Maturity of concrete

Maturity of concrete is the product of curing time and temperature above a datum temperature. It lets the strength of concrete cured at different temperatures be compared, since strength is a function of maturity (Saul's rule).

$$M = \sum (T - T_0)\,\Delta t$$

where $T$ = mean temperature of concrete during the interval $\Delta t$ (°C), $T_0$ = datum temperature (about $-10.5$ °C as per Saul; $-11$ °C is often used), and the unit of $M$ is °C-hours (or °C-days).

Concrete of the same mix that has the same maturity has about the same strength, whatever its temperature history.

Example. Concrete cured at 20 °C for 28 days has maturity $= (20+10)\times 28\times 24 = 20160$ °C-h. Concrete cured at 10 °C reaches the same maturity in $20160/((10+10)\times 24)= 42$ days. Concrete at 30 °C needs only $20160/((30+10)\times 24) = 21$ days.

Use: estimating in-situ strength to decide stripping time, hot/cold weather planning and steam-cured precast products. The rule works well only for the early age and when the concrete is not dried out.