manufacturing and quality control of cement

2015

Abhishek Garai, M.Sc Chemistry

NIT Rourkela, Orissa.

OCL India Ltd.

5/2/2015

Cement Manufacturing & Quality Control

Abhishek Garai (M.Sc Chemistry) NIT Rourkela, Orissa Page 1

ACKNOWLEDGEMENT

I wish to express my profound gratitude to the management

of OCL India limited for providing me this golden opportunity to

do this Industrial training in the Cement plant Rajgangpur. I also

express my sincere gratitude to Mr. Chandan Sengupta, Sr.

Manager of Quality Assurance department of OCL for his guidance

in learning and help me to make this project beside of his busy

life.

I am also grateful to Mr Ashraf Khan, Mr Subhasis Dash sir

indispensable help for clarifying my various doubts with their

lucid and elaborate explanation .The co-operation of Mr Sashi

Bhusan Singh , Mr S K Barik and all other personnel in physical

,chemical laboratories are also highly appreciated.

I am also indebted to the staff at the Central Control Room

(CCR) for explaining me the whole cement manufacturing process

and various control and operational aspects of process.

Thanking You Rajgangpur.


SCOPE

This report gives the descriptions of cement manufacturing

process and the chemical and physical quality determination of

Cement at OCL, that I have learned during the period of my

training. While emphasizing the application of the Chemistry I

dealt with Chemical analysis (Gravimetric & EDTA analysis ),

XRF-analysis , XRD-analysis and test for physical properties

determination i,e NC, Setting Time, Compressive Strength,

Fineness, Soundness, etc.

The major unit operations encountered during cement

production are size material transport, grinding and dust

separation in ESP and Bag filters the unit processing involved

are dehydrations, de-carbonation and clinkerization. Hot exit

gases from the kiln are circulated to different units for better

heat economy. Materials balance is used in the raw mix design.

Quality control is essential for producing that meets the desired

quality of cement.

While I have taken every effort to keep this report free of errors,

any suggestions are welcomed.


Contents

Fuel Analysis.

Reactions during Processing.

Cement Chemistry.

Waste Utilization.

Problem.

Conclusion.

Biblography.

Introduction

Profile of OCL

History

Varieties of Cement,Properties and their diffrent applications.

Raw materials & Handling of Raw materials.

Production Process

Quality Control & Assurence Procedure.

* Various Technique Used for analysis and their prinnciple of Operation.


Cement is an inorganic, non-metallic substance with hydraulic

binding properties, and is used as a binding agent in building

materials. It is a fine powder, usually grey in colour that consists of a

mixture of the hydraulic cement minerals to which one or more forms

of calcium sulphate have been added. Mixed with water it forms a

paste, which hardens due to formation of cement mineral hydrates.

Cement is the binding agent in concrete, which is a combination of

cement, mineral aggregates and water. Concrete is a key building

material for a variety of applications.

The cement industries first grind the raw materials then make clinker

in rotary kiln by firing coal and feeding grind raw materials with

proper raw mix design. Then the clicker is grinded again and made

cement with mixing various additives and gypsum.

Clinker is produced through a controlled high-temperature burn in a

kiln of a measured blend of calcareous rocks (usually limestone) and

lesser quantities of siliceous, aluminous, and ferrous materials. The

kiln feed blend (also called raw meal or raw mix) is adjusted

depending on the chemical composition of the raw materials and the

type of cement desired. Portland cement is the major cement product

in India. Although other cements are also made for very minor

amount.

Cement plants are typically constructed in areas with substantial raw

materials deposits (e.g. 50 years or longer).There are almost 207

cement manufacturing plant in INDIA in 2014 spread all over India.

Total 71 companies are now present in India for cement among them

‘UltraTech’ has the highest no of plant that is 22.Then ‘Jaypee

Cement’, ‘ACC cement’ take their position with 20 & 17 no of plant

respectively.


Type Private

Industry Cement Manufacturing.

Founded 1949

Founder/Co-Founder

Sjt. Jaidayal Dalmia

Managing Director

Sjt. Puneet Dalmia

CEO Sjt. Mahendra Singhi

Executive

Director

DD ATAL

Head Office 4 Scindia House, Connaught Palace, New Delhi

Cement Manufacturing

Capacity

4.0 Million TPA at Rajgangpur

Products OPC-43,OPC-53,OPC-53 S

PSC, PPC, SRPC, Masonry Cement.

Contacts www.ocl.in

[email protected], [email protected]

http://www.ocl.in/


In 1950-51 at the request of Government of Odisha to manufacture of

super grade cement in the construction of Hirakud Dam ,Sit.Jaidayalji

Dalmia an Industrialist farsighted his vision to set up a cement

manufacturing plant at Rajgangpur with the supply of main raw materials

from Langiberna .

The origin of OCL was seeded in the time that signalled India's

independence. A dream unleashed. A blue print of growth was drawn.

Endeavours to reconstruct economy set in. Indian industry woke up to the

key challenge of self-reliance. Agriculture took a turn to modernity with

construction of dams across the country. Against such a bubbling

background Sjt. Jaidayalji Dalmia, an industrialist of farsighted vision set

up a cement plant at Rajgangpur during 1950-51 at the request of

Government of Odisha to manufacture super grade cement for use in the

construction of Hirakud dam. The plant that went on steam as Orissa

cement limited during 1952 transformed itself into OCL India Limited

during 1996 to better reflect its multifarious activities.

Period Achievements

1949 Company got incorporated.

1951 Cement manufacturing started with a 500 TPD Wet process plant.

1988 Conversion from Wet to Dry process with capacity enhancement to 5.25 Lakh TPA.

1997 First in India to install Vertical Roller Mill for cement grinding (CVRM) and enhancing the cement manufacturing capacity to 10 Lakh TPA.

1998 Obtained ISO 9002 Certification.

2003 The first Cement manufacturer in eastern India granted with the right to use American Petroleum Institutes (API) monogram for its OIL Well Cement.

2004 Obtained ISO 9001-2000 Certification.

2005 3rd CVRM installed.

2009 2nd line Clinkerisation unit commissioned with installed capacity of 17 lakh TPA.

2009 Project activities commenced for Captive Thermal Plant 2 X 27 MW capacity.


2009 Bagged National Award for Energy efficiency in Cement Industry from NCCBM.

2010

Obtained ISO 9001-2008 Certification.

2010 Obtained Certification for Environment Management System as per IS/ISO 14001:2004 and Occupational Health and safety Management System as per IS/ISO 18001:2007 from BIS.

From a modest 500 TPD capacity imported single wet process Kiln of FL

Smidth make of Denmark, the house of 'Konark' brand cement has

journeyed a long way. To cater the growing demand the company enhanced

its installed capacity with addition of its second wet process 600

TPD kiln in 1957.Keeping a steady progress with time and

technology, OCL has produced the first clinker through modernized and

fully Automated dry process plant in 1988 and further enhanced its

installed capacity by adding its 2nd clinkerization unit in 2009.

In the early fifties OCL has installed four numbers of Ball mills of FL

Smidth for cement grinding purpose. Later on, to keep pace with the

technological advancement and facilitating manufacture of blended

cement, three giant Vertical Roller Mills with combined and separate

grinding systems were installed during the period of 1997 to 2005.

To ensure easy availability and timely supply of cement to the customers

in the coastal area of Odisha, a split level cement grinding unit Kapilas

Cement Works was set up near Cuttack in 2008. The urge to modernize

and continuously upgrade technology has gone beyond the plant and

transformed OCL's limestone mines into one of totally mechanized

operations from the earlier system of manual mining.

The drive for excellence through continuous technological up-gradation

has resulted in many 'Firsts' for OCL. A few of them are, The first auto kiln

control system based on fuzzy logic in India, The world's largest cement

and slag grinding Vertical Roller Mill during 1997,The second such Cement

Vertical Roller Mill during 2001, The third Cement

Vertical Roller Mill again with 60% additional capacity and first in the

world market in 2005.

The target centric investments in R&D and application specific product

development have both enabled OCL to enlarge and include in its product

range various grades of Ordinary Portland Cement (OPC) like 43 and 53

grades; 53S Grade cement for use in the manufacture of railway sleepers;


Portland Slag Cement (PSC); Fly Ash based Portland Pozzolana Cement

(PPC), Sulphate Resisting Portland Cement (SRPC); Masonry Cement.

For a brief spell OCL also ventured into manufacture of a wide range of

cement allied products including spun pipes etc., in early sixties of the last

millennium and became a prime source of high strength reinforced spun

pipes and pre-stressed concrete poles. It was the first manufacturer of pre-

stressed concrete railway sleepers. Decades later, the company still reigns

supreme as a supplier of railway sleeper grade cement in India.

Industrial Research & Development had always been the backbone of

OCL's product supremacy. Apart from harnessing the fruits of in-house

research for direct application to product and process development

related spheres, OCL regularly commissions the services of Dalmia

Institute of Scientific and Industrial Research (DISIR) in carrying out

application oriented specific research projects. This immensely helps OCL

to draw upon the knowledge of scientific community as well and use it for

the betterment of both the industry and the consumer to whom the

benefits of such research ultimately reach.

A company is primarily known for the products it makes and the services

it renders. In the ultimate count it is quality that holds the key.

'Konark' Brand cement of OCL has been

extensively used in the construction of the prestigious Hirakud Dam in

Odisha and in building some of India's largest roads, bridges

and Industrial plants - including the Vidyasagar Setu in Kolkata ,the

Gandhi Sagar Bridge in Patna , as well as in the construction of port

facilities at Haldia and Paradip. OCL is proud that it was 'Konark' cement,

which was exclusively used in essential restoration

repairs by Archaeological Survey of India in Lord Jagannath Temple at

Puri. To name a few remarkable Projects where Konark Cement has been

recently used are Modernisation of TISCO/Jamshedpur plant, 2.2 Million

ton Integrated Steel plant of Electro Steel

Integrated in Bokaro, Jharkhand , A 3 Million ton Integrated Steel Plant of

Jindal Steel and Power at Angul, Odisha An all-weather new private Port

at Dhamara near Bhadrak in Odisha built jointly by TISCO and L&T

placed confidence on Konark in using its cement. A first all concrete road

connecting the busiest commercial town of Odisha with

its only Port Paradip in underway with all its requirement met from Konark

cement A 3 Million ton integrated steel plant of Bhushan Steel and Power

along with 500mw of power plant placed its confidence on Konark for its


vital installations and used maximum quantity for installation of BF and

other systems. Vedanta Aluminium, Jharsuguda -building a world class

Aluminium Refinery and a 2400MW IPP is another testimony of the

confidence placed in Konark. Besides these, numerous Large and medium

projects of Irrigation, Power, Sponge Iron and Steel have used Konark

cement in shaping up their dream which shows the confidence the brand

enjoys in the minds of its consumers.

As on date Konark Brand Cement enjoys rock solid customer satisfaction

across the country and is very popular in the state of Odisha where for the

last almost 60 years it is the most demanded premier lead brand. It is a

name ‘Cemented to Quality’. After its recent up gradation and

enhancement of its capacity, Konark Cement has entered

into the states of Bihar where it has been so well received that it commands

a substantial market share immediately after its entry in the markets.

OCL is proud of its dedicated team of people - its employees, its ever-

increasing list of satisfied customers, its dealers, its Bankers and Financial

Institutions, its representatives and associates who have all immensely

contributed to making what OCL is today.


According to the Indian Standard Specifications total 14 type of cement are available in India now. Indian standard Specification on cement:

Title of the QC Order: Cement (Quality Control) Order 2003

QC Notification: Ministry of Commerce & Industry, Department of Industrial policy & promotion.

Implementing Authority: Officers appointed by state /Central Govt.

SL.NO

Type of Cement

1. 33 Grade ordinary Portland Cement (OPC-33) (IS-269).

2. 43 Grade Ordinary Portland Cement (OPC-43) (IS-8112).

3. 53 Grade Ordinary Portland Cement (OPC-53/53S) (IS-12269).

4. Portland Slag Cement (PSC) (IS-455).

5. Portland Pozzolana Cement (PPC) (IS-1489). 1. Fly Ash based

2. Calcined Clay Based. 6. Sulphate resistant Portland Cement (SRPC) (IS-12330).

7. Masonry Cement (IS-3466).

8. Oil Well Cement (IS-8229).

9. High Alumina Cement for Structural Use (IS-6452).

10. Super sulphated Cement (IS-6909).

11. Rapid Hardening Portland Cement (IS-8041).

12. White Portland Cement (IS-8042).

13. Hydrophobic Portland Cement (IS-8043).

14. Low Heat Portland Cement (IS-12600).


Varieties of Cement, their properties & application.

Ordinary Portland Cement 33 grade (IS-269).

Ordinary Portland cement is generally made by

grinding the Clinker with Gypsum. According to the BIS

(Bureau of Indian Standard) the minimum

compressive strength of 33 grade OPC cement should

be 33MPa.

Chemical Composition: OPC 33 grade is generally

low C3S content 45% and where 95% clinker & 4-5 % gypsum were

mixed.

Properties :

Chemical Properties(BIS Requirement):

Properties

%LOI %MgO %SO3 %IR %Cl LSF A/F

OPC-33 5.0 6.0 *2.5/3.0 4.0 0.1 0.66-1.02

0.66

Physical Properties(BIS Requirement):

Properties Fineness: Specific Surface Area M2/Kg

Setting time

Compressive Strength(CCS) in MPa

Soundness

Initial Final 3-day 7-day 28-day

LeChtelier In mm

Autoclave (%)

OPC-33 225 30 600 16 22 33 10 0.8

Applications.

Used for general low-rise civil construction works

under normal environmental conditions.


Ordinary Portland Cement 43 grade (IS-8112:1989).

Ordinary Portland cement 43 grade is a moderate

strength Portland cement where according to BIS

requirement the compressive strength of this

cement should not be less than 43 MPa after 28

days.

Chemical Composition: The strength is obtained because of high

percentage of C3S content about 50%.90-95% clinker is grinded

with 4 to 5 % of gypsum to make this cement.

Properties :


Properties

%LOI %MgO %SO3 %IR %Cl LSF A/F

OPC-43 5.0 6.0 *2.5/3.0 3.0 0.1 0.80-1.02 0.66



Setting time


Soundness


LeChtelier In mm

Autoclave (%)

OPC-43 225 30 600 23 33 43 10 0.8

Applications. General civil engineering construction works

including residential commercial & industrial

buildings like roads, bridges, fly overs under normal

environmental conditions.

Pre-cast items such as blocks, tiles and pipes.

Asbestos products such as sheets and pipes.

Non-structural works such as plastering and

flooring.


Ordinary Portland Cement 53 grade (IS-12269). 53-grade OPC is high strength cement.

