3. Cement is a substance (often a ceramic) that by a chemical
reaction binds particulates aggregates into a cohesive structure.
( hydraulic binder). The quality of raw material is the main point
in maintaining of quality of cement. The mineral compounds
containing the main components of cement: lime, silica, alumina
and iron oxide are used in cement manufacturing process.
Therefore it is usually necessary to select a measured mixture of a
high lime component with a component which is lower in lime,
containing however more silica, alumina and iron oxide
(clay component). The purpose of calculating the composition
of the raw mix is to determine the quantitative proportions of the
raw components, in order to give the clinker the desired chemical
and mineralogical composition
What is cement ?
4.
5. In 1824, Joseph Aspdin, a British stone mason, obtained a patent for a
cement he produced in his kitchen. The inventor heated a mixture of finely
ground limestone and clay in his kitchen stove and ground the mixture into a
powder create a hydraulic cement-one that hardens with the addition of
water.Aspdin named the product portland cement because it resembled a
stone quarried on the Isle of Portland off the British Coast. With this invention,
Aspdin laid the foundation for today's portland cement industry
History of Cement
Manufacture of cement has a history, which traces back to millennia. The
Romans who were prolific builders used burnt calcareous (calcium bearing)
rocks along with pozzolanic materials in an era Before Christ. The structures
built by them, like the Pantheon, are still there for us to see proving the
goodness of cementitious materials as input material for construction. The
Roman called it as Opus cementum and pozzalana as Pozzolui.
Post industrialization and as infrastructure development started globally,
demands for cement have been growing steadily both quantitatively &
qualitatively.
6. Background
Although the use of cements (both hydraulic
and non-hydraulic) goes back many thousands
of years (to ancient Egyptian
times at least), the first occurrence of portland
cement" came about in the 19th century. In
1824, Joseph Aspdin, a Leeds mason took out a
patent on a hydraulic cement that he coined
"Portland" cement (1824) He named the
cement because it produced a concrete that
resembled the color of the natural limestone
Quarried on the Isle of Portland, a peninsula in
the English Channel Since then, the name
"portland cement" has stuck and is written in all
lower case because it is now recognized as a
trade name for a type of material and not a
specific reference to Portland, England.
7. few years later, in 1845, Isaac Johnson made the first modern
Portland Cement by firing a mixture of chalk and clay at much higher
temperatures, similar to those used today. At these temperatures
(1400C-1500C), clinkering occurs and minerals form which are very
reactive and more strongly cementitious.
While Johnson used the same materials to make Portland cement as
we use now, three important developments in the manufacturing
process lead to modern Portland cement:
- Development of rotary kilns
- Addition of gypsum to control setting
- Use of ball mills to grind clinker and raw materials
Rotary kilns gradually replaced the original vertical shaft kilns used for
making lime from the 1890s. Rotary kilns heat the clinker mainly by
radiative heat transfer and this is more efficient at higher
temperatures, enabling higher burning temperatures to be achieved.
Also, because the clinker is constantly moving within the kiln, a fairly
uniform clinkering temperature is achieved in the hottest part of the
kiln, the burning zone.
8.
