Work out concrete strength estimate instantly with clear inputs, formula shown and shareable results.
The ACI maturity relation fc(t) = fc28 x t / (a + b t) describes strength gain with age, where a and b depend on cement type and curing method. For Type I moist-cured concrete, a = 4 and b = 0.85, which reproduces the familiar milestones of roughly 45 percent at three days and 65 percent at seven.
Strength gain
fc(t) = fc28 x t / (a + b x t)
Preliminary estimate only. Do not use for formwork striking or load application decisions; rely on tested cube or cylinder strengths.
fc(t) = fc28 x t / (a + b x t). The ACI maturity relation fc(t) = fc28 x t / (a + b t) describes strength gain with age, where a and b depend on cement type and curing method.
No. Formwork removal must be justified by actual cube or in-situ tests, or by code-specified minimum periods. The relation is for planning only.
This calculator takes 3 inputs: Design 28 day strength, Age of concrete, Cement and curing. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.