According to the BIS requirements, 53-grade OPC

has a 28-day compressive strength of 53 MPa

minimum. For certain specialized products, such as

pre-stressed concrete and certain pre-cast concrete

items requiring high strength, 53-grade OPC is considered useful as it can

produce high-grade concrete at lower cement content levels. 53-grade OPC

is produced by exposing the clinker to the grinding process for longer

period of time, which results in a higher density and stronger cement. As

the grinding process requires a significant amount of power, finer grinding

for the 53-grade OPC requires more power and is therefore priced higher

compared to lower grades of OPC.

Chemical Composition: This a very high strength cement & this is

obtained because of very high percentage of C3S content in the

clinker about 52-53%.95% clinker is grinded with 4 to 5 % of

gypsum to make this cement.

Properties :


Properties %LOI %MgO %SO3 %IR %Cl LSF A/F C3S

Min C3A Max

OPC-53 4.0 6.0 *2.5/3.0 3.0 0.1 .80-1.02

0.66

OPC-53S 4.0 6.0 *2.5/3.0 3.0 .1 .80-1.02

0.66 45.0 10.0



Setting time


Soundness


LeChtelier In mm

Autoclave (%)

OPC-53 225 30 600 27 37 53 10 0.8

OPC-53S 370 30 600 37.5 5 0.8


Applications. A high strength OPC is used for high rise buildings,

bridges, flyovers, chimneys where high grade concrete is

normally required.

OPC-53S are used for railway sleeper making.

Pre-cast concrete items such as paving blocks, tiles and

building blocks.

Pre-stressed concrete components and

Runways, concrete roads and bridges.

Portland Slag Cement (IS-455)

Portland slag cement is now the most innovative product

in the cement industry. Portland slag cement is made by

grinding Portland cement Clinker with gypsum and Blast

furnace granulated Slag obtained as a waste materials of

iron Blast furnace of steel plants. It is also manufactured by

blending OPC with ground granulated blast furnace slag

(GGBS). Slag also contain that constituents contained in the

raw materials so by mixing in intimate proportion of clinker

and slag ultimate properties of cement can be obtained. This cement has

strength comparable to OPC -33, 43, 53 Grade cement. It has very unique

properties:

It shrinkage is very low.

It has very low water demand that mean very low %NC.

It has high ultimate strength with higher rate of gain of

strength than normal OPC available in market.

Its strength gradually increases in longer period of time.

PSC reduces the usage of clinker hence the cost of the

cement decreases.

Huge amount on waste from sponge iron industry are

consumed in production of PSC cement so this way waste

utilization is done.

PORTLAND SLAG CEMENT


By producing PSC cement we can reduce the production of

total CO2 in calcination process indirectly by producing

low amount of Clinker.

Chemical Composition: Portland slag cement is manufactured by

grinding cement clinker, gypsum and 25-70% slag according to the

requirement of strength.

Chemical Composition of Slag:

Properties :


Properties

%LOI %MgO %SO3 %IR %Cl %Slag

PSC 5.0 10.0 3.0 3.0 0.1 25-70%



Setting time

Compressive Strength(CCS)

in MPa

Soundness

Initial Final 3-day

7-day

28-day

LeChtelier In mm

Autoclave (%)

PSC 225 30 600 16 22 33 10 0.8

Applications: General civil engineering construction works

Blast Furnace Slag


But mainly preferred for construction of marine

structures and in coastal areas where excessive

amount of chloride and sulphate are present.

It can also be used for mass concrete works.

Portland Pozzolona Cement (IS-1489)

Portland pozzolona cement is also an environment

friendly product of cement which uses hazardous

substituents like “Fly ash” coming out from thermal

Power plant. PPC is manufactured by grinding clinker

with fly ash and gypsum with proper proportion. The

major constituents of Fly Ash is SiO2 which is an

essential components of Cement. According to BIS, the

compressive strength of PPC cement should not be less

than 33 MPa after 28 days. Some specific properties of

this cement are:

It is manufactured with carefully selected Pozzolana (Fly

ash) as per the requirement laid down in IS 3812:1981

which is ideal for denser and more durable concrete .

It is having low heat of hydration and corresponding

resistance to exposure in various environmental chemicals

such as salt water. It is particularly suitable for marine and

hydraulic construction and other mass concrete structures.

Chemical Composition: Portland Pozzolona Cement (PPC) is

manufactured by grinding clinker, gypsum and 15-35% Fly Ash.

Portland Pozzolona Cement


Chemical Composition of Fly Ash:

Properties :


Properties

%LOI %MgO %SO3 %Fly Ash

PPC 5.0 6.0 3.0 15-35%



Setting time

Compressive Strength(CCS) in

MPa

Soundness

Initial Final 3-day

7-day

28-day

LeChtelier In mm

Autoclave (%)

PPC 225 30 600 16 22 33 10 0.8

Applications: Useful for general construction works and especially

suitable for works in aggressive environmental

conditions.

It is employed for water retaining structures, marine

works, mass concreting such as Dams, Retaining Walls,

and sewage pipes.

Fly Ash


Sulphate resistant Portland Cement (IS-12330)

Among the four major substituents of Cement Tricalcium

Aluminate (C3A: 3CaO,Al2O3) Substrate is reacts with

sulphate salt present in soil and water forming TriCalcium

Sulphoaluminate whose volume is more than twice of C3A

thus induces a stress in the concrete leading to crack and

disruption of these concrete. But this SRPC Cement is free

from these effect by maintaining the proportion of

constituents in Cement. SRPC cement is made by inter

grinding the special quality of clinker and gypsum.

Chemical Composition: The C3A component in the Clinker is

controlled to very less percentage by proper raw mix design so that it

can’t react with sulphate salt. Other Components are mixed

accordingly.

Properties :


Properties %LOI %MgO %SO3 %IR %LSF C3A

Max

(C4AF+2C3A) Max

SRPC 5.0 6.0 2.5 4.0 0.66-1.02

5.0 25.0



Setting time

Compressive Strength(CCS) in

MPa

Soundness

Initial Final 3-day

7-day

28-day

LeChtelier In mm

Autoclave (%)

Sulphate Expansion In 14 days

SRPC 225 30 600 10 16 33 10 0.8 0.045

Applications: Use for underground structures in sulphate salt rich

environment, effluent treatment plants.

Used in Sugar & other chemical industries where civil

works are likely to be subjected to be sulphate attack.


Oil Well Cement (IS-8229)

This is a special type of cement which is suitable in high pressure and

temperature. This type of cement is specially formulated for petroleum

industry foe cementing the steel casting the walls of the Oil wells. That’s

why its name “Oil Well” Cement. The temperature of the wall ranges from

180-2500 C while the pressure varies from 1300-2000 Kg/Cm2

Features: This cement is specially formulated so that its slurry remain

pumpable at this temperature and pressure for a required length of time.

Chemical Composition: This special type of cement has very high

C3S content ranging from 48-65 % which gives very high strength

to the cement also the quantity of Gypsum is reduced for easy

setting. The percentage of C3A are also reduced to less than 3%.

Properties :


Properties

%LOI %Mgo %SO3 %IR Max

C3S Min

C3S Max

C3A Max

(C4AF+2C3A) Max

Na2O Max

Oil Well

3.0 6.0 3.0 0.75 48.0 65.0 3.0 24.0 0.75


Properties Initial Consistency

(BC)

CCS at (MPa) (Min)

Soundness Thickening Time

At 38oC

At 60oC

%of Water

by mass of

fluid

%of Free Fluid max

%of Free

Water max

Autoclave Expansion

(%)

(in minutes)

Oil Well

30 2.1 10.3 44.0 5.9 1.4 0.8 90-120

Applications: Used for the petroleum industry for cementing

the steel casting to the walls of the oil wells.


Masonry Cement (IS-3466)

Masonry Cement is a special type of Cement

which is exclusively used for Plastering and brick

work. It is very smooth and gives super surface finish

.Masonry Cement is produced by intimately grinding

Portland cement clinker with pozzolonic materials or

inert materials and gypsum.

Special Features:

It has low compressive strength that is

why it can’t be used for structural concrete, flooring and

foundation work.

It contains air-entering agents which improve air

retentivity, Plasticity, and workability of motors.

Very smooth and super surface finish of the plasters.

More plastic mortar mix.

Minimum fall of mortar while plastering walls or ceiling.

Properties: All properties are in Chart 1.a following.

Applications: Used for making mortars for brickwork.

Exclusively used for plastering works.

Used for smooth surface finishing works.

High Alumina Cement (HAC) (IS-6452).

Essentially it is refractory cement. It has got high early strength

development due to its high C3A content and low Gypsum Content. It got

nearly 30 MPa in only one day. According to BIS requirement the proportion

of Alumina in the cement should not be less than 32.0%.

Super Sulphated Cement (SSC) (IS-6909).

This Cement is typically formulated for resisting the high concentrated

sulphur attack.


Applications: Used for a variety of aggressive conditions e.g. marine

structures.

Used in reinforced concrete pipes in ground water.

Concrete construction in sulphur bearing soils.

Chemical works involving exposure to high

concentration of sulphates

Concrete sewers carrying industrial effluents.

Rapid Hardening Cement (RHC) (IS-8041).

This cement is basically ordinary Portland cement with very high fineness.

This type of cement is specially used for repairing and rehabilitation works

are done where the speed of construction is fast and early completion is

required due to the limitation of work.

White Portland cement (WPC) (IS-8042).

Meant for non-structural and decorative use. Normally used for flooring,

general architectural purposes, such as mosaic tiles, decorative concrete

wall paintings and special effects.

Hydrophobic Portland cement (HPC) (IS-8043).

Manufactured specially for high rainfall areas to improve the cement’s self-life. During manufacture the cement particles are given a chemical coating which imparts water repelling property where by the cement is not affected by high humidity and hence be stored without deterioration for a longer period.

Low Heat Portland cement (LHC) (IS-12600).

Used for making concrete for dams and other water retaining structures, bridge abutments, massive retaining walls etc. In mass concreting, there is often considerable rise in temperature from the heat of hydration of the cement with resultant expansion, and the slow rate at which it is dissipated from the surface. The shrinkage which takes place on subsequent cooling may develop cracks.


Chart of BIS Requirement of properties :


Basic Components of cements.

Cement has these four major constituents

Calcium, Silicon, Iron, and Aluminium.

They are in the form of:

Tricalcium Silicate (C3S)

Dicalcium Silicate (C2S)

Tricalcium Aluminate (C3A)

Tetracalcium Aluminoferrite (C4AF)

Apart from this other constituents as additives are

Gypsum CaSO4,2H2O (CSH2), Calcite CaO.CO3(CC).

The source of these constituents in cement are mainly two type of raw

materials they are:-

Calcareous Raw Materials.

Argillaceous Raw Materials.

Each component of the raw mix has individual(C, A, S and F) and combined

[(Lime Saturation Factor (LSF), Silica Modulus (SM), Alumina Modulus

(AM),] effects on burnability. The formula, limiting range and the preferable

range of the LSF, SM & AM is shown in table.

Parameter Formula Limiting Range Preferable Range

LSF 0.66-1.02 0.92-0.96

SM 1.9-3.2 2.3-2.7

AM 1.5-2.5 1.3-1.6

The different source of these above type of raw materials are following.

Calcium

(Ca)

Silicon

(Si)

Iron

(Fe)

Aluminium

(Al)


Mainly supply CaO


Although Now a days some alternative raw materials except above are

used for production of cement. Like –

Handling of raw materials.

Lime stone are the predominant raw materials for cement which

accounts for the 60% of the total raw materials of cement and its quality

ultimately characterises the quality of cement. So proper handling of raw

materials is necessary for ensuring the quality of cement. Time to time

limestone samples are tested in the laboratory to evaluate the deposit of

quarry by Computer Aided Deposit Evaluation done by M/s Holtech

Consultancy. Day by day drill dust samples analysis are done at laboratory

and the results are communicated to quarry enabling them to preblend for

dispatching the uniform quality of limestone. As per the preblend,

Limestone is dug vertically from the open cast mines after drilling and

blasting loaded on to the dumpers which transport the materials into the

hoppers of the limestone crusher which grind the lime stone into 75 mm

size. Crushed limestone are blended by stacker and Reclaimer for ensuring

proper blending. Then the crushed limestone is transported to the plant by

Cross Country Belt Conveyer (CCBC) or Narrow

Gauge Train Line. Morrum are collected locally by

truck and feed into hopper. Slug is collected from

iron industry. Fly ash is transported by closed truck

from Thermal Power Plant. Coal taken from Coal

mines although now a days Pet Coke are used as

alternative fuel.

CCBC


Morrum

Sandstone

Clay

Hopper for proper Raw mix Design

Grinding

Raw Meal

Raw Meal

Silo

Vertical Roller mill

for Grinding.

Preheater

Rotary Klin

Clinker

Production Process

Co

al

FiriADDITIVES (Gypsum, Slag, Fly Ash)

Cement


The cement manufacture process from the mines to packing of cement can

be divided into five steps:

Raw materials acquisition and handling.

Kiln feed preparation.

Clinker Production (Pyro-Processing).

Finished grinding.

Packing & Dispatch.

Each of these steps are described briefly below.

Raw materials acquisition and handling:

The initial production step in Portland cement manufacturing is raw

materials acquisition. Calcium, the element of highest concentration in

Portland cement, is obtained from a variety of calcareous raw materials,

including limestone, chalk, marl, sea shells, aragonite, and an impure

limestone known as "natural cement rock". Typically, these raw materials

are obtained from open-face quarries, but underground mines or dredging

operations are also used. Raw materials vary from facility to facility. Some

quarries produce relatively pure limestone that requires the use of

additional raw materials to provide the correct chemical blend in the raw

mix. The raw materials are selected, crushed, and proportioned so that the

resulting mixture has the desired the minimum percentage of chemical

composition requirement of raw materials. Because a large fraction

(approximately one third) of the mass of this primary material is lost as

carbon dioxide (CO2) in the kiln, Portland cement plants are located close

to a calcareous raw material source whenever possible. The raw materials

limestone is then transported to the plant by Cross Country Belt Conveyer

(CCBC) or by railway wagons.

Stacking and Reclaiming of Limestone: After crushing, the crushed

limestone is piled longitudinally by an equipment called stacker /

reclaimer. The stacker deposits limestone longitudinally in the form

of a pile. The pile is normally 250 to 300 m long and 8-10 m high. The

reclaimer cuts the pile vertically, simultaneously from top to bottom

to ensure homogenization of limestone.


The crushed limestone from pile is transported through belt

conveyor to hopper. Similarly, other raw materials like clay, morrum,

sand stone etc. are also transported by belt conveyor from storage

yard to respective hoppers. All raw materials are proportioned in

requisite quantity through weigh feeders.

Crushing Stacking and Reclaiming of Coal: The process of making

cement clinker requires heat. Coal is used as the fuel for providing heat.

Raw Coal received from collieries is stored in a coal yard. Raw Coal is

dropped on a belt conveyer from a hopper and is taken to and crushed

in a crusher. Crushed coal discharged from the Coal Crusher is stored in

a longitudinal stockpile from where it is reclaimed by a reclaimer and

taken to the coal mill hoppers for grinding of the coal.

