🏗️ Compressive Strength of Concrete
In short
Determination of compressive strength of concrete specimens (cubes, cylinders) using a hydraulic press. The test is performed according to PN-EN 12390-3:2019; Specimen dimensions: Cubes 150×150×150 mm or cylinders Ø150×300 mm. The procedure comprises 10 steps (about 28 days 28 min–28 days 35 min in total); it is used for: Classification of concrete into strength classes (C8/10 to C100/115), Factory production control of ready-mixed concrete (FPC), Acceptance of concrete structures on construction sites.
At a glance
- Standard: PN-EN 12390-3:2019
- Category: Construction
- Procedure steps: 10
- Total time of stages: 28 days 28 min–28 days 35 min
- Specimen dimensions: Cubes 150×150×150 mm or cylinders Ø150×300 mm
- Loading rate: 0.6 ± 0.2 MPa/s (150 mm cubes)
- Press capacity: 200–3000 kN (class 1 accuracy)
Overview
Compressive strength is the most important mechanical property of concrete, serving as the basis for classifying concrete into appropriate strength classes (e.g., C20/25, C30/37). The test involves loading a concrete specimen (cubic 150×150×150 mm or cylindrical Ø150×300 mm) with a compressive force at a constant rate until failure. The result is expressed in megapascals (MPa) and represents the ratio of the maximum failure force to the cross-sectional area of the specimen.
The PN-EN 12390-3 standard is a key document in the quality control system for ready-mixed and structural concrete in Poland and Europe. Every concrete plant, road and construction laboratory performs this test routinely. The results form the basis for acceptance of concrete structures — without positive strength test results, structures cannot be approved for use.
Test specimens are molded according to PN-EN 12390-2, stored under standard conditions (water or humidity chamber, 20 ± 2°C) and tested after a specified curing period — most commonly after 28 days, but also after 7 and 90 days. The result is the arithmetic mean of at least 2 specimens. The loading rate is 0.6 ± 0.2 MPa/s for 150 mm cubes.
Testing is mandatory as part of factory production control of concrete (FPC), assessment of conformity of concrete in structures (PN-EN 13791), and quality control on construction sites. Laboratories performing these tests must be accredited by PCA.
Method principle
A concrete specimen of known dimensions is placed centrally on the lower platen of a hydraulic press. The compressive force is applied perpendicular to the direction of casting, at a constant stress rate of 0.6 ± 0.2 MPa/s (for 150 mm cubes). The load increases smoothly until specimen failure. Compressive strength fc is calculated as the ratio of maximum failure force F to cross-sectional area Ac: fc = F / Ac [MPa]. The result is rounded to 0.1 MPa.
Applications
- Classification of concrete into strength classes (C8/10 to C100/115)
- Factory production control of ready-mixed concrete (FPC)
- Acceptance of concrete structures on construction sites
- Assessment of concrete strength in existing structures (core samples)
- Quality control of precast concrete elements
- Testing of concrete pavements for roads and airports
- Technical expertise of buildings and bridges
- Research and development of new concrete mixtures
Key parameters
| Parameter | Value |
|---|---|
| Specimen dimensions | Cubes 150×150×150 mm or cylinders Ø150×300 mm |
| Loading rate | 0.6 ± 0.2 MPa/s (150 mm cubes) |
| Press capacity | 200–3000 kN (class 1 accuracy) |
| Curing time | 7, 28 or 90 days (20 ± 2°C, RH ≥95%) |
| Test temperature | 20 ± 5°C |
| Accuracy | ±1% of force range (class 1 per PN-EN 12390-4) |
Standard
- Standard number
- PN-EN 12390-3:2019
- Title (PL)
- Badania betonu — Część 3: Wytrzymałość na ściskanie próbek do badań
- Title (EN)
- Testing hardened concrete — Part 3: Compressive strength of test specimens
Step-by-step procedure
-
Sampling and specimen preparation
Mold specimens according to PN-EN 12390-2 from concrete mix. Compact on vibrating table or by tamping. Mark specimens.
-
Specimen curing
After demolding (after 16–24 h), place in curing chamber or water bath (20 ± 2°C, humidity ≥95%). Store until test day.
-
Removal and preparation for testing
Remove specimens from water/chamber. Dry surface. Measure dimensions to 0.1 mm accuracy. Weigh. Check flatness of end surfaces.