9. Raw materials required to make cement
• Lime stone ( calcareous material , Calcium carbonate)
• Shale , low grade lime stone , clay ( argillaceous materials, Silica)
• Aluminous mateial ( clay, bauxite or Laterite)
• Ferrous material, haematite ( iron ore , ferric oxide )
10. Cement quality – type of cement
Clinker quality
Fuel chemistry
Raw mix design
OPC, PPC, WC, OWC, SRC,SC
Ordinary portland cement,
Pozalona portland cement
White cement,
Oil well cement,
Sulfate resistant cement,
Slag cement
Other cements for special application
Gpsum&fly ash or
Other additive quality
11. quality
Factors influencing the cement quality
1. Mechanical handling of clinker
2. Chemical and mineralogical
composition of raw mix
3. Chemical and mineralogical composition
of clinker
4. Burning process & cooling process
5. Chemical composition of fuels (ash)
6. Circulation phenomena (volatiles)
15. Mining
• Core drilling (bore) holes to explore the mines
• Drill holes for blast
• Blasting
• Excavation and haulage
• Transportation to crusher
• Size reduction for process requirements
16. Mining
Quarry planning
• Ensure - that the required quality & quantity on
daily / monthly/ yearly is available to the plant
• Minimise – total operating and capital costs
• Optimise - raw feed quality
• Fulfil – all the safety and legislative requirement
• Maximise – return on capital employed
• Achieve - peak quarring / plant efficiency
17. overburden
Good quality lime stone
Moderate quality
Poor quality
overburden
Good quality lime stone
Moderate quality
Poor quality
selfish mining – short term benefits
Efficient mining –for well blended – long term benefits
Well developed mine
Long term benefits
Bench = 10 M
18. Picture of a well developed mine
All benches are used effectively
to improve the mine blend and
increase the reserve for long term
business
19. Mining on hill & under ground mining
is challenge to the mining engineer
24. The released energy of the explosive
is converted into various other forms
of energy
• heat
• seismic energy ( stress waves)
• new surface energy ( rock fragmentation)
• concussion and noise ( airblast)
Explosion
• kinetic energy of spoil ( throw) rock
displacement
26. Material breakage involved in crushing process
Impact Attrition shearing compression
Crushing process
Size reduction stages
Primary n = 5
secondary n = 8
Tertiary n = 6
31. Crushing
Crushing is a process which does size reduction
Crushers are chosen depending upon the material characteristics
such as hardness ,abrasiveness, feed input size,
moisture content etc
The commonly used crushers are hammer crushers,
Impact crushers, roll crushers, gyratory crushers, jaw crushers.
Size reduction depends upon the grinding system to be adopted
ie., ball mill or vertical mill
Size reduction ratio
Max feed size ( linear edge dimension)
Maximum feed size of crushed product
=---------------------------------------------------
( linear edge dimension)
33. Stress type-1
Between two solid
Surfaces( compression,
Shearing)
Stress type-2
at solid
Surface( impact)
Stress type-3
Not at a solid
Surface , but by action of
The surrounding medium
(shear stress)
Stress type-4
Non mechanical introduction
Of energy ( thermal shock,
explosive shattering &
electro hydraulic)
41. Advantage and disadvantages of circular and linear piles
Circular pile
Advantages
• space saving and hence low capital cost
• end cone problem is avoided
• un interrupted operation
Disadvantages
• pile correction is not possible and it depends on mines operation
with less variation
Linear pile
Advantages
• it occupies more space
• while shunting the operation has interruption
• end cone problem
Disadvantages
• Pile correction is possible if quality varies
42. Chevcon method ( at Ariyalur)
Chevcon - was developed for a circular stockpile arrangement.
the stacker boom slews back and forth over the curved stockpile
ridge maintaining a constant pile length. With each individual
movement, the end of one movement or the start of the next movement
is advanced by the dimension ∆L. In that way many layers - similar to
the Chevron mode - are superimposed and the stockpile grows
continuously in one direction.
Chevcon configuration refers on to circular stock piles and relates to Chevron
when it is applied to a circle. In this cofiguration the chevcon layers are
inclined as in the side of a cone , each layer runs from the full height of the
stock pile to the ground
43. Well blended slice without end cone
End cone
problems
Linear stock pile
Blending ratio = S in / S out
More variation, high std
Less variation, low std
44. X (t)
Quantity(t)
X (t)
Reclaiming
Slices transversely
Stacking in
Equal layers
Material quantity
Per layer = t
Material quantity
Per slice = q
Variations in the raw material composition homogenised
in the blending bed
∆τ ∆τ
∆Q ∆Q
∆Q ∆Q
∆τ
∆τ
∆τ
45. Assessment of blending method
S in
S out
Blending ratio =
S in
S out
Blending efficiency n n = number of layers
n = V*(S*3600) / d
d = volume discharged cum/hr
S = cross sectional area, sq m
V = travelling speed of the stacker
η
46. Homogenising systems
3.1 Variabilitv and standard deviation
The normally accepted method of measuring variability is in the form of a
term called standard deviation. The standard deviation of a property can
be calculated by taking a number of measurements on the property (such
as LSF, SR etc.), and applying the following formula:-
Where X is the measured variable (e.g. LSF)
X is the variable mean (or average)
N is the number of measurements or observations
Table 1 illustrates a worked example using actual kiln feed LSF data:-
Blending ratio = Std in/ Std out , = 1 for an ideal blending system.
