Optimisation of raw mix

1. Optimisation of Raw Mix Design to
Improve Clinker and
Cement Quality

2. Cement quality general requirements are
1. Strengths developments early& later ages
2. Reasonable setting time (initial & Final)
3. fineness to easy hydration
4. minimum or nil expansions like
le chatlier, autoclave
5. minimum or nil shrinkage after drying
6. low heat of hydration
7. long durability
Clinker ( which is contributing 95-99% in Cement )
should be prepared accordingly to achieve the above properties in cement
The clinker properties depends on chemical ,
mineralogical, and granulometric properties

3. Cement
Any bonding material is called cement
An adhesive material which is capable of bonding together fragments or particles of solid matter in to a compact whole
Cement will be in the form of fine powder when reacts with liquid it sets in few minutes and develops strength and hardens to stone like material
Cement
Hydraulic cements
Non hydraulic cements
Ordinary Portland Cements OPC33
OPC43
OPC53
Special OPC OPC43-S
OPC53-S
1.Sulphate Resistance Portland Cement(SRPC)
2.Rapid Hardening Cement (RHC)
3.Low Heat Cement (LHC)
4.White Portland Cement(WPC)
5.Supar Sulphate Cement(SSC)
6. High Alumina Cement(HAC)
Special cements 7. Oil Well Cement(OWC)
OWC-type E
OWC-type F
OWC-type G
OWC-type H
OWC-type J
OWC-special type
8. Hydrophobic Portland Cement(HPC)
9.Masonary Cement
Blended Cements 1.Portland Pozzolana Cement (PPC)
A) flyash based
B) Calcined clay based
2.Portland Slag Cement (PSC)

4. OPC33 OPC43 OPC53 OPC43-S OPC53-S SRPC PPC PSC RHC WPC HPC LHC SSC
IS269
(2013)
IS8112
(2013)
IS12269
(2013)
IS8112
(2013)
IS12269
(2013)
IS12330
(1988)
IS1489
(1991)
IS455
(1989)
IS8041
(1990)
IS8042
1989)
IS8043
(1991)
IS12600
(1989)
IS6909
(1990)
I
Chemical requirements
LSF 0.66-1.02 0.66-1.02 0.80-1.02 0.66-1.02 0.80-1.02 0.66-1.02 pozzolana=x%
slag% 25min-
65max
0.66-
1.02 0.66-1.02 0.66-1.02
A/F ≥ 0.66 0.66 0.66 0.66 0.66 x= >15%<35% 0.66 Fe2O3Max 1% 0.66 Al2O
R max% 5.00 4.00 4.00 3.00 3.00 4.00
x+{4.0(100-
x)/100} 4.00 4.00 2.00 4.00 4.00 4.00
MgO max% 6.00 6.00 6.00 5.00 5.00 6.00 6.00 8.00 6.00 6.00 6.00 6.00 10.00
O3 Max% 3.50 3.50 3.50 3.50 3.50 2.50 3.00 3.00 2.50 2.75 ifC3A<7% 2.50 2.50 6
3.00 3.00 if C3A>7% 3.00
(sulphide
sulphur max)1.5
OI Max% 5.00 5.00 4.00 5.00 4.00 5.00 5.00 5.00 5.00 5.00 5.00
es other than
psum max% 5.00 5.00 5.00 5.00 5.00
sulphide
sulphur=1.5 5.00 5.00
rides max% 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10
3A max 10.00 10.00 5
degree of
whiteness>70%
hydrophobicity test
should pass
C3S min 45.00 45.00
2C3A+C4AF
max 25
lkalies 0.05/0.6 0.05/0.6 0.05/0.6 0.05/0.6 0.05/0.6
Physical requirements
m²/kg min 225 225 225 370 370 225 300 225 325 225 350 320 400
ST min (mts) 30 30 30 60 60 30 30 30 30 30 30 60 30
ST max (hrs) 10 10 10 10 10 10 10 10 10 10 10 10 10
tlier soundness max(mm)
unareated 10 10 10 5 5 10 10 10 10 10 10 10 cold exp 5
areated 5 5 5 5 5 5 5 5 5 5 5 5
toclave soundness max%
unareated 0.80 0.8 0.8 0.80 0.8 0.8 0.8 0.8 0.80 0.8 0.80 0.8
areated 0.60 0.6 0.6 0.60 0.6 0.6 0.6 0.6 0.60 0.6 0.60 0.6
compressive strength min (MPa)
24hrs±30mts 15.69 30
72 hrs ±1hr 16 23 27 23 27 10 16 16 26.97 90% of 16 15.69 100Kg/cm2 15 35
168 hrs ±2hr 22 33 37 37.5 37.5 16 22 22 90% of 22 21.57 160Kg/cm2 22
672hrs ±4hr
33
48max
43
58 max 53 43 53 33 33 33 90% of 33 30.40 350Kg/cm2 30
Heat of Hydration max
7days-
65cal/gm

