Concrete Curing and Maturity Calculator
Turn curing temperature into maturity and equivalent age, and check the code minimum.
Inputs
Result
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.
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.
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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.