The concept of concrete maturity is based on the thermodynamics and kinetics of cement hydration. Hydration is an exothermic chemical reaction where water and cement particles react to form binding compounds, primarily calcium silicate hydrate (C-S-H).
The rate of this CSH gel formation and of strength development strongly depends on internal temperature of the concrete. At higher temperatures, the additional thermal energy accelerates the rate of hydration, while low temperatures slows down the formation of hydration products.
Heat produced during the cement hydration causes increase in internal temperature initially, which in turn directly influences the progress of hydration.
Time also plays a crucial role, since heat of hydration builds up continuously as long as the concrete sustains uniform temperature and moisture, and strength increases as this hydration progresses.
Thus, maturity functions mathematically express hydration rate sensitivity to temperature. The Nurse–Saul method assumes a linear relationship between temperature and hydration rate which makes it suitable for moderate temperature ranges.
The Arrhenius approach is based on activation energy that captures nonlinear temperature effects more accurately, especially under extreme hot or cold conditions.
In practice the maturity allows prediction of strength using maturity curves developed in controlled laboratory settings. By testing cylinders at different curing periods while recording maturity, a relationship between maturity index and compressive strength can be established. This curve then becomes the reference for estimating in-place concrete strength.
