Concrete Curing Time Calculator

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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.

Cement Type

Type I – Normal Portland Type II – Moderate Type III – High Early Strength Type IV – Low Heat Type V – Sulfate Resistant

Ambient Temperature (°C)

Water-Cement Ratio (w/c)

Target Strength (% of 28-day)

Calculate Fill in the fields above and click Calculate.

function conCalc() { var resultDiv = document.getElementById('con-result');

var cementType = document.getElementById('con-cement-type').value; var T = parseFloat(document.getElementById('con-temperature').value); var wc = parseFloat(document.getElementById('con-wc-ratio').value); var targetPct = parseFloat(document.getElementById('con-target-strength').value);

// --- Validation --- if (isNaN(T) || T 50) { resultDiv.innerHTML = '⚠ Temperature must be between -10°C and 50°C.'; return; } if (isNaN(wc) || wc 0.80) { resultDiv.innerHTML = '⚠ Water-cement ratio must be between 0.30 and 0.80.'; return; } if (isNaN(targetPct) || targetPct 100) { resultDiv.innerHTML = '⚠ Target strength must be between 10% and 100%.'; return; } if (T ⚠ Curing is not effective at or below 0°C. Use cold-weather curing methods.'; return; }

/ * MATURITY METHOD (Nurse-Saul) + Strength-Maturity Relationship * * 1. Equivalent Age (te) at reference temperature Tr = 20°C: * te = t * exp[ (Ea/R) * (1/Tr_K - 1/T_K) ] * where Ea = activation energy (J/mol), R = 8.314 J/(mol·K) * * 2. Strength-Maturity (Freiesleben Hansen & Pedersen): * S(te) = Su * exp[ -(tau / te)^beta ] * Su = ultimate strength ratio (≈ 1.0 for 28-day basis) * tau = time constant (days), beta = shape parameter * Both tau and beta depend on cement type and w/c ratio. * * 3. Solve for te given S(te)/Su = targetPct/100: * te = tau / (-ln(targetPct/100))^(1/beta) * * 4. Convert te back to real time t: * t = te / exp[ (Ea/R) * (1/Tr_K - 1/T_K) ] /

// Activation energy by cement type (J/mol) var EaMap = { 'I': 40000, 'II': 38000, 'III': 43000, 'IV': 35000, 'V': 37000 }; var Ea = EaMap[cementType]; var R = 8.314; var Tr_K = 293.15; // 20°C in Kelvin var T_K = T + 273.15;

// Age conversion factor (dimensionless) — ratio of reaction rate at T vs Tr var ageFactor = Math.exp((Ea / R) * (1.0 / Tr_K - 1.0 / T_K));

/ * tau and beta parameters (calibrated to ACI 209 / literature data): * tau (days at 20°C) increases with w/c (more water = slower hydration kinetics) * beta is relatively stable but slightly varies by cement type * * Base tau at w/c = 0.50 (reference): * Type I: tau0 = 1.0, beta = 0.90 * Type II: tau0 = 1.3, beta = 0.85 * Type III: tau0 = 0.55, beta = 0.95 * Type IV: tau0 = 2.0, beta = 0.80 * Type V: tau0 = 1.6, beta = 0.82 * * w/c adjustment: tau = tau0 * (wc / 0.50)^1.2 * (higher w/c → slower strength gain per unit time) / var cementParams = { 'I': { tau0: 1.0, beta: 0.90 }, 'II': { tau0: 1.3, beta: 0.85 }, 'III': { tau0: 0.55, beta: 0.95 }, 'IV': { tau0: 2.0, beta: 0.80 }, 'V': { tau0: 1.6, beta: 0.82 } }; var params = cementParams[cementType]; var tau = params.tau0 * Math.pow(wc / 0.50, 1.2); var beta = params.beta;

// Solve for equivalent age te: // targetPct/100 = exp(-(tau/te)^beta) // ln(targetPct/100) = -(tau/te)^beta // (tau/te)^beta = -ln(targetPct/100) // te = tau / (-ln(targetPct/100))^(1/beta)

var lnVal = -Math.log(targetPct / 100.0); if (lnVal ⚠ Target strength of 100% is theoretically never fully reached. Try 99% or less.'; return; }

var te = tau / Math.pow(lnVal, 1.0 / beta);

// Real curing time at ambient temperature T: var t_days = te / ageFactor;

// Practical lower bound: fresh concrete needs at least a few hours to set if (t_days 35) { warningMsg = '⚠ High temperature warning: Rapid moisture loss may occur above 35°C. Ensure adequate wet curing.

'; }

resultDiv.innerHTML = '### Estimated Curing Time: ' + displayTime + ' ' + 'To reach ' + targetPct + '% of 28-day strength using ' + cementNames[cementType] + ' at ' + T + '°C with w/c = ' + wc + '.

' + warningMsg + '' + '' + 'Age (days)' + 'Strength (% of 28-day)' + '' + '1' + s1 + '%' + '3' + s3 + '%' + '7' + s7 + '%' + '14' + s14 + '%' + '28' + s28 + '%' + ''; }

#### 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

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