A practical guide to how combined cement flexural and compressive strength testers work, the international standards they follow, and what to look for when choosing one.
Why Cement Strength Testing Matters
Cement is the most widely used construction material in the world, and its strength is the single most important property governing the safety, durability and service life of concrete structures. Before any cement can be used on site, its mechanical strength must be verified through standardized laboratory testing.
Strength testing is the backbone of cement quality control. Manufacturers rely on it to certify strength classes (such as 32.5, 42.5 and 52.5 under EN 197-1) and to monitor production consistency. Engineers and specifiers reference it in project specifications, while independent laboratories use it for third-party verification, product acceptance and dispute resolution.
Because these results drive critical engineering decisions, testing must be accurate, repeatable and traceable to recognized standards. This is exactly what a cement flexure compression testing machine is designed to deliver.
Fig. 4 Typical strength development of cement mortar: compressive strength grows quickly in the first seven days and then slows, while flexural strength develops more gradually.
What Is a Cement Flexure Compression Testing Machine
A cement flexure compression testing machine - also called a combined cement flexural/compressive tester - is a servo-hydraulic or electro-mechanical press used to measure the mechanical strength of cement mortar specimens. A combined machine performs both tests on a single platform:
Flexural (bending) strength - measured on 40 mm × 40 mm × 160 mm prism specimens using a three-point bending fixture.
Compressive strength - measured on the two halves of the prism after the flexural test, or on standard mortar cubes.
Fig. 1 A combined automatic cement flexure and compression testing machine with dual test stations and touchscreen control.
By integrating both tests into one machine, laboratories save floor space, shorten the work cycle, and avoid the cost of purchasing and maintaining two separate presses.
How the Machine Works: Two Tests, One Platform
The Flexural (Three-Point Bending) Test
The flexural test evaluates the tensile-bending resistance of the cement mortar. A prism specimen is placed horizontally on two support rollers with a standard span of 100 mm. A central loading roller applies a steadily increasing vertical force at mid-span until the prism fractures into two halves.
Under EN 196-1 the loading rate is held constant at 50 ± 10 N/s, applied through rollers of about 10 mm diameter. The flexural strength is calculated from the maximum load at fracture:
Rf = 1.5 × Ff × l / b³
where Ff is the breaking force, l is the support span (100 mm) and b is the side dimension of the prism cross-section (40 mm).
Fig. 2 Three-point flexural strength test on a 40 × 40 × 160 mm mortar prism.
The Compressive Strength Test
The two halves broken during the flexural test are then tested in compression. Each half-prism is centred between the machine's hardened platens with its 40 mm × 40 mm end face loaded axially. A self-aligning spherical seat ensures the load is applied evenly and perpendicular to the specimen face.
Under EN 196-1 the load is increased continuously at 2400 ± 200 N/s until the specimen fails. The compressive strength is:
Rc = Fc / A
where Fc is the maximum crushing force and A is the bearing area (1600 mm² for a 40 mm × 40 mm face). Three prisms yield six compressive data points, from which the mean compressive strength is reported after removing statistical outliers.
Fig. 3 Compressive strength test on a half-prism with a 40 mm × 40 mm bearing face.
Key International Standards
Different markets follow different standards, and the machine must be configured to comply with the ones that apply in your market. The table below lists the most common standards covered by combined cement flexure/compression machines.
|
Standard |
Test |
Specimen |
|
EN 196-1 |
Flexural and compressive strength of cement mortar |
40 × 40 × 160 mm prism |
|
ASTM C348 |
Flexural strength of hydraulic-cement mortars |
40 × 40 × 160 mm prism |
|
ASTM C349 |
Compressive strength using portions of prisms broken in flexure |
40 × 40 mm half-prism |
|
ASTM C109 |
Compressive strength of hydraulic-cement mortars |
50 mm (2 in.) cube |
|
GB/T 17671-2021 |
Cement mortar strength (ISO method, ISO 679:2009, MOD) |
40 × 40 × 160 mm prism |
Table 1 Common standards covered by combined cement flexure/compression machines.
Machine Design and Key Specifications
|
Parameter |
Typical specification |
|
Compression capacity |
200 – 300 kN (for example, 300 kN) |
|
Flexural capacity |
10 – 15 kN |
|
Accuracy / class |
±1% (class 1 in accordance with EN ISO 7500-1) |
|
Loading control |
Closed-loop servo-hydraulic or electro-mechanical, constant rate |
|
Force measurement |
High-resolution load cell with rate control |
|
Platens |
Hardened steel or tungsten carbide, hardness ≥ 600 HV, self-aligning spherical seating |
|
Specimens |
40 × 40 × 160 mm prism; 40 × 40 mm and 50 mm cube accessories |
|
Control & data |
Touchscreen, automatic test cycle, data logging and export |
|
Standards |
EN 196-1, ASTM C109 / C348 / C349, GB/T 17671, ISO 679 |
Table 2 Typical specification ranges for automatic cement flexure/compression machines.
How to Select the Right Machine
Determine the test standards that apply in your market. This decides the specimen geometry and the required loading rates.
Check capacity and force range. Make sure the compression range covers the highest strength class you will test.
Verify accuracy and class. Look for a machine verified to class 1 (or better) in accordance with EN ISO 7500-1.
Consider automation. Closed-loop rate control, an automatic flexural-to-compression workflow and touchscreen data management reduce operator error and improve repeatability.
Check accessories and fixtures - the flexural jig, compression platens, cube accessories and spare rollers.
Evaluate calibration, spare parts and after-sales support from the manufacturer.
Maintenance, Calibration and Compliance
Regular calibration against reference load cells keeps readings accurate and traceable. Annual calibration by an accredited body is standard practice in certified laboratories.
Daily care includes keeping the platens and rollers clean, checking hydraulic oil levels, and inspecting the load cell and safety guards. A properly maintained machine delivers years of reliable service and keeps your laboratory compliant with ISO/IEC 17025 and national accreditation requirements.
Conclusion
A cement flexure compression testing machine is an indispensable tool for cement manufacturers, construction laboratories and testing institutions. It provides the accurate, repeatable and standards-compliant flexural and compressive strength data that protect product quality and engineering safety.
When choosing a machine, prioritize compliance with your market's standards, verified accuracy, automation and reliable manufacturer support. The right machine will serve your quality-control workflow for many years.
For detailed specifications, a quotation or help selecting the right model for your laboratory, contact our team.