The cement compressive strength test to EN 196-1 is the reference method for classifying cement, determining the strength developed by a standard mortar at fixed ages.
What the Test Measures
Standard mortar prisms (40 × 40 × 160 mm) are made with CEN reference sand at a fixed water/cement ratio. Each prism is first broken in flexure; the two halves are then tested in compression. The 28-day compressive strength defines the cement strength class (e.g. 42.5, 52.5).
Apparatus Required
- Compression machine with 40 mm platens (and a flexural device)
- Prism moulds (40 × 40 × 160 mm) and a standard jolting/mortar mixer
- CEN standard sand and curing tank
- Calibrated load measurement
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Test Procedure
- Mix standard mortar and cast prisms, compacting on the jolting apparatus.
- Cure prisms in water at 20°C to the test age (commonly 2 and 28 days).
- Break each prism in flexure to obtain two halves.
- Compress each half between 40 mm platens, loading at 2400 ± 200 N/s.
- Record the maximum load for each half.
Calculation & Reporting
Compressive strength = Maximum load ÷ 1600 mm² (the 40 × 40 mm platen area), reported as the mean of the six half-prism results in MPa.
Acceptance Criteria
The 28-day mean must meet the limits for the declared strength class under EN 197-1 (for example ≥ 42.5 MPa for class 42.5 N). Early-age (2-day) strength confirms the N or R sub-class.
Frequently Asked Questions
Why test the prism halves and not separate cubes?
EN 196-1 derives compressive specimens from the flexural test halves, which is efficient and standardised; the 40 mm platen area fixes the stressed area.
Is EN 196-1 the same as ASTM C109?
Both measure mortar compressive strength but differ in specimen (EN uses prism halves, ASTM uses 50 mm cubes) and sand, so results are not directly interchangeable.
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