Products Prerequisites Rawmix Ratios N: Complete Guide & Dow

Between the chemistry of the raw materials and the physics of the kiln stands the arithmetic of the mix: the lime saturation factor, the silica module and the alumina module, the three ratios that translate the quarry into the feed and the feed into the phases. This prerequisite module, the fifth of the products course series (the n3-03-2002 module of the package), teaches the ratios from their definitions to their daily use: the target bands, the correction practice and the consequences of every deviation in the kiln and the product.

The module is the bridge between the role module and the Bogue module of the series: the roles explained who does what, the Bogue counted the phases, and the raw mix ratios now design the chemistry that produces the count. The engineer who masters the three ratios reads any raw mix discussion of the industry with the numbers in the head, and this module gives him those numbers.

1. The Place of the Module in the Prerequisites Series

The module is the fifth of the products prerequisite series, and its position follows the logic of the curriculum:

• The modules before it: the role module explained the actors of the system, and the Bogue module taught the counting of the phases: this module now directs the chemistry upstream, at the design of the feed the phases will come from;
• The module’s own subject: the three ratios of the raw mix: the lime saturation of the silicates, the silica proportion against the flux and the alumina proportion against the iron: the mathematics of the mix design;
• The modules after it: the minor elements module adds the guests and the interaction module completes the pairs: the ratios remain the backbone, and the guests refine it;
• The destination: the products course applies the ratio logic to the phase budgets of the cement types: this module provides the design arithmetic the products chapters assume;

The reader who finishes the module carries the three ratios as the daily language of the raw mix control: the target numbers, the correction arithmetic and the kiln consequences, all in one instrument set.

2. The Lime Saturation Factor: The Gauge of the Lime in the Mix

The lime saturation factor (LSF) is the most important ratio of the mix, the gauge that measures how far the available lime approaches the maximum the silicates can take:

• The idea behind it: the calcium oxide of the mix combines with the silica, the alumina and the iron into the phases; the LSF expresses the CaO present as the percentage of the CaO the fully saturated clinker requires: the 100% is the theoretical saturation of the complete alite formation;
• The formula logic: the LSF compares the actual CaO with the 2.80 times the SiO2 plus the 1.18 times the Al2O3 plus the 0.65 times the Fe2O3: the denominator is the lime demand of the assumed phases of the fully saturated clinker: the ratio of the two is the factor;
• The target bands: the ordinary Portland clinkers run at the 92-98 LSF: the values above the 100% force the excessive burning temperature and leave the free lime, and the values below the 90% drop the alite and the strength: the band is the operating window of the industry;
• The burnability consequence: the higher the LSF, the harder the burning: the feed of the 96-98 requires the hotter burning zone, the longer retention or the better mix: the ratio is bought in the fuel, the lining and the risk of the underburned clinker;

The LSF chapters give the reader the interpretation of every value: the 93 of the easy-burning plants, the 97 of the high-strength producers, the 85 of the belite-rich special mixes: the number tells the burning strategy of the plant at the glance.

3. The Silica Module: The Proportion of the Silicates against the Flux

The silica module, also called the silica ratio, controls the balance between the silicate phases and the intersti… the molten part of the burning chemistry:

• The definition: the silica module (SM) is the SiO2 divided by the Al2O3 plus the Fe2O3: the ratio of the silicate-forming oxide to the flux-forming oxides of the mix;
• The target bands: the ordinary Portland practice holds the silica module at the 2.2-2.8, with the high-strength mixes at the upper half and the easy-burning mixes at the lower: the industry band is tight because the consequences are strong;
• The burnability effect: the high silica module means the less flux and the less liquid at the burning temperature: the clinker burns harder, the kiln is harder to line-protect, and the dusting risk appears at the extreme: the low silica module means the more liquid, the easier burning and the thicker coating with the nodule quality problems of its own;
• The strength effect: the silica module decides the total silicates of the clinker: the higher the SM, the more the alite plus the belite in the phase picture and the less the interstitial phases: the strength potential of the ordinary cement rides on this balance;

The silica module chapters teach the reader the middle-path wisdom of the industry: the kiln and the strength pull in the opposite directions, and the plant tunes the SM in the band where both demands are met without the heroics.

