precast factories and third‑party construction material inspection agencies, EN 12390‑5 delivers critical performance data for concrete mix design, incoming material quality control and structural acceptance testing.
UnitedTest produces professional concrete flexural strength testing machines fully compliant with EN 12390‑5. Our test systems provide accurate, repeatable bending‑load test results for hardened concrete prisms, supporting daily QC, material research and construction project validation.
Test Principle
A prismatic concrete specimen is loaded through upper and lower rollers to induce a bending moment. The load is applied under two-point (two-load-point) loading, which is the reference method:
Two lower supporting rollers hold the specimen.
Two upper loading rollers, mounted on an articulated cross-member that splits the load equally, press down on the specimen.
The maximum load sustained is recorded and the flexural strength is calculated from the bending moment formula. The two-point approach produces a constant bending moment region between the inner rollers, giving a more uniform stress state than centre-point loading.
Test Methods
1 Two-Point Loading (Reference Method)
Outer support span l = 3d (where d is the specimen width).
Distance between the two inner loading rollers = d.
Inner rollers are equally spaced between the outer supports.
Positional tolerance for all roller locations: ±2.0 mm.
2 Centre-Point Loading
A single loading roller is placed at mid-span.
Uses a different calculation formula.
Test Specimen Information
The specimens are prisms, and must conform to EN 12390-1:
| Shape | Prism (rectangular cross-section) |
| Nominal sizes (d) | Standard square-section prisms have cross-section side length d (mm): 70, 100, 150, 200, 250, 300. Specimen total length L ≥ 3.5d to fit the test span l=3d defined in EN 12390-5. Common industrial standard size: 150 mm × 150 mm × 750 mm (d=150mm).
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| Designated size | Within ±10% of nominal size |
| Perpendicularity of sides to base | 0.5 mm |
| Straightness of roller-contact surface (flexural test) | 0.3 mm |
| Production | Cast in moulds conforming to EN 12390-1 and EN 12350-1, cured per EN 12390-2; sawn specimens meeting EN 12390-1 are also permitted |
EN 12390-5 Flexural Strength Test of Hardened Concrete test equipmnet required:
Include environmental control facilities, specimen preparation equipment and Strength testing machines.
| Strength testing machines | Recommend UnitedTest Compression/Flexural Testing Machine |
| Compressive testing machine | Conform to EN 12390-4 (testing machines for compressive strength – the same machine class is used). |
| Roller Loading Assembly | Comprises two supporting rollers and two upper (loading) rollers. All rollers: steel, circular cross-section, diameter 20–40 mm. Roller length must be at least 10 mm longer than the specimen width. The three rollers (including the two upper ones) must be capable of free rotation about their axis and inclination in a plane normal to the specimen's longitudinal axis to ensure even load distribution.
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Key Test Parameters:
| Support span (l) | 3 × specimen width d |
| Inner roller spacing | d |
| Positional tolerance | ±2.0 mm |
| Stress rate | 0.04 – 0.06 MPa/s (constant) |
| Initial preload | ≤ ~20% of expected failure load |
| Rate tolerance during final loading | ±10% of selected rate |
| Time from removal from cure to test | As soon as practicable, within 10 hours |
Standard Test Stipulations & Regulatory Rules
Specimens shall conform to EN 12390-1; mould-cast specimens additionally comply with EN 12350-1 and EN 12390-2.
Direction of loading must be perpendicular to the casting direction of the specimen – the casting direction is identified and marked on the specimen.
The specimen is correctly centred with its longitudinal axis at right angles to the longitudinal axis of the upper and lower rollers.
Load is not applied until all rollers rest evenly against the specimen.
The load is applied without shock and increased continuously to failure.
Good practice: measure density before the flexural test (per EN 12390-7) as a check on concrete compaction.
Step-by-Step Test Procedure of EN 12390-5 Flexural Strength Test of Hardened Concrete
Machine preparation: Clean testing machine rollers, calibrate force reading function, install either two-point or centre-point loading frame and verify roller positions within ±2.0 mm tolerance.
Specimen placement: Centre prism on lower support rollers, ensure casting direction is perpendicular to loading force axis.
