The concept of concrete maturity is based on the thermodynamics and kinetics of cement hydration. Hydration is an exothermic chemical reaction in which water reacts with cement particles to form binding compounds, mainly calcium silicate hydrate (C-S-H).
The rate at which this C-S-H gel forms and the strength of concrete develops mainly depends on the internal temperature of the concrete. When the temperature is higher, the extra heat speeds up hydration. When the temperature is lower, the formation of hydration products becomes slower.
The heat released during cement hydration increases the internal temperature of the concrete in the early stages, which directly affects how quickly hydration continues.
Time is also very important, because hydration keeps progressing as long as suitable temperature and moisture conditions are maintained, and the strength keeps increasing with time.
Maturity functions are mathematical models that show how sensitive hydration is to temperature. The Nurse–Saul method assumes a simple linear relationship between temperature and hydration rate, so it works well for normal temperature conditions.
The Arrhenius method is based on activation energy and gives a more accurate representation when temperature conditions are very high or very low, because it considers non-linear effects.
In practical use, concrete maturity is used to estimate strength using maturity curves created in laboratory conditions. Cylinders are tested at different curing ages while maturity is recorded. This helps create a relationship between maturity value and compressive strength. This curve is then used to estimate the strength of concrete in actual structures.