4. The Alumina Module: The Proportion of the Alumina to the Iron

The alumina module, the alumina ratio (AM), closes the trio by balancing the two interstitial oxides against each other:

• The definition: the alumina module (AM) is the Al2O3 divided by the Fe2O3: the ratio of the aluminate-forming alumina to the ferrite-forming iron of the mix;
• The target bands: the ordinary Portland clinkers run the alumina module at the 1.3-1.7, with the special types deviating: the sulfate-resistant cements need the low AM (the iron-rich, the aluminate-poor) and the white cements the extreme high (the iron-free);
• The phase and the product effect: the AM decides the split of the interstitial phases between the C3A and the C4AF: the high AM raises the aluminate (the fast reaction, the sulfate demand, the heat) and the low AM raises the ferrite (the color, the burnability aid, the sulfate resistance): the ratio is the phase switch of the interstitial world;
• The burning effect: the iron-rich mixes (the low AM) melt at the lower temperatures and support the nodulization and the coating; the alumina-rich mixes (the high AM) melt less easily and the kiln works harder at the same LSF: the AM is the third handle of the burnability;

The alumina module chapters connect the ratio directly to the product decision: the plant that must hold the sulfate-resistant certificate designs its mix around the low AM, and the reader learns the design in this module.

5. The Three Ratios Together: The Trade Triangle of the Mix

The three ratios act as one system, and the module presents the triangle of their interaction with the practical table the industry uses:

Ratio direction	Burning consequence	Product consequence	Typical use of the direction
The high LSF (96-98)	Harder burning, higher temperature	Higher C3S, higher strength potential	High-strength 52.5 producers
The high SM (2.6-2.8)	Less flux, thinner coating	More silicates, slower early strength	Low-heat and dusty-risk mixes
The high AM (1.6-1.7)	Less iron melt, harder nodulization	Higher C3A, faster reaction, more gypsum	Rapid cements, high heat
The low LSF (90-93)	Easy burning, free lime margin	Lower alite, slower early strength	Easy-burning plants, low fuels
The low AM (1.2-1.3)	Easy melt, good coating	Higher ferrite, sulfate resistance	SR clinkers, iron-rich raw

The triangle chapters teach the simultaneous reading: every target change of one ratio moves the other two in the consequences, and the mix design is the balance of the three against the kiln capability, the fuel price and the product portfolio.

The practical numbers of the balance accompany the table: the raw meal of the modern plants is ground to the residue targets of the 12-15% on the 90-micron sieve and the 1-2% on the 200-micron, because the coarse quartz particles of the mix react slowly in the kiln and become the free lime and the belite pockets of the clinker: the fineness of the raw meal and the ratios of the mix are the two hands of the raw mix preparation, and the module keeps both in the reader’s sight throughout the correction arithmetic.

6. The Correction Practice: From the Target Ratios to the Mix Adjustment

The ratios are not the decoration of the design: they are the working instruments of the correction loop, and the module teaches the full practice:

• The measured basis: the XRF analyses of the raw materials (the limestone, the marl, the clay, the corrective sand and the iron source) with their moisture and the loss on ignition: the correction arithmetic starts from the real compositions;
• The adjustment movements: the iron ore and the bauxite to lift the LSF, the sand to raise the SM, the iron to lower the AM: each corrective material moves the three ratios in its own pattern, and the module gives the movement table of the common correctives;
• The calculation loop: the mix proportions of the day computed against the targets, the deviations of the modules and the correction recommendations: the loop runs on the shift basis with the weighfeeder settings as the output;
• The practical limits: the available correctives, the homogenization dead time and the kiln tolerance: the correction must respect the reality of the stockyard, and the module teaches the feasible correction, not only the arithmetic one;

The correction chapters make the reader the mix designer of the shift: the target modules in the head, the corrective movements in the hand and the feasibility in the eye: the daily profession of the raw materials engineer.

