FORM - 2

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THE PATENTS ACT, 1970 /poOfS* ****** *+ * (39 of 1970)

THE PATENTS RULES, 2003
COMPLETE
Specification
(See section 10 and rule 13)
A PROCESS FOR MANUFACTURING OF PORTLAND SLAG CEMENT
GRASIM INDUSTRIES LIMITED
an Indian Company
of BIRLAGRAM, Nagda 456 331,
Madhya Pradesh, India
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
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FIELD OF INVENTION
This invention relates to a process for manufacturing of Portland Slag Cement without using Gypsum.
INTRODUCTION
Portland Slag Cement is manufactured by intergrinding Portland cement clinker; gypsum and granulated slag obtained from steel and Ferro alloys industries. PSC is also manufactured by blending Ordinary Portland Cement (OPC) with ground granulated blast furnace slag (ggbs) through mechanical blenders. The slag is non-metallic product consisting essentially of glass containing silicates and alumina silicates of lime and other bases. The granulated blast furnace is obtained by further processing the molten slag by rapidly chilling or quenching it with water or steam or air. The granulated slag used for manufacture of slag cement should confirm to IS: 12089 -1987. The slag constituent should not be less than 25% and not more than 70% in Portland Slag Cement as per IS 455 - 1989.
Slag Cement is mainly used for construction of marine structures and in coastal areas where excessive amounts of chlorides and sulfate salts are simultaneously present. In addition, it has low heat of hydration and can be used for mass concrete works with advantage. Its compressive strength is equivalent to that of 33 grade OPC as per the IS code, however in market slag cements of strength equivalent to OPC 53 grade OPC are available. Slag cement is suitable for general construction works and can be effectively used where OPC or PPC are used. The curing period for slag cement is also more as compared to OPC and IS 456 - 2000 specifies a minimum curing period of 14 days.
After having gone through various research studies conducted world wide, initiative had been taken to achieve the objective.
BACKGROUND OF THE INVENTION
In the present investigation the role of alkali activators performing the dual function of activating the slag at initial ages (i.e. 1 day), as well as activating the dormant sulfur phases in the clinker, is innovatively tapped.
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Though there are many activators like NaOH, Na2S04, water glass (Na2Si03), Na2C03, KOH, K2S04 for alkaline activation of slag, not all would perform the aforementioned dual objectives. Hence, the key for success lies in selection, assessment of particular activator, and its compatibility with the given slag and clinker composition.
The initial stage of investigation was mainly concentrated in selecting the right kind of activator / activators compatible with the given slag and clinker compositions. After this stage is over, the next phase of investigation carried out to fix the proper dose of activator, proper proportioning of slags from two different sources in view of achieving the desired quality in the cement and economy. The laboratory trials carried out have been reconfirmed by repeated trials before taking trials in plant scale.
In present study, clinker, slags and activator have been interground in a cement ball mill to predetermined fineness and evaluated its performance in the laboratory. During the investigation one of the important ingredients in cement manufacture i.e. gypsum has been eliminated totally, primarily due to the use of sulfur containing phases from clinker in lieu of gypsum. This is an exception in cement manufacturing process as per Bureau of Indian Standards (IS 455 - 1989) for Portland Slag Cement Specification.
Portland Slag Cement is manufactured by Jntergrinding Portland cement clinker, gypsum and granulated slag obtained from steel and Ferro alloys industries. Portland Slag Cement is also manufactured by blending Ordinary Portland Cement (OPC) with ground granulated blast furnace slag (ggbs) through mechanical blenders. The slag is non-metallic product consisting essentially of glass containing silicates and alumina silicates of lime and other bases. The granulated blast furnace is obtained by further processing the molten slag by rapidly chilling or quenching it with water or steam or air. The granulated slag used for manufacture of slag cement should confirm to IS: 12089 - 1987. The slag constituent shall not be less than 25% and not more than 70% in Portland Slag Cement as per IS 455 - 1989
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Slag Cement is mainly used for construction of marine structures and in coastal areas where excessive amounts of chlorides and sulfate salts are simultaneously present. In addition, it has low heat of hydration and can be used for mass concrete works with advantage. Its compressive strength is equivalent to that of 33 grade OPC as per the IS code, however in market slag cements of strength equivalent to OPC 53 grade OPC are available. Slag cement is suitable for general construction works and can be effectively used where OPC or PPC are used. The curing period for slag cement is also more as compared to OPC and IS 456 - 2000 specifies a minimum curing period of 14 days.
Alkaline activation of slag
The principle of alkaline activation of slag has been known since 1940's. Although many attempts have been made to explain the hydration process of alkali activated slag cement, the roles of activators are still not well documented.
It is generally agreed that the performance and microstructure of alkali activated slag are determined by the chemical and mineralogical compositions of slag and the dosage and nature of the activator / s used. Thus it is not surprising that different results are obtained in different laboratories, since the raw materials used in various laboratories could be different