Stacker of Limestone

Stacker of Coal

Reclaimer of Lime Stone

Reclaimer of Coal


Kiln Feed preparation: The second step in Portland cement manufacture is preparing the raw

mix, or kiln feed, for the pyroprocessing operation. Raw material

preparation includes a variety of blending and sizing operations that

are designed to provide a feed with appropriate chemical and physical

properties. Based on Raw mix design and availability of additives and

quality of limestone received, proportioning of raw materials is

achieved through electronically controlled weigh feeders. Cement raw

materials are received with an initial moisture content varying from 1

to more than 50 percent. If the facility uses dry process kilns, this

moisture is usually reduced to less than 1 percent before or during

grinding. Drying alone can be accomplished in impact dryers, drum

dryers, paddle-equipped rapid dryers, air separators, or autogenous

mills. However, drying can also be accomplished during grinding in

ball-and-tube mills or roller mills. While thermal energy for drying

can be supplied by exhaust gases from separate, direct-fired coal, oil,

or gas burners, the most efficient and widely used source of heat for

drying is the hot exit gases from the pyroprocessing system.

Raw Mix design:


Limestone and other additives in

desired proportions are fed to

Vertical Roller Mill (VRM) by belt

conveyer where they are ground to

fine powder. A part of the hot exit

gas (from the kiln) that has been

sucked by the pH fan is sent to VRM

through GAS CONDITIONING

TOWER (GCT-to reduce

temperature) to remove the

moisture in the raw materials. The dust produced is carried by the hot gas

and it is separated by Electro Static Precipitator (ESP) by charging the dust

particles which then fall into hopper for recycling. The ‘Raw Meal’ produced

after grinding by Vertical roller mill is air swept from inside from VRM and

transported to specially designed ‘RAW MEAL SILO’ where blending is done

by injecting compressed air for maintaining its homogeneous nature.

VRM: Raw meal is ground in VRM to

give a residue of +90µm 12-14%.

VRM contains a horizontal circular

table rotated by a motor and three

conically tapered grinding roller.

Material grinding process motor

through reducer rotating drive disc,

the material falls from the mill

under the central entrance and exit,

under the action of centrifugal force

to the disc edge by the roller to

move and the crushing, grinding

out lap after the material was speed

up the flow to and vertical mill with

one of the separator, after the meal

by the separator back to the mill,

the re-grinding; powder while

grinding out with air, dust

collection equipment in the system to collect down, that is, products.


Established through the mill in the pneumatic conveying of materials, a

larger air flow rate, which can use waste heat of gas, at the same time dry

grinding operations.

ESP: An electrostatic

precipitator (ESP) is a filtration

device that removes fine particles,

like dust and smoke, from a flowing

gas using the force of an

induced electrostatic

charge minimally impeding the flow

of gases through the unit.

Clinkerisation (Pyroprocessing):

The heart of the Portland cement manufacturing

process is the pyroprocessing system. This system

transforms the raw mix into clinkers, which are grey,

glass-hard, spherically shaped nodules that range

from 0.32 to 5.1 centimetres (cm) (0.125 to 2.0 inches

[in.]) in diameter. The pyroprocessing system of

clinkerisation section consists of a rotary kiln with 5

stage preheater with in line precalciner. In the

preheater the raw meal gets heated up with the use of

kiln waste gases, and in the precalciner the raw meal is partially calcined

to the extent of 85 to 95% by partly firing coal in the precalciner with the

help of hot air recovered from clinker cooler. The partially calcined raw

meal enters the rotary kiln. Coal, ground to desired fineness is fired into

kiln from the discharge end. In these rotary kilns a tube with a diameter

up to 25 feet is installed at a 3-4 degree angle that rotates 1-3 times per

minute. The ground raw material, fed into the top of the kiln, moves down

the tube counter current to the flow of gases and toward the flame-end of

Preheater

http://en.wikipedia.org/wiki/Electrostatic_charge

http://en.wikipedia.org/wiki/Electrostatic_charge


the rotary kiln, where the raw meal is dried, calcined, and enters into the

sintering zone. In the sintering (or clinkering) zone, the combustion gas

reaches a temperature of 3300-3600 °F. While many different fuels can be

used in the kiln, coal has been the primary fuel although now a days Pet

Coke (Bi-Product of petroleum industry) are also used. The raw mix in the

kiln melts first into liquid form and then transforms into nodules due to

the effect of the rotation of the kiln. There are two zones inside the kiln,

namely calcining zone and burning zone. The zone where raw mix enters

into the kiln is called calcining zone. Where temperature would be 950-

1000 C. Burning zone starts after this zone where temperature would be

1350-1450 C. The chemical reactions and physical processes that

constitute the transformation are

quite complex, but they can be

viewed conceptually as the following

sequential events:

1. Evaporation of free water;

2. Evolution of combined water in

the argillaceous components;

3. Calcination of the calcium

carbonate (CaCO3) to calcium oxide (CaO);

4. Reaction of CaO with silica to form dicalcium silicate;

5. Reaction of CaO with the aluminium and iron-bearing constituents to

form the liquid phase;

6. Formation of the clinker nodules;

7. Evaporation of volatile constituents (e. g., sodium, potassium,

chlorides, and sulphates)

8. Reaction of excess CaO with dicalcium silicate to form tricalcium

silicate.

After the formation of clinker cooling is necessary for quality

maintenance. The temperature of the clinker is brought to 80-90 oC from

1350-1450 oC by Clinker Cooler. Fast cooling is very essential to get good

Rotary Kiln


quality clinker. If cooling is not quick, the compound stability in clinker will

be adversely affected resulting in lower strength of cement after grinding.

The hot gas produced in the clinker cooler is used in kiln, VRM and pyro

cyclone. The cooled clinker produced are transported to Clinker storage

Silo by Deep Drawn Pan Conveyer (DDPC).

Clinker


Finish Grinding: The final step in cement

manufacturing involves a sequence of blending

and grinding operations that transforms clinker to

finished cement. To produce powdered cement

clinker is ground to the consistency of face

powder. The clinker from silos are fed into

grinding ball mill or vertical roller mill along with

requisite amount of gypsum and other additives

like Fly ash , Slag etc depending on the

requirement of proper strength, setting time.

Packing & Dispatch: The Cement produced after grinding are stored

in silos from where it is extracted to automatic rotopackers with

electronically controlled weight capacity. When the cement packing

bag is of 50 kg it will automatically stop pouring into that bag after the

bag will be automatically sealed and transported to bag cement

storage. After that cement is being loaded in the wagons and racks

through automatic loaders and finally dispatch in rail and road.

VRM

Automatic Rotopackers


The quality of cement in India is maintained according to “Bureau of Indian

Standards” specifications. The quality is assured by the analysis of raw

materials, clinker, and cement in regular basis according to BIS procedure.

Apart from that the processing parameter in Kiln, silo, VRM are also

maintained by CCR.

ASSURENCE PROCEDURE:

Objective:

a) Ensuring the quality of the incoming, intermediate, semi-finished and

final product.

b) Ensuring conformity with the laid down norms by BIS (Bureau of

Indian Standards.)

QUALITY CONTROL OF INCOMING MATERIALS.

LIMESTONE: Limestone is the predominant raw materials in cement

manufacturing its quality ultimately characterises the quality of clinker

and cement.

Time to time limestone samples are tested at laboratory to evaluate

the deposit of quarry by computer aided Deposit Evaluation by M/S

Holtech Consultancy.

Day to day drill dust samples analysis are done at laboratory and the

results are communicated to quarry enabling them to make the pre

blend for dispatching the uniform quality of lime stone.

As peer pre blended, limestone are crushed and loaded in the hopper

and finally it is transported to the plant by Cross Country Belt

Conveyer sometimes by Narrow Gauge Train lines.

The material is stacked horizontally trough stacker to form a

cheveron type of stockpile up to a quantity of 1500 MT. During

stacking the quality is monitored and the samples are being collected

from the belt in hourly basis through a continuous auto sampling


system and analysed through X-Ray analyser. The test results are fed

to the quarry on hourly basis to take the necessary correction before

the next dispatch to meet the prefixed norms for every 5000 MT

stock.

The cumulative chemical composition of the limestone stockpile is

estimated based on the hourly test results and use to prepare the raw

mix design.

QUALITY CONTROL OF OTHER ADDITIVES:

Clay, Fly ash, Cinder, Morrum are the additives are generally used in

the raw meal although some other additives are also can be used.

Received raw materials are tested to check its conformity w.r.t the

predefined norms. The test data are used for preparing the raw mix

design.

Coal is used mainly as a fuel although Pet coke are also used now a

days. Received Coal and pet Coke are tested to check its conformity

w.r.t to the predefined norms.

Blast furnace granulated slag, fly Ash, and gypsum are used in the

cement grinding stage. The received materials are tested to check

its conformity w.r.t to predefined norms laid down by BIS.

QUALITY CONTROL OF RAWMEAL.

Raw Meal: Limestone stockpile is being reclaimed vertically trough a

reclaimer to get a uniform quality of limestone all along. The limestone is

intimately mixed with known quality of argillaceous materials in a definite

proportion through weigh feeders as determined by the QCX blend expert

system based on the quality targets of the raw meal determined through

raw mix design. This mixed materials is ground in a vertical roller mill. The

mill output materials is stored inside the specified silos.

During grinding process samples are being collected on hourly basis

through a continuous auto sampling system and being tested through X-Ray

fluorescence spectrometer.

The results are in turn fed to QCX blend expert system to change the

proportion of raw materials to meet the target values.


QUALITY CONTROL OF INTERMEDIATE MATERIALS.

Clinker: The raw meal from the silo is fed to the kiln through two string

five stages preheater with inline calciner and sintered at a temp of 1400

degree centigrade for complete clinker formation. The clinker is then

passed through a grade cooler and stored in the Clinker Gantry.

The fuel used in the pyro system is coal pulverised through a ball mill and

the samples is being taken to check and maintain the ash content to meet

the target value.

Hourly clinker sample is collected from DDPC and is being tested by X-Ray

Fluorescence spectrometer and X-ray Diffractometer for their complete

elemental composition and phase evaluation. This definitely helps for

controlling and monitoring the clinker quality as per the target designed

value on hourly basis and for taking any effective action in the raw meal if

required.

QUALITY CONTROL OF FINAL PRODUCT.

Cement Grinding: Known quality of Clinker, Gypsum, Slag, Fly Ash are fed

into respective hoppers of the grinding mills from which required

proportion of these materials are fed to the mills through weigh feeders as

per the requirement of manufacturing different quality of cement.

Mills out samples are collected through continuous auto sampling system

a tested for complete quality evaluation and taking necessary corrective

actions.

Cement Packing: Finally the cement is packed through automatic

rotopackers. During packing samples are being collected through

autosamplers on hourly basis to assure the quality of cement supplied to

the customers.

Ensuring Conformity with the laid down norms by BIS

To ensure the compliance of statutory requirements of BIS following

activities are performed-


All IS specifications required for carrying out the quality control

functions are identified and kept in a separate file at an identified

location.

Incase of any amendment or change in version of IS specification the

old one is replaced and new version is incorporated in the file.

The test records related to the quality input and output of the

products required to provide evidence of conformity to the IS

requirements are maintained and duly signed by the respective

authorised person.

Sectional Incharge is authorized to ensure compliance of statutory

requirements of BIS.

Action is initiated for timely renewal of the product licenses.

The following analysis are done in prescribed time intervals for assuring

the quality -


Total 3 type of tests are done in cement industry namely

1. Chemical Analysis.

2. Physical Analysis.

3. Fuel Analysis.

Chemical Analysis (Various Technique used for analysis and

their principle of operation):

Chemical analysis is required in cement manufacture for evaluating the

quality of raw materials, raw meal & finish grinding product and for

effecting quality control. Chemical composition is determined by two

methods-

Instrumental Techniques.

Laboratory tests.

Instrumental Techniques.

Now the chemical composition and other properties of

cement, clinker, raw materials can be is easily determined by using

instrument like -

1. X-ray Fluorescence Spectrometer.

2. X-Ray Diffraction.

3. Microscope.

4. Flame Photometer.

Let us discuss about those instruments and their principle of operation.

Principle: Samples for X-ray fluorescence are

prepared by

grinding the

samples with

cellouse power

and then pressed under the pressure

of 20 ton for 10-15 seconds and make

sample pellet. The samples are excited

by an X-ray radiation produced in X


ray tube operated in a potential between 10-100 kv. When materials are

exposed to short wavelength X-rays

or to gamma rays, ionization of their component atoms may take place.

Ionization consists of the ejection of one or more electrons from the atom,

and may occur if the atom is exposed to radiation with an energy greater

than its ionization potential.

X-rays and gamma rays can be energetic

enough to expel tightly held electrons from the inner orbitals of the atom.

The removal of an electron in this way makes the electronic structure of the

atom unstable, and electrons in higher orbitals fall into the lower orbital to

fill the hole left behind. In falling, energy is released in the form of a photon,

the energy of which is equal to the energy difference of the two orbitals

involved. Thus, the material emits radiation, which has energy

characteristic of the atoms present. The term fluorescence is applied to

phenomena in which the absorption of radiation of a specific energy results

in the re-emission of radiation of a different energy (generally lower). The

intensity of these characteristic radiation is measured with a suitable x ray

spectrometer and it is compared with standard samples.

Calibration: In preparing an analytical program to measure unknown

concentration trough XRF it is necessary to make a series of standard

samples with known concentrations for all the elements to be measured

.These samples are called calibration samples. Calibration samples are

grouped by matrices. The name of the matrices represents the link with a


calibration is a process to relate measured element intensities of

concentration.

Procedure:

For a particular analytical program minimum 6 samples of the same

matrix and different range of element are to be selected and analysed

trough conventional method of chemical analysis.

The samples are to be pelletized as per WI No CFQA0308.

Intensity is measured for the programmed element.

These intensity are stored in computer under selected analytical

program.

Element wise chemical analysis data (concentration) of different

samples are also stored for that particular analytical program.

The computer plots calibration curve for each of the element for the

particular analytical program.

When an unknown samples is excited with X ray radiation it emits the

fluorescence radiations with characteristic wavelength of each

elements. The intensity of those fluorescence radiation of each

element are

measured and

compared with

that of the

standard

samples from

the calibration

curve to

calculate the

corresponding

concentration.

Calibration Curve


X-ray powder diffraction (XRD) is a rapid analytical technique primarily

used for phase identification of a crystalline material and can provide

information on unit cell dimensions. The analysed material is finely ground,

homogenized, and average bulk composition is determined.

Principle: Max von Laue, in 1912, discovered that crystalline substances

act as three-dimensional diffraction

gratings for X-ray wavelengths similar

to the spacing of planes in a crystal

lattice. X-ray diffraction is now a

common technique for the study of

crystal structures and atomic spacing.

