What is a concrete cube test register?
A register of concrete cube samples cast on site and their compressive strength results at 7 and 28 days. It is a mandatory quality record on almost every reinforced concrete contract, and the evidence that the concrete supplied met the specified grade.
What is in the cube test register workbook?
- Project Details — project particulars, laboratory, cube size and the derived cross-sectional area.
- Cube Test Register — one row per cube, grouped in sets of three, with strengths and set averages calculated.
- Filled Sample — four sets of illustrative results.
How does the cube test register sheet calculate?
- Cross-sectional area = cube size × cube size; 150 mm cubes give 22,500 sq mm.
- Compressive strength (N/sq mm) = failure load in kN × 1,000 ÷ cross-sectional area in sq mm, for both the 7-day and 28-day tests.
- Set average = the average of the three 28-day strengths in the set.
- The acceptance value for your grade is entered by you from IS 456:2000 Clause 16 and Table 11. The register records and compares; it does not apply the acceptance criteria for you.
Worked example from the sample sheet: a 150 mm cube failing at 640.2 kN has a strength of 640.2 × 1,000 ÷ 22,500 = 28.45 N/sq mm. With the other two cubes of the set at 29.27 and 28.84 N/sq mm, the set average is 28.85 N/sq mm.
How do you use the cube test register template?
- Confirm the cube size on Project Details. The cross-sectional area used in every strength calculation is worked out from it.
- Enter one row per cube, three rows per set. Record the cube ID, casting date, the member and location the sample came from, the grade and the slump measured.
- Enter the failure load in kN at 7 days and at 28 days. Compressive strength calculates automatically.
- Enter the acceptance value for your grade, taken from IS 456:2000 and your specification, against each set.
- The set average of the three 28-day results calculates itself and is shown once per set.
What should you check before relying on the cube test register?
- This template calculates strength from load. It does not judge acceptance for you — IS 456 judges concrete on groups of consecutive results as well as on individual results, and the criteria depend on your grade and specification.
- Record the exact member and location each sample came from. A result that cannot be traced back to a specific pour is of little use if a question arises later.
- Slump should be the value measured at the point of placing, not at the batching plant.
- Cube identification marks must be made before the cubes leave site and must match the laboratory's report.
What does each column mean?
| Column | What goes in it |
|---|---|
| Set No. | The sample set. Three cubes per set; the set number repeats across its three rows. |
| Cube ID | The identification mark on the cube, made before it leaves site and matching the lab report. |
| Date of Casting | The day the cube was cast. |
| Member / Location | The member and location the sample was taken from. A result that cannot be traced to a pour is of little use later. |
| Grade | The specified grade of the concrete — M20, M25, and so on. |
| Slump (mm) | Slump measured at the point of placing, not at the batching plant. |
| Date of Test (7 d) | The day the 7-day cube was tested. |
| 7-day Load (kN) | Failure load of the 7-day cube. |
| 7-day Strength (N/sq mm) | Auto-calculated. Load divided by the cube cross-sectional area. |
| Date of Test (28 d) | The day the 28-day cube was tested. |
| 28-day Load (kN) | Failure load of the 28-day cube. |
| 28-day Strength (N/sq mm) | Auto-calculated. Load divided by the cube area. |
| Set Average (N/sq mm) | Auto-calculated. Mean of the three 28-day results, shown once per set. |
| Acceptance Value (N/sq mm) | The acceptance value for the grade, from IS 456 and your specification. This template calculates strength; it does not judge acceptance for you. |
The quality record and the daily record are read together. Each sample logged here comes from a pour in the concrete pour register — the cube set IDs tie the two — and that day's daily progress report.
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