Although slag without an activator does react with water, the rate of hydration is very slow. Ground Granulated Blast-Furnace slag (GGBFS) is a glassy granular material formed when molten blast-furnace slag is rapidly cooled, usually by immersion in water, and then ground to improve its reactivity. The major components of blast-furnace slag are Si02, CaO, MgO and Al203/ which are common components in commercial silicate glasses. Its hydraulic reactivity depends on chemical composition, glass phase content, particle size distribution and surface morphology.
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Research on alkali-activated slag (AAS) has provided basic information about the mechanism of alkali - activation. Mehta reported that coatings of aluminosilicate form on the surface of slag grains within a few minutes of exposure to water, and these coatings were impermeable to water. Unless a chemical activator is present, further hydration is inhibited. Portland cement, gypsum and many alkalis have been used as activators, and it has been observed that the rate of hydration is faster at high alkali concentrations.
C-S-H with low C/S ratio is the major hydration product of alkali slag cement although the minor hydration products may vary with the nature of slag and activator used. Solubility curves of C-S-H and N-C-S-H in corporate into C-S-H in 3 different mechanisms: (a) neutralization of acidic Si - OH groups by Na+ or K+, (2) ion exchange of Na/K for Ca (3) Cleavage of Si - 0 - Si bonds by Na+ or K+ with attachment of Na+ or K+ to Si. Depending on the C/S ratio of C-S-H one or another mechanism may dominate, however the 3 mechanisms co-exist.
The incorporation of alkali into C-S-H increases as C/S ratio of the C-S-H decreases. The main restriction for the incorporation of alkali into the structure of C-S-H is probably the condition of electro neutrality. The incorporation of alkalis affects the solubility curve of C-S-H. However, alkalis in C-S-H can be leached out easily. The lumping out of alkalis from C-S-H moves its solubility curve towards its original curves.
The presence of alkalis keeps a high pH value in the solution, which is important to initiate and to continue the hydration of the slag. However, alkalis are not really involved in the hydration process and hydration products. Alkalis can be simply regarded as catalysts rather than reactants. However, anion or anion groups of activators have a great effect on the hydration, structure formation and properties of hardened alkali activated slag cements.
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'S' containing phases in clinker
Sulfur is incorporated into the clinker during the pyroprocessing operations. Sulfur could enter the system through the limestone or fuel (petcoke/coal). The distribution of sulfur in the clinker mineral phases was determined by examining the clinkers using X-ray fluorescence, X-ray diffraction and selective extraction techniques.
The alkali content in most plants is low, which indicates that the sulfur available in the system may not be fully matched by alkalis to form alkali sulfates. Hence, there exists a possibility of the formation of other sulfur bearing compounds or incorporation of sulfur in the clinker mineral phases.
The XRD pattern analysis as shown in the figure 1 indicates that the major sulfate containing phase is the anhydrite (CaS04) and calcium langbeinite (Ca2K2(S04)3). This may be attributed to the low concentration of alkali in the kiln feed.
Typically, 50% of the sulfates are incorporated in the silicate phases, while the rest remain in the interstitial phase as anhydrite and needle-shaped crystals of calcium langbeinite.
Activation of'S' containing phases in clinker
Sulfate is added to cement to control aluminate hydration and to enhance tricalcium silicate hydration, promoting improved strength development. The amount, form and fineness of sulfate dictate its solubility and, therefore, its effect on aluminate hydration. This interaction between the sulfate and clinker phases is important as it influences concrete workability, strength, setting time, drying/shrinkage and expansion and, hence, durability.
During the process of grinding cement clinker, the friction inside the grinding mill generates heat. When it reaches to certain temperature, the gypsum added in the grinding mill in the manufacture of Portland slag
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cement, may undergo partial or complete dehydration to form gypsum hemihydrate (CaS04. 1/2H20) or anhydrite (CaS04) respectively or both.
The figure 2 depicts the solubilities of the different CaS04 phases.
Gypsum hemihydrate, upon addition of water dissolves rapidly and precipitates to form gypsum dihydrate. If the composition of hemihydrate is very high, it may undergo rapid hydration to produce false set, otherwise known as premature stiffening in hydrated cement. Sometimes false set occurs in the product after being aerated or in storage. Also, low hemihydrate content would lead to inadequate control of aluminate hydration. The hydration of aluminate phases would lead to voluminous hexagonal aluminate hydrates form instead of combining with sulfate to form ettringite.
Anhydrite that is formed within the grinding mill (at temperatures of about 100 - 200°C) is also highly soluble, as it develops from the hemihydrate phase, and has the same crystal structure.
However, anhydrite, which is formed in the cement kiln (at temperatures higher than 600°C), is much harder than gypsum and has the slowest dissolution rate of the three sulfate forms, in part due to its large size resulting from its hardness. It undergoes hydration very slowly with a very low reactivity. As such, it is not of much practical utility. However, when certain activators are added to the hydrating anhydrite, the hydration and subsequent reactions could be enhanced considerably.
