Raw Mix: Complete Technical Guide

The raw mix design is the arithmetic heart of the cement factory: the four or five raw materials of the quarry are blended so that the kiln feed carries exactly the right oxides: the limestone carries the calcium, the clay carries the silica and the alumina, the iron ore corrects the colour: the mix is the recipe that the kiln bakes into clinker at 1450 degrees, and every estate bag of cement in the world begins as a row in the raw mix calculation: the raw mix is the first formula of the cement process, and it is the formula that this article and its companion file teach in full.

The raw mix is never a fixed number: it is a living target: the quarry changes, the moisture changes, the analysis of yesterday differs from the analysis of today: therefore the design of the raw mix is a discipline, not a one-time table: the constants of the discipline are the moduli of the kiln feed (the lime saturation factor LSF, the silica ratio SR, the alumina ratio AR) and the methods that convert the quarry materials into a batch, a daily dosage, and a basic report of proportions: the file that accompanies this article walks the method line by line: the definitions, the equations, the worked example, the table of typical values, and the words of the engineers who run the mix from the silo.

Everything about the cement that follows depends on this chapter: the raw mix decides the burnability of the kiln, the output, the thermal consumption and the quality of the clinker; the complete package (931 files: the books, the courses, the Excel tools and the plant documents: 249.99 US dollars one-time: instant download by PayPal) includes the raw mix chapters and white spreadsheet calculators: this article follows the method of the file, so the reader can return from it with a mix design ready to check against the laboratory values of his own plant.

1. The Raw Materials and the Target Oxides of the Kiln Feed

The cement raw feed is the womb of the Portland clinker: four oxides compose 95 of the 100 parts: the calcium oxide CaO, the silica SiO2, the alumina Al2O3 and the iron oxide Fe2O3: the remaining oxides (magnesia, the alkalis, the sulfur, the phosphorus, the chlorine, the titanium) ride along in small quantities that the plant watches closely; the raw materials bring these oxides in very different proportions, and the recipes of the plant must mix and match for the planned composition.

Raw material	Typical CaO %	Typical SiO2 %	Typical Al2O3 %	Typical Fe2O3 %	Role in the mix
Limestone (high purity)	50-54	1-4	0.3-1.0	0.2-0.8	Calcium carrier (75-85% of batch)
Marl	40-48	8-14	2-4	1-3	Balanced natural mix
Clay / shale	2-10	50-62	12-20	5-8	Silica + alumina carrier (10-18%)
Iron ore / bauxite	0-2	5-30	40-80	20-70	Minor correction 1-3%
Quartz sand	0.2-1	95-98	0.5-2	0.2-1	Silica ratio correction
Gypsum (raw feed)	32-38	1-4	0.3-1	0.3-1	Sulfur source (rare in feed)

The limestone figure is the anchor: 76 to 82 percent of the typical batch: the clays and shales bring the silica and the alumina that the limestone lacks; iron ore or bauxite corrections are thin islets, but even 2 percent of a rich oxide material has the power to move the alumina ratio by several points: the reason the table above appears in every raw mix file: the plant sees its own quarry in the same language.

The target composition is not chosen at random: it is the oxides that burn into the best clinker at the lowest thermal bill: the industrial reference ranges are conservative and widely reproduced in the handbooks; the full file of the package tabulates them for every clinker type from the true Portland to the sulfate-resistant.

Oxide / modulus	Portland clinker typical range	Notes
CaO	63-67 %	Below 60 the mix cannot make enough C3S
SiO2	20-23 %	The structural network former
Al2O3	4.5-6.5 %	Higher = more C3A (early heat)
Fe2O3	2.5-4.5 %	Higher = darker clinker, more flux
MgO	0-5 % (max	Saturation limit by soundness
SO3	0.5-2 %	Processed via fuel and feed
Alkalis Na2O eq	0.2-1.2 %	Controlled for standard handling

The target feed is written in two languages: the oxide column and the modulus column: the engineer reports the kiln feed by oxides for the laboratory comparisons, and the reliable moduli for the process decisions, since the moduli normalize the concentrations and give the geometry of the mix at one glance.

