Calculator Inputs
Formula Used
The split tensile strength of a concrete cylinder is computed using:
ft = 2P / (π · L · D)
- P = peak applied load at failure
- L = cylinder length
- D = cylinder diameter
- ft = split tensile strength (N/mm² = MPa when using N and mm)
How to Use This Calculator
- Select your preferred load and length units.
- Enter the peak load, length, and diameter for each specimen.
- Add rows for replicate cylinders from the same batch.
- Press calculate to view individual results and summary statistics.
- Use CSV or PDF export buttons for documentation.
Example Data Table
| Specimen | Peak Load (kN) | Length (mm) | Diameter (mm) | Split Tensile (MPa) |
|---|---|---|---|---|
| 1 | 180 | 300 | 150 | 5.093 |
| 2 | 172 | 300 | 150 | 4.866 |
| 3 | 165 | 300 | 150 | 4.668 |
Values are illustrative for learning and verification.
Professional Notes for Split Tensile Results
1) Why the splitting test is used
Concrete is relatively weak in direct tension, yet many field failures start with cracking from tensile stress. The cylinder splitting method provides a practical way to estimate tensile capacity using standard compression frames, producing repeatable values for mix comparisons, curing checks, and acceptance documentation.
2) Typical strength ranges you may see
For normal-weight concrete, split tensile strength commonly falls in the range of about 2 to 5 MPa, with higher values possible for high-strength mixes. Lightweight concrete often trends lower at the same compressive strength. Track results by age (7, 14, 28 days) to confirm gain curves.
3) Specimen geometry and how it affects output
Because the formula uses both cylinder length and diameter, geometry matters. A 150 mm × 300 mm cylinder is widely used, but other sizes are permitted by various standards. Always report the actual measured dimensions; small diameter errors can shift calculated strength noticeably.
4) Loading conditions and bearing strips
The splitting test applies a line load along the cylinder length. Bearing strips or plywood pads distribute the load and help reduce local crushing at the contact line. Consistent strip material, thickness, and alignment improve repeatability and reduce scatter between technicians.
5) Unit consistency and reporting practice
The calculator converts inputs to a common base before computing strength. If load is entered in kN and dimensions in mm, the result is MPa (N/mm²). Exported reports should include units, rounding, specimen size, and the selected reference standard label.
6) Linking tensile to compressive strength
Split tensile strength is often a fraction of compressive strength, influenced by aggregate type, paste quality, and curing. While broad correlations exist, project decisions should rely on test history for the specific mix design rather than a generic ratio.
7) Variability and quality control signals
Replicate cylinders help identify meaningful trends. A high standard deviation can indicate poor end preparation, misalignment, inconsistent curing, or batching issues. Review the min–max spread and compare against control limits used by your QA plan.
8) Practical acceptance and documentation workflow
Use the specimen table to capture every break, then export CSV for lab logs and PDF for submittals. Pair results with date, mix ID, curing method, and test age to support traceable decisions during inspections and closeout.
FAQs
1) What load value should I enter?
Enter the peak load at failure recorded by the test machine. Use the maximum sustained value, not the seating load. Keep the same unit selection across all specimens.
2) Do I need to measure cylinder dimensions or use nominal sizes?
Measure actual length and diameter when possible. Small dimensional differences can change the calculated tensile strength, especially for smaller cylinders or worn molds.
3) Why does the report show MPa even when I select psi?
MPa is the baseline calculation unit because it matches N/mm² when using N and mm. The tool converts the final value to your selected output unit for reporting.
4) How many specimens should I test for a reliable average?
Three specimens is common for a single age and batch, but more improves confidence. Use the standard deviation to judge variability and whether additional breaks are needed.
5) What causes unusually low split tensile strength?
Common causes include poor curing, incorrect mix water, segregation, weak aggregate, misalignment during loading, or damaged specimens. Confirm dimensions and test setup before concluding the mix is deficient.
6) Can this method replace direct tensile testing?
No. It is an indirect tensile estimate that is practical and repeatable, but it is not the same as a true direct tension test. Use project specifications to select the required method.
7) What if my cylinder size is different from 150 × 300 mm?
You can enter any valid length and diameter. Ensure your dimensions match your standard’s permitted specimen sizes and that your bearing strip setup is suitable for that geometry.