The dormant anhydrite within the clinker phases could be activated using such activators to have an appropriate amount of sulfate ions available, which would control the aluminate hydration, leading to paste of proper plasticity, normal setting and hardening properties.
A mechanism of conversion of anhydrite into gypsum in the presence of activators is suggested. The hydration of anhydrite involves a dissolution-
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nucleation-growth process. Typically, the dissolution takes place through the formation of transient double salts.
The most suitable activators would be those which fulfil the dual function of the activation of slags as well as the activation of anhydrite simultaneously. This would ensure that the slag is available for the cementitious as well as subsequent pozzolanic reactions; while the aluminate hydration is also retarded using the sulphates already existing within the clinker.
Many trials have been conducted with different activators, viz., Na2C03, Na2S04, KOH, NaOH, and K2S04 at different doses. The trials with these activators indicated that the activators exhibiting the best properties due to the slag activation and the retardation of aluminate hydration were Na2S04 and K2S04.
The XRD pattern analysis as shown in the figure 3 indicates that the ettringite phase is formed even in the absence of addition of gypsum in the mill. This may be attributed to the reaction of sulfur-containing phases (such as insoluble anhydrite) in the clinker.
The optimum dosage of the best activator was determined based on the best performance of the cement in terms of its early age strength as well as its 28-day strength. Based on the test results, it has been concluded that 0.3% Na2S04 is the optimum activating entity to achieve the objectives of the investigation.
OBJECT OF THE INVENTION
The object of the invention is to provide a process for manufacturing of Portland Slag Cement.
Another object of the invention is to take advantage of the role of alkali activators performing the dual function of activating the slag at initial ages (i.e. 1 day), as well as activating the dormant sulfur phases in the clinker.
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Another object of the invention is to totally eliminate use of gypsum in the manufacturing of Portland Slag Cement resulting in savings in manufacturing cost.
Another object of the invention is to improve the rate of production of the cement mill which results in the reduction of power consumption.
Another object of the invention is to improve the quality of the product in terms of compressive strength remarkably particularly at initial ages (i.e. 1 day).
SUMMARY OF THE INVENTION
According to this invention, therefore there is provided a process for manufacturing Portland Slag Cement, comprising the following steps,
a) Mixing blast furnace slag and sodium sulfate as per predetermined ratio to obtain slag mixture,
b) Dosing Cement Clinker with slag mixture as per predetermined ratio to obtain slag clinker mixture,
c) Grinding slag clinker mixture in a ball mill to obtain Portland cement.
In accordance with one embodiment of the invention, the blast furnace slag consists of compounds selected from a group of compounds consisting of silicates, alumino silicates, calcium-alumino-silicates, CaO, Si02, Al203( MgO, Fe203/ MnO, sulfur, Ti02, Na20, K20, sulfides and chlorides.
Typically, the mass of blast furnace slag ranges from 45 to 60%.
In accordance with another embodiment of the invention, the Cement Clinker consists of compounds selected from a group of compounds consisting of calcium silicates, lime (CaO), silica (Si02), alumina (Al203), iron oxide (Fe203), MgO, Fe203, MnO, l\la20, K20, (Ca0)3.Si02, (Ca0)2.Si02, (CaO)3.Al203, (CaO)4.Al203.Fe203 and Free Lime.
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Typically, the mass of Cement Clinker ranges from 40 to 50%.
Typically, the mass of sodium sulfate ranges from 0.2 to 1.0%.
Typically, the mass of sodium sulfate ranges from 0.2 to 0.4%.
Typically, the mass of sodium sulfate purity ranges from 80 to 100%.
In accordance with another embodiment of the invention, the ball mill is an open circuit two chambered ball mill separated by a diaphragm having 9.2 meter length and 2.0 meter diameter.
In accordance with another embodiment of the invention, the ball mill has liners, diaphragms and grinding balls made up of nichrome metal.
DESCRIPTION OF THE FIGURES
The XRD pattern analysis as shown in the figure 1 indicates that the major sulfate containing phase is the anhydrite (CaS04) and calcium langbeinite (Ca2K2(S04)3).
The figure 2 depicts the solubilities of the different CaS04 phases.
The XRD pattern analysis as shown in the figure 3 indicates that the ettringite phase (Ca6Al2(S04)3(OH)i2 - 26H20, Hydrated Calcium Aluminium Sulfate Hydroxide) is formed even in the absence of addition of gypsum in the mill.
DETAILED DESCRIPTION OF THE INVENTION
The studies and results are described as below:
Description of raw materials i. Granulated blast furnace slag
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It is a non-metallic co-product produced in the production of iron. Iron ore, iron scrap and fluxes (limestone and dolomite) are charged into blast furnace along with coke or fuel. The coke is combusted and produced carbon monoxide, which reduces the iron ore to a molten iron product. It consists primarily of silicates, alumino silicates, and calcium-alumino-silicates. If the molten slag is cooled and solidified by rapid water quenching to a glassy state, little or no crystallization occurs.
The chemical composition of slag can vary over a wide range depending on the nature of the ore, the composition of limestone flux, the coke consumption and kind of iron being made. These variations affected the relative content of four major constituents, lime, silica, alumina and magnesia. Table 1 gives chemical composition of slags from different countries.