σ =
Σ ( X - X ) 2
N - 1
47. Main parameters for raw mix design
Lime saturation factor = CaO / (2.8 SiO2+1.65Al2O3 + 0.65 Fe2O3)
( LSF)
Silica modulus = SiO2 / ( Al2O3+Fe2O3)
Alumina modulus = Al2O3 / Fe2O3
AlM
Here we have apply the formula (as per British Standard)
CaO-0.7SO3
(2.8*SiO2 + 1.2* Al2O3 + 0.65*Fe2O3)
(SIM)
LSF =
48. Lime saturation factor on clinker basis
If MgO is below 2 %
LSF = 100( CaO – free CaO+0.75 MgO)
(2.85 SiO2) + ( 1.18 Al2O3) +(0.65 Fe2O3)
If MgO is above 2 %
LSF = 100( CaO – free CaO+1.5 MgO)
(2.85 SiO2) + ( 1.18 Al2O3) +(0.65 Fe2O3)
95 –harder to burn, tendency to high free lime & C3S clinker
, high early strength high fuel consumption
< 95 , easy to burn , excess coating , excess liquid phase ,
possible brick infiltration reduced cement strength , low free lime
acceptable standard deviation = 1.2
54. qopEffective
interval
q >>> qop ; balls hit
each other, not grinding
material
At critical
speed
qmax
q <<< qop ;
The ball waves through the
material
= 42.3/ D effectiveCritical speed
cascading
cataracting
Ball mill grinding
63. Separator
Residue = 12 – 18 % on 90 µ
= 1.5 – 2.5 % on 212 µ
An efficient separator is one which operates with no fines
in coarse return ( rejects) and no coarse in product fines
68. Advantages of vertical mills
• Energy consumption is less compared to ball mills
• Flexiblity in operation as all forces can be controlled
• Drying capcity is better than ball mills
• Noise level (noise pollution) is much less than ball mills
• Particle size distribution better than ball mills
71. In homogeneous homogeneous
Kiln feed uniformity index (KFUI)
KFUI= n ( C3S actual - C3S target )2
n
i - n
C3S actual = the calculated C3S of one instantaneous daily sample of kiln raw mix feed
C3S Target = the C3S target established for the mill product
n = number of samples ( calculation of average C3S is done monthly)
Target for KFUI is < 10
( an instantaneous sample is one made up of 5 consecutive increments taken at short intervals)
73. Blending silo
The efficient blending silo does efficient blending with
minimum energy
The variation in chemistry at the silo outlet is to be at the
minimum possible ,
Standard deviation of LSF < 1
Standard deviation of CaO < 0.2
Standard deviation of Silica ratio < 0.1
Standard deviation of A/F < 0.01
74. Flow properties of powders :
• Importance of measuring flow properties
• Various problems in powder handling and storage
Arching Channeling Segregation
78. Controlled flow
inverted cone
blending SiloCapacity = 18000 t
18 M
40 MAdvantages
• low inventory
• low capital cost
Disdvantages
• can not be operated on low stock as raw mill operation directly affect
silo effciency and hence the quality and production.
