influence of process on quality
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Influence of process on quality
And quality control on process
Why we maintain quality ?
It is need of the customer
Customer is the king .He sees us in quality price ratio
To day mason decides the quality but tomorrow engineerwill decide the quality in our country ( house construction , etc)
What will happen to us ?
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.
Mining
crushing
preblending
Raw meal preparation
Raw meal blending
Pyroprocess
Clinkercooling
Cement grinding
Packing & despatch
Process stepsConcern for Environment
Quality control
Process flow diagram and integration of quality
Quality control
Variation makes the process and quality to struggle and customeunhappy
customer
Mining
Well developed mines
Geology and location of boreholes
BoreHolesample
Function of PGNA Analyser
Cf 252
Variation is a devilIn any process
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 limeacceptable standard deviation = 1.2
Raw meal residue Depends upon theMineralogy , ieCalcite or quartz90 mic = 8 – 15 %212 mic = 0.5 – 3 %
time
Variation frommines
Variation Afterpre blending
Variation afterRaw milling
Variation in quality control
Set point
Auto sampler position
- 20 mm
Liter weight
. Rapid burning ( short burning zone ) and rapid cooling of clinkerimproves the clinker quality. smaller C3S crystals withmicro cracks)
Slow burningFast burning
C3S
Clinker when it is quenched in cooler it creates micro cracks whichneeds less energy for comminution during grinding.
C3S
Clinker cooling
C2S
Reactions during clinker cooling
Resorption of alite
Liquid phase + C3S � C2S + C3A + C2(A,F)
Decomposition of alitevery slow coolingreducing conditionsC3S � C2S + CaOCrystallization of liquid phase
Slow cooling: large crystals – improved reactivityMgO crystals grow oncooling (periclase)
Properties of cement
• Portland cement
• Portland pozzolana cement
• Portland slag cement
• Sulfate resistant cement
• Oil well cement
• Rapid hardening cement
• White cement
Cement quality tests
• Setting time
• Compressive strength (mortar)
• Modulus of rupture ( bending strength)
• Fineness( blaine or Particle size distribution)
• Expansion ( Le Chatelier & Auto clave)( soundness)
• Chemical analysis
X-4.0(100-X) /100 < 35%
3.03.03.0Insoluble residue % (max)
0.8 -1.02
0.8 -1.02
0.66 -1.02
LSF CaO- 0.7 SO3/(2.8S+1.2A+0.65F)
PPC53S53 Gr43 Grspecifications
5.04.04.05.0LOI
3.03.03.03.0SO3 % max
6.05.06.06.0Magnesia ,MgO %,max
0.050.100.10Cl max
> 45C3S
10.0----C3A max
BIS specifications for various grades of cement
1051010.0Soundness ,LeChat expansion , (mm) max
30/60060/60030/60030/600Setting time, initial ( min) / final (max) , minutes
300.0370.0225.0225.0Fineness sqm /kg , min
162727233 days+/_ 1 hr
Compressive strength, Mpa , min
0.80.80.80.8Soundness, Autoclave %
0.15Drying shrinkage
3353534328 days +/ - 4 hrs
2237.533337 Days +/_ 2 hrs
Blaine apparatus airpermeability test
(Part - 5) Determination of Initial and Final Setting Times4031 (Part-5)
Early stiffening – false set or flash set
If less gypsum no gypsum flash set occursIf cement temperature > 130 deg c gypsum dehydrates and flash set occurs
Setting time ASTM specification
In concrete chemistry ettringite is a hexacalcium aluminate trisulfate hydrate, of general formula: (CaO)6(Al2O3)(SO3)3·32H2O or; CaO)3(Al2O3)(CaSO4)3·32H2O
Influencing parameters onCement strength
1 3 7 28 90 days
Strength MPa
C3S
C2S
C3A
C4AF60
0
20
30
40
50
= f (C3S)
28
7
3
1
MPa 70
60
50
40
30
20
10
40 45 50 55 60 65 % C3S
= 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 LOIresult in decrease instrength
1 day by 25 %2 8days by 3 % and90 days by 2 %
Cement strength is measured in 1 day, 3 days ,7days and 28 days
Measurement compressive strength BIS 4031 (Part-8)1988(Part - 8)Determination of Compressive strength of hydraulic Cement
Compression testing
50*50mm
Compressive strength – influencing parameters
Compressive strength
1 d 3 d 7 d 28 d
Influencing Normal range 5 – 15 20 – 35 30 - 45 45 - 60Parameters OPC
C3S 45 – 65 % + + + +
C3A 6 – 12 % + + + +
Ks 0.2 – 1.5 % + + +/0/- -
SO3 2 – 4 % +/0/- +/0/- +/0/- +/0/-
Blaine 280 – 300 + + + +m2/kg
Wk 0 - 0.3% - - - -
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)
One day strength is contributed mainly byC3A , Soluble alkalies, and C3S
3 day is contributed mainly by C3S
7 days strength is contributed by mainlyC3S
28 days strength is mainly contributed byC2S
Apart from the above cement strength is enhanced byhigher fineness of cement Less C3S crystal size achieved by rapid burningand quenching the clinker in coolerHigher fineness of rawmeal also reduces the crystal size of clinker minerals , ie ., C3S & C2S whichenhances the hydraulic reactivity
Cement strength – influencing parameters
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 mustto evacuate moisture and silo cleaning.cements having soluble alkalis and sulfates preferably packed inpaper bags to avoid depletion of strength.
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 alkalicontent 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
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 theuniformity factor n really influences the development of cement strength.The influence of 3 - 32 mm fraction and the uniformity factor is higher incement with higher in specific surface ( > 3400 cm2/ g)
2. The fractions with particle size less than 3 mm contributes only to earlystrength while the fraction with particle size more than 24 mm influencesstrength 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 continuousand steep ( with high uniformity factor) distribution with a high (65 %)content in 3 – 32 mm fraction and specifically in 16 - 24 mm fraction andlow content of fine particles ( < 3 mm , 10 % ) and specific surface of2500 – 3000 cm2/ g according to Blaine.( high efficiency separator andgrinding media distribution plays significantly here)
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 nilContribution 14 days 14 days beyond one day
Late strength less later high later nil nil contribution
Resistance to moderate high poor highChemical attack
Drying shrinkage nil low nil nil
Measurement of expansion for free lime ( IS 4031 Part3 -1988
Expansion due to free CaO=< 10 mm
Auto clave test forexpansion of cement
(Part - 3) Determination of Soundness
1988
4031 (Part-3)
25*25*282mm
Expansion limit < 0.8mm
Autoclave
Calorie meter
Tube samplers for bulk cement
MgO Crystals Or Periclase
Free lime clusters
Problems and solutions
1. Grinding problemsa) False set lower cement mill temperature
add less gypsumadd part anhydrite
b) reduced strength high mill temperatureless water cooling correct water cooling
2. Silo storagea) False set short storage time
cooling of cement < 70 deg c
b) reduced strength increase gypsum dehydration inmill
c) lump formation and add less gypsum, use partlysilo blockage (syngenite anhydrate , decrease K2O contentformation, K2SO4.2CaSO4.H2O to avoid the formation of Syngenite
Problems solutions
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
qualityProcess
Quality is a set point and process is variable
Right
Processquality
Process is a set point and quality is variable
wrong
Thanks you for your kind attention And spending your valuable business hours
K.P.PRADEEP KUMARSr.GM OperationKarikkali worksChettinad Cements Ltd