Table 1 - Chemical Composition of blast furnace Slags
Source CaO Si02 Al203 MgO Fe203 MnO S
UK 40 35 16 6 0;8 0.6 1.7
Canada 40 37 8 lu"'-:7*' 1.2 0.7 2.0
France 43 35 12 8 2.0 0.5 0.9
Germany 42 35 12 7 0.3 0.8 1.6
Japan 43 34 16 5 0.5 0.6 0.9
Russia 39 34 14 9 1.3 1.1 1.1
South Africa 34 33 16 14 1.7 0.5 1.0
USA 41 34 10 11 0.8 0.5 1.3
The following characteristics are considered in judging the suitability of blast furnace slag in our country as per in IS: 12089.

a. The percentage oxide shall satisfy the following:
CaO + MgO + AI2Ch > 1.0
Si02
b. Manganese oxide - 5.5% (max)
c. Magnesium Oxide - 17.0% (max)
d. Sulfide Sulfur - 2.0% (max)
e. Glass Content - 85.0% (min)

Table 2 - Chemical and Physical Characteristics of blast furnace slags in the present investigation.
Parameter Slag 1 Slag 2
Chemical (%)
Si02 33.9 - 36.0 32.1 - 37.0
Al203 16.0- 19.0 16.0 - 20.0
Fe203 1.1 -2.2 0.5- 1.5
CaO 32.0 - 35.0 32.0 - 35.0
MgO 8.0-9.4 7.9 - 10.0
Sulfide Sulfur 0.5 - 1.5 0.8- 1.6
MnO 0.4 - 0.6 0.2-0.5
Ti02 0.3-0.5 -
Na20 0.4 - 0.65 0.3 - 0.5
K20 0.4-0.7 0.4 - 0.6
Chlorides Traces Traces
Physical
Glass Content (%) 85.0 - 96.0 85.0-97.0
Density (kg/lit) 1.0 - 1.5 0.8- 1.2
Moisture (%) 0-2.0 2.0- 10.0
Granulometry (%) + 3.35 mm = 40 -43%+ 1.18 mm = 85 -92%- 1.18 mm = 8 -11% 1 - 3% 16 - 18% 80 - 85%
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ii. Portland Cement Clinker
The second ingredient in cement composition in accordance with this invention is cement clinker. Clinker, consisting mostly of calcium silicates, obtained by heating to incipient fusion a predetermined and homogeneous mixture of materials principally containing lime (CaO) and silica (Si02) with smaller proportion of alumina (Al203) and iron oxide (Fe203). The range of chemical composition of Portland clinker is shown in the table 3 and table 4:

Table 3 - General range of chemical and phase of composition of clinker
Parameter %
Si02 19 - 25
Al203 2-8
Fe203 3-6
CaO 60-65
MgO 1-6
Alkalis (as Na20 equivalent) 0.2-1.5
LSF 0.66 - 1.02
C3S 20-60
C2S 20-30
C3A 0-16
C4AF 1-16
Free Lime 0-3
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Table 4 - Chemical and Phase composition of clinker in the present investigation
Parameter %
Si02 21.67 - 22.03
AI2O3 5.14-5.54
Fe203 4.36-4.96
CaO 65.0 - 65.69
MgO 0.82 - 1.36
Na20 0.1 -0.3
K20 0.3 -0.4
Alkalis as Na20 0.22 - 0.38
LSF 0.91 -0.93
C3S 46.6- 51.0
C2S 24.0 - 27.0
C3A 5.0 - 7.2
C4AF 13.3- 15.2
Free Lime 1.1 -2.0
iii. Sodium Sulfate (Na2S04):
Sodium sulfate is white powder and free flowing. The characteristics of the same are given in Table 5:

Table 5 - Characteristics of Sodium Sulfate used present investigation. in the
Parameters Characteristics
Colour White
Flow ability Good, free flowing
Moisture (%) < 0.5%
PH 6.5 - 10.0
Purity (%) > 99.0
Chloride content (%) < 0.2
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Experimental
Various feasibility trials with different activators, single and combinations at different doses, at different fineness of slag, at different slag content have been carried out to identify the suitable activator for incorporating 50 % plus slag without hampering the quality of the product. By these investigations it is deciphered that sodium sulfate (Na2S04) with given composition of slags and clinker will give the desired results.
In order to optimize, (i) the dosage of sodium sulfate, (ii) percentage incorporation of both Slag 1 and Slag 2 (ratio) (iii) fineness of resultant product, many trials have been conducted using Na2S04 (Chemical grade) in the laboratory.
Methodology:
The physical and chemical characteristics of resultant Portland Slag Cement have been evaluated as per the procedure given in Indian Standard specification IS: 4031 and IS: 4032.
Many trials have been conducted with different activators, viz., Na2C03, Na2S04, KOH, NaOH, and K2S04 at different doses. Based on the test results, it has been concluded that Na2S04 with 0.3% is the optimum activating entity to achieve the objectives of the investigation.
Subsequently, some more trials were conducted by using commercial grade l\la2S04 with 0.3% and the results are shown in table 6.
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Table 6 Lab Ball Mill Trial with 50% Slag Cement Ground With 0.3% Sodium Sulfate
Feed Composition & Test Carried Out Sample (A) Sample (B)
Clinker (%) 50.00 50.00
Slag 1 30.00 29.82
Slag 2 19.50 19.88
Gypsum (%) 0.50 Nil
Sodium Sulfate (%) Nil 0.30
Residue (90mic)% 2.35 2.50
Blaine's (m2/kg) 326.00 325.00
N, C (%) 27.00 27.00
Compressive Strength (Mpa)
1 Day 8.50 12.3
3 Days 20.20 23.2
7 Days 30.30 32.70
28 Days 51.20 53.5
Finally, confirmatory trials have been carried out to establish the repeatability before initiating the production of Portland Slag Cement on large scale at plant. Table 7 shows the results of confirmatory trials