Pre-contact adjustment: Lower upper roller assembly until all rollers evenly rest on prism top surface with no gaps.
Loading setup: Calculate target loading rate R from the stress rate 0.04–0.06 MPa/s using the matching formula for the loading method in use.
Continuous loading: Apply preload (<20% failure load), then increase force at constant calibrated rate without impact until the prism fractures and load peaks drop.
Data recording: Log the maximum failure load F, record fracture position, note any abnormal concrete surface defects.
Calculation: Compute flexural strength using the corresponding formula, round result to 0.1 MPa precision.
Applicable Industry Fields
EN 12390-5 is essential in any context where concrete is subjected to bending or tensile stresses due to flexure. Primary application areas include:
Concrete pavements / rigid road pavements – flexural strength (modulus of rupture) is the primary design parameter, often more relevant than compressive strength.
Precast concrete beams, slabs, and structural elements – quality control and acceptance testing.
Floor slabs and industrial ground floors.
Bridge deck elements and other flexural members.
Concrete products manufacturing – verification of mix design performance and production consistency.
Research and development – studying concrete fracture behaviour, toughness, and the effect of additives or new materials.
Product certification and compliance testing for CE marking under the Construction Products Regulation (EU) No 305/2011.
Typical users: materials and concrete testing laboratories, precast manufacturers, contractors, structural and pavement engineers, and product certification bodies.
Related Test Standard
Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50-mm] Cube Specimens) | |
| ISO 4012 | Concrete; Determination of compressive strength of test specimens |
| ASTM C293 | Standard Test Method for Flexural Strength of Concrete (Using Simple Beam With Center-Point Loading) |
| ASTM C78 | Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading) |
| EN 12390-13 | Secant elastic modulus in compression (combines with flexural strength for structural deformation analysis). |
| EN 12390-1 | Defines prism specimen geometry, mould tolerances and dimensional rules (direct prerequisite for specimen preparation). |
| EN 12390-4 | Universal testing machine performance and calibration specifications. |
| EN 12390-5 | Testing hardened concrete. Flexural strength of test specimens |
| EN 12390-3 | Tensile splitting strength test (alternative indirect tensile measurement, produces different tensile stress values than flexural test). |
| EN 12390-6 | Admixtures for concrete, mortar and grout-Admixtures for grout for prestressing tendons. Definitions, requirements, conformity, marking and labelling |
Why the Test Is Important for the Material
Concrete has very high compressive strength but relatively low tensile/flexural strength – typically only 10–15% of its compressive strength (fₑ′). Many real-world concrete structures fail not in compression but in bending or tension:
Pavements crack and fail under wheel loads due to flexural stresses.
Beams and slabs develop tensile cracks at the soffit under bending moments.
Precast elements are handled and transported in a flexural state.
Therefore, the flexural strength test:
Provides the key design parameter for pavements and other flexural members, where modulus of rupture is used directly in structural design.
Assesses the tensile-side performance of concrete, complementing the compressive strength test (EN 12390-3).
Verifies the effectiveness of mix designs – especially those with fibres, polymers, or novel admixtures that aim to improve tensile/flexural behaviour.
Controls production quality – ensuring consistency across batches.
Checks compaction quality – density measurement (EN 12390-7) before the flexural test serves as an indicator of proper compaction; poor compaction reduces flexural strength significantly.
Enables comparison and specification compliance – providing a standardized, repeatable method across Europe and internationally.
Keywords: EN 12390‑5 concrete flexural strength test, hardened concrete bending strength tester, concrete prism flexural testing machine, EN 12390‑5 concrete test equipment, EN 12390‑5 test for flexural strength of hardened concrete specimens, laboratory flexural strength tester for concrete prisms, concrete tensile capacity indirect test per EN 12390‑5, UnitedTest EN 12390‑5 compliant concrete flexural tester, construction lab hardened concrete bending test machine
Related products and device
Related Standard
ASTM C109 is the fundamental test method for determining the compressive strength of hydraulic cement using 2-inch (50-mm) mortar cubes. It specifies a standardized procedure to prepare, cure, and test 50-mm (2-in.) cube mortar specimens for compressive strength. The mortar mix ratio is 1 part cement to 2.75 parts standard sand (by mass). For Portland/air-entraining Portland/Portland-limestone cements, water content is fixed; for other cements, water is adjusted to achieve a flow of 110±5 (per 25 drops on a flow table, ASTM C230). Specimens are compacted in two layers by tamping, cured, and loaded in compression until failure to calculate strength as peak load divided by cross-sectional area.
