Quality & Inspections · Mandatory · Construction
Concrete Test Record
A record of concrete testing including slump tests and cube samples taken during pours.
Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. BS EN 206 remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.
| Legal basis | BS EN 206 + BS 8500 + BS EN 12350 (fresh) + BS EN 12390 (hardened) |
| Slump test | Measures fresh concrete workability at point of discharge. Acceptance within specified consistency class (S1–S5) or ±30mm of target |
| Cube test | 150mm cubes, minimum 3 per sample, cured at 20°C, tested at 7 days (indicator) and 28 days (conformity) |
| Strength notation | C25/30 means cylinder 25 N/mm² / cube 30 N/mm². UK uses cube strength |
| Delivery ticket | Primary documentary evidence of mix supplied — retain ALL tickets |
| Failed cubes | Inform structural engineer immediately. Never proceed to load the structure pending investigation |
1. Concrete Testing — Documentary Evidence of Specification Compliance
Once concrete is placed and hardened, the only reliable way to verify its strength is through cube testing. The slump test at discharge is the first quality check — confirming that the concrete delivered has the correct workability for the intended application. The 28-day cube test is the conformity evidence that the concrete has achieved the specified characteristic strength.
The concrete test record links every cube result back to the specific element poured, the delivery ticket, the date and time of placement, and the person who took the sample. Without this traceability, a cube result is just a number — it cannot demonstrate that a specific structural element achieved the required strength. The record must be maintained in real time as pours are carried out, not compiled retrospectively from laboratory reports.
Never add water on site
Never add water to concrete on site to restore workability — it reduces strength and voids the producer's conformity declaration. If slump is outside the specified range at discharge, reject the load.
2. Concrete Test Record — Content
The concrete test record must capture every data point required to demonstrate traceability from the delivered mix through to the confirmed 28-day strength result. Each row represents a single sample taken from a specific delivery, linked to the structural element being poured.
| Column | Description |
|---|---|
| Project / element | The project name and the specific structural element being poured (e.g. pad foundation F12, ground floor slab bay 3) |
| Date / time | Date and time of sampling, aligned with the pour record |
| Delivery ticket ref | Unique reference number from the concrete delivery ticket — links the sample to the batch supplied |
| Specified grade | The specified concrete grade (e.g. C25/30, C32/40) including any additional requirements (sulfate resistance, water/cement ratio) |
| Slump measured | Slump value recorded at point of discharge in mm, compared to the specified consistency class |
| Cube ID | Unique identification number or mark applied to each cube at the time of casting |
| Cube dimensions | Cube size — typically 150mm for standard testing |
| Curing | Curing method and conditions — standard curing at 20°C ±2°C in water |
| Lab reference | Reference number assigned by the UKAS-accredited testing laboratory |
| 7-day result | Compressive strength at 7 days in N/mm² — early indicator of 28-day performance |
| 28-day result | Compressive strength at 28 days in N/mm² — the conformity result |
| Sampled by | Name of the person who took the sample and cast the cubes |
| Engineer notification | Record of notification to the structural engineer of any failed or marginal results |
3. Common Mistakes
Sampling from the first or last part of the discharge
Concrete samples must be taken from the middle portion of the discharge to be representative of the batch. The first and last portions may have different water content and aggregate distribution. BS EN 12350 specifies the sampling procedure — samples taken from unrepresentative portions will produce misleading results.
Not conducting the slump test at the point of discharge
The slump test must be carried out at the point of discharge from the truck mixer, before any additional water or admixture is added. Testing concrete after it has been placed in a pump hopper or after water has been added does not reflect the as-delivered properties of the mix.
Not recording cube results against the element poured
A cube result that cannot be traced back to the specific structural element it represents has limited value. The test record must link each cube set to the delivery ticket, the element poured, and the date/time of placement. Without this link, failed cubes cannot be investigated effectively.
Using a non-UKAS accredited laboratory
Cube testing must be carried out by a UKAS-accredited laboratory to BS EN 12390. Results from non-accredited laboratories may not be accepted by the engineer or client and may not satisfy contractual or regulatory requirements for conformity evidence.
Not retaining delivery tickets
The delivery ticket is the primary documentary evidence of the concrete mix supplied. It records the mix design, batch quantities, water/cement ratio, admixtures, and time of batching. All delivery tickets must be retained as permanent project records — they are essential for any future investigation into concrete quality.
4. Frequently Asked Questions
How many cube samples are required per pour?▾
As a minimum, 1 sample per 200m³ of concrete and at least 1 sample per day of placing. Each sample typically consists of 3 cubes — one tested at 7 days and two tested at 28 days. The specification or contract may require a higher sampling frequency for critical elements.
What does the 7-day result tell us?▾
The 7-day result is an early indicator of likely 28-day strength. Typically, concrete achieves 65-70% of its 28-day strength at 7 days. A low 7-day result provides an early warning that the 28-day result may fail, allowing investigation and contingency planning before the 28-day test. It is not a conformity result in itself.
What happens if 28-day cubes fail?▾
Notify the structural engineer immediately. The investigation may include reviewing the delivery tickets, checking the mix design, reviewing curing conditions, and potentially coring the in-situ concrete to test actual strength. The structure must not be loaded beyond its confirmed capacity pending the outcome of the investigation.
What is the difference between specified and characteristic strength?▾
The specified strength is the minimum strength required by the structural design. The characteristic strength is the 5th percentile value — meaning that statistically, no more than 5% of test results should fall below this value. Conformity is assessed against the characteristic strength using the rules in BS EN 206 and BS 8500.
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