X-ray diffraction is based on

constructive interference of

monochromatic X-rays and a crystalline sample. These X-rays are generated

by a cathode ray tube, filtered to produce monochromatic radiation,

collimated to concentrate, and directed toward the sample. The interaction

of the incident rays with the sample produces constructive interference

(and a diffracted ray) when conditions satisfy Bragg's Law (nλ=2d sin θ).

This law relates the wavelength of electromagnetic radiation to the

diffraction angle and the lattice spacing in a crystalline sample. These

diffracted X-rays are then detected, processed and counted. By scanning the

sample through a range of 2θ angles, all possible diffraction directions of

the lattice should be attained due to the random orientation of the

powdered material. Conversion of the diffraction peaks to d-spacings

allows identification of the mineral because each mineral has a set of

unique d-spacings. Typically, this is achieved by comparison of d-spacings

with standard reference patterns.

All diffraction methods are based on generation of X-rays in an X-ray tube.

These X-rays are directed at the sample, and the diffracted rays are

collected. A key component of all diffraction is the angle between the

incident and diffracted rays. Powder and single crystal diffraction vary in

instrumentation beyond this.


Applications:

XRD is used for phase identification of cement clinker. Difficulty in cement

identification results in large peak overlap but also in large polymorphs

coexistence. Indeed, C3S exists in 3 different forms: Monoclinic, Triclinic

and Rhomboedric. C2S can also exist in 3 different polymorphs: α, β and γ.

However, C2S beta is the most used and expected due to its reactivity; it is

the most common in cement. α shows a slower reactivity and γ does not

react. C3A is also well known to have two possible polymorphs in cement

like cubic or orthorhombic phases. Moreover, more to the polymorph

coexistence, some trace phases are present (lime, portlandite, periclase…)

and some additives are added in cement to improve final properties.

Gypsum is one of them and will control the milling dehydration process;

this phase is often accompanied with bassanite, anhydrite and hemi

hydrate phases.

Phase identification takes place in three steps: background subtraction is

the first one and it is always required in this kind of material, then a peak

finder procedure has to be performed and finally a search/match can be

processed quickly. For a more efficient search/match, a cement database

can be created with the software.

Scan of calcium aluminate cement during hydration process Peak intensity variation during hydration


A valuable, simple, very handy, inexpensive, low maintenance cost quality

control tool for quality evaluation of clinker, limestone, kiln feed,

aggregates and slag.

Common Morphological features of clinker phases .


Optical Properties of Clinker Phases.

Sl.no Clinker Phase

Colour Shape Microstructure

1. ALITE-C3S (3CaO,SiO2)

STRAW YELLOW, BROWN, YELLOWISH BROWN, BROWNISH YELLOW

HEXAGONAL, PSEUDO- HEXAGONAL, LATH, SUBHEDRAL, ANHEDRAL ETC.

FUSED GRAINS, STRETCHED, TWINNED, GRANULATED, BROKEN OUT LINE GRAIN

2. BELITE-C2S (2CaO,SiO2)

BLUE, BLUISH YELLOW YELLOWISH BLUE,GREENISH YELLOW, YELLOWISH GREEN

ROUNDED SUB ROUNDED ELLIPTICAL, SUBHEDRAL, ANHEDRAL ETC.

CLUSTERS OF VARIOUS SIZE, FUSED GRAINS, TWINNED GRAINS, CORRODED GRAIN MARGINS, STRIATIONS ON BELITE GRIN SURFACES, AS INCLUSION.

3. FREE LIME -CaO

MULITPLE HIGH ORDER INTERFERENCE COLOURS OF PINK, GREEN, YELLOW, BLUE ETC.

ROUNDED, SUB- ROUNDED, SUBHEDRAL, ANHEDRTAL ETC.

CLUSTERS, STRIATIONS ON THE GRAIN SURFACES, AS INCLUSIONS


Pictures of different forms:

By using this microscopic technique both qualitatively and quantitatively

we can measure the phases and composition in clinker and cement in

different forms.

A photoelectric flame photometer is a device used in inorganic

chemical analysis to determine the concentration of certain metal ions,

among them sodium, potassium, lithium, and calcium. Group 1 and Group

2 metals are quite sensitive to Flame Photometry due to their low excitation

energies.

Alite Balite

Free Lime


In principle, it is a controlled flame test with the intensity of the flame

colour quantified by photoelectric

circuitry. Flame photometry is

concerned with the emission of

characteristic radiation in flame and

correlation of emission intensity with

the concentration of the solution. When

a liquid sample containing a metallic

salt solution is introduced in the flame,

the solvent get vaporized leaving

particles of the solid salt. The atoms are

ionised and get thermally excited and go

to the higher energy state, when they come into lower energy state these

atom release same amount of energy. If E1 and E2 represent the higher and

lower energy state respectively then the radiation emitted during the

transition may be defined as the following equation E1-E2=hγ. So the

intensity of the colour will depend on the energy that had been absorbed

by the atoms that was sufficient to vaporise them. The sample is introduced

to the flame at a constant rate. Filters select which colours the photometer

detects and exclude the influence of other ions. Before use, the device

requires calibration with a series of standard solutions of the ion to be

tested.

From this flame photometry chemical composition in of unknown cement

sample, raw materials can be determined through calibration plot with

respect to the intensity of standard solution.

Instrumentation:-

Generally the flame photometer has six parts

i. Pressure Regulator

ii. Atomizers

iii. Burner

iv. Optical System

v. Photosensitive Detector

vi. Instrument for recording the output of the detector.


Procedure:-

1. Turn on the flame photometer and adjust the air pressure to 0.5

Kg/cm2.Adjust the fuel and light of the burner to get a clear conical

flame.

2. Rinse the atomiser with distilled water for half an hour.

3. Select the filter what you want to determine like Na2O, K2O etc.

4. Aspirate the reagent blank solution and set the digital reading at 0.

5. Aspirate the 10 ppm solution and adjust the digital reading at 100.

6. Readjust the zero with blank.

7. Aspirate the 1,2,4,6,8,10 ppm solution and note the reading.

8. Draw the calibration curve of ppm vs digital reading.

9. Now the ppm of the unknown samples are estimated by using the

following formula. PPM= Concentration in ppm * Volume in ml *Dilution Factor *100

Weight of the samples * 106

Laboratory Tests. Although various methods are available for the

quantitative estimation of the different composition in cement, clinker,

raw materials. But in India the estimation is done by following “IS-4032-

1985” procedure of Bureau of Indian Standards.

Conventional chemical analysis is done mainly on two methods –

1. Gravimetric Method.

2. Volumetric and Complexmetric Method.

1. Gravimetric Method. It is the process of sequential & weighting an

element or definite compound of the element in as pure form as

possible. The compound is precipitated filtered and then ignited t give

the most suitable form of the element for weighting.

2. Volumetric and Complexmetric Method: It is quantitative chemical

quantitative chemical analysis by measure consists essentially in

determining the volume of the solution of accurately known

concentration which required to react quantitatively with the

substrate being determined.

In Complexmetric method the metals react with the

indicator and gives a colour at a controlled pH. The volume of the


polydentate ligand complexes with the metal cation realising the

indicator. Which gives a different colour.

Chemical analysis is done mainly to determine the following things.

% of LOI (Loss on Ignition).

% of Fe2O3.

% of CaO.

% of SiO2.

% of MgO.

% of SO3.

% of Na2O

% of K2O.

% of LOI (Loss on Ignition): Loss on ignition is determined by taking a

known weight of sample approx. 1.0 gm accurately weighted in a

platinum crucible and heated in a Muffle Furnace for 15-20 min in a

temperature range of 1000-1200 o C. Then the sample is cooled in

desiccator and the weight of the sample taken. Repeat the procedure till

the constant weight observed.

Loss on ignition = (W1-W2)*100

W

W1= Weight of the sample + Weight of the crucible.

W2= Weight of the empty crucible.

W = Weight of the sample taken.

% of Fe2O3

Procedure for determination of Fe2O3 by K2Cr2O7 in Clinker, Cement and

Gypsum:


1. 1 gm of sample is weighted accurately and taken in 400 ml Beaker

and dissolved in concentrated HCl and around 100 ml of distilled

water and transfer in 500 ml conical flask.

2. The solution is boiled with some porcelain chips.

3. Fe 3+ is reduced to Fe 2+ by adding SnCl2 drop wise till the solution

become colourless.

Rxn: Sn2+ - 2e Sn4+

2Fe3++2e 2 Fe2+

4. The flask is cooled rapidly to room temperature and 20-25 ml

Mercuric Chloride is added followed by sulphuric Orthophosphoric

acid into the solution.

5. 3-4 drops of Barium Di-phenyl amino sulphonate indicator is added

and titrate against (N/16) K2Cr2O7 solution till a stable violet –blue

end point appears.

6. % of Fe2O3 = ( Consumption of K2Cr2O7)/2

Procedure for determination of Fe2O3 by K2Cr2O7 in LIMESTONE, Additives

and other than MORRUM and Raw Meal.

1. Weight accurately 1 gm of sample in a platinum crucible

2. Add around 8-10 gm of fusion mixture in it and fuse it in a muffle

furnace at 950 C for 15-20 min.

3. Extract the sample with 1 N of 100 ml of 1:1 HCl.

4. Add 5-6 of Bromine water to the solution and keep it on heater till

complete evaporation of the Bromine Water.

5. Remove the solution from the heater and around 10 gm of solid

Ammonium chloride and dissolve it by stirring with a glass rod.

6. Add ammonium hydroxide drop wise to the solution till complete

precipitation.

7. Warm the solution on the heater and filter through 541 whatmann

filter paper.

8. Wash the residue with hot distilled water.

9. Transfer the residue in a 500 ml conical flask and dissolve in

concentrated HCl.

7. The solution is boiled with some porcelain chips.


8. Fe 3+ is reduced to Fe 2+ by adding SnCl2 drop wise till the solution

become colourless.

Rxn: Sn2+ - 2e Sn4+

2Fe3+ + 2e 2 Fe2+

10. The flask is cooled rapidly to room temperature and 20-25 ml

Mercuric Chloride is added followed by sulphuric Orthophosphoric

acid into the solution

11. 3-4 drops of Barium Di-phenyl amino sulphonate indicator is

added and titrate against (N/16) K2Cr2O7 solution till a stable violet

–blue end point appears.

12. % of Fe2O3 = ( Consumption of K2Cr2O7)/2

13. % of Fe2O3 = ( Consumption of K2Cr2O7)*2.5 (for Morrum)

Calculation:

Molar Weight of Fe2O3 = (55.847*2) +48 = 159.694

Molar weight of K2Cr2O7 = (39.0983*2) + (51.996*2)+16*7=294.1886

1 N K2Cr2O7 = (294.1886/6)=49.03 gm

1 N K2Cr2O7 = 159.694/2=79.847 gm Fe2O3

1 ml of 1 N K2Cr2O7 =0.07985 gm of Fe2O3

For 0.5 gm sample if we want to recg. a factor of 1 the normality of the

K2Cr2O7 solution will be –

F= Normality of K2Cr2O7 *0.07985*100/0.5

Normality = (1*0.5)/(0.07985*100)=0.62617N=(N/16)

% of CaO: Procedure for determination of CaO by KMnO4 for GYPSUM, CLINKER,

and CEMENT:

1. 0.5 gm of sample is weight and take in 500 ml beaker.

2. Dissolve it with concentrated HCl and some distilled water is added to

make the solution.

3. One two drop of methyl orange is add and heat.

4. Reduce the colour of the solution by drop wise addition of ammonium

hydroxide of yellow colour.


5. Again add oxalic acid and bring the colour to red.

6. Add 50 ml of ammonium oxalate to the boiled solution.

7. Cool down to 50-60 C then filter with whatmann 41 and wash the

residue with distilled water.

8. Titrate against 0.18 N KMnO4 solution.

9. % of CaO= Consumption of KMnO4*factor.

Preparation and standardisation of KMnO4 Solution and determination of

Factor.

1. Dissolve 5.6 gm of KMnO4 per litre distilled water and mix it properly.

2. Standardise the solution by taking 0.67 gm of sodium oxalate and

dissolving it 10 ml 1:1 H2SO4 mixed with 10 ml of hot distilled water.

Then titrate against the prepared KMnO4 soln. Let’s the consumption

be X ml Factor = (Consumption of KMnO4 soln)/56.

Procedure for determination of CaO by KMnO4 for LIMESTONE, CLAY,

SHALE, MORRUM, RAW MEAL AND COAL ASH:

1. Weight accurately 1 gm of sample in a platinum crucible.

2. Add around 10-15gm of fusion mixture and heated in a muffle

furnace at 900 C for 15 minutes.

3. Extract the sample with 1 N of 100 ml of 1:1 HCl.

4. Add 5-6 of Bromine water to the solution and keep it on heater till

complete evaporation of the Bromine Water.

5. Remove the solution from heater and add 10 gm of Ammonium

chloride added and dissolve it by stirring it by glass rod.

6. Add Ammonium hydroxide drop wise until precipitation.

7. Warm the solution on heater and filter it through whatmann 541

filter paper.

8. Collect the filtrate in 600 ml beaker and wash the residue by hot

distilled water for two three times.

9. Boil the filtrate and add boil Ammonium Oxalate about 80 ml and

further boil it.

10. Cool the solution and allow the precipitate to settle down.

11. Filter the solution through double 41 filter paper and wash the

precipitate by distilled water.


12. Take out the precipitate along with the filter paper and dissolve

it by 15 ml 1:1 H2SO4 along with 15 ml of distilled water.

13. Titrate against 0.18 N of KMnO4

14. % of CaO = (Consumption of KMMnO4 solution/2)* Factor.

15. The factor is determined as per the method described earlier.

% of SiO2

1. SiO2(Silicon dioxide)

Silica is one of the major constituents of the raw materials required for

cement. It is usually analysed by volumetric method. The soluble silicates

e.g. Clinker and cement are decomposed by HCl, The insoluble silicates like

clay and pozzolanic materials, raw mix are made soluble by treating with

fusion mixture. This is followed by double evaporation to convert silicon

dioxide to insoluble form. The solution is filtered and the insoluble silica in

residue is ignited and weighted. Silicon dioxide is volatilized in the form of

silicon tetra fluoride by hydrofluoric acid in presence of sulphuric acid. The

loss of weight is reported as pure SiO2.