Table 7 Lab Ball Mill Trial With 0.3% Of Na2S04 (Sodium Confirmatory Trial Sulfate) -
Feed Composition & Test Carried Out Sample (C) Sample (D)
Clinker (%) 50.00 50.00
Slag 1 29.82 29.82
Slag 2 19.88 19.88
Gypsum (%) Nil Nil
Sodium Sulfate (%) 0.3 0.30
90mic Residue % 2.70 2.60
Blaine's (m2/kg) 330 324.00
Compressive Strength (Mpa)
1 Day 12.5 12.10
3 Day 24.6 23.50
7 Day 33.0 32.70
28 Day 54.2 54.5
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The typical composition in accordance with this invention is as follows:
Cement clinker: 40 to 50%
Total slag: 45 to 60%
Sodium Sulfate: 0.2 to 1.00%
Improvements in the early strength in Portland Slag Cement manufactured with 50% Slag with activator are as below:
Table 8 Quality of the Cement

Parameters 35% slagCement(Before) 50% slagCement(Present) % of Improvements
Residue% (90 mic) 1.6 1.40
Blaines (m2/kg) 329 338
Compressive Strength (Mpa)
1 day 10.3 13.6 32.0
3 days 25.7 27.1 5.5
7 days 36.9 38.4 4.1
28 days 54.7 54.1
The process of manufacture of Portland Slag Cement (PSC) in the present investigation comprises following steps:
1. Storage of different raw material.
2. Mixing slag 1 and sodium sulfate as per desired proportions.
3. Proportioning of two different slags as per pre determined ratios.
4. Feeding of different raw materials at respective hoppers.
5. Dosing of different raw materials through table feeders.
6. Cement grinding in ball mill.
7. Packing
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Storage of raw materials
i. Clinker:
Portland Cement Clinker received from one of our group units by trucks are unloaded through truck tipplers and stored in covered shed.
/'/'. Blast Furnace Slag
Plant is getting blast furnace slags from two different sources by trucks. The 2 different slags are stored separately in the form of heap in a covered shed, slag 1 is dry material and is directly stored in a shed whereas slag 2 contains moisture and therefore it is sun dried before shifting into covered shed for use in the Portland Slag Cement manufacture
/'/'/. Sodium Sulfate (Na2S04):
Sodium sulfate packed in 50 Kg laminated HDPE bag is received at plant by trucks and is stored separately in a covered shed.
a) Mixing of slag 1 and Sodium Sulfate
As mentioned earlier, Sodium Sulfate received in bags are repacked (as per the requirement) before mixing with slag 1. Sodium Sulfate with 0.3% (of clinker weight) is thoroughly mixed with the help of pay loader and stored in the form a heap before filling into overhead hopper. Mixing of these two components has become easy as both are in dried form and the granulometry of these two materials are matching.
b) Proportioning of two different slags
Based on physical characteristics, quality and economy, an optimum ratio has been derived for using these two slags. Accordingly, both the slags are filled in respective hoppers.
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c) Feeding of raw materials to hoppers.
The different raw material stored in the form of heaps is fed one by one through belt conveyor in their respective hoppers. Pay loader is used for feeding of raw materials.
d) Dosing of raw materials
The three hoppers, 1st one for clinker, 2nd one for mixture of slag 1 + Sodium sulfate, 3rd one for slag 2 are attached to table feeder (3 nos.) meant for dosing as per the requirement. In order to dose these 3 components as per the requirement, table feeder revolutions are controlled by variable speed dyno drive motor. Example, table feeder meant for slag 2 has got a RPM of 200 - 250, clinker table feeder RPM is 200 - 220 and mixture of slag 1 + sodium sulfate is 120 - 150 RPM.
It is imperative to mention here that in order to improve the accuracy and precision of dosing of table feeders some modifications were carried for telescopic chute, scrapper and dyno drive.
Cement grinding
The proportioned / dosed raw materials are fed into an open circuit ball mill with 9.2 meter length and 2.0 meter diameter. It is a two chambered ball mill separated by a diaphragm. Liners, diaphragms and grinding balls are made up of nichrome metal. The technical details of ball mills are shown below:
Ist Compartment
• Effective diameter - 1.9 meter
• Effective length - 2.76 meter
• Effective volume - 7.828 m3
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IInd Compartment
• Effective diameter - 1.93 meter
• Effective length - 5.725 meter
• Effective volume - 16.755 meter

Table 9 - Grinding media change
1st Compartment Compartment
80 mm dia 25 mm dia
70 mm dia 20 mm dia
60 mm dia
50 mm dia
40 mm dia
The cement mill equipped with bag filter (for fulfilling pollution control norms) with differential pressure of 65 - 70 mm.
In order to control the particle size distribution of the end product and to enhance the rate of production the mill the following changes have been made in the grinding media charge inside the mill in the present investigation as given in table 10

