Concrete Curing and Maturity Calculator
Turn curing temperature into maturity and equivalent age, and check the code minimum.
Quick answer
With the default inputs: Mean curing temperature 20 ℃ · Days cured 7 d · Cement type Ordinary Portland etc.Equivalent age at 20°C 7.0 d
Edit the inputs below to recalculate.Inputs
Result
Equivalent age at 20°C
7.0d
| Maturity | 5040℃·h |
| Estimated strength | 65% |
| Minimum curing | 7d |
| Days still required | 0.0d |
| To 28-day equivalent | 21.0d |
| Temperature factor | 1.00 |
The strength percentage is an empirical curve for ordinary Portland cement and is indicative only. Striking, tensioning and loading must follow site-cured specimens or in-situ testing.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Maturity | M = Σ (T + 10) × Δt (T in °C, Δt in hours) |
| Equivalent age | te = t × (T + 10) ÷ 30 |
| Temperature factor | k = (T + 10) ÷ 30 |
| Minimum curing | 7 days OPC, 14 days slag, 14 days watertight |
Seven days at 20°C gives 5040 °C·h of maturity, an equivalent age of 7.0 days and about 65% strength — just meeting the 7-day minimum for OPC. At a mean of 10°C the equivalent age falls to 4.7 days and strength to about 53%, so curing must be extended.
How to work it out
- Record the measured concrete temperature (surface or core), not the weather forecast.
- Compute the equivalent age te = actual days × (T + 10) ÷ 30, converting any temperature to days at 20 °C.
- Or compute maturity M = Σ(T + 10) × Δt (T in °C, Δt in hours); 600 °C·h is roughly 60% of the 28-day strength at 20 °C.
- Set the minimum curing period by cement type: 7 days for ordinary Portland, 14 for slag or pozzolanic, 14 with retarders or where impermeability is required.
- Judge striking separately: side forms at ≥1.2 MPa on field-cured specimens (no arris damage), soffits by the strength percentage for the span.
Where it goes wrong
- Using air temperature — 10 °C at noon in winter can mean 2 °C at the concrete surface, halving the equivalent age.
- Assuming enough watering days is enough — curing is temperature × time; below 5 °C even 14 days of watering falls short and insulation is what is needed.
- Using a daily mean and ignoring night lows — 25 °C by day and 5 °C by night averages 15, but hydration is not linear and the cold hours are over-credited.
Material and cost
Covers run 1-2 per m² for polythene and 3-5 for geotextile, usually used together. Winter work needs heating (enclosures, heating blankets, thermal blankets) at 3-5 times the normal cost, and that belongs in the winter premium.
On site
- Impermeable concrete must be cured for at least 14 days — mandatory, not advisory.
- Mass concrete needs the core-to-surface differential held to 25 °C or less through insulation, not by watering it cool.
- Keep measured temperatures in the curing record; it is the only evidence for acceptance and for settling winter premiums.
Basis
- GB 50666-2011 Code for construction of concrete structures, Section 8.5 (curing)
- GB 50204-2015 Code for acceptance of concrete structures, Section 7.4
- GB 50496-2018 Standard for construction of mass concrete (differential limits and monitoring)
FAQ
Why does winter curing take longer?
Hydration is temperature-driven and roughly halves for every 10°C drop — hence the T+10 term in the maturity function. Seven days at 10°C is only equivalent to 4.7 days at 20°C, a whole strength step lower. In winter, extend curing, insulate or heat, or use an accelerator; summer durations do not transfer.
Is 7 days of curing enough?
That is the code minimum: 7 days for OPC, 14 days with retarders, watertight requirements or slag cement, longer for mass concrete. At 7 days strength is around 65% — enough to strike side forms but still a third short of the 28-day design value. Cure important members for 14 days.
When can formwork be struck?
Side forms once the concrete will not spall — usually 1-2 days. Soffits depend on span: slabs up to 2 m need 50% of design strength, over 2 m need 75%; beams and arches up to 8 m need 75%, over 8 m need 100%; cantilevers need 100%. Those percentages refer to site-cured specimen results, not the estimate here.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Concrete Curing and Maturity Calculator. 2026-10-25. https://jianzhujisuan.com/en/concrete-curing
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.