2. The Moduli of the Kiln Feed: the LSF, the SR, the AR and the Hydraulic

Three numbers carry the whole design culture of the cement raw mix: the LSF (the lime saturation factor), the SR (the silica ratio) and the AR (the alumina ratio): they condense six oxide percentages into three dimensionless descriptors that the kiln operator has used since the times of Kuhl and Le Chatelier; the Hydraulic ratio is the oldest of the family:

The LSF (conventional definition): LSF = 100 * (CaO) / (2.8 SiO2 + 1.2 Al2O3 + 0.65 Fe2O3), all oxides in mass percent on the feed basis: the classic formula (which the package reproduces with the assumptions) measures how close the calcium content reaches the saturation of the total calcium: the Portland cement reference is around 90 to 100; at 100 the mix is exactly saturated and the kiln will fight the uncombinated lime.

The SR: SR = SiO2 / (Al2O3 + Fe2O3). The ratio of the acid oxide to the fluxing oxides; the range 2.0 to 3.5 typical: a high SR produces the hard-to-fuse, hot kiln, strong clinker control; a low SR swamps the reaction with flux and makes the burning zone sticky; the mix balances the two.

The AR or AM (the alumina ratio): AR = Al2O3 / Fe2O3: the ratio decides the proportion of the liquid phase: values 1.0 to 2.5 work in normality; above 2.5 the melt is thin and the kiln hangs at low; below 1.0 the melt is iron-rich and the clinker hard: the AR also programs the sulphate attack of the concrete far down the line.

The hydraulic ratio: HR = CaO / (SiO2 + Al2O3 + Fe2O3): the old ratio (0.9 to 2.0 target window), still found in the older files, simpler than the LSF and similar in the direction.

The rules of thumb that the file recommends: pick the LSF from the clinker strategy (the white grades, the high early strength); adjust SR by adding sand; adjust AR by iron ore or bauxite/red mud swap; and always remember the moduli are sensitive to active the same per every percentages.

3. The Calculation of the Raw Mix: the Balance Equations and the Method

The classic formation problem is solved with a linear system: the plant has K raw materials with known oxide percentages from the laboratory, and should find the weights w_i such that the mixture meets the three moduli targets: the three unknown proportions solve three equations: the mass balance (sum = 1) and two of the modulus equations; the typical formulation with three raw materials (limestone + clay + iron ore or sand):

• Equation of calcium: CaO_feed = L * CaO_limestone + C * CaO_clay + A * CaO_addition yields the CaO per 100 parts of the feed;
• Equation of silica: SiO2_feed = L * SiO2_limestone + C * SiO2_clay + A * SiO2_addition covers the second oxide;
• Equation of the modulus: the SR and the AR equations add two more rows when four materials are used (the linear system becomes 4×4 with LSF+SR+AR+trace);
• The sum rule: L + C + A = 100, which the spreadsheet solves by closure.

Worked example, three components: Given in weight %: Limestone CaO 52.0, SiO2 2.0, Al2O3 0.6, Fe2O3 0.4; Clay CaO 3.0, SiO2 58.0, Al2O3 16, Fe2O3 7; Iron ore Fe2O3 85, SiO2 8 and the target LSF 95, SR 2.4, AR 1.4: solving the linear system yields approximately: L 77.1%, C 21.2 %, iron ore 1.7%: check: CaO = 0.771*52 + 0.212*3 + 0.017*0 = 40.9+0.64+0 = 41.8 total calcium with LOI; on the clinker basis this raises to about 65%: the oxide and the moduli land inside the windows: the numbers from this simple example are the full exercise that most plants repeat each morning; the Excel in the package solves the system and recomputes the moduli in seconds after each laboratory update.

The reality dims the math only slightly: the moisture of each material changes the wet dosage (add the water deduction), the LOI (loss on ignition) changes the transit from the feed to the clinker (add the calcination), and the transport delays of the quarry mean the plant corrects the feed with its own feedback: but the linear core of the recipe stays exactly the equations above.

4. The From Feeding to Clinker: the LOI Transformation

The raw mix calculators must convert between three basis: (1) the wet raw materials as weighed at the weigher, (2) the dry raw feed as it enters the kiln system, and (3) the clinker produced out the other end: the difference is water + loss on ignition, mostly CO2 from the limestone; the conversion is total jargon: the clinker percent = 100 – LOI of the feed; a feed with LOI 35.3 yields a clinker of 64.7 parts: the moduli calculated on the feed basis must be re-based to be truly clinker, because the LOI of the two materials differ: the design tables of the file carry both rows (feed basis, clinker basis) and the engineers of the plant always answer the question “which basis?” before quoting the numbers.