Table 10 - Grinding media change in the investigation. present
Compartment Media change in ton (before) Grinding change in (present) media ton
1st Compartment
80 mm dia 1.2 0.5
70 mm dia 1.5 1.0
60 mm dia 2.2 2.5
50 mm dia 2.3 2.5
40 mm dia 2.3 3.0
Total 9.5 9.5
2nd Compartment
25 mm dia 11.0 9.0
20 mm dia 11.0 13.0
Total 22.0 22.0
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Packing
Cement is extracted form the cement silo by means of screw feeder and transported to packer plant where it is first screened to remove any foreign particles and then stored into hoppers for packing with the help of packers. Spillage if any during packing is collected into spillage hopper and recycled into the system. The packed bags are handled by belt conveyor and loaded into the trucks.
Thus it is apparent that there has been provided, in accordance with the invention, a product and process that fully satisfy the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.
References:
1. IS 455- 1989
2. IS 12089 - 1987
3. Darko Krizon et.al. (2005): The influence of different parameters on the hydration process of binders based on alkali activated slag J. Serb. Chemical Society. 70 (1), p.p. 97 - 105.
4. Caijun Sh: (2003): On the state and role of alkalis during the activation of alkali activated slag cement. Prose, of 11th International National Congress on Chemistry of cement., p.p. 2097 - 2105.
5. B. Mus (2003): Improved performance of blast furnace slag cement made with high alkali clinker proceed of 11th International National Congress on Chemistry of Cement, p.p. 958 - 970.
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6. Chen Jian - Xiong et.al (2003): a study on complex alkali slag environmental concrete International National workshop on Sustainable Development and Concrete tech., p.p. 299 - 306.
7. P. Z. Wang (2003: Influence of the Structural Change of granulated blast furnace slag on the hydraulic activity. Prose of 11th International National Congress on Chemistry of Cement, p.p. 1020 - 1026.
8. S. Song et.al (2000): Hydration of alkali activated ground granulated blast furnace slag Tour of Materials Science, 35, p.p. 249 - 257.
9. US patent 4011092: Stanner sulfate and gypsum mixture as a retarder in grinding Portland Cement and blended hydraulic cement for improving the quality of cement, mortar and concrete.
10.J. Trenkwalder: Producing slag cements by separate grinding and subsequent mixing at eh Karlstadt.
11.Lea's Chemistry of cement and concrete (1998): Edited by Peter C. Hewlett, 4th edition, p.p. 635.
12.Qian Jueshi, Shi Caijun and Wang Zhi (2000): Activation of blended cements containing fly ash. Cemi. Cone. Res., 31, pp. 1121 - 1127.
EXAMPLES
Example 1: Effect of addition of slag at different contents with or without addition of Na2S04 on the properties of Cement
Trials were conducted with different slag contents, viz. 40%, 45%, 50%, 60% and 70% with or without addition of Na2S04 to know its effect on properties of cement. The percentage of addition of Na2S04 was kept constant (0.3%) through out the trials. The results are shown in table 11.
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Table 11. Effect of different Slag contents with or without addition of Na2S04 on properties of Cement
Sr. No Slag% Clinker% Na2S04 % Residue on % (90 mic) Blaines (m2/kg) Settingtimes(minutes) Compressive (MPa) Strengths
1ST FST 1 day 3 day 7 day 28 day
1A IB 40 60 NIL 2.2 384 100 170 16.2 32.3 46.1 60
60 0.3 2.1 371 105 195 19 34.5 48 60.7
2A 2B 45 55 NIL 1.22 412 105 180 14.1 29.2 45.2 56.4
55 0.3 1.26 423 120 200 17.6 33.7 51 57.8
3A 3B so 50 NIL 2.35 326 100 175 8.5 20.2 30.3 53.8
50 0.3 2.5 325 140 190 11.7 21.9 32.7 54.1
4A 4B 60 40 NIL 2.3 338 135 210 7.4 16.9 24.2 48.6
40 0.3 2.1 331 155 240 8.9 18.6 25.7 49.3
5A 5B 70 30 NIL 1.1 418 140 225 7.2 14.8 21.4 44.6
30 0.3 1.24 424 150 270 8.8 16.3 23.9 46.3
Note: A - Denotes trial without addition of Na2S04 B - Denotes trial with addition of Na2S04
Observations
i. Compressive strength: Compressive strength decreases at all ages as slag content increases irrespective of the addition of Na2S04
ii. Effect of Na2S04: The effect of Na2S04 is quite evident in enhancing compressive strength vis-a-vis without addition of Na2S04 at all ages irrespective of higher addition of slag.
iii. Setting time: Both initial and final setting times have prolonged as slag contents were on the higher side.
Example 2: Effect of addition of slag from different sources with or without addition of Na2S04 on properties of cements
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Experiments have been carried out by using slag from Vizag and Jindal Steel Plants with and without Na2S04 to understand its effect on slag from different sources (apart from slag from Goa). The table 12 shows the results.
Observations
Vizag Slag (A.P.)
The results reveal that there is a increase of 1, 3, 7 and 28 day strength with 0.3% Na2S04 vis-a-vis without the usage of Na2S04. The resultant cement is in line with the findings mentioned in invention report.
24

Jindal Slag (Karnataka):