The reaction involved are following-

MSiO3+2HCl=MCl2+H2SiO3 m= Silicic Acid

2MSiO3 + Na2O3+K2CO3 = 2MCO3 + Na2SiO3 + K2SiO3

Insoluble silicate Fusion Mixture

MCO3+ Na2SiO3+K2SiO3+6HCl = MCl2+2NaCl+2KCl+CO2 +2H2SiO3+H2O

H2SiO3+H2O=H2SiO4 H2SiO4 +nH2O= H2SiO4, nH2O

SiO2 + Impurities +4HF=SiF4 + 2H2O

3 SiF4+ 3H2O= H2SiO3 + 2 H2SiF6

Silicic Acid Hydrofluoro Silicic Acid

1.1 Transfer 0.5 g of the sample to an evaporating dish, moisten with 10

ml of distilled water at room temperature to prevent lumping, add 5 to 10

ml of hydrochloric acid, and digest with the aid of gentle heat and agitation

until the sample is completely dissolved. Dissolution may be aided by light

pressure with the flattened end of a glass rod. Evaporate the solution to


dryness on a steam-bath. Without heating the residue any further treat it

with 5 to 10 ml of hydrochloric acid and then with an equal amount of

water, or pour at once upon the residue 10 to 20 ml of hydrochloric acid

(1 : 1). Then cover the dish and digest for 10 minutes on the water-

bath or hot-plate. Dilute the solution with an equal volume of hot water,

immediately filter through an ash less filter paper (Whatman No. 40 or its

equivalent), and wash the separated silica (SiO2) thoroughly with hot

water and reserve the residue.

1.2 Again evaporate the filtrate to dryness, baking the residue in an oven

for one hour at 105 to 110°C. Then treat the residue with 10 to 15 ml of

hydrochloric acid (1:1) and heat the solution on water-bath or hot-plate.

Dilute the solution with an equal volume of hot water catch and wash the

small amount of silica it contains on another filter paper. Reserve the

filtrate and washings for the determination of combined alumina and ferric

oxide.

1.3 Transfer the papers containing the residues to a weighed platinum

crucible. Dry and ignite the papers, first at a low heat until the carbon of

the filter paper is completely consumed without inflaming, and finally at 1

100 to 1 200°C until the weight remains constant.

1.4 Treat the ignited residue thus obtained, which will contain small

amounts of impurities, with 1 to 2 ml of distilled water, about 10 ml of

hydrofluoric acid and 2 drops of sulphuric acid and evaporate cautiously to

dryness. Finally heat the small residue at 1050 to 1100°C for a minute or

two; cool and weigh. The difference between this weight and the weight of

ignited sample represents the amounts of silica:

Silica percent = 200 (W1 - W2)

Where W1 = weight of silica + (insoluble impurities - residue), and W2 =

weight of impurities.

1.4.1 To this amount of silica, add the amount of silica recovered from

the residue derived from the combined precipitates of alumina

and ferric oxide as indicated under 1.5


So the total percentage of silica will be = (W1-W2) +W3 ×100

W4

Where W1= Weight of the silica and insoluble impurities

W2= Weight of the crucible after hydrofluorization

W3=Weight of the silica recovered from iron and aluminium oxide

W4=Weight of the sample taken.

1.5 Add 0.5 g of sodium or potassium persulphate to the crucible and heat

below red heat until the small residue of impurities is dissolved in the melt.

Cool, dissolve the fused mass in water, and add it to the filtrate and

washings reserved for the determination of the combined alumina and

ferric oxide.

% of Fe2O3, Al2O3, CaO and MgO(Gravimetric & EDTA)

2. Fe2O3 (Iron Oxide)

2.1 Method 1 (Potassium Permanganate Method) — To one gram of the

sample, add 40 ml of cold water and, while the mixture is being stirred

vigorously, add 15 ml of hydrochloric acid. If necessary, heat the solution

and grind the cement with the flattened end of a glass rod until it is evident

that the cement is digested fully. Heat the solution to boiling and treat it

with stannous chloride solution added drop by drop while stirring, until

the solution is decolourized. Add a few drops of stannous chloride solution

in excess and cool the solution to room temperature. Rinse the inside

of the vessel with water, and add 15 ml of a saturated solution of mercuric

chloride in one lot. Stir, add 25 ml of manganese sulphate solution and

titrate with standard solution of potassium permanganate until the

permanent pink colour is obtained. Calculate iron as ferric oxide.

2.2 Method 2 (EDTA Method) Prepare filtrate as given in 1.2 and 1.5. Mix

the filtrates and make up the volume in a 250-ml volumetric flask.

2.2.1 Take 25 ml of solution reserved in 2.2 and add dilute ammonium

hydroxide (1 : 6) till turbidity appears. Clear the turbidity with a minimum

amount of dilute hydrochloric acid (1:10) and add a few drops in excess to

adjust the pH to approximately 1 to 1.5. Shake well. Then add 100 mg of


sulphosalicylic acid and titrate with 0.01 M EDTA solution carefully to a

colourless or pale yellow solution.

2.2.2 Calculation — Calculate the percentage of Fe2O3 as below:

1 ml of 0.01 M EDTA ≡ 0.7985 mg of Fe2O3

Iron oxide (Fe2O3) percent = (.7985*V)/W

Where V = Volume of EDTA used in ml, and W = Weight of the sample in g.

3. Alumina (Al2O3)

3.1 Method 1 (Gravimetric Method) — Subtract the calculated weight of

ferric oxide and small amount of silica from the total weight of oxides found

under 4.4.3. The remainder is the weight of alumina and small amounts of

other oxides which are to be reported as alumina.

3.2 Method 2 (EDTA Method) — Take 25 ml of solution reserved under 2.2

and titrate iron at pH approximately 1 to 1.5 with EDTA using

sulphosalicylic acid as indicator. Add 15 ml standard EDTA solution. Add 1

ml of phosphoric acid (1 : 3), 5 ml of sulphuric acid (1 : 3) and one drop of

thymol blue into the titration flask. Add ammonium acetate solution by

stirring until the colour changes from red to yellow. Add 25 ml of

ammonium acetate in excess to obtain pH approximately 6. Heat the

solution to boiling for one minute and then cool. Add 50 mg of solid xylenol

orange indicator and bismuth nitrate solution slowly with stirring until the

colour of the solution changes from yellow to red. Add 2 to 3 ml of bismuth

nitrate solution in excess. Titrate with 0.01 M EDTA solution to a sharp

yellow end point red colour.

4.6.2.1 Calculation — Calculate the percentage of Al2O3 as below:

V = V1 - V2 - (V3 × E)

Where V= Volume of EDTA for alumina in ml, V1=Total volume of EDTA used

in the titration in ml, V2 = Volume of EDTA used for iron in ml, V3= Total

volume of bismuth nitrate solution used in the titration in ml, and E=

Equivalence of 1 ml of bismuth nitrate solution.

1 ml of 0.01 M EDTA ≡0.5098 mg of Al2O3


Aluminium oxide (Al2O3) percent = (0.5098*V)/W

Where W = Weight of the sample in g.

NOTE — Equivalence of bismuth nitrate solution is obtained as follows:

Transfer 100 ml of bismuth nitrate solution to a 500-ml flask and dilute

with about 100 ml distilled water. Add a few drops of thymol blue solution

and ammonium acetate solution until the colour changes from red to

yellow. Add 50 mg of xylenol orange indicator and titrate with 0.01 M EDTA

solution until the colour changes from red to yellow. The equivalence (ml

of EDTA) of 1 ml of bismuth nitrate solution is calculated as follows:

E = -----

100 Where V4 = Volume of EDTA solution in ml.

4. CaO (Calcium Oxide):

Method 1 (Gravimetric Method) — Acidify the combined filtrates set aside

under 2.2 with hydrochloric acid and evaporate them to a volume of about

100 ml. Add 40 ml of saturated bromine water to the hot solution and

immediately add ammonium hydroxide until the solution is distinctly

alkaline. Boil the solution for 5 minutes or more, making certain that the

solution is at all times distinctly alkaline. Allow the precipitate to settle;

filter and wash with hot water. Wash the beaker and filter once with nitric

acid (1.33) that has been previously boiled to expel nitrous acid, and finally

with hot water. Discard any precipitate (of manganese dioxide) that may

be left on the funnel. Acidify the filtrate with hydrochloric acid and boil

until all the bromine is expelled. Add 5 ml of hydrochloric acid, dilute to

200 ml, add a few drops of methyl red indicator and 30 ml of warm

ammonium oxalate solution. Heat the solution to 70 to 80°C and add

the ammonium hydroxide (1 : 1) dropwise, while stirring, until the colour

changes from red to yellow. Allow the calcium oxalate precipitate to stand

without further heating for one hour, with occasional stirring during the

first 30 minutes; filter through Whatmann filter paper No. 42 or equivalent,

and wash moderately with cold 0.1 percent ammonium oxalate solution.

Set aside the filtrate and washings for estimating magnesia.


4.1 Dry the precipitate in a weighed, covered platinum crucible, char the

paper without inflaming, burn the carbon at as low temperature as

possible, and finally heat with the crucible tightly covered in an electric

furnace or over a blast lamp at a temperature of 1100 to 1 200°C. Cool in a

desiccator (to guard against absorption of moisture by ignited calcium

oxide) and weigh as calcium oxide. Repeat the ignition to a constant weight.

4.2 Calculation — Calculate the percentage of CaO by multiplying the

weight in grams of 200 residue (CaO) by 200 [100 divided by the weight of

sample used (0.5 g)]

CaO percent = weight of residue × 200

4.3 Method 2 (EDTA Method) — Take 10 ml of solution reserved under 2.2

in a 250-ml concial flask. Add 5 ml of 1:1 glycerol with constant stirring and

5 ml of diethylamine. To this add 10 ml of 4N sodium hydroxide solution

and shake well to adjust pH to highly alkaline range of 12 or slightly

more. Add approximately 50 ml of distilled water and 50 mg of solid

Patton-Reeder’s indicator. Titrate against 0.01 M EDTA solution to a sharp

change in colour from wine red to clear blue.

4.4 Calculations — calculate the percentage of CaO as below:

1 ml of 0.01 M EDTA ≡ 0.5608 mg of CaO

Calcium Oxide (CaO) percent = (.05608×25×V)/W

Where V = Volume of EDTA used in ml, and W = Weight of the sample in g.

5. Magnesia (MgO)

5.1 Method 1 (Gravimetric Method) — Acidify the filtrate set aside under

4.1 with hydrochloric acid and concentrate to about 150 ml. Add to this

solution about 10 ml of ammonium hydrogen phosphate (250 g/l) and cool

the solution by placing in a beaker of ice water. After cooling, add

ammonium hydroxide drop by drop, while stirring constantly, until the

magnesium ammonium phosphate crystals begin to form, and then add the

reagent in moderate excess (5 to 10 percent of the volume of the solution),

the stirring being continued for several minutes. Set the solution aside

for at least 16 hours in a cool atmosphere and then filter, using


Whatmann No. 42 filter paper or its equivalent. Wash the precipitate with

ammonium nitrate wash solution (100 g ammonium nitrate dissolved in

water, 200 ml of ammonium hydroxide added and diluted to one litre).

Place in a weighed platinum crucible, slowly char the paper and carefully

burn off the resulting carbon. Ignite the precipitate at 1100 to 1200°C to

constant weight taking care to avoid bringing the pyrophosphate to

melting. The product of the weight of magnesia (MgO), pyrophosphate

obtained and a factor, 0.3621, shall be the magnesium content of the

material tested.

5.1.1 Calculation — Calculate the percentage of MgO as below:

MgO percent = W × 72.4

5.2 Method 2 ( EDTA Method) — Take 10 ml of solution reserved under

2.2 Add 5 ml of 1:1 triethanolamine with constant shaking and 20 ml of

buffer solution pH 10. Add 50 mg of the solid thymol phthalexone indicator

followed by approximately 50 ml of distilled water. Titrate it against

standard 0.01 M EDTA solution until the colour changes from blue to clear

pink. This titration gives the sum of calcium and magnesium oxide present

in the solution. Titre value of magnesium oxide is obtained by subtracting

the titre value of calcium oxide from the total titre value.

5.2.1 Calculations — Calculate the percentage of MgO as given below:

1 ml of 0.01 M EDTA ≡ 0.4032 mg of MgO

Magnesium oxide (MgO) percent =0.04032 × 25 × (V1-V2)/W

Where V1= Volume of EDTA used in this titration in ml, V=Volume of EDTA

used in CaO determination in ml, and W=Weight of the sample in g.

% of SO3

6. Sulphuric Anhydride — To one gram of the sample, add 25 ml of cold

water, and while the mixture is stirred vigorously add 5 ml of hydrochloric

acid. If necessary, heat the solution and grind the material with flattened

end of a glass rod until it is evident that the decomposition of the cement

is complete. Dilute the solution to 50 ml and digest for 15 minutes at a

temperature just below boiling. Filter and wash the residue thoroughly


with hot water. Set aside the filter paper with the residue. Dilute the filtrate

to 250 ml and heat to boiling.

Add slowly drop by drop, 10 ml of hot barium chloride (100 g/l) solution

and continue the boiling until the precipitate is well formed. Digest the

solution on a steam-bath for 4 hours or preferably overnight. Filter the

precipitate through a Whatmann No. 42 filter paper or equivalent and wash

the precipitate thoroughly. Place the filter paper and the contents in a

weighed platinum or porcelain crucible and slowly incinerate the paper

without inflaming. Then ignite at 800 to 900°C, cool in a desiccator and

weigh the barium sulphate obtained, calculate the sulphuric anhydride

content of the material taken for the test.

6.1 Calculation — Calculate the percentage of SO3 as follows:

SO3 percent = W × 34.3

Where W= weight of residue (BaSO4) in g; and 34.3= molecular ratio of SO3

to BaSO4 (0.343), multiplied by 100.

Chemistry Of EDTA titration: Ethylene Diamine tetra acetic acid (EDTA)

disodium salt is a complexing agent, which form polydentate ligand with

metal cations. In presence of metallo chrome indicator usually azodyes the

metal forms metal indicator complex then reacts with EDTA and releases

another colour. The change in colour should be sufficiently large to be

observed by human eye, EDTA titration are pH sensitive. The reaction takes

place for the titration is follows-

NaOOC CH2 CH2 COONa

N-CH2-CH2-N

HOOC CH2 CH2 COOH

M+In = Metal Indicator Complex

MIn + Na2H2Y = MY-4 + 2 Na++ +2H++ + In

EDTA Free Indicator


% of Na2O & K2O

Sodium and potassium oxide are determined by flame photometry using

direct intensity principle. The Instrumentation and working principle of

Flame Photometry is discussed in previous topic.

Reagents and Materials:

i. Aluminium Solution – Dissolve 10.85 g pure aluminium foil + 1 dop of

mercury in 120 ml of concentrated nitric acid and 40 ml of 1:1

sulphuric acid, make up to 1 litre in a volumetric flask with distilled

water. This aluminium sulphate solution contains 20000 ppm Al2O3.

ii. Caesium Sulphate solution – Dissolve .41 g of caesium sulphate in

distilled water and make upto 1 litre with distilled water. This

solution contain 300 ppm (CS)2SO4.

iii. Potassium Chloride (KCl)

iv. Sodium Chloride (NaCl)

v. Nitric Acid (Con.)