5. From the specification we infer cements should have following properties
1. A minimum value for parameters like BF,IST &CS
2. It should not cross the maximum value for un wanted parameters like
LS, AS, MgO, IR, LOI, Na2O, K2O, Cl, FST ect
Significance of specification
1. LoI a) Un burnt or inhomogeneous burning of clinker
b)Adulteration of cement
c) Partially hydrated(aged) cement
2. IR a) Un burnt or inhomogeneous burning of clinker
b) Adulteration of cement
3.MgO causes unsoundness
4. Free CaO causes unsoundness
5. Alkalies (Na2O, K2O) causes unsoundness
6. LSF if more than 1.02 gives free lime
if less than 0.66 clinker formation will not complete
7. chlorides causes corrosion (durability) in the concrete reinforcement
8. Fineness for providing free access to hydrate
9. setting time(IST,FST) required for workability of concrete
10. LS indicates the presence of free lime causes unsoundness
11. AS indicates MgO presence causes unsoundness

6. Cement quality /behavior depends on
1. different combinations of
C3S,C2S,C3A,C4AF
2. Fineness of cement
3.Free CaO content
4.MgO content

7. In cement chemistry
C=CaO S=SiO2 A=Al2O3 F=Fe2O3
Bogues formulas
C3S = 4.071 CaO-(7.602 SiO2 +6.718 Al2O3+1.43 Fe2O3+2.852 SO3)
C2S = 2.867 SiO2 - 0.7544 C3S
C3A = 2.65 Al2O3 - 1.692 Fe2O3
C4AF =3.043 Fe2O3
-------------------------------------------------------------------------------------
Fe2O3 = 0.326 C4AF
Al2O3 = 0.377 C3A +0.64 Fe2O3 = 0.377 C3A + 0.2098 C4AF
CaO = 0.737 C3S +0.651 C2S +0.621 C3A +0.456 C4AF +Free CaO
SiO2=0.26 C3S +0.35 C2S

8. C3S : gives early strength and more heat of hydration
C2S : gives later strength and low heat of hydration
C3A: responsible for setting time of cement, gives
maximum heat of hydration Porosity to the clinker,
plasticity in concrete
C4AF: reduces the clinker burning temperature

9. Raw materials
Stage-1 (Normal temperature)
1.Limestone 2.clay/bauxite 3.Ironore /Latarite
SiO2 CaCO3 Al2O3 2SiO22H2O Fe2O3
Stage-2 (after calcination)
SiO2 CaO Al2O3 -SiO2 Fe2O3
Stage-3 (12500C-13000C)
C2S CaO Al2O3 -SiO2 Fe2O3
Stage-4 (13500C-14500C)
C2S C4AF C3A CaO
C3S C3A C4AF C2S
Clinker
C3S, C2S, C3A, C4AF
Clinker + gypsum = cement

10. ►Lime Saturation Factor (LSF)= CaO - 0.7 SO3
2.8 SiO2 + 1.2 Al2O3 + 0.65 Fe2O3
When LSF approaches unity, the clinker is difficult to burn and often shows excessive high free lime
contents.
A clinker having LSF 0.97 and above approaches the threshold of being “over limed”
wherein the free lime content could remain at high levels regardless of how much more fuel is fed to the
kiln
Higher LSF increases C3S reduces C2S ,causes slow setting with high early strength
Preferable range 0.90 ± 0.02
►Alumina Modulus/ratio (A/F) = Al2O3/ Fe2O3
Clinker with high Alumina ratio produce cement with high early strength (1to 3 days)
But makes the reaction between silica and calcium oxide in the burning zone more difficult
Higher Alumina ratios increases C3A and reduces C4AF
Tends to render cement quick setting and strong at early ages
Preferable range 1.20 ± 0.20

