Maturity, or the temperature-time history of concrete, is a relatively common approach to estimate the compressive strength of concrete as a function of temperature and time. This technique takes the hydration process as a function, which means that as the temperature or curing time increases, then the hydration process accelerates and, as a result, the compressive strength of the concrete increases. Although maturity is a convenient concept in practice, useful for instances such as time of formwork stripping, early-age strength prediction, and time-dependent prestressing, there are several scientific and practical reasons that maturity alone is not a representative indication of compressive strength.
Reasons Why Maturity Fails to Accurately Represent Concrete Strength:
- Neglecting the Effects of Material Properties and Mix Design
The maturity model is only based on temperature and time and does not account for the type of cement, the mix design or the presence of supplementary cementitious materials (SCMs), such as slag, fly ash, or silica fume. Such ingredients can effect hydration and strength development to a great extent (ASTM C1074, 2020). - Different Microstructures at Higher Curing Temperatures
While higher curing temperatures may result in accelerated strength development, they can also result in more porous microstructures and lower strength at 28 days or beyond. In short, early and long-term strength are not always directly related (Bamforth, 2007; Neville, 2011). - Poor Prediction at Ages Beyond 28 Days
In the case of concrete incorporating pozzolanic materials or blended cements, it has been found that the maturity method can indeed provide relatively accurate prediction of strength at the early age with little accuracy in predicting it at later ages because of the retardation in the onset of pozzolanic reactions (Thomas & Bamforth, 1999). - Low Accuracy in Anormal Environmental Conditions
In situations of varying ambient or freeze-thaw cycles, the maturity method does not adequately recognize temperature fluctuations and the resulting hydration consequence (ACI 228.1R-19). - Inconsistency with the Strength of Cores or Direct Evaluation Techniques
In field situations, strengths predicted by the Maturity Method and those obtained by core or cylinder tests are frequently not in good agreement, which shows the limitation of the method (ACI 209R-92).
In summary, although the maturity method serves as a helpful tool for estimating early-age concrete strength, it falls short as a standalone and precise indicator of compressive strength, particularly in the presence of blended cements, SCMs, or variable environmental conditions. For quality assurance in critical structures, maturity-based estimations should be validated with direct strength testing of specimens.
