Concrete & Civil Testing · CUBE
Concrete Compression Testing
The crush that certifies the pour.
Concrete compression testing measures the compressive strength of concrete by loading standard specimens — cubes cast at the pour, or cores cut from the structure — to failure in a calibrated press. Tested to I.S. EN 12390-3 (cubes) and I.S. EN 12504-1 (cores), the failure load divided by the bearing area is the strength on which structures are accepted.
The explainer
Watch how it works.
Schematic · loops automatically
1Sample and cast
Fresh concrete is sampled at the pour; cubes are moulded in layers, compacted, marked and protected.
2Cure under control
Specimens cure in water at controlled temperature — curing is part of the test, not storage.
3Weigh, measure, centre
Density is recorded (the free health check), dimensions verified, and the cube centred between the platens.
4Load at constant rate
Force climbs steadily; the cube resists, micro-cracks knit — then the double-pyramid failure lets go at peak load.
5Strength versus class
Peak load over area gives N/mm²; results are certified against the specified class and failures flagged immediately.
The physics
Concrete is a compression material: designs put it to work carrying load in crush, so the acceptance test crushes it. A cube (150 mm or 100 mm) is cast from sampled fresh concrete, compacted and cured under controlled conditions, then loaded between hardened platens at a specified, constant rate until it fails. Peak force over bearing area — newtons per square millimetre — is the number the whole contract turns on.
The failure itself is diagnostic. A properly tested cube fails in the classic double-pyramid (hourglass) pattern as friction at the platens confines the ends while the mid-height shears — the standard illustrates satisfactory and unsatisfactory failure patterns, and an odd fracture flags specimen or machine problems rather than concrete. Density, recorded before the crush, is the early-warning companion: a light cube is almost always a badly made cube.
Where the question moves from “was the batch right?” to “what is in the structure?”, cores answer. Cut, examined and tested to I.S. EN 12504-1, cores measure in-situ strength — informing assessments, change-of-use checks and investigations of non-conforming cube results, with corrections for geometry and direction of loading applied by the standard’s rules.
Where it earns its keep
Typical applications
- Contract acceptance of structural pours
- Investigating non-conforming results via cores
- Structural assessment for reuse and modification
- Pavement-quality concrete and precast verification
Standards & schemes
| Designation | Covers |
|---|---|
| I.S. EN 12390-3 | Compressive strength of test specimens |
| I.S. EN 12390-7 | Density of hardened concrete |
| I.S. EN 12504-1 | Cores — cutting, examination and compression testing |
| I.S. EN 206 + NA | Specification and conformity framework the results serve |
Sampling, curing and testing are performed under Metlab’s laboratory quality system in Cork and Dublin, with certificates issued on the day of test and failures escalated to the responsible engineer.
What does a “satisfactory failure” of a cube look like?
The classic pattern is the double pyramid — cracking that leaves opposing cones as the platens confine the cube ends. Explosive edge failures, single-plane shears or spalling to one face suggest specimen or machine issues, and the standard requires the failure pattern to be assessed, not just the number recorded.
Cube or core — which is “right”?
Both, for different questions. Cubes judge the delivered batch under standard curing; cores judge the structure as built, including compaction and site curing. When cubes fail, cores are usually the arbiter of what the structure actually achieved.
Why do you record density with every strength result?
Because density exposes specimen problems before they masquerade as weak concrete: an under-compacted or badly made cube is light, and its strength result is meaningless. Density with every crush is cheap insurance for everyone relying on the number.
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