11. ► Silica Modulus (SR ) = SiO2
Al2O3 + Fe2O3
Clinker with a high silica ratio is more difficult to burn and exhibits poor coating formation properties in the burning zone
Low silica ratios often lead to ring formations within the kiln and low early strengths
(3 and 7days) in cement
Preferable range 2.20 ± 0.20
►Liquid =1.13 C3A + 1.35 C4AF +MgO + Alkalies
=2.95 Al2O3+2.20 Fe2O3+MgO+ Alkalies
Preferable range 28 ± 3
►Hydraulic ratio (HR) = CaO
SiO2 + Al2O3 + Fe2O3
►Hardening Ratio (ME) = C3S
C2S
Higher the ME there is an increase in the initial strength of cement,
an increase in heat of hydration and a reduced resistance to chemical attack .
►Burnability Index(BI) = C3S
C3A+C4AF
The higher the index number , the harder the clinker is to burn
►Burnability factor (BF) = LSF +10 SR – 3(MgO + alkalies)
Higher burnability factors yield a clinker that is to harder to burn
►Theoretical heat requirement for clinker formation
Q clinker= 7.646 CaO + 6.484 MgO + 4.11 Al2O3 - 5.116 SiO2 - 0.589 Fe2O3

12. C3S 47 SiO2 21.50
C2S 28 Fe2O3 5.00
C3A 10 Al2O3 5.50
C4AF 10 CaO 64.00
F-CaO 1 F-CaO 1.00
Mgo 1 MgO 1.00
alk 1 alk 1.00 99.00
Fe2O3 3.26 C3S 53.00
C2S 21.66
Al2O3 5.87 C3A 6.12
C4AF 15.22
CaO 64.64 LSF 0.91
A/F 1.10
SiO2 22.02 SM 2.05
liquid 29.23
liquid 26.48

13. Raw mix design
Raw mix will be designed using materials
With no option (since available at plant site)
1. Limestone a) using available limestone
b) if different purity of limestons are available Judicious utilization
With limited option (being costly and have to depend on supply)
2. Coal ash absorption to be considered
By choosing
3. Corrective materials
Points to be noted
1.The alkalis, chlorides, sulphates present in the raw mix entirely will not go to clinker
2.Chemical composition may not exactly tally between kilnfeed and clinkar because of dust losses,
so depending on the clinker produced final corrections have to be made
3.The phase composition calculated on oxide values may not exactly tally with actual values
4. The behavior of clinker/cement will not only depend on chemical oxide composition but also many
other factors
5.The burning properties may vary depending on the raw materials nature
even though the final chemical composition is same

14. Arrive approximate required oxide composition of clinker
Calculate the limestone required for getting the required lime in the clinker
Calculate the coal ash absorption depending on coal quality and heat consumption for
clinker
After knowing the amount of silica ,iron and alumina from limestone and coal ash ,
the additional required quantities can be added by choosing proper corrective
material/materials
For example
For silica and alumina bauxite can be used
For iron and alumina laterite can be used
For iron alone iron ore can be used

15. Points to be noted
1.The alkalis, chlorides, sulphates present in the raw mix entirely will(may) not go to clinker
2.Chemical composition may not exactly tally between kilnfeed and clinkar because of dust losses,
so depending on the clinker produced final corrections have to be made
3.The phase composition calculated on oxide values may not exactly tally with actual values
4. The behavior of clinker/cement will not only depend on chemical oxide composition
but also many other factors
5.The burning properties may vary depending on the raw materials nature
even though the final chemical composition is same

16. Calculation of coal ash absorption
coal CV 5200
ash 26%
heat consumption 790 cal/gm
coal consumption (790/5200)X(100) 15.19%
ash absorption coal consumption (ash%) = 15.19 X 0.26 = 3.95

17. Single component
limestone Coalash 4%ash abs
LOI 36.34 1.57
SiO2 11.46 17.99 66.64 19.94
Fe2O3 1.63 2.56 4.32 2.63
Al2O3 3.05 4.79 21.12 5.44
CaO 43.21 67.84 2.69 65.23
MgO 2.54 3.99 0.12 3.83
SO3
C3S 73.68
C2S 1.58
C3A 9.97
C4AF 8.00
LSF 1.02
A/F 2.07
SM 2.47
liquid 25.67