7. The Raw Mix Design Workflow: From the Quarry Analyses to the Daily Targets

The ratios live in a workflow, and the module follows the design from the quarry face to the weighfeeder settings:

• The material knowledge: the quarry survey analyses, the stockpile management and the blend of the extraction faces: the average chemistry the design starts from: the module gives the sampling and the averaging discipline of the quarry;
• The target setting: the ratio targets of the plant chosen from the product portfolio, the kiln capability and the fuel economy: the monthly design decision of the quality manager, reviewed against the strength results: the module teaches the target-setting logic;
• The daily operation: the shift XRF of the raw mix, the comparison with the targets and the correction of the weighfeeders: the hourly loop of the raw mill: the module gives the operator rules and the correction reaction times;
• The review rhythm: the weekly module statistics, the strength correlation and the quarterly design adjustment: the longer loop that keeps the design alive against the quarry drift and the product changes;

The workflow chapters give the reader the complete picture of the raw mix profession: the design is not the one-time calculation but the living process, and the module trains the process from the quarry to the review meeting.

8. The Ratio Bands across the Cement Families: The Design Table

The same three ratios design the different product families with the different bands, and the module presents the family table of the industry:

Cement family	LSF	SM	AM	Design logic
Ordinary Portland 42.5	93-96	2.3-2.6	1.4-1.6	Balanced strength and burnability
High strength 52.5	95-98	2.4-2.7	1.5-1.7	Alite-rich, hard burning accepted
Sulfate resistant	90-94	2.4-2.7	1.0-1.3	Aluminate-poor, ferrite-rich
Low heat	90-93	2.6-3.0	1.3-1.6	Belite-rich, low heat release
White cement	93-97	2.6-3.4	Very high (iron-free)	Color chemistry of the special mix

The family table closes the design chapter: the reader sees that the product catalog of the company is a set of the ratio designs, and the plant that plans its portfolio plans its raw mix bands first.

9. The Effects of the Ratios on the Kiln Operation: The Process Side

The ratios decide more than the phases: they shape the behavior of the kiln itself, and the module gives the process consequences the operator must expect:

• The nodulization: the clinker nodule quality follows the liquid content: the low-SM high-AM mixes form the wet sticky nodules and the high-SM mixes the dusty fragile ones: the nodule quality is the visible weather of the ratio design;
• The coating stability: the burning zone coating is the child of the flux: the adequate liquid at the clinkering temperature builds and holds the coating that protects the lining: the extreme ratios (the very high SM or the very low AM) starve the coating and shorten the refractory campaigns;
• The burning stability: the ratio changes move the temperature requirement of the clinker: the LSF jump of the two points demands the hotter burning, and the kiln responds with the free lime and the instability until the feed catches up: the operator sees the ratio events in the burning zone temperature;
• The dusting: the high SM and the high LSF together favor the belite dusting in the cooling clinker: the dusty clinker troubles the cooler, the mill and the quality: the module gives the warning signs and the design remedies;

The process chapters complete the ratio triangle with the kiln side: the same arithmetic that designs the phases runs the burning behavior, and the engineer who sees the ratios in the operator language runs the plant with the design in the head.

10. The Ratios in the Clinker Quality: The Link to the Phases and the Strength

The ratios were designed upstream, and they return downstream as the phase picture of the clinker, the link this module makes explicit:

• The LSF and the alite: the lime saturation sets the ceiling of the alite formation: the higher the LSF, the more the alite the burning can produce, provided the temperature and the residence deliver: the LSF is the strength potential of the design;
• The SM and the silicate total: the silica module fixes the total of the alite plus the belite in the phase picture: the SM is the silicate budget of the clinker, the budget the strength and the heat both draw from;
• The AM and the interstitial switch: the alumina module decides the aluminate against the ferrite: the C3A level of the certificate, the gypsum demand and the sulfate resistance of the product all follow the AM of the design;
• The strength correlation practice: the plant correlates its 28-day strength history with the ratio history and learns its own response slopes: the module gives the correlation analysis method and the interpretation cautions of the industrial statistics;

The quality chapters bind the module to the Bogue arithmetic of the previous module and the products course beyond: the ratios design the phases, the Bogue counts them and the strength certificate pays the account.