Basis	Meaning	Typical use
Wet feed	As weighed at the dosing rails	Dosage settings, the belt equations
Dry feed	After the moisture removed	Moduli computations
Rawklin feed	Dry after 100% calcination & weighting	Clinker chemistry comparisons
Clinker	After the burning and the lime	Specifications, QA reports

The correction rule: caO_vol_feed * (100/ (100 – LOI)) = the CLInker oxide: the same factor multiplies SiO2, Al2O3, Fe2O3 while the vol / loss on ignition variants cancel; the 1% in the damping of the hazardous SOM (precalciner) hold: the LSF on the clinker basis is about 0.35 to 0.45 higher than the same on the feed basis, and this nuance qualifies many expressed questions in the industrial reporting.

5. The Homogenization Philosophy: the same Mix, Again and Again

The equation of the recipe is trivially true if the oxides are what the lab said: the realked detail is the variability: the quarry benches deliver limestone with the calcium swinging between 48 and 54 in the week: the plant must transform these swings into a constant feed; the discipline is three tools working in series:

• The pre-homogenization yard: the material stored in long layers and reclaimed by the side-cut contains the natural averaging by mixing the whole mass in 100 to 200 layers;
• The weigh feeders and flow meters: the proportioning bunkers dose each material at the set point computed from the noon analysis;
• The homogenization silo: the aerated silo blends the fed pellet, turning the seconds-oscillations of the dosing errors into minute-level constant mix: the standard silo claims the ratio 1:8 to 1:12 of input to output variability;

The whole trio is the reason a cement plant can sell its product with the LSF spread as small as +/- 1.5 points; the raw mix design file of the package includes the silo blending workbook and the yard lay-up sheets; the quality section of this guide (chapter 8 in the file) gives the statistics so the engineer can size the inventory that the plant needs.

6. The Batch Composition with the Statistical Mixes: the Common Worked Models

The single most practical pages of the file are the standard cases that the engineer re-uses: (I) the two-material case: limestone + clay, only the LSF (the SR fixed by the two materials alone); (II) three-material: limestone + clay + iron ore, solving the LSF and SR; (III) four material: limestone + marl + sand + iron ore, solving LSF, SR and AR; (IV) the complex: with alternative fuels and a waste materials column.

The two-material worked numbers: let the limestone ((A=1.80% MgO free) CaO 50.0, SiO2 2.5, LOI 42.0) and clay (CaO 5.0, SiO2 60.0, LOI 12): total those with the LSF 96: the solver returns clay around 19.2-20%, limestone 80: LSF = 100*(0.8*50 + 0.2*5) / (2.65*(0.8*2.5+0.2*60) + 1.2*(0.8*0.5+0.2*15) + 0.65*(0.8*0.3+0.2*5)) = 4100 / (2.65*14+1.2*3.4+0.65*1.24) = 4100 / (37.1+4.1+0.8) = 4100/42.0 ≈ 97.6 which the solver iterates back to the target with the 80/20 fractions; the same numbers spread in the spreadsheet of every quarry in the Nile valley; slight variations in the LOI change the LSF by ~junior; the formula: the LSF is the presser of the mix, and the engineering hand knows where the +-1.5 tolerance lives.

Two warnings the file repeats: first, do not average the moduli; the mix-in averages of the oxide space and then the moduli are recomputed from the totals; second, when the material has the high LOI, convert all the percentages to the same basis before forming the ratio — mixing the wet % of one with the dry % of the other gives the famous off-by-2 LSF that the kiln punishes all night.

7. The Typical Recipes: the Files of the Industry and their Ranges

Below, the ranges the file pins from the repeated industrial practice (the actual plant data may deviate, and the table is meant as the frame, not the fat for the report):

Mix type	Limestone share %	Clay / shale %	Corrective %	LSF target	SR
Portland (classic)	76-82	16-21	1-3 (Fe or sand)	93-98	2.3-2.8
White cement raw	78-85	low-Fe clay	Al2O3 brings, no iron	98-102	3.5-5
Oil-well cement	76-80	high-silica clay	sand 3-8	95-100	3-4
Sulfate-resistant	78-82	low-Al clay	iron form	93-96	2.2-2.6
Limestone calcined clay	70-75	kaolin clay 20-25	gypsum	91-95	2.5-3

These rows are the same of the industry in Europe and the Middle East as they burn: the reader will find the same numbers in the classical textbooks of the cement technology (Duda, Peray); the value of the file of the package is that the tables are followed by the exact equations and the solver sheets, so the reader can build the gray rectangle and cross-check the two.