Preparation of Solution:

i. Sodium Potassium oxide stock solution: Analytical dry reagent grade

of NaCl and KCl at 250 C, weight 0.1885 g of NaCl and 0.1583 g of KCl

and dissolve in water and make up to 1 litre. This will correspond to

100 ppm of Na2O and K2O.

ii. Reagent Blank Solution: Mix 2.5 ml nitric Acid, 2.5 ml of ammonium

solution and 2.5 ml caesium sulphate solution make up to 250 ml of

water.

iii. Standard solution : Dispense 1,2,4,6,8 and 10 ml of stock solution of

sodium and potassium in each 100 ml of volumetric flask marked

A,B,C,D,E and F respectively. Add 1 ml of 1:1 nitric acid, 2.5 ml of

20000 ppm Al2O3 solution and 1 ml of 30 ppm caesium sulphate

solution in each of flasks. Make up the volumes to the mark with

distilled water.

iv. Laboratory Container: All glassware shall be made of Borosilicate

glass. All polythene containers shall be made of a high density

polythene having a wall of thickness of at least on mm.

CALIBRATION:


i. Dispense 1,2,4,6,8 and 10 ml of stock solution of sodium ,potassium

oxide in each 100 ml Volumetric flask of 100 ml capacity, add 1 ml of

1:3 nitric acid, 2.5 ml of 200000 ppm Al2O3 and make up to the mark.

ii. Measure the emission intensity of 10 ppm solution in the flame and

adjust it to 100 against blank. Similarly 1,2,4,6 and 8 ppm solution will

give their emission intensities as 10, 20, 40, 60, 80 respectively.

iii. Draw a calibration graph between concentration and emission

intensities.

iv. Measure the emission intensity of cement/raw mix design and find

out the concentration of Na2O/K2O from the graph.

ESTIMATION OF Na2O & K2O:

Solution of cement.

i. Place 25±0001 g of cement sample in 150 ml beaker, wet it with a few

drops of water and add 5.0 ml of HNO3(1:3).

ii. Digest on steam bath or hot plate for 15 min breaking up any lumps of

cement remaining undispersed with a flat- end stirring rod. Dilute the

mass to 50-60 ml of distilled water.

iii. Filter through medium textured filter paper in 100 ml volumetric

flask, wash beaker and paper thoroughly with hot water. Cool contents

of flask to room temp.

iv. Add 10 ml 20000 ppm Al2O3 solution and make to mark.

v. Aspirate the solution and note the meter reading (emission intensity).

Read the concentration graph.

CALCULATION:

Na2O (100 ppm) = 0.1885 g/litre (NaCl)

K2O (100 ppm) = 0.1585 g/litre (KCl)

Na2O Concentration (ppm) from graph factor ×100×100×Dilution

Or = -----------------------------------------------------------------------------------

K2O Weight of the sample ×106


Determination of free lime in Clinker.

Procedure:

a) Weight 1 gm of ground clinker sample and transfer to 100 ml conical

flask.

b) Add 20-25 ml of Ethylene Glycol and 2 gm of washed and dried coarse

ennore sand.

c) Shake the contents wall.

d) Put the flask having a cork with a vertical glass tube on a hot plate/

water bath/sand bath at 60-70 C for approximately 1 hour.

e) Filter the contents under suction to a 500 ml Erlenmeyer flask using

whatmann filter paper 40.

f) Wash the residue twice with addition of 5 ml of Ethylene Glycol at each

time.

g) Titrate against N/10 HCl using Bromothymol Blue Indicator till the

colour changes from blue to straw yellow.

Calculation:

% of free CaO=0.28*Volume of N/10 HCl consumed in titration.


Physical Analysis (Various Technique used for analysis and

their principle of operation):

Physical tests are done in cement for the determination of strength and

other physical properties like surface area, fineness, expansion etc. These

tests are essential for the maintaining the proper quality of cement.

The Following tests of physical properties are done mainly-

Normal Consistency (NC).

Setting time (final and initial).

Fineness determination by Blane Apparatus.

Soundness.

Compressive Strength.

Now let us discus about the procedure for determining the above

properties.

Normal Consistency (NC).

Consistency refers to the relative mobility of a freshly mixed cement paste

or mortar or its ability to flow. Normal Consistency of a cement is defined

as the percentage of water required to make a cement paste of standard

consistency which allows the Vicat Plunger a penetration of 5-7 mm from

the bottom of Vicat mould.

Experimental Conditions: The standard experimental conditions according

to the BIS procedure IS-4031 is , The temperature of the experimental room

should be 27±2 oC and the relative humidity of that room

should be maintained at 65±5 %.

Apparatus: The Normal consistency of the cement is

measured by Vicat Apparatus conforming IS-5513-1976.

Procedure: The standard consistency of a cement paste is

defined as the consistency which will permit the Vicat

Plunger to penetrate through it to a point of 5-7 mm from Vicat Apparatus with plunger


the bottom of the Vicat mould when the cement paste is tested.

A cement paste is prepared by a weighted quantity of cement and a

weighted quantity of portable or distilled water within the Gauging time

period 3-5 min with the circular gap of 50-70mm. Gauzing time is

calculated from the time of addition of water into the cement. The Vicat

mould is filled with the cement paste and the mould is rested on a non-

porous plate. After complete filling smoothen of the surface is done and a

level is made on the top. The mould is slightly shaken to expel the air.

Place the test block in the mould together with the non-porous plate

under the rod bearing the plunger. Lower the plunger gently touch to the

surface and quickly release it to sink into the paste.

The procedure is repeated with trial paste of varying percentage of

water until the amount of water necessary for the standard consistency.

Calculation: Normal Consistency = (Amount of Water used / Amount of

cement sample taken) *100

Setting Time of Cement.

The term is used to describe the stiffening tendency of cement paste.

Setting time is the time when cement paste starts setting and hardening.

By measuring the setting time we can determine the use of cement in

specific purpose. Initial setting time is the time from the instant at which

water is added to the cement until the paste ceases to be fluid and plastic

which corresponds to the time at which The Vicat initial

set needle fails to pierce to the block beyond 5+/-0.5 mm

measured from the bottom of the special mould. Final

setting time is the time required for the paste to acquire

certain degree of hardness. This corresponds to the time

at which the Vicat final set needle makes an impression on

the paste surface but the cutting edge fails to do so.

Gypsum in the cement regulates the setting time although

it is affected by cement fineness, w/c ratio, and

admixtures. Vicat Apparatus


Experimental Conditions: The temperature of moulding room, dry

materials and water shall be maintained at 27 ± 2°C. The relative

humidity of the laboratory shall be greater than 65 percent.

Apparatus: The setting time of the cement is measured by Vicat Apparatus

conforming IS-5513-1976.

Procedure:

Preparation of Test Block - A neat cement paste is prepared by gauging

the cement with 0.85 times the water required to give a paste of standard

consistency. Potable or distilled water shall be used in preparing the paste.

The paste shall be gauged in the manner and under the conditions

prescribed in IS: 4031 (Part 4)-1988. Stopwatch is started at the instant

when water is added to the cement. The Vicat mould is filled with a cement

paste gauged as above, the mould resting on a nonporous plate. Fill the

mould completely and smooth off the surface of the paste making it level

with the top of the mould. The cement block thus prepared in the mould is

the test block. Immediately after moulding, place the test block in the moist

closet or moist room and allow it to remain.

Determination of Initial Setting Time: Placed

the test block confined in the mould and resting

on the non-porous plate, under the rod bearing

the needle, lower the needle gently until it comes

in contact with the surface of the test block and

it is quickly released allowing it to penetrate into

the test block. In the beginning, the needle will

completely pierce the test block. This procedure is

repeated until the needle, when brought in contact

with the test block and released as described

above, fails to pierce the block beyond 5.0 ± 0.5 mm

measured from the bottom of the mould. The period

elapsing between the time when water is added to

the cement and the time at which the needle fails to

Initial and final needle of Vicat Apparatus


pierce the test block to a point 5.0 ± 0.5 mm measured from the bottom

of the mould is the initial setting time.

Determination of Final Setting Time: The previous needle of the Vicat

apparatus is replaced by the needle with an annular attachment. The

cement shall be considered as finally set when, upon applying the needle

gently to the surface of the test block, the needle makes an impression

thereon, while the attachment fails to do so. The period elapsing between

the time when water is added to the cement and the time at which the

needle makes an impression on the surface of test block while the

attachment fails to do so shall be the final setting time. In the event of

a scum forming on the surface of the test block, use the underside of the

block for the determination.

Fineness of Cement.

Fineness is the property which allow us more surface area more reacting

sites and better reactivity during hydration reaction. Fineness also effects

the heat released during hydration and it also accelerates the strength

development principally during first seven days. Determination of fineness

is done by BLAINE AIR PERMIEABILITY method.

Experimental Conditions: The standard experimental conditions

according to the BIS procedure IS-4031 is , The temperature

of the experimental room should be 27+- 2 oC and the relative

humidity of that room should not be exceeding 65% .

Apparatus: The setting time of the cement is measured by

Variable flow type air Permeability method (Blaine Type)

according to IS-5516.

Procedure:

The samples is weighted as per weight determined formula following

W= pV(1-e) W= Gram of sample required. p= Density of the sample

V=Bulk Volume of the bed of cement. e= Desired porosity of the bed of

cement which is generally 0.5


The weighted sample is transferred to the cell over a metal disc

covered with a whatmann 40 filter paper of same size and one same

size filter paper is placed at the top of the cement inside the cell.

Plunger is inserted inside the cell gently and pressed with moderate

pressure with plum to form a bed.

The plunger is removed from the cell and fitted in the cell on the

rubber cork over the manometer tube firmly.

The liquid level is raised in the manometer U tube by sucking the air

and operating the two way stopcock.

Suction of the liquid is stopped while reaching the 1st mark in the

manometer.

Switch on the timer, when lower meniscus of the liquid touches the

2nd mark of the meniscus and switch it off when the lower meniscus

of the liquid touches the 3rd mark of the manometer.

Time is noted down taken by the liquid to come 1st mark to 3rd mark

of the manometer.

Calculation: Specific surface area is calculated as per following formula.

S= Ss * T or S= KT where K (Factor) = Ss /Ts

Ts

S= Specific surface area in m2/Kg of the test sample.

Ss =Specific Surface area of the standard sample supplied by NCCBM for

calibrating the Apparatus.

T= Measured time interval in seconds of the manometer liquid drop of the

test sample.

Ts = Measured time interval in seconds of the manometer liquid drop of

the standard sample for calibrating the apparatus.

Soundness of cement.

Soundness refers to the ability of a hardened cement paste to retain its

volume after setting without delayed destructive expansion. Unsoundness


of cement is due to presence of excessive amount of hard-burned free lime

or magnesia.



humidity of the laboratory shall be greater than 65 percent.

The moist room shall be maintained at 27 ± 2°C at a relative humidity not

less than 90 percent.

Apparatus: Soundness of the cement may be determined by two methods

namely La-Chatelier method and autoclave method. The apparatus for

conducting the La-Chatelier test shall be conform to IS:5514-1969.

Procedure:

La-Chatelier Method: 50 gm cement is

accurately weighted and gauge it with 0.78

times water required to give a paste of standard

consistency. The La-Chatelier mould placed on

a glass sheet and filled with cement paste

taking care to keep the edge of the mould

gently together while this operation is being

performed. The mould is covered with another piece of glass sheet and

placed a weight on it. Submerged this set into water at a temp of 27 ± 2°C

for 24 hours. After 24 hours the set is taken out and the distance between

the indicator points is measured to nearest 0.5 mm. Again submerged the

mould into boiler containing water and within 30 min the water temp is

taken to 100 C the then it kept boiling for 3 hours. Then the mould is

removed from water and allow it to cool then the distance between the

indicator points is measured. The difference between the indicator points

is expressed as the La-Chatelier expansion in mm.

Calculation: La Chatelier expansion = Y-X

Where X= Initial expansion of the mould after 24 hours water curing.

Y=Final Expansion of the mould after boiling in water.

La-Chatelier Mould


Autoclave Method: 400 gm cement is weighted

accurately and gauged it with required water to give a

paste of standard consistency. The bar mould of size

25*25 and 282 internal length with an effective gauge

length of 250 mm is filled with the paste. The paste shall

be cut off flush with the top of the mould and the surface

of the mould is smoothed with a few strokes of the

trowel. Mould is shake gently to expel the air. The

reference is adjusted to obtain an effective gauge length

of 250 mm. The specimen along with the mould is kept

in moist room for 24 hours. Then the test bar is demoulded and its length

is measured through a length comparator. After initial measurement the

specimen bar is placed in autoclave chamber with 7-10% volume of the

autoclave filled with distilled water. The temp of the autoclave shall be

raised to 215.7 ± 1.7°C at a rate to bring the gauge pressure of the steam

2.1 Mpa in 1 to 1.25 hour from the heater turned on. The temperature and

pressure shall be maintained for 3 hours. At the end of 3 hours period the

heat supply to be shut off and the auto clave is cooled at a rate such the

pressure will be less than 0.1 Mpa at the end of the hour. The autoclave is

then opened and the test specimens are to be immersed under water

having temperature more than 90 C . The specimen bar is then surface

dried and its length is measured again through the length comparator.

Calculation: Final Length – Initial length

------------------------------------ ×100

Effective Gauge length

Compressive Strength of Cement.

It is the study of strength of materials, the compressive strength is the

capacity of a materials or structure to withstand loads tending to reduce

size. It can be measured by plotting applied force against the deformation

of the testing materials in testing machine. Compressive strength is a key

value for design of structures.

Autoclave




humidity of the laboratory shall be greater than 65 percent. The moist

room shall be maintained at 27 ± 2°C at a

relative humidity not less than 90

percent.

Apparatus: The compressive strength is

measured by compressive strength

machine.

Procedure: The interior faces of the

specimen moulds is covered with oil or light

grease first. The cement slurry is placed in all

compartments of the moulds in a layer of

approximately one half of the mould depth and

puddle in an evenly distributed pattern, 27

times per specimen using a glass rod. The

remaining slurry is stirred in the mixture cup by

the glass rod and fill all the specimen compartments of the 50 mm cube

moulds to overflow and puddle the same as done for the first layer. Strike

off the excess slurry even with the top of the mould using a straightedge

and a clean dry cover plate is placed at the top. Four no of specimen moulds

is placed in one constant temperature bath maintained at a temp 38±2°C

and the other four no of specimen moulds are placed in another temp of

60±2°C for a period of 7h 15 min. The test specimen are placed in the curing

vessel within 5 min of mixing. Take out the moulds from the curing bath at

the end of requirement time period and removed the specimens from the

moulds. Transfer the specimen under a water bath maintained at a temp

27±3°C for a period of 45 min. The test specimens are removed from the

water bath at the end of requirement time period and wipe each specimen

to remove any loose materials from the faces. Then the load is applied to

the specimen faces that were in contact of the plane surface of the mould.

The rate of loading is 72±7 KN per min for the specimen expected to have

CCS

Mould For compressive strength Determination


strength greater than 3.4 Mpa and 18±2 KN per min expected to have

strength less than 3.4 Mpa.

Calculation:

The measured compressive strength of the cubes shall be calculated by

dividing the maximum load applied to the cubes during the test by the cross

sectional area of the cube. The compressive strength is expressed in Mpa

unit.

