Lime Saturation Factor (LSF) Calculator
Calculate the lime saturation factor of Portland cement clinker or raw meal from its oxide analysis, following Lea's Chemistry of Cement and Concrete, 5th edition, Section 7.3.1 (Equations 7.5 and 7.6) and Sections 2.1.1 and 4.6.1. The calculator gives LSF = 100 × CaO / (2.80 SiO2 + 1.18 Al2O3 + 0.65 Fe2O3), the ratio of CaO to that denominator, the LSF allowing for MgO, and the silica and alumina moduli.
Results
LSF (Equation 7.5)
92.72 %
Ratio CaO / D
0.9272
LSF with MgO (Equation 7.6)
—
Silica modulus SM
2.44
Alumina modulus AM
1.25
MgO above 2 percent, the formula uses 2 percent; the excess tends to be free MgO (periclase).
Formulas with your numbers
- D = 2.80 × 22 + 1.18 × 5 + 0.65 × 4 = 61.6000 + 5.9000 + 2.6000 = 70.1000
- LSF = 100 × 65 / 70.1000 = 92.72 %
- CaO / D = 65 / 70.1000 = 0.9272
- SM = 22 / (5 + 4) = 22 / 9 = 2.44
- AM = 5 / 4 = 1.25
Correct the highlighted input to see the results.
How to use the calculator
- Enter CaO, SiO2, Al2O3 and Fe2O3 in mass percent, all from the same oxide analysis of clinker, or of raw meal on the same basis.
- If you want the LSF allowing for MgO (Equation 7.6), enter MgO in mass percent; otherwise leave it empty.
- Press Calculate.
- Read the LSF, the ratio CaO / D, the LSF with MgO when MgO is entered, and the silica and alumina moduli, and check each result against the formula shown with your numbers.
Note
- The LSF represents fairly well the maximum lime that can combine in clinker (Lea, Section 7.3.1).
- At LSF 100 (ratio 1.0) the CaO is just enough to form C3S, C3A and C4AF only, and the proportion of alite is maximised.
- In practice, clinker LSF is typically 94 to 98 (Lea, Section 2.1.1).
- Values above 100 indicate that free lime is probably present (JZS-A, University of Sulaimani, 2020).
- Typical SM in Portland clinker is 2.0 to 3.0 and AM 1.5 to 2.5 (as quoted in the same JZS-A paper).
- Some texts print 1.2 instead of 1.18 for the Al2O3 coefficient.
- The MgO refinement allows for the MgO combined in C3S. About 2 percent is the maximum MgO that can be inserted; any excess is free MgO and makes the formula inappropriate, so the calculation uses at most 2 percent.
This is an estimate from the oxide analysis entered, not a substitute for plant quality control.