• as the buffer stock is only for 1 day the incoming raw meal std must
be < 1 for LSF and Silical modulus < 0.1
83. Pyro process
• Wet process
• Semi dry process
• Semi wet process
• Dry process
( wet milling and slurry is fed into the kiln )
(dry milling , water sprinkled to make
nodulation, nodules are fed into the kiln)
(wet milling , dried in vacuum drier, caked
dried , powedered and fed into kiln
(dry milling , dry meal is fed into kiln)
• VSK process
Vertical shaft kiln
( First process invented in cement process )
90. Refractories
The function of the refractories are
• to protect the shell from the heat
• to insulate to reduce heat losses
• to withstand thermal stresses
• to with stand thermo-chemical stresses
• to withstand thermo-mechanical stresses
91. Kiln refractory lining
Refractories are lined inside the kiln shell and preheater cyclones to the metal
from heat as well as to insulate to conserve heat.The bricks used are low
alumina , high alumina bricks, magchrome bricks and spinel bricks. Mag chrome
bricks are banned due to health hazard.Chromium is poisenous.For severe
conditions special bricks like zirconia based , are used.
1400-1500 deg C
1200 -1250 deg C
1000-1100 deg C
1100-1200 degc Gas temperature
Refractory brick
92. Always to be remembered
If coal is mixed it is burnt
If flame is wrong everything goes wrong
whatever you may do with chemistry or
higher heat input through calciner or kiln.
The burning zone needs heat and it can be
only obtained from well shaped radiant
flame.i.e., short, snappy and convergent
flame .
95. 7 8 9
Burner positioning
We do positioning of the
burner for centering the
flame.The positions
1,2,3, 4 and 7are close
to the refractory and
they are away from the
charge.
Positions9 and 8
are close to charge .
Only 5 is close to charge
and refractory and this is
best as the flame in this
gives the best thermal
distribution to do
effective burning.
Position 8 & 9 is very
close to charge if coal is
trapped it has serious
negative
impact.Position 1,4 & 7
is very close to refractory
and it can burn the
refractory.
4 5 6
1 2 3
96. Heat exchange in kiln is
• mainly radiation of heat from flame to refractory wall
and to charge
• conduction of heat from refractory and to charge
• convection of heat within the charge ( particle to particle
contact)
radiation
conduction
convection
Heat flows from hotter body to colder body
Gases flow from high pressure area to low pressure area
97. 1800 deg c
1300 deg C
1400 deg C
1500 deg C
1600 deg c
1700 deg c
radiation
conduction
convection
98. Lower rpm , high % filling , less active
Layer , high free lime, high radiation
losses
high rpm , low % filling , more active
Layer , low free lime and low radiation
losses
Influence of revolutions / minute on kiln operation
Optimum % filling = 9 – 11 with raw meal retention time of 20 -25 minutes
unfavorable favorable
Passive
layer
active
layer
99. Different flames
Normal flame
Flame with low
Secondary air temp
Distorted nozzle
Flame –poor
hood geometry
Or distorted nozzle
Flame at the center
Flame downward
Flame upward
100. Flame length
Long flame, unstable coating,
High back end temp
Low shell temperature
Short intense divergent flame
Good for burning
Low back end temperature
Poor refractory life, high
Shell temperature
Convergent flame
Good for burning
Good for refractory
Stable coating
Low shell temperature
101. The Ideal Flame
hot !
short !
stable !
T"long" flame
"short" flame
Complete combustion:
- CO = 0
- SO2, NOX ↓
Homogeneous:
- no temperature peaks
- no local CO on the clinker bed
Longer flame increase the back end temperature resulting in
Heat loss at kiln exit and hot meal clogging
102. Burning zone, Flame-profile
• Low momentum burner
• High momentum burner
rings12m (~3xD) burning zone
Rotaflam
~16 m
Flame !☺!
rings
~23 m Flame
17m (~4xD) burning zone
! !
Burner Operation
106. Heat transfer
by radiation
and convectionHeat moves
to clinker edge
by conduction
Air flows over
clinker cooling
surface
How cooling is accomplished
800 O C
100 O C
107. • Convection - Surface to Air
• Conduction - Inside to Surface
• Heat transfer is driven by temperature
difference
• Takes place at the clinker surface
• To maximize it:
– Increase the air/material contact time
with:
• Deeper bed ( ⇒ more power)
• Slower air flow (⇒ larger cooler)
Heat transfer in clinker
109. Old conventional grate plates
create sand blasting effect or fluidization
This creates poor heat exchange
Modern cooler plates flow resistance
branch off the air , creates
less fluidization , better heat exchange
Cross flow
Counter current
Mechanical flow regulator
110. Temperature
Bedthickness
clinker
air
Fixed bed
Fluidized bed
Air in
Air out
Clinker
Air in
Air out
Clinker
Temperature
Bedthickness
clinker
air
More efficient recovery with fixed
bed
Air flow requirement
Has reduced from
4 kg air/ kg.cl to
2.2 kgair / kg cl
Heat exchange between clinker and air
111. 1. The hotter the inlet temperature the hotter the clinker
outlet temperature.