Fuel Analysis.

Fuel is a very important thing for cement industry. The heart stage of

cement manufacturing is the formation of clinker in rotary kiln. In Rotary

Kiln at about 1400 deg. Centigrade raw meal get converted into clinker and

that high temp in rotary kiln maintained by fuel combustion. Mainly in

cement industry Coal is used as a fuel for combustion although now a days

Pet Coke is blended with Coal for its up gradation of GCV value. Now let us

discuss about coal-

Introduction: Coal is the most abundant fossil fuel available on the Earth.

It can be defined as a complex heterogeneous mixture of plant substances

which are altered due to physical and chemical processes. These processes

have been taking place for several million years and have been

accomplished by bacteria, heat and pressure inside the Earth’s crust. It

primarily consists of Carbon along with Hydrogen, Oxygen, Sulphur etc. as

secondary components. Coal formation starts from the plant debris and

ends at Graphite at its highest maturity. This process may be complete or

may be stopped at any stage giving rise to coal of varying maturity thus

various Ranks.

Coal rank:

Based upon composition and properties coals are assigned to a rank

progression that corresponds to their level of organic metamorphism.


A. Peat- Peat is organic sediment. Burial, compaction and coalification will

transform it into coal, a rock. It has a carbon content of less than 60% on a

dry ash-free basis.

B. Lignite- Lignite is the lowest rank of coal. It is a peat that has been

transformed into a rock and that rock is a brown-black coal. Lignite

sometimes contains recognizable plant structures. . It has a carbon content

of between 60 and 70% on a dry ash-free basis.

C. Sub Bituminous- Sub bituminous coal is lignite that has been subjected

to an increased level of organic metamorphism. This metamorphism has

driven off some of the oxygen and hydrogen in the coal. That loss produces

coal with higher carbon content (71 to 77% on a dry ash-free basis).

D. Bituminous- Bituminous coal is formed when a sub bituminous coal is

subjected to increased levels of organic metamorphism. It has a carbon

content of between 77 and 87% on a dry ash-free basis and a heating value

that is much higher than lignite or sub bituminous coal.

E. Anthracite- Anthracite is the highest rank of coal. It has a carbon

content of over 87% on a dry ash-free basis. Anthracite coal generally has

the highest heating value per ton on a mineral matter free basis.

Parameters %

Carbon

%

volatiles

Energy (KJ/kg)

Anthracite 80 - 87 3-9 36000

Bituminous 45 -78 10-36 35000

Lignite 60-71 < 36 25000

Table-1-Composition of different rank of coal

The common coals used in Indian industry are bituminous and sub-

bituminous coal. The gradation of Indian coal based on its calorific value is

as follows:


Grade Calorific Value Range ( in kCal/kg)

Rank

A Exceeding 6200 Graphite

B 5600-6200 Anthracite

C 4940-5600 Bituminous

D 4200-4940 Lignite –Indian coal

E 3360-4200

peat F 2400-3360

G 1300-2400

Table-2-Gradation of coal


Coal is mined in over 100 countries, and on all continents except Antarctica.

The largest reserves are found in the United States, Russia, China, Australia

and India.

Table 3 Application of Various Grades of Coal

Fig.1 Global share of recoverable coal resources


There are two methods: ultimate analysis and proximate analysis.

A. The "ultimate" analysis" gives the composition of the biomass in wt%

of carbon, hydrogen and oxygen (the major components) as well as sulfur

and nitrogen (if any). The carbon determination includes that present in

the organic coal substance and any originally present as mineral carbonate.

The hydrogen determination includes that in the organic materials in coal

and in all water associated with the coal. All nitrogen determined is

assumed to be part of the organic materials in coal.

B. The "proximate" analysis gives moisture content, volatile content,

consisting of gases and vapors driven off during pyrolysis (when heated to

950 C), the fixed carbon and the ash, the inorganic residue remaining after

combustion in the sample and the high heating value (HHV) based on the

complete combustion of the sample to carbon dioxide and liquid water.

Proximate analysis is the most often used analysis for characterizing coals

in connection with their utilization.

Pet Coke is a bi product of petroleum industry. It’s having high calorific

value around 8000-9000 Cal/gm. It is also used in cement industry as a fuel

with pet coke. For pet coke also proximate analysis is done.

1. PROXIMATE ANALYSIS OF COAL AND COKE.

1.1 Preparation of Coal/Coke Sample:

Normally the coal samples contain superficially adsorbed moisture

in addition to the inherent moisture content. So before the analysis this

inherent moisture should be removed. As per IS-1350 9(1984) the coal

samples before analysis is put under equilibrated conditions i,e 40 0 C and

60 % relative humidity in a humidity cabinet for 72 hours. During this

period superficially adsorbed moisture disappeared leaving only the

inherent moisture. About 300 g of coal and coke ground to pass IS Sieve

no 20(212 micron) is stored in sealed container to be used for subsequent

analysis. The fine grinding normally to be found to ensure reasonable

agreement between repeat determination. Such coal samples are known

as “equilibrated” coal/coke sample.


1.2 Determination of moisture:

The Coal samples has a property of adsorbing or losing the

moisture. According to humidity and temperature to which it has been

exposed. The coal which has been exposed to contact with water in the

steam or washry or coal/coke wetted by rain may carry free or visible

water. Total moisture refers this water and the inherent moisture in

samples.

The Presence of moisture in coal is undesirable because more heat is

required in the furnace to evaporate the same there by reducing the

efficiency of the fuel. Moreover during transportation freight has to be

paid on the increased weight due to the presence of moisture in the coal.

This necessitates the determination of moisture in order to select proper

coal heating value.

PROCEDURE:

a) Take the weighted ground coal samples passing 212 micron IS sieve

and equilibrated at 40 C and 60% relative humidity in a petridish.

b) Place the samples in an oven maintained at a temperature 108±2 o C

for 2 hours.

c) Cool the petridish in a desiccator & weighted.

d) The loss in weight gives the percentage moisture.

e) The experiment is repeated till constant weight is attained.

Calculation:

% Moisture = Loss in weight of coal X 100

Weight of coal initially taken

1.3 Determination of Volatile matter:

The volatile matter is of particular importance is assessing the use of coal

by itself or in connection with other characteristics. The volatile matter of

coal consists of organic matter present in coal like Benzene, Antracene,

Pyridene, thiophene,etc and also combustible gases like Hydrogen, Carbon

monoxide, Methane and other saturated/unsaturated hydrocarbons.


A high content volatile matter means that a large portion of fuel will be

distilled and turned as a gas or vapour. A high volatile matter content gives

long flame while low volatile matter means short flame.

PROCEDURE:

a) Take a known weight of the equilibrated coal/coke samples inn a

platinum crucible or silica crucible made for volatile matter

estimation is covered with tight lid to ensure non oxidizing condition.

In case of coke, add 1-2 drops of benzene to ensure a non- oxidizing

condition.

b) Keep the crucible along with air tight lid in the furnace for seven min

at 900±10 o C.

c) Take out the crucible from the furnace keep in a desiccator cool and

weight.

d) Repeat the process till constant weight is attained.

e) Loss in weight gives the volatile matter

Calculation: Loss in weight

Volatile matter = × 100

Weight of sample –(%of Moisture)

Or Loss in weight of moisture free coal

= × 100

Weight of moisture free coal

1.4 Determination of Ash Content:

The inorganic residue left after coal is incinerated at 815×10 OC until it no

longer changes its weight, is known as ash content of the coal. Ash is highly

undesirable because it not only reduces the heating value of the coal but

also creates cleaning and disposal problems. Therefore low ash coal are

supposed to good quality coal as their calorific value is high.

PROCEDURE:


a) Weight accurately about one to two gm of equilibrated coal/coke

samples in a dry already weighted platinum dish/flat bottom silica

crucible.

b) Distribute the materials, so that the quality does not exceed 0.15

gm/cm2.

c) Insert the uncovered dish into the muffle furnace at room

temperature.

d) Raise the temp of the furnace to 500 OC in 30 min and to 815±10 OC in

next 30 to 60 min. Maintain this temperature for 60 min.

e) Remove the dish from the dish from the muffle furnace and allow to

cool in a desiccator and their weight.

f) Repeat the experiment until the change in mass of ash is less than

0.001 gm.

CALCULATION:

W3 - W1

Ash Content (%) = × 100

W2 - W1

Where W1= Mass of dish. W2=Mass of dish and sample. W3= Mass of dish

and ash.

1.5 Determination of Fixed Carbon:

Fixed carbon is determined by subtracting the resultant summation of

percentage of ash, moisture, volatile matter from 100. It is infact measure

of the solid combustible materials in coal after expulsion of volatile matter.

Fixed Carbon plus ash represents the approximate yield of coke from coal.

% Fixed Carbon = 100 – (moisture % + volatile matter % + ash %)


2. DETERMINATION of GCV (Gross Calorific Value).

2.1 Calorific Value: Number of heat units liberated when a unit mass of

the fuel is burnt at constant volume of oxygen saturated with water vapour,

the original material and final product

being at approximately 250C. The residual

product are taken as carbon dioxide,

Sulphur dioxide, Nitrogen and water.

The methods have been described to

determine the calorific value of coal/coke

are either by adiabatic bomb calorimeter

or ISO thermal bomb calorimeter. The

calorific value determined in these

method is the gross calorific value of

coke/coal at constant volume expressed

in calories/gm. Coal/Coke is burnt in bomb calorimeter of known heat

capacity. The principle observation is that of a temp rise, which when

corrected for error, of temperature thermometer and multiplied by

effective heat capacity at mean temperature of the chief period gives the

heat release.

2.2 Procedure: The experiment for the calorific value determination is

as given below:

a) The coal used for determination of calorific value is ground to pass

through 212 micron IS sieve. The samples is exposed in a thin layer

for minimum time necessary for the moisture content to reach the

equilibrium.

b) Weight the crucible to nearest 0.1 mg and introduce into it sufficient

quantity of sample to cause a temperature rise of 2-3 0 C. Weight the

crucible and it’s content to determine the weight of the sample.

c) Connect the piece of firing wire tightly across the terminals of the

bomb. Tie a known weight of cotton to firing wire, arrange ends of the

cotton so that these touch the sample.

d) Put 1 ml of distilled water in the bomb. Assemble and charge it slowly

with oxygen to a pressure of 3.0×106 N/m2 (30 atm.)

e) Put sufficiently water in calorimeter vessel to cover the flat upper

surface of the bomb. Start the stirring and switch on the calorimeter

Bomb Calorimeter


so that the temp of the outer and inner jacket is equal and note down

the initial temp t1.

f) Ignite the samples and note the rise temp till it stabilizers, let it be t2.

Remove the bomb calorimeter vessel, release the pressure and

dismantle the bomb.

g) Wash the contents of the bomb into a beaker with distilled water and

calculate the calorific value.

Calculation:

GCV= Heat Capacity × (t2 - t1)

Weight of the sample

Although small correction should be applied ----

1. Heat of ignition-335 Cal/gm of nickel chrome wire

2. Cotton of corrotion-4180 Cal/gm of cellulose.

3. Heat of formation of acids- The heat gain due to the formation of

sulphuric acid and nitric acid is subtracted from the total heat

released. The correction amounts to 3.6 Cal/mml of 0.1 N H2SO4

and 1.43 Cal/ml of 0.1 N HNO3.

Chemical reaction for Clinker formation starts from the Preheater. The raw meal is injected into the gas flow at the top of the cyclone stages in the preheater. In the cyclone tower, the meal is dried and the clay minerals dehydrate and decompose. In this preheating process, the meal temperature is typically increased to about 700°C, while the temperature of the counter flowing gas is reduced from about 900 to about 350°C.

In the precalciner, the meal is calcined at a temperature of about 900°C. Up to 85-90% calcination process takes place here. The solids residence time in the preheater and precalciner is about 2 minutes.

After coming at the lower cyclone stage (which is sometimes regarded as being part of the precalciner), the precalcined meal enters the rotary kiln. In the kiln, the meal is first completely calcined, then the clinker formation reactions take place. The combination of the slight inclination (typically


3°) and the revolution of the kiln cause the solid material to be transported slowly through it. Typically, the residence time in the rotary kiln is 30 minutes. After reaching at a maximum temperature of approximately 1450-1500°C, the clinker is discharged from the kiln and cooled in the clinker cooler, the residence time in the cooler being about 15 minutes. The purpose of the cooler is both to recover heat from the hot clinker and to cool the clinker to a suitable level of temperature.

In the cyclone tower, the meal is conveyed by the hot gas from one cyclone to another. In the cyclones, typically 80% of the solid phase is separated from the gas. The gas phase, containing the remaining solids, flows to the cyclone stage above. Usually, double-cyclones are used in the uppermost cyclone stage on each string, giving higher cyclone efficiency, typically 95%.

The energy required for the process in the rotary kiln is supplied by burning various types of fuel (primary fuel) in the main burner (primary burner). Today, pulverized coal and petroleum coke (pet coke) are the fuels most commonly used. However, oil and gas as well as liquid and solid waste fuels are the most commonly used fuels. The air supplied through the main burner is called primary air. With indirect firing, it contributes about 10% to the total combustion air required in the primary burning zone. The secondary air, which is preheated in the cooler to about 900°C, constituents the major part of the combustion air.

~100°C→ free water evaporates.

~150-350C°→ loosely bound water is lost from clay.

~350-650°C→decomposition of clay→SiO2&Al2O3

~600°C→decomposition of MgCO3→MgO&CO2 (evaporates)

~900°C→decomposition of CaCO3→CaO&CO2 (evaporates)

~1250-1280°C→liquid formation & start of compound formation.

~1280°C→clinkering begins.

~1400-1500°C→clinkering.

~100°C→clinker leaves the kiln & falls into a cooler.

Sometimes the burning process of raw materials is performed in two stages: preheating upto 900°C & rotary kiln.

REACTIONS IN THE KILN


The raw mix enters at the upper end of the kiln and slowly works its way

downward to the hottest area at the bottom over a period of 60-90 minutes,

undergoing several different reactions as the temperature increases. It is

important that the mix move slowly enough to allow each reaction to be

completed at the appropriate temperature. Because the initial reactions

are endothermic (energy absorbing), it is difficult to heat the mix up to a

higher temperature until a given reaction is complete.

Dehydration zone (up to ~ 450˚C): This is simply the evaporation and

removal of the free water. Even in the “dry process” there is some adsorbed

moisture in the raw mix. Although the temperatures required to do this are

not high, this requires significant time and energy. In the wet process, the

dehydration zone would require up to half the length of the kiln, while the

dry process requires a somewhat shorter distance.