Table 13: Physical Characteristics of Cements by using Slag from Jindal
Steel Plant
Composition / Tests carried out Without Na2S04 With Na2S04
1) Clinker (%) 50 50
2) Jindal Slag (%) 49.7 49.7
3) Sodium Sulfate (%) (Na2S04) NIL 0.3
4) Test Results:-
a) Residue (90 mic) (%) 1.4 1.45
b) Blaines (m2/kg) 352 347
c) N.C. (%) 27.5 27
d) Setting time (minutes)
(i) 1ST (Initial Setting Time) 125 110
(ii) FST (Final Setting Time) 230 200
(e) Compressive Strength (MPa)
(i) 1 Day 11.9 13.7
(ii) 3 Days 23 ;W,; 25.4
(iii) 7 Days 36.8 : ;v''"l-:v' ■:. 40.5
(iv) 28 Days 55.2 57.1
Same sets of experiments have been carried out for Jindal slag also. Table 13 shows the same.
Observation
The Observation is same as above in case of Vizag Slag.
Example 3: Effect of clinker and slag composition, with Na2S04 (other than used in present invention) on properties of cement
Trials are carried out to understand the effect of clinker, slag and Na2S04 (both from different source other than used in Invention) to find out whether it is possible to obtain desired properties in resultant cement in line
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with the present invention. Table 15 and 16 show chemical characteristics of clinker and granulated blast furnace slag respectively. Table 10 gives the results of trials at (i) With or without the addition of Na2S04 (ii) With and without addition of gypsum (iii) with different level of addition of slag. In all the above trials clinker content was kept constant.

Table 14 - General range of Chemical and Phase composition of clinker (Other than clinker used in the present invention)
Parameter %
Si02 19-25
Al203 2-6
Fe203 3.0-4.0
CaO 63.0 - 65.0
MgO 1.0- 3.0
Alkalies Na20 1 - 1.5
LSF 0.9 - 0.93
C3S 42.0 - 51.0
C2S 23.0-31.0
C3A 8.0-9.5
C4AF 10.0 - 11.5
F. CaO 0.9- 1.8
C3S = (CaO)3.Si02
C2S = (CaO)2.Si02
C3A = (CaO)3.AI203
C4AF = (CaO)4.AI203.Fe203
Lime Saturation factor, LSF = for
2.%Si02 + \.65Al203 + 0.35Fe2O3
—2-2- >0.64 Fe203
The lime saturation factor (LSF) is a concept of great importance in cement technology, which represents the ratio (in percent) of quantity of lime actually present in cement to the quantity of lime
26

required by acidic oxides to the resulting clinker compounds, viz., C3S, C2S, C3A and C4AF.

Table 15 - Chemical characteristics of blast furnace slag (other than slag used in the present Invention)
Parameter %
Si02 31-34
Al203 17-19
Fe203 0.5- 1.0
CaO 31 -33
MgO 10- 13
S03 0.5- 1.5
Na20 0.2 - 0.4
K20 0.5-0.7
S 0.3 -0.8

Table 16 - Performance of resultant cements
Sr■No■ Composition (%) Blaine s(m2/ kg) Settingtimes(minutes) Compressive Strengths (MPa)
Clink er Slag Gypsu m Na2S 04 1ST FST 1 day 3 day 7 day 28 day
1 50.0 47. 0 3.0 0.0 345.0 210 300 10.8 27.0 40.0 56.7
' vControl sar J
nples
2 50.0 49.7 0.0 0.3 350.0 50 100 11.0 26.4 35.0 52.3
3 50.0 49. 4 0.0 0.6 348.0 35 75 11.4 25.3 34.0 50.0

Observations
a) Compressive strengths at 3, 7 and 28 days are decreasing vis-a-vis control sample even at 0.3 and 0.6% addition of Na2S04
b) Both initial and final setting times are drastically reduced (cannot be workable at site) vis-a-vis control sample.
The above results reveal that the present invention does not apply with the raw materials used in above trials.
The final ingredient in the cement composition in accordance with this invention is activator in the form of Sodium Sulfate (Na2S04):
Example 4: Effect of Na2S04 on Portland Slag Cement at different level of addition
Trials were carried out with addition of Na2S04a from ,0.1% to 1% to understand its effect on cement properties especially on strengths at all stages (1, 3, 7, and 28 day) and setting properties by keeping clinker component constant (50%). The results are shown in table 17.

Table 17: Effect of addition of Na2S04 at different doses on cement properties
Sr. No. Composition (%) NC% Residue on 90 (mic) -% Blaines (m2/kg) Setting times (minutes) Compressive (MPa) Strengths
Clinker Slag Na2S04 1ST FST 1 day 3 day 7 day 28 day
1 50.0 50.0 0.0 27.25 2.70 412 115 170 10 25.2 40.5 55.9
2 50.0 49.8 0.2 27.25 2.65 400 115 167 12.5 26.6 41.3 56.2
3 50.0 49.7 0.3 27.35 2.50 394 110 160 13.7 28.5 44.3 57.6
4 50.0 49.5 0.5 27.60 2.30 409 100 160 13.9 28.62 42.3 55
5 50.0 49.3 0.7 26.80 2.00 381 95 140 14 27.2 42.1 52.28
6 50.0 49.0 1.0 26.50 1.90 370 85 131 16.3 27.45 37.3 52
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Observations
i. Compressive strength: 1 day strengths show upward trend but strengths at later ages are (3, 7 and 28 days) showing decreasing trend
ii. Setting times: Both Initial and final setting times are reduced with higher percentage addition of Na2S04
Example 5: Effect of purity of Na2S04 on cement
Two experiments have been conducted with different purity of Na2S04 (i.e. 80% and > 99%) to ascertain its effect on compressive strength properties. The results are enumerated in Table 18.