2. The hotter the cooling air temperature the hotter the
clinker outlet temperature.
3. The longer the air/material contact time the cooler the
clinker outlet temperature.
General truths ( all coolers)
4. Quicker the clinker cooling ( quenching) the smaller the
crystals, results in micro cracks of the minerals, improves
the soundness of the clinker ( when MgO % exceeds 1.5 %)
113. • Microscopic
A mixture of different mineral phases
Particle size ≈ 0 – 100 µm
• Macroscopic
A gray, granulated, rocky material
Grain size ≈ 0 – 50 mm
What is portland cement clinker
114. Uniform nodule Sizes
Rather uniform-sized nodules are
ingeneral an advantage regarding
burning efforts and uniform degree of
burning.
115. Quickly cooled clinkers are favourable for the early strength potential; no
alite is lost. The fine crystalline liquid phase prevents aluminate from an early
hydration. The influence of aluminate on the setting time is limited in quickly
cooled clinker.
116. Influence of cooling on clinker phases
Fast cooling
Well distributed
small crystals
Slow cooling
Larger crystals
117. C3S
Clinker when it is quenched in cooler it creates micro cracks which
needs less energy for comminution during grinding.
C3S
Clinker cooling
C2S
118. Fuels used in cement industry
• Solid fuels ( coal , pet coke, lignite, anthracite )
• Liquid fuels ( furnace oil)
• Gas fuels ( natural gas)
• Alternate fuels ( shredded tyres,waste wood
chemical waste, animal meal)
119. Solid fuel preparation
Fuel lumps are crushed to suitable size depending on the grinding system
and Hard groove index of fuel. The residue depends on the volatile matter
121. Coal grinding
Inert grinding
O2 % < 12 % ( preheater gases&
Hot air generators)
Non inert grinding
O2 % > 12 % ( cooler air)
Coal grinding is designed also on the basis of explosion index
( safety index) , residue , HGI
Ball mill
circuit
Vertical mill
circuit
Non-inert operation
122. mills with inert operation
mills with non inert operation
Using cooler gases for drying the coal is non inert
operation as it contains > 20 % O2
123. The acceptable feed size is
2 % of the roller diameter
Built in separator
Grinding table
Grinding roller
Vertical mill for coal grinding
124. For pet coke
and anthracite
For bituminous coal
The residue on 90 microns is 50 % of the volatiles as a thumb rule
Residue vs volatiles
125. Relationship between coal types,composition
and grinding fineness
Petcoke < 10 < 1.0
4%< + 0.09 mm
0 %< + 0.2 mm
Normally the residue on 90 mic is
50 of the % volatiles.
128. Roller press
•Pressure applied to material
varies from 3,000 a 4,000
kg/cm2. They are over
dimensioned in order to operate
at lower pressures (2500).
•Requires a subsequent de-
lump, in order to separate the
resulting paste, except in the
case the roller press feeds a ball
mill.
•Pressure application angle
should be around 6°.
•Press consumes 20 to 25
kWh/ton of cement.
•Circulation factors range from 6
to 10.
•Requires great maintenance.
•Wear out elements expected
lifetime: 10,000 hours
129. Horizontal roller mill
•Rotates at hypercritical
speed (1.2 times critical
speed), having no feed.
•Pressure on material
ranging from 700 to 1,000
kg/cm2.
•Pressure application
angle: 15 to 20°.
•Circulation factors: 3 a 8.
•Requires great
maintenance.
•Consumes 25 to 30
kWh/ton of cement.