8. The Quality Loop and the Daily Dosage: From the Lab to the Weigher

The raw mix is engineered in the morning and adjusted all day: the loop of the plant runs four beats:

• The sample of the feed: the compositing sampler at the raw mill inlet, the daily composite to the XRF laboratory, the moisture caught at the weigher;
• The XRF run: 50 seconds of the analysis giving CaO, SiO2, Al2O3, Fe2O3 + the trace (<2000 impacts);
• The recalculation: feed the chemistry in the workbook, read the new correction for each raw material (a LSF low -> plus limestone fraction; plus SR -> plus sand), the Excel of the package does it in the minute;
• The dosage delivery: the staff sets the knife: the feed-rate set points of the weigh feeders (or the raw mill hoppers) to the new %; the silo + the sampler confirm the result of the hours;

The control philosophy has the correct frequency: 1 sample per shift with 8 correction cycles is normal for an average plant; a volatile chemical (e.g. the ash of the high-ash coal in the kiln) requires the hourly check because the ash CO in fly, the sulfur and the coal ash come out of the mix; the raw-mix control is not the fancy of the laboratory but the tables that the shift ensures with respect.

The file of the package includes the sample collection protocol (45), the templates of the daily raw mix report, and the Excel control sheet pre-programmed with the three moduli + the color codes when the target is violated; the institutionalization of the daily loop is the same in all countries that maintain the cement quality data, and the reader the region model.

9. The Trabajos Edge: The Minor Constituents and their Governance

Even the perfect LSF/SSR crater is disqualified when the octагональ myravam: a table of the trips the authority:

• MgO: the periclase crystals in the clinker expand in the autoclave: the raw feed keeps the MgO under ~3% (the norm burns) and plants with the dolomite in the stone use the blending + the healing of the clinker;
• Alkalis (Na2O+K2O): the volatile circuit: the alkalis evaporate in the kiln, condense in the preheater, feed concentration loops; the feed limit is set by the circulation and the standards; the literature: 0.6-1.2% limit of the clinker for the P (the cements with the alkali limit), the extraction from the dust when the plants run the by-pass;
• SO3 Cl: the chloride of the fuel and the waste creates the preheater blockages: the maximum Cl in the feed + fuel is about the 0.01-0.03% level before the kettles, so the plants verify the grain: the S-Ratio (the SO3 / alkali) reverts the mud; the package the file on the alkalis cycles;
• P2O5: the phosphorus of the bone or the phosphate rock: above 2.5-3% it kills the C3S and the phosphates deposits; track the P when the plant takes the waste;
• Cr and other: not an oxide but the element meassured at the guard; the CRM (the raw meal) tests hold the targets when the product is the SR cements or the platform of the hardened spec;

Each of these has a threshold and a mitigation, and the naive avoids the chemistry of the mixture: — the variations of the satellite 1% in the SO4 and chlorine are enough to stop the preheater without witness: the auxiliary tables of the package, alone with the ward, teach the reader which of the constituents to watch in its location.

10. The Excel Tools of the Raw Mix in the Package

Part of the professional daily labor of the cement production is in the spreadsheets, and the package carries the raw mix instruments as they run in the offices:

• The Mix-Calculator: input the 4-10 material columns; press the solver; output the % doses and the moduli per relationship with the % screen of targets;
• The daily dosage keeper: the registry of the XRF outcomes trends the LSF/SR/AR over the months, and detects the drift of the quarry long before the clinker Q;
• The LOI converter: the wet/dry/clinker triple conversion in the one sheet, with the tamper for the humidity entered by the team;
• The silo blending estimation: the grader of the homogenization performance (the blending ratio) and the calculator of the blend time from the yard automatic tests;
• The energy companion: the same moduli translate into the clinker energy forecast by the phase (the C3S weight probes), the virtual consumption, and the CO2 module used in the country reporting;

The package wraps the same logic as the file: the Excel is only the tool, the formula is the spirit: the engineer who masters the method builds his own, and the tools of the package only remove the typos: the reader demand: at $249.99 once, the 931 files including these sheets, the byline of the package: instant download with the PayPal link (the yellow pay button below); the alternative to the tool of the wrapper is the paper and the laborious they fall — each cycle, years of the Excel of the plant.

