Influence of process on quality

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