•Expected lifetime: 10,000
hrs.
Roller and ball mills hybrid.
Being the most recent one,
its utilization is not
widespread.
130. Tubular mill (ball mill)
•Rotates at 0.7-0.8 of critical speed.
•Lacks pressure system.
•Lacks application angles.
•Consume 35 to 40 kWh/ton.
•Circulation factors: 1 to 3.
•Requires little maintenance.
•Expected lifetime measured in
years.
It is the most widely used for
cement milling. Its drying capacity is
proportional to D2, so in cement the
L/D proportion is 3.
In raw meal milling L/D is 1.5, if
humidity is not greater than 3%, a
single chamber mill is
recommended. In case the material
has humidity greater than 7%, it is
necessary to incorporate a flash
dryer or change to a vertical mill.
The % of material in suspension will
determine which type of mill should
be used.
131. Cement mill cooling
The setting properties depend the water molecules of
Gypsum CaSO4.2H2O
If water is dehydrated ( at 125 deg C) it results in false set
If it is partially dehydrated, CaSO4.1/2 H2O, called
Hemihydate it contributes to initial strength. Hence
cement temperature is to be maitained > 100 deg c and
< 125 deg C
133. Vertical mill (roller mill)
•Pressure on material:300 to 500
kg/cm2.
•Application angle: 12°. The width
of the material layer is proportional
to this angle and to the rollers
diameter.
•Consumes 25 to 35 kWh/ton of
cement.
•Circulation factors: 3 to 5.
•Requires great maintenance.
•Wear out elements expected
lifetime: 15,000 hrs.
•Recommended in cases where
humidity is greater than 7%, taking
into consideration that abrasive
content must remain low. This is
why it is commonly used in raw
meal milling. It works better than a
ball mill on plastic materials (clay).
140. Principles of the function of ESP
Collecting plate
Charged dust particles
Dust removal
Dust layer
Gas molecules and ions
Corona
generation
Discharge electrodes
H2O
SO2
O2
N2
Gas flow
T/R set
142. Migration velocity and collection efficiency
η
ω =
q Ep
( 4 π µ r)
= 1 – exp ( - W.A / Q)
ω = migration velocity
Ep = strength of field in which particles are collected , volts/ meter
µ = Viscosity of gas Pa-s
r = radius of the particle- µ m
η = fractional collectional efficiency
A = collection surface of the particles
Q = gas volumetric flow rate
W = drift velocity
148. No dampers:
Only possible to do on-line cleaning.
Maintenance:
On-line not possible.
Example A
One dirty gas chamber.
One clean gas chamber.
With inlet and outlet dampers:
Possible to do on and of-line cleaning.
Maintenance:
On-line possible when separate hoppers
Multiple dirty gas chambers.
Multiple clean gas chambers.
Example B
Fabric Filter
Optional Arrangements
154. = f (Wk)
28
7
3
1
0
MPa 70
60
50
40
30
20
10
0 0.5 1.0 % Wk
A 1% increase in LOI
result in decrease in
strength
1 day by 25 %
2 8days by 3 % and
90 days by 2 %
156. Quantitative rules of thumb
C3S : 1 – 28 d : + 0.5 Mpa / %
Ks ; 1 d : + 4 Mpa / %
: 3 d : + 4 Mpa / %
: 7 d : - 2 Mpa / %
: 28 d : - 10 Mpa / %
(SO3) tot : 1 - 28 d : - 5 Mpa / % from
optimum
Blaine : 1 d : + 0.04 Mpa / (m2/ kg)
3- 28 d : + 0.08 Mpa / (m2/ kg)
157. One day strength is contributed mainly by
C3A , Soluble alkalies, and C3S
3 day is contributed mainly by C3S
7 days strength is contributed by mainly
C3S
28 days strength is mainly contributed by
C2S
Apart from the above cement strength is enhanced by
higher fineness of cement
Less C3S crystal size achieved by rapid burning
and quenching the clinker in cooler
Higher fineness of rawmeal also reduces the
crystal size of clinker minerals , ie ., C3S & C2S which
enhances the hydraulic reactivity
Cement strength – influencing parameters
158. Wk , prehydration of clinker
Prehydration of clinker minerals can occur
1. As a result of incorrect internal water cooling in cement mill
2. when storing too hot cement in a silo
3. When clinker and especially cement is exposed to humidity
Please note:
If clinker has more soluble alkalis and sulfates it is highly
hygroscopic especially when pet coke is fired.