11. The Raw Mix in the Kiln: The behavior of the Feed inside the equipment

The mix that leaves the silo is transformed in the five stages of the burning; the ceramics of the operations:

• The preheat and the evaporation: 100-600 °C: the free water flees and the clays lose their absorbed water (the quantity is big, the 5-8% of the wet feed);
• The calcination zone: 600-900 °C endothermic: CaCO3 -> CaO + CO2; the absorption of the heat is the biggest of the stage (1750 kJ/ton of feed), and here the LSF modulates the heat: the available carbon; awaits the CCR;
• The exothermic decay and the C3A : 900-1300 occurring the C3A and the C4AF parties form; a LSF outlined can combine; below a certain temperature the C3A demand reacts;
• The burning zone: 1300-1500: the melt, the free-oxide, the burning (the flame), the clinker module = the rate of the burning; the operators control the zone by the flame, the residence and the viscosity which depends on the AR and the SR;
• The cooling: the cooling cuts the phase size (the cooling 1000 °C per second at the consumer); the reactivity of the C3A in the concrete window; the cooling ramp and the air.

The map of the kiln says why the LSF/SSR is a compromise: high LSF plus total of delicate without the flux to form the liquid; low LSF yields the soft drive of the low C3Clinker. The “optimum” of the file: LS 94-97, SR 2.2-2.6, AR 1.3-2.0 for the type O cement: the table in the product layer; the engineer is at the middle by the tests.

12. The Frequently Asked Questions

What is the difference between the LSF on the raw feed and the LSF on the clinker basis?

About one-half to one unit, LSF is not a ratio of the oxides but a function: it is scale-tolerant: when you recompute the same dry feed in the clinker base (dividing by 0.65, the S100-LOI), the CaO, the SiO2 rank up in the equal % so the ratio stays identical – the true step is that in the clinker base all the extra SO3 and alkali are no longer present: the ratio is a measurement of the carbon: the exact the file calculates both to remove the ambiguity.

Can the mix be calculated with only the XRF and no mineralogy?

Yes, for daily steps the XRF columns are enough; the mineralogy becomes essential when the reactivity or the burnability deviates (the quartz with the coarse silica, the hard crystalline calcites frenah) and the plant must explain why the same LSF burns as slow: the file includes the burnability index sheet that adds the raw data from the liberation, and the mineral report from the petrographic.

What happens if the SR is too high?

The mix becomes hard to burn: the liquid amount falls, the flame rises, the kiln loads the power and the ring forms; the clinker has the small C3S and the low early strength; the remedy of the floor is the sand reduction, more limestone grick part of the total, or the shot with the shape flux; the correction is usually 1-2 points of an additive FR of the SR.

Why the plant uses the 3-4 materials, not a single

Because no deposit alone meets the four constraints simultaneously (the calcium, the moduli, the minor oxides, the grindability): the fallback “digging the purest stone” gives the clinker of the C2S-rich; clinical the composition from 4 sources and the homogenized them is the way of the industry since 1950.

Is the raw mix the same as the “kiln feed composition” in the inspection reports?

Yes, the terms are interchangeable, with the nuance that the “kiln feed” includes the moisture and possibly the modifier fuel (if coal is added to the machine); the “raw mix” refers to the designed dry proportions; the audit report sheets of the package the underscore: the target % versus the actual kg per hour of each separator.

13. Conclusion

The raw mix design is the first page of the cement encyclopedia, and the whole production reads from the same books: the targets of the LSF, the SR-the-AR define the clinker, define the grinding, define the cement of the order: the method is linear: the materials in, the moduli out, the recipe back into the weighers, the LOOP daily: this is the craft that the file of this article works with and the many tables of the package, and it is the assembly the reader can port to any plant on the planet.

The Complete Cement Technical Package includes the Raw Mix section with the full formulas, the proportioning workbook the Excel interpretation tables, the typical plant recipes, and the control templates: a 931-file library at a one-time 249.99 USD with instant download and the PayPal payment, the refuse low: the plant of a single operator and the consultant begin the raw mix the same way: with the measured limestone and the arithmetic of this file.

This file is part of the Complete Cement Technical Package (931 files) available from cementequipment.org. Respective rights holders; library copy for the licensed single user.