11. The Common Mistakes of the Ratio Arithmetic

The ratio practice carries its classic errors, and the module collects them so the reader avoids the traps of the generations:

• The lost-on-ignition confusion: the ratios computed on the raw meal as analyzed (with the CO2 of the carbonate and the water still inside) versus the calcined basis: the LSF must use the consistent basis, and the module gives the conversion discipline between the two;
• The moisture neglect: the weighfeeder proportions corrected without the moisture of the wet materials: the chemistry of the hour drifts from the design: the module teaches the moisture-corrected proportioning of the wet seasons;
• The single-sample decisions: the correction taken from the one spot sample of the noisy process: the ratio corrections belong to the trend statistics, not the single samples: the module prescribes the decision rules of the plant;
• The over-correction dance: the corrective action that overshoots the target and triggers the opposite correction the next shift: the dead-time oscillation the plants know too well: the module gives the damped correction policy;

The mistakes chapter is the operational wisdom of the module: the arithmetic is simple and the practice is subtle, and the engineer who learned the traps in the classroom spares the plant the weeks of the drift.

12. The Worked Example: The Correction of a Mix in Trouble

The module closes the practice with the full worked example of the mix correction, the way the shift engineer performs it:

• The starting point: the raw mix of the day at the LSF 89.2, the SM 2.1 and the AM 1.2 against the targets of the 95.0, the 2.4 and the 1.5: the kiln reports the dusty clinker, the free lime climbing and the strength trending down: the diagnosis begins;
• The material arithmetic: the corrective movements of the limestone (for the LSF), the sand (for the SM) and the bauxite (for the AM) computed from the available stock analyses: the module walks the simultaneous solution of the three corrections;
• The applied correction: the weighfeeder proportions changed in the one step with the calculated new mix, the raw mill chemistry re-verified within the hour and the kiln feed corrected with the lag of the silo volume respected;
• The result confirmation: the clinker phases of the following days returning to the design bands, the free lime settling and the strength certificate recovering: the example with the numbers and the timing of every step;

The worked example is the graduation exercise of the module: the reader who followed the arithmetic by the hand has performed the raw mix correction of the industry, and the products course will find him ready for the chemistry of the product.

13. The Ratios and the Homogenization: The Stability of the Chemistry

The best ratio design is worth nothing when the chemistry arrives at the kiln swinging, and the module gives the stability chapter that connects the mix design to the homogenization:

• The stability requirement: the kiln burns the feed of the hour, not the average of the week: the swinging modules force the alternating overburning and underburning, the free lime excursions and the rejected clinker: the stability of the ratios is a product quality in itself;
• The homogenization equipment: the raw meal silos of the continuous and the batch systems, the blending air and the recycling loops: the homogenization efficiency that damps the chemistry swings: the module gives the efficiency numbers the plants measure (the homogenizing factors of the 5-15 on the good circuits);
• The measuring of the stability: the standard deviation of the LSF at the kiln feed, the trend charts of the modules and the statistical process control: the instruments that show the stability as the number: the module teaches the metrics of the swing;
• The correction interplay: the homogenization dead time against the correction speed: the efficient silo lets the raw mill react calmly, and the weak circuit forces the frenetic corrections: the module links the raw mix correction policy to the homogenization capability of the plant;

The stability chapter closes the loop that began at the quarry: the same modules that design the phases must be delivered steadily to the kiln, and the engineer who manages the stability manages the product quality at the source.