In cement silos they form Syngenite , K2SO4.2 CaSO4. H2O which
forms lumps and block the cement silos. Hence venting is must
to evacuate moisture and silo cleaning.
cements having soluble alkalis and sulfates preferably packed in
paper bags to avoid depletion of strength.
159. Thumb rule formulae for prediction of strength
FLS predicted the formula for cement ground to 300 kgs/ m2
With 4 % gypsum
strength,
d28 = 52 - 10.( Ks) + 0.15.(C3S)
The content of soluble alkalis Ks is dependent on the total alkali
content and SO3 content in clinker.
As per Knofel it is
F 28 = (3*C3S)+ (2*C2S) + C3A – C4AF N / mm2
Strength prediction
for 3 d = 97 + 35.8 Ma + 38.1K2SO4 + 28.7 Ms – 1.3 C3S Kg/ cm2
7 d = 300 + 13.4 Ms + 2.8 C2S + 56.1 Ma – 15.4 K2SO4 + 15.5 Na2O
28 d = 490 – 55.3 K2SO4 + 1.3 C3S (or)
= 490 – 86 K2O + 2 C3S – 26 Na2O
160. Influence of fineness on cement strength
For cements with the same specific surface the increase of the uniformity
factor results in increase of strength of all ages.
1. The specific surface , the percentage of fractions 3- 32 mm and the
uniformity factor n really influences the development of cement strength.
The influence of 3 - 32 mm fraction and the uniformity factor is higher in
cement with higher in specific surface ( > 3400 cm2/ g)
2. The fractions with particle size less than 3 mm contributes only to early
strength while the fraction with particle size more than 24 mm influences
strength development significantly.
3. While the fractions 3 – 16 mm and 16 – 32 mm seems to be more
significant factor for specific surface 3500 – 4000 cm2/ g) . This is
relevant only if the granulometric distribution is continuous and steep.
4. The optimistic granulometric distribution of a cement is a continuous
and steep ( with high uniformity factor) distribution with a high (65 %)
content in 3 – 32 mm fraction and specifically in 16 - 24 mm fraction and
low content of fine particles ( < 3 mm , 10 % ) and specific surface of
2500 – 3000 cm2/ g according to Blaine.( high efficiency separator and
grinding media distribution plays significantly here)
161. Properties of cement minerals
Characteristics C3S C2S C3A C4AF
Setting quick slow rapid nil
Hydration rapid slow rapid nil
3 days heat 1.1 cal / g 0.4 cal / g 2 cal / g nil
liberation
Early strength high upto low upto not much nil
Contribution 14 days 14 days beyond one day
Late strength less later high later nil nil
contribution
Resistance to moderate high poor high
Chemical attack
Drying shrinkage nil low nil nil
162. Problems and solutions
1. Grinding problems
a) False set lower cement mill temperature
add less gypsum
add part anhydrite
b) reduced strength high mill temperature
less water cooling
correct water cooling
2. Silo storage
a) False set short storage time
cooling of cement < 70 deg c
b) reduced strength increase gypsum dehydration in
mill
c) lump formation and add less gypsum, use partly
silo blockage (syngenite anhydrate , decrease K2O content
formation, K2SO4.2CaSO4.H2O to avoid the formation of Syngenite
Problems solutions
163. 3 ) Bag storage
a. reduced strength short storage time
b. lump formation add TEA during grinding
(tri ethanal amine)
add hydrophobic agents
c. crust formation plastic coated bags
d. abnormal setting plastic covering pallets
167. Customer is the king. He is a better business man than you.
Tomorrow’s market is competitive with quality/ price ratio.
Customer creates the customers.
Bon’t brand the quality alone , brand your service too.