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Surface leveling (capping)
If irregularities >0.1 mm — apply sulfur capping or use neoprene pads. Ensure perpendicularity and parallelism of surfaces.
-
Specimen placement in press
Place specimen centrally on lower press platen. Loading direction perpendicular to casting direction. Check centering.
-
Specimen loading
Start press. Apply preload. Continue at constant rate 0.6 ± 0.2 MPa/s until specimen failure.
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Reading and recording results
Read maximum failure force F [kN]. Calculate strength: fc = F/Ac. Note failure type (correct — double pyramid).
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Assessment of failure type
Compare with reference patterns per PN-EN 12390-3 (figure in standard). Incorrect failure (e.g., diagonal) may indicate centering error.
-
Final result calculation
Result = arithmetic mean of minimum 2 specimens. If scatter >10% — discard outlier and repeat test.
-
Documentation and reporting
Prepare test report including: specimen dimensions, mass, curing conditions, failure force, strength, failure type.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| 3000 kN hydraulic press | Controls Automax, Matest C070, Form+Test MEGA 3, Testing GmbH | 80 000–250 000 PLN |
| 150 mm specimen molds | Three-part steel molds 150×150×150 mm, Controls, Matest | 800–2 500 PLN/pc |
| Curing chamber | Controls 10-D1428, Matest — temp. 20 ± 2°C, RH ≥95% | 15 000–50 000 PLN |
| Caliper / measuring ruler | Mitutoyo 500-197-30, accuracy 0.01 mm | 200–800 PLN |
| Laboratory balance 30 kg | Radwag WLC 30/A2, accuracy 1 g | 2 000–5 000 PLN |
| Vibrating table for compaction | Controls 55-C0161/Z, Matest C160 | 5 000–15 000 PLN |
| Result recording software | Controls DATAMANAGER, Form+Test TestXpert | 5 000–20 000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Mold release oil (anti-adhesive agent) | — | For lubricating molds before concreting, not affecting concrete |
| Tap water | — | For storing specimens under standard conditions (20 ± 2°C) |
| Sulfur or cement paste (capping) | 7704-34-9 | For leveling specimen end surfaces (alternative: neoprene pads) |
Health and safety (OHS)
- Hydraulic press — crushing hazard, never insert hands between platens during operation
- Concrete fragments during failure — mandatory safety glasses and press guard
- Heavy specimens (approx. 8 kg for 150 mm cube) — injury risk when handling
- Sulfur for capping — toxic fumes, use exhaust and protective mask
- Protective gloves when handling fresh concrete (alkaline action)
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN 12390-3:2019 — “Testing hardened concrete — Part 3: Compressive strength of test specimens”.
How does this method work?
A concrete specimen of known dimensions is placed centrally on the lower platen of a hydraulic press. The compressive force is applied perpendicular to the direction of casting, at a constant stress rate of 0.
What is the measuring range and accuracy?
Specimen dimensions: Cubes 150×150×150 mm or cylinders Ø150×300 mm; Loading rate: 0.6 ± 0.2 MPa/s (150 mm cubes); Press capacity: 200–3000 kN (class 1 accuracy); Curing time: 7, 28 or 90 days (20 ± 2°C, RH ≥95%).
How long does the test take?
The times given for the individual stages add up to approximately 28 days 28 min–28 days 35 min. The procedure comprises 10 steps.
What equipment is required?
3000 kN hydraulic press, 150 mm specimen molds, Curing chamber, Caliper / measuring ruler, Laboratory balance 30 kg, Vibrating table for compaction, Result recording software. Indicative cost of the core instrument (3000 kN hydraulic press): 80 000–250 000 PLN.
Where is this test used?
Classification of concrete into strength classes (C8/10 to C100/115); Factory production control of ready-mixed concrete (FPC); Acceptance of concrete structures on construction sites; Assessment of concrete strength in existing structures (core samples); Quality control of precast concrete elements; Testing of concrete pavements for roads and airports; Technical expertise of buildings and bridges; Research and development of new concrete mixtures.
What safety precautions apply?
Hydraulic press — crushing hazard, never insert hands between platens during operation; Concrete fragments during failure — mandatory safety glasses and press guard; Heavy specimens (approx. 8 kg for 150 mm cube) — injury risk when handling; Sulfur for capping — toxic fumes, use exhaust and protective mask; Protective gloves when handling fresh concrete (alkaline action).
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN 12390-3.