ISO 679 determining the compressive strength (and optionally flexural strength) of cement, using a standardized mortar mix rather than testing pure cement paste or concrete. It is the benchmark that allows different cements from different plants and countries to be compared on a level playing field.
FAQs for EN 12390-5 Concrete Flexural Strength Test
UnitedTest EN 12390-5 Concrete Flexural Strength Testing Machine | Two-Point & Centre-Point Loading Compliant Tester for Hardened Concrete Prisms
UnitedTest is professional manufacturer of EN 12390-5:2019 compliant concrete flexural testing machine, fully matching EN 12390-1 & EN 12390-4 standards. Our servo-controlled flexural tester supports two-point reference loading and normative centre-point loading for 100/150/200mm concrete prisms, constant stress rate 0.04–0.06MPa/s automatic control, calibrated steel roller assembly ±2mm position tolerance. Ideal for civil engineering labs, precast concrete factory QC, highway pavement material testing, Eurocode 2 structural compliance inspection. Customizable frame capacity, auto data calculation & EN standard test report export, 1-year global warranty, EU certification available.
Q1: What is EN 12390-5, and why is this flexural strength test important for concrete?
A: EN 12390-5 is the harmonized European standard for measuring flexural strength (modulus of rupture) of hardened concrete prisms.
This test is critical because concrete is extremely weak in tension (only ~1/10 of compressive strength). Most pavement, slab, precast panel failures start with bending tensile cracks; compressive cube tests cannot reflect tensile bending capacity. Engineers rely on EN 12390-5 data for Eurocode 2 structural design, pavement mix design, factory quality control, and long-term durability evaluation of bending-bearing concrete elements (roads, bridge decks, curb stones).
Q2: What are the two loading methods in EN 12390-5, and what’s the key difference?
A: Two-point (third-point) loading (Main text, reference method): Two upper loading rollers spaced d apart over span l=3d, creates a pure bending zone with zero shear stress – official reference for compliance testing.
Centre-point single loading (Normative Annex A): One central roller at mid-span for simplified testing.
Lab intercomparison data proves centre-point results are 13% consistently higher than two-point values. Test reports must clearly state which loading setup is used to avoid comparison errors.
Q3: What size concrete prism is most widely used for EN 12390-5 testing?
A: The industry standard size is 150 mm × 150 mm × 750 mm prism (d=150 mm). The support span l=450 mm (3×150 mm), total length L=750 mm ≥3.5d (525 mm). Smaller 100×100 mm prisms are allowed only if d ≥3.5 × concrete maximum aggregate size Dmax (EN 12390-1 rule).
Q4: Why must loading direction be perpendicular to concrete casting direction?
A: Concrete internal aggregate layering forms during pouring, creating directional strength anisotropy. Loading parallel to casting direction will deliver artificially low/high strength values that do not represent real structural performance. The casting direction must be marked on every prism for test alignment.
Q5: What is the mandatory loading stress rate range for EN 12390-5?
A: Constant stress rate must be controlled between 0.04 MPa/s ~ 0.06 MPa/s, with allowable ±10% fluctuation near specimen failure. Separate N/s loading rate formulas apply for two-point and centre-point setups, calculated from prism cross-section dimensions and span length.
Q6: What if the concrete fracture occurs outside the upper loading rollers during test?
A: This fracture location must be explicitly recorded in the formal test report per Clause 9 of EN 12390-5. Cracks outside the pure bending zone indicate potential specimen defects, uneven roller contact, or misalignment, and the data may require supplementary re-testing.
Q7: Why are my repeated flexural test results highly scattered?
A: Top common non-compliance causes against EN 12390-5:
Roller positions exceed ±2.0 mm tolerance, creating eccentric loading.