18. coal CV 5200 ash%26 heat consumption 790 cal/gm
coal consumption (790/5200)(100)
ash absorption coal consumption(ash%) 3.95
Two component
98% 2%
limestone laterite coalash 4%ash abs
LOI 36.34 8.37 35.78 1.56
SiO2 11.46 22.28 11.68 18.22 66.64 20.15
Fe2O3 1.63 46.42 2.53 3.94 4.32 3.96
Al2O3 3.05 5.89 3.11 4.85 21.12 5.50
CaO 43.21 10.91 42.56 66.40 2.69 63.85
MgO 2.54 0.67 2.50 3.90 0.12 3.75
SO3
C3S 64.15
C2S 9.38
C3A 7.88
C4AF 12.04
LSF 0.97
A/F 1.39
SM 2.13
liquid 28.67

19. coal 29% ash assuming 5000CV consumption15.5%
ash abaorption 15.5(0.29)=4.50
three component
90% 4% 6%
limestone Laterite Ochre coalash 4.50%
LOI 37.84 13.76 17.8 35.67 1.55
SiO2 10.71 17.96 52.71 13.52 20.96 56.43 22.55
Fe2O3 0.71 46.77 2.35 2.65 4.11 7.54 4.26
Al2O3 1.56 9.76 5.15 2.10 3.26 25.39 4.26
CaO 47.24 10.08 20.3 44.14 68.41 6.15 65.61
MgO 1.04 0.6 0.31 0.98 1.52 0.67 1.48
SO3
C3S 60.97
C2S 18.66
C3A 4.07
C4AF 12.97
LSF 0.92
A/F 1.00
SM 2.65
liquid 23.41

20. four component
92% 3% 3% 2%
L/S1 flyash Laterite ironore coalash 4.8%ash
LOI 37.64 1.24 13 4.90 35.15 1.54
SiO2 10.74 61.49 35.89 5.60 12.91 19.89 63.02 21.96
Fe2O3 1.02 4.9 26.44 85.20 3.58 5.52 6.18 5.55
Al2O3 2.20 28.94 16.44 2.20 3.43 5.28 21.21 6.05
CaO 46.96 1.57 6.32 0.26 43.45 66.91 4.7 63.92
MgO 0.78 0.55 0.62 0.32 0.76 1.17 1.56 1.19
SO3
C3S 44.74
C2S 29.20
C3A 6.63
C4AF 16.89
LSF 0.88
A/F 1.09
SM 1.89
liquid 31.23

21. Influence of raw material characteristics on burnability
1.limestone is the major component in the raw mix .
limestone hardness , granulometry, presence of coarse silica and/or calcite and
amount and distribution plays a major role on burnability
2.homogenization is at both chemical and mineralogical levels to ensure the
burning of raw mix is steady and trouble free. even fuel homogenization may be necessary
3.particle size distribution (psd) has enormous bearing on the
pyro processing, clinkerisation and clinker granulometry.
4.while fineness ( 30 to 75 micron ) gives very improved burning and lime absorption,
the tail end of the distribution namely <10 and > 90 micron pose serious problems

22. 5. Excessive level of 90 or even 212 micron sizes give rise to coarse calcite and
quartz and affect burnability and the clinker micro structure adversely. C3Sand C2S
sizes and distribution are very non-uniform. add to this with the coarse ash we end
up with poor quality of clinker
6. On the other hand, superfines lead to unnecessary dust recirculation,
degradation of high quality heat in the burning zone, bulid-ups in cyclones,
production loss, higher electrical and thermal consumption
the “ span” may be a good indicator : ( d90 – d10) / d50 based on passing
size . a factor between 2 and 4 will be satisfactory , the lower the better
7.kiln atmosphere
a) oxidation
b) reduction
(exit gases monitoring)
C + O2  CO2 + 7829 cal/gm
C + ½ O2  CO + 2400 cal/gm
Under reducing conditions Fe2O3  FeO + O2
Theoretical heat requirement for clinker formation
Q clinker= 7.646 CaO + 6.484 MgO + 4.11 Al2O3 - 5.116 SiO2 - 0.589 Fe2O3