Concrete Curing Time Calculator
Estimate the number of days required for concrete to reach a target percentage of its 28-day design strength, based on cement type, ambient temperature, and water-cement ratio.
Fill in the fields above and click Calculate.
Formulas Used
1. Equivalent Age (Maturity Method – Arrhenius):
te = t × exp[ (Ea/R) × (1/Tr − 1/T) ]
Where Ea = activation energy (J/mol), R = 8.314 J/(mol·K), Tr = 293.15 K (20°C reference), T = ambient temperature in Kelvin.
2. Strength–Maturity Relationship (Freiesleben Hansen & Pedersen):
S(te) = Su × exp[ −(τ / te)β ]
Where τ = time constant (days), β = shape parameter, Su = ultimate strength (normalised to 28-day = 100%).
3. Solving for curing time:
te = τ / [−ln(S/Su)]1/β → t = te / age_factor
4. w/c Adjustment for τ:
τ = τ0 × (w/c / 0.50)1.2
Assumptions & References
- Strength gain modelled using the Freiesleben Hansen & Pedersen (1977) exponential maturity function.
- Temperature sensitivity uses the Arrhenius activation energy approach per ASTM C1074 and ACI 308R.
- Activation energies: Type I = 40 kJ/mol, Type II = 38 kJ/mol, Type III = 43 kJ/mol, Type IV = 35 kJ/mol, Type V = 37 kJ/mol (based on published literature ranges).
- τ and β parameters calibrated to ACI 209R-92 strength development curves at w/c = 0.50 reference.
- w/c ratio adjustment follows a power-law relationship; higher w/c slows early strength gain.
- Results represent minimum curing time under ideal moist-curing conditions. Actual site conditions may require longer curing.
- Curing below 5°C or above 35°C requires special measures per ACI 306R (cold weather) and ACI 305R (hot weather).
- This calculator does not account for admixtures (accelerators/retarders), supplementary cementitious materials (SCMs), or curing compound efficiency.