Specimen surfaces unground, uneven roller contact leading to stress concentration.
Loading rate faster/slower than 0.04–0.06 MPa/s, or shock sudden loading.
Specimen dried out before testing (over 4 hours uncovered in lab).
Loading parallel instead of perpendicular to casting direction.
UnitedTest machines feature automatic constant stress rate control and calibrated roller jigs to eliminate most repeatability errors.
Q8: How does EN 12390-5 differ from splitting tensile test EN 12390-6?
A: EN 12390-5 measures tensile stress from pure bending (simulates real slab/pavement bending loads). EN 12390-6 splitting test generates indirect tension via diametral compression; splitting tensile values cannot be converted directly to flexural strength for structural bending design, so flexural testing is required for pavement and slab compliance.
Q9. What types of concrete elements benefit most from this test?
A: Elements where bending or tensile stresses dominate:
Concrete pavements / rigid road pavements
Precast concrete beams, slabs, and structural elements
Floor slabs and industrial ground floors
Bridge deck elements
Concrete kerbs, paving flags, and natural stone slabs
Q10. Why might my flexural strength results be lower than expected?
A: Common causes:
Poor compaction — density check per EN 12390-7 before testing is recommended
Incorrect loading direction relative to casting direction
Specimen non-conformity — dimensional or shape deviations exceeding EN 12390-1 tolerances
Improper roller alignment — positional tolerance exceeds ±2.0 mm
Loading rate too high or inconsistent — outside the 0.04–0.06 MPa/s range
Premature drying of the specimen before testing
Q11. Why Choose UnitedTest for Your EN 12390-5 Testing Needs?
A: 1. Full EN 12390-5 Normative Compliance
Our integrated loading jig is pre-equipped with dual-mode roller sets for both reference two-point loading and Annex A centre-point single loading. All steel rollers follow standard dimensions (20–40mm diameter, overlength specimen contact design), fixed positioning fixture ensures ±2.0mm maximum positional error as required by EN 12390-5. The servo-hydraulic control system maintains strict constant stress loading rate 0.04 MPa/s to 0.06 MPa/s with ±10% allowable deviation, eliminating manual loading fluctuations that cause invalid test data.
2. Wide Compatibility with EN 12390-1 Standard Prisms
Supports all nominal prism sizes defined in EN 12390-1: 70, 100, 150, 200, 250, 300 mm square cross-section prisms with L≥3.5d length. Adjustable support span base easily locks l=3d span length for every specimen dimension; platform surface flatness meets specimen grinding inspection auxiliary requirements, suitable for cast lab prisms and sawn structural concrete test blocks.
3. Automated EN Standard Test Workflow & Data Output
Built-in industrial control software preloads EN 12390-5 flexural strength calculation formulas for both loading methods. After recording maximum failure load F, the system instantly computes fct,fl value rounded to 0.1 MPa precision, auto-logging test temperature, specimen dimension, fracture position, loading mode, specimen curing age. Export editable test reports fully matching EN 12390-5 Clause 9 reporting checklist, directly usable for EU construction certification, precast factory quality audit and road pavement material submission.
4. UnitedTest Manufacturer Advantages
Direct factory supply: No middlemen, custom frame load capacity (10kN–200kN flexural force range) available for special large prism testing.
EU safety & calibration certification: Each machine delivered with factory calibration certificate aligned to EN 12390-4 force accuracy rules.
Global after-sales service: Local technical support for Europe, Southeast Asia, Middle East; 12-month full machine warranty, spare roller kits included.
All-in-one optional upgrade: Combined compression-flexural integrated machine for EN 12390-3 compressive + EN 12390-5 flexural dual testing to save lab space.
Moisture-proof heavy-duty frame design, stable performance under long-term continuous lab operation, reducing frequent re-calibration frequency.
Searching for a reliable EN 12390-5 compliant concrete flexural strength testing machine? Contact UnitedTest manufacturer team for free technical datasheet, test video demonstration and customized quotation matching your laboratory prism size and daily test throughput requirements. Our engineers provide professional standard compliance guidance for all EN 12390 series concrete testing equipment.
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