Table 18: Effect of purity of Na2S04 on cement properties
Composition / Tests carried A B
out
1) Clinker (%) 50 50
2) Vizag Slag (%) 49.7 49.7
3) Sodium Sulfate (%) (Na2S04) 0.3 0.3
Purity of Sodium Sulfate Used % 80 >99.0
4) Test Results: -
a) Residue (90 mic) (%) 1.45 1.41
b) Blaines (m2/kg) (Specific surface) 345 342
c) N.C. (%) 28 27.5
d) Setting time (minutes)
(i) 1ST (Initial Setting Time) 115 105
(ii) FST (Final Setting Time) 195 170
(e) Compressive Strength (MPa)
(i) 1 Day 13.2 14.6
(ii) 3 Days 24.4 25.8
(iii) 7 Days 38.5 42.3
(iv) 28 Days 51.3 54.5

Observation
i. As the purity of Na2S04 increases there is an increase of compressive strengths at all ages.
As the purity of Na2S04 increases there is a decrease of setting times
Conclusion
Based on the present invention, the optimum combinations derived are as follows:
• Cement Clinker - 40 to 50%
• Total Slag - 45 to 60%
• Sodium Sulfate - 0.2.to 1.0%
Thus in accordance with this invention gypsum is eliminated in the process totally and this result in a saving in manufacturing cost. By use of the process in accordance with one aspect of the invention, the rate of production of the cement mill is also improved which results in the reduction of power consumption. At the same time, the quality of the product in terms of compressive strength has improved remarkably particularly at initial ages (i.e. 1 day) as required by customers.
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We Claim:
1. A process for manufacturing Portland Slag Cement, comprising the
following steps,
a) Mixing blast furnace slag and sodium sulfate as per predetermined ratio to obtain slag mixture,
b) Dosing Cement Clinker with slag mixture as per predetermined ratio to obtain slag clinker mixture,
c) Grinding slag clinker mixture in a ball mill to obtain Portland cement.

2. A process for manufacturing Portland Slag Cement as claimed in claim 1, wherein the blast furnace slag consists of compounds selected from a group of compounds consisting of silicates, alumino silicates, calcium-alumino-silicates, CaO, Si02, Al203, MgO, Fe203, MnO, sulfur, Ti02, Na20, K20, sulfides and chlorides.
3. A process for manufacturing of Portland Slag Cement as claimed in claim 1, wherein the mass of blast furnace slag ranges from 45 to 60%.
4. A process for manufacturing of Portland Slag Cement as claimed in claim 1, wherein the Cement Clinker consists of compounds selected from a group of compounds consisting of calcium silicates, lime (CaO), silica (Si02), alumina (Al203), iron oxide (Fe203), MgO, Fe203/ MnO, Na20, K20, (Ca0)3.Si02, (Ca0)2.Si02, (CaO)3.Al203, (CaO)4.Al203.Fe203and Free Lime.
5. A process for manufacturing of Portland Slag Cement as claimed in claim 1, wherein the mass of Cement Clinker ranges from 40 to 50%.
6. A process for manufacturing of Portland Slag Cement as claimed in claim 1, wherein the mass of sodium sulfate ranges from 0.2 to 1.0%.
7. A process for manufacturing of Portland Slag Cement as claimed in claim 1, wherein the mass of sodium sulfate ranges from 0.2 to 0.4%.
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8. A process for manufacturing of Portland Slag Cement as claimed in claim 1, wherein the sodium sulfate purity ranges from 80 to 100%.
9. A process for manufacturing of Portland Slag Cement as claimed in claim 1, wherein the ball mill is an open circuit two chambered ball mill separated by a diaphragm having 9.2 meter length and 2.0 meter diameter.
10. A process for manufacturing of Portland Slag Cement as claimed in claim 1, wherein the ball mill has liners, diaphragms and grinding balls made up of nichrome metal.
11.A process for manufacturing of Portland Slag Cement substantially as herein described with reference to the examples and figures accompanying the specification.
12.A product prepared by the process for manufacturing of Portland Slag Cement as claimed in claim 1 to 11, substantially as herein described with reference to the examples and figures accompanying the specification.
Dated this 10th day of August, 2006.
MOrMN DEWAN
OF R. K. DEWAN & COMPANY
APPLICANTS' PATENT ATTORNEY
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ABSTRACT
The present invention concerns a process for manufacturing of Portland Slag Cement, in which blast furnace slag and sodium sulfate are mixed as per predetermined ratio, which is dosed with Cement Clinker as per predetermined ratio and then grinding slag clinker mixture in a ball mill to obtain Portland cement.
,10 AUG W6