14. The Ratio Statistics of the Quality Control: The Trend Instruments

The module closes the quality side with the statistical instruments that turn the ratio data into the control decisions:

• The control charts: the modules plotted against the targets with the warning and the action limits: the Shewhart-style charts of the raw mix quality: the module gives the chart setup and the interpretation rules of the industry;
• The capability analysis: the standard deviation of the LSF compared with the tolerance the kiln demands: the capable mix control (the sigma within the limits) versus the incapable process that no correction policy can rescue: the capability arithmetic of the module;
• The correlation registry: the strength result against the ratio history, the free lime against the LSF and the coating events against the SM: the correlations the plant accumulates and the module teaches to maintain: the memory of the quality department;
• The review reports: the monthly ratio statistics with the corrective actions taken and the results: the report format the module provides and the quality manager presents: the discipline that keeps the design honest;

The statistics chapters complete the module with the office instruments: the ratios are the chemistry, the statistics are the evidence, and the engineer who reads both runs the raw mix control as the profession the industry expects.

15. The Bridge to the Products Chapters: The Ratios in the Course Logic

The module closes the technical body with the deliberate bridge into the products course, because the raw mix design is the beginning of the product story:

• The phases as the product contract: the ratios design the phases, and the phases are the contract the cement certificate reports: the C3S and the C3A of the certificate are the echoes of the raw mix bands of the months before: the reader sees the product as the delayed witness of the mix design;
• The product planning backward: the product portfolio of the company (the 42.5, the 52.5, the SR, the white) is planned backward into the raw mix families: the plant that cannot change its quarry chemistry cannot change its product mix: the strategic dimension of the ratio design;
• The quality language of the customer: the specifiers and the auditors speak the certificate language, and the certificate language is the phase language, and the phase language is the ratio language: the reader of this module speaks with the customer in the full chain;
• The continuity of the series: the minor elements module and the interaction module that follow refine the design with the guests and the pairs, and the products course chapters apply the refined design to the standards and the types: the path is continuous, and this module marked its point;

The bridge chapter closes the module where the series continues: the ratio knowledge is not the end but the launch point, and the engineer who continues the series carries the design arithmetic into every later chapter.

16. The Frequently Asked Questions

Q: Why are the ratios called the lime saturation, the silica module and the alumina module at the same time?

A: The names come from the history of the industry: the LSF is also called the lime saturation factor, the SM the silica ratio, and the AM the alumina or the iron ratio: the module uses the names interchangeably and teaches the reader the family of the terms.

Q: What is the LSF of the sulfate-resistant clinker?

A: The SR clinkers typically run the lower LSF (the 90-94) with the low AM (the 1.0-1.3): the reduced alite and the aluminate with the raised ferrite serve the durability profile of the type.

Q: How fast can the kiln respond to the ratio corrections?

A: The raw meal curve and the kiln together hold the residence of the hours to the day: the correction takes effect in the shifts, and the module teaches the lead-lag thinking of the corrective actions.

Q: Do the ratios apply to the white cement raw mixes?

A> The same ratios apply with the extreme values: the white mixes run the very high AM (the iron-free) and the adjusted LSF for the low-melting chemistry: the module notes the special mix families alongside the ordinary ones.

Q: Which module comes after this one in the series?

A: The minor elements module (the sixth of the series) adds the guests of the clinker, and the interaction module (the seventh) completes the pairs: the ratios of this module remain the design backbone throughout.

17. The Closing of the Module

The fifth module of the prerequisites has given the reader the design arithmetic of the clinker: the lime saturation that gauges the calcium, the silica module that balances the silicates against the flux, and the alumina module that switches the interstitial phases, all tuned together in the correction loop of the plant. The engineer who leaves this module reads the raw mix reports with the designer’s eye, sets the targets with the kiln in the head and corrects the feed with the product in mind. The minor elements and the interactions that follow will refine the picture, and the products course will apply the designs this module has taught to the catalog of the cement types.

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.