Calcination zone (450˚C – 900˚C): The term calcination refers to the process

of decomposing a solid material so that one of its constituents is driven off

as a gas. At about 600˚C the bound water is driven out of the clays, and by

Kiln Feed

3800C

7500C

10000C 9000C Kiln

800C

8700C

6000C

8500C

14500C

1100C

11000C

Clinker

Cooler

Typical Calciner-Kiln System

100-3500C : Escape of Adsorbed Water

600-8000C : Decomposition of Clay,

metakaolinites & others. With formation of

reactive oxide mixture

800-1000C : Decpmposition of CaCO3, with

formation of CS,CA.

CA+ 2C => C3A

CS+ C => C2S

S + 2C => C2S

CA+ 3C + F =>C4AF

C3A

C2S + C => C3S


900˚C the calcium carbonate is decomposed, releasing carbon dioxide. By

the end of the calcination zone, the mix consists of oxides of the four main

elements which are ready to undergo further reaction into cement

minerals. Because calcination does not involve melting, the mix is still a

free-flowing powder at this point.

Rxn: CaCO3 → CaO + CO2

Clay→ SiO2 + Al2O3 + Fe2O3 + H2O

CaO + Al2O3 → CaO.Al2O3 (CA)

CaO + SiO2 = CaO. SiO2 (CS)

Solid-state reaction zone (900˚ - 1300˚C): This zone slightly overlaps, and is

sometimes included with, the calcination zone. As the temperature

continues to increase above ~ 900˚C there is still no melting, but solid-state

reactions begin to occur. CaO and reactive silica combine to form small

crystals of C2S (dicalcium silicate-Belite), one of the four main cement

minerals. In addition, intermediate calcium aluminates and calcium ferrite

compounds form. These play an important role in the clinkering process

as fluxing agents, in that they melt at a relatively low temperature of ~

1300˚C, allowing a significant increase in the rate of reaction. Without

these fluxing agents, the formation of the calcium silicate cement minerals

would be slow and difficult. In fact, the formation of fluxing agents is the

primary reason that Portland (calcium silicate) cements contain

aluminium and iron at all. The final aluminium- and iron-containing

cement minerals (C3A and C4AF) in a Portland cement contribute little to

the final properties. As the mix passes through solid-state reaction zone it

becomes “sticky” due to the tendency for adjacent particles to fuse together.

Rxn: 2CaO + SiO2 → 2CaO•SiO2 (C2S-Belite)

3CaO•Al2O3 + CaO + Fe2O3 → 4CaO•Al2O3•Fe2O3 (C4AF- Ferrite)

CaO•Al2O3 + 2CaO → 3CaO•Al2O3 (C3A-Cellite)

Clinkering zone (1300˚C – 1550˚C): This is the hottest zone where the

formation of the most important cement mineral, C3S (Alite), occurs. The

zone begins as soon as the intermediate calcium aluminate and ferrite

phases melt. The presence of the melt phase causes the mix to agglomerate


into relatively large nodules about the size of marbles consisting of many

small solid particles bound together by a thin layer of liquid. Inside the

liquid phase, C3S forms by reaction between C2S crystals and CaO. Crystals

of solid C3S grow within the liquid, while crystals of belite formed earlier

decrease in number but grow in size. The clinkering process is complete

when all of silica is in the C3S and C2S crystals and the amount of free lime

(CaO) is reduced to a minimal level (<1%).

Rxn: 2CaO•SiO2+ CaO → 3CaO•SiO2 (C3S-Alite)

Cooling zone: As the clinker moves past the bottom of the kiln the

temperature drops rapidly and the liquid phase solidifies, forming the

other two cement minerals C3A (aluminate) and C4AF (ferrite). In addition,

alkalis (primarily K) and sulphate dissolved in the liquid combine to form

K2SO4 and Na2SO4. The nodules formed in the clinkering zone are now

hard, and the resulting product is called cement clinker. The rate of cooling

from the maximum temperature down to about 1100˚C is important, with

rapid cooling giving a more reactive cement. This occurs because in this

temperature range the C3S can decompose back into C2S and CaO, among

other reasons. It is thus typical to blow air or spray water onto the clinker

to cool it more rapidly as it exits the kiln.


About 90-95% of a Portland cement is comprised of the four main cement minerals, which are C3S, C2S, C3A, and C4AF, with the remainder consisting of calcium sulphate, alkali sulphates, unreacted (free) CaO, MgO, and other minor constituents left over from the clinkering and grinding steps. The four cement minerals play very different roles in the hydration process that converts the dry cement into hardened cement paste. The C3S and the C2S contribute virtually all of the beneficial properties by generating the main hydration product, C-S-H gel. However, the C3S hydrates much more quickly than the C2S and thus is responsible for the early strength development. The C3A and C4AF minerals also hydrate, but the products that are formed contribute little to the properties of the cement paste. These minerals are present because pure calcium silicate cements would be virtually impossible to produce economically.

Bogue’s Compound Composition

• C3S=4.07(CaO)-7.6(SiO2) - 6.72(Al2O3)-1.43(Fe2O3) - 2.85(SO3)

• C2S= 2.87 (SiO2) - 0.75(3Cao. SiO2)

• C3A= 2.65(Al2O3) - 1.69 (Fe2O3)

• C4AF = 3.04 (Fe2O3)

Tricalcium Silicate (C3S): C3S is the most abundant mineral in portland cement, occupying 40–70 wt% of the cement, and it is also the most important. The hydration of C3S gives cement paste most of its strength, particularly at early times.

Pure C3S can form with three different crystal structures. At temperatures below 980˚C the equilibrium structure is triclinic. At temperatures between 980˚C – 1070˚C the structure is monoclinic, and above 1070˚C it is rhombohedral. In addition, the triclinic and monoclinic structures each have three polymorphs, so there are a total of seven possible structures. However, all of these structures are rather similar and there are no significant differences in the reactivity. The most important feature of the structure is an awkward and asymmetric packing of the calcium and oxygen ions that leaves large “holes” in the crystal lattice. Essentially, the ions do not fit together

Name Chemical formula Abbreviation 1. Tricalcium silicate 3CaO.SiO2 C3S 2. Dicalcium silicate 2CaO.SiO2 C2S 3. Tricalcium aluminate 3CaO.Al2O3 C3A 4. Tetra calcium alumina ferrite 4CaO.Al2O3.Fe2O3 C4AF


very well, causing the crystal structure to have a high internal energy. As a result, C3S is highly reactive.

The C3S that forms in a cement clinker contains about 3-4% of oxides other than CaO and SiO2. Strictly speaking, this mineral should therefore be called alite rather than C3S. However, as discussed in Section 3.2, we will avoid using mineral names in this monograph. In a typical clinker the C3S would contain about 1 wt% each of MgO, Al2O3, and Fe2O3, along with much smaller amounts of Na2O, K2O, P2O5, and SO3. These amounts can vary considerably with the composition of the raw materials used to make the cement, however. Of the three major impurities, Mg and Fe replace Ca, while Al replaces Si.

One effect of the impurities is to “stabilize” the monoclinic structure, meaning that the structural transformation from monoclinic to triclinic that would normally occur on cooling is prevented. Most cements thus contain one of the monoclinic polymorphs of C3S.

Dicalcium Silicate (C2S): As with C3S, C2S can form with a variety of different structures. There is a high temperature a structure with three polymorphs, a b structure in that is in equilibrium at intermediate temperatures, and a low temperature g structure. An important aspect of C2S is that g-C2S has a very stable crystal structure that is completely unreactive in water. Fortunately, the b structure is easily stabilized by the other oxide components of the clinker and thus the g form is never present in Portland cement. The crystal structure of b-C2S is irregular, but considerably less so than that of C3S, and this accounts for the lower reactivity of C2S. The C2S in cement contains slightly higher levels of impurities than C3S. According to Taylor, the overall substitution of oxides is 4-6%, with significant amounts of Al2O3, Fe2O3, and K2O.

Tricalcium Aluminate (C3A): Tricalcium aluminate (C3A) comprises anywhere from zero to 14% of a Portland cement. Like C3S, it is highly reactive, releasing a significant amount of exothermic heat during the early hydration period. Unfortunately, the hydration products of formed from C3A contribute little to the strength or other engineering properties of cement paste. In certain environmental conditions (i.e., the presence of sulphate ions), C3A and its products can actually harm the concrete by participating in expansive reactions that lead to stress and cracking.

Pure C3A forms only with a cubic crystal structure. The structure is characterized by Ca+2 atoms and rings of six AlO4 tetrahedra. As with C3S, the bonds are distorted from their equilibrium positions, leading to a high internal energy and thus a high reactivity. Significant amounts of CaO and the Al2O3 in the C3A structure can be replaced by other oxides, and at high levels of substitution this can lead to other crystal structures. The C3A in Portland cement clinker, which typically contains about 13% oxide substitution, is primarily cubic, with smaller amounts of orthorhombic C3A. The C3A and C4AF minerals form by simultaneous precipitation as the liquid phase formed during the clinkering process cools, and thus they are closely intermixed. This makes it difficult to ascertain the exact compositions of the two phases. The cubic form generally contains ~4% substitution of SiO2, ~5%


substitution of Fe2O3, and about 1% each of Na2O, K2O, and MgO. The orthorhombic form has similar levels, but with a greater (~5%) substitution of K2O.

Tetracalcium Aluminoferrite (C4AF): A stable compound with any composition between C2A and C2F can be formed, and the cement mineral termed C4AF is an approximation that simply the represents the midpoint of this compositional series. The crystal structure is complex, and is believed to be related to that of the mineral perovskite. The actual composition of C4AF in cement clinker is generally higher in aluminium than in iron, and there is considerable substitution of SiO2 and MgO. Taylor reports a typical composition (in normal chemical notation) to be Ca2AlFe0.6Mg0.2Si0.15Ti0.5O5. However, the composition will vary somewhat depending on the overall composition of the cement clinker.

When Portland cement is mixed with water its chemical compound constituents undergo a series of chemical reactions that cause it to harden. This chemical reaction with water is called "hydration". Each one of these reactions occur at a different time and rate. Together, the results of these reactions determine how Portland cement hardens and gains strength.

The hydration of cement can be thought of as a two-step process. In the first step, called dissolution, the cement dissolves, releasing ions into the mix water. The mix water is thus no longer pure H2O, but an aqueous solution containing a variety of ionic species, called the pore solution. The gypsum and the cement minerals C3S and C3A are all highly soluble, meaning that they dissolve quickly. Therefore the concentrations of ionic species in the pore solution increase rapidly as soon as the cement and water are combined. Eventually the concentrations increase to the point that the pore solution is supersaturated, meaning that it is energetically favourable for some of the ions to combine into new solid phases rather than remain dissolved. This second step of the hydration process is called precipitation. A key point, of course, is that these new precipitated solid phases, called hydration products, are different from the starting cement minerals. Precipitation relieves the supersaturation of the pore solution and allows dissolution of the cement minerals to continue. Thus cement hydration is a continuous process by which the cement minerals are replaced by new hydration products, with the pore solution acting as a necessary transition zone between the two solid states. The reactions between Portland cement and water have been studied for more than a hundred years, and the fact that hydration proceeds by a dissolution-precipitation process was first elaborated by the famous chemist Le Chatelier. There are two reasons that the hydration products are different from the cement minerals. One reason is that there is a new reactant in the system: water. Not only does the water facilitate the hydration process by dissolving the cement minerals, but it also contributes ions, in the form of hydroxyl groups (OH-), to the hydration products. The second reason is the tendency for all processes to approach thermodynamic equilibrium. This dictates that the solid phases that precipitate out of the pore solution are the ones that are the most stable under the current conditions. The stability of a phase is defined by a parameter called the free energy,


which can be roughly defined as the amount of chemical and thermal energy contained in the phase. The lower the free energy, the more stable the phase. The cement minerals are formed at temperatures exceeding 14000C, because they have the lowest free energy under those extreme conditions. At the much lower temperatures present during cement hydration, the cement minerals are actually quite unstable, meaning that there are many other solid phases that will form preferentially in their place once they dissolve. In fact, the whole point behind the high-temperature cement manufacturing process is to create solid phases that will readily dissolve in water, allowing new phases to form. When one phase is converted into another phase with a lower free energy, there is usually a release of excess energy in the form of heat. Such a reaction is termed exothermic, and the exothermic heat associated with cement hydration has already been defined as the heat of hydration. Figure 1-1 shows a graph of the rate of cement hydration over time, with the hydration process divided into four somewhat arbitrary stages. Information about the rate of a reaction is called kinetics, an. Here we will use the general behavior shown in Figure 1-1 to discuss the various processes that occur during hydration.

As noted above, some of the cement minerals and constituents are very soluble, and thus when cement and water are first combined there is a short period of fast reaction and heat output as the cement dissolves, lasting for less than one minute (Stage 1). Stage 1 is brief because of the rapid formation of an amorphous layer of hydration product around the cement particles, which separates them from the pore solution and prevents further rapid dissolution. This is followed by the induction period, during which almost no reaction occurs (Stage 2). The precise nature of the induction period, and in particular the reason for its end, is not fully known, or perhaps it should be stated that it is not fully agreed upon, as there are strongly held but differing opinions among cement chemists. During Stage 3, the rapid reaction period, the rate of reaction increases rapidly, reaching a maximum at a time that is usually less than 24 hours after initial mixing, and then decreases rapidly again to less than half of its maximum value. This behaviour is due almost entirely to the hydration of the C3S, and the rate of hydration is controlled by the rate at which the hydration products nucleate and grow. Both the maximum reaction rate and the time at which it occurs depend strongly on the temperature and on the average particle size of the cement. This reaction period is sometimes divided into two stages (before and after the maximum rate) but as the rate-controlling mechanism is the same throughout (nucleation and growth) it is preferable to treat this as single stage. At the end of Stage 3 about 30% of the initial cement has hydrated, and the paste has undergone both initial and final set. Stage 3 is characterized by a continuous and relatively rapid deposition of hydration products (primarily C-S-H gel and CH) into the capillary porosity, which is the space originally occupied by the mix water. This

Figure 1-1: Schematic of the rate of hydration or heat evolution as a function of time


causes a large decrease in the total pore volume and a concurrent increase in strength. The microstructure of the paste at this point consists of unreacted cores of the cement particles surrounded by a continuous layer of hydration product, which has a very fine internal porosity filled with pore solution, and larger pores called capillary pores. In order for further hydration to take place, the dissolved ions from the cement must diffuse outward and precipitate into the capillary pores, or water must diffuse inward to reach the unreacted cement cores. These diffusion processes become slower and slower as the layer of hydration product around the cement particles becomes thicker and thicker. This final period (Stage 4) is called the diffusion-limited reaction period. Figure 1-2 shows the microstructure of a cement paste at it hydrates, as simulated by a realistic digital image based model. The yellow phase is the main hydration product, C-S-H gel. At the end of Stage 3, the yellow rims if hydration product have become interconnected, causing final set and giving paste some minimal strength. By 28 days the image is dominated by C-S-H gel and the porosity has noticeably decreased. The final amount of porosity will depends strongly on the initial w/c of the paste.

The overall progress of the hydration reactions is described by the degree of hydration, , which is simply the fraction of the cement that has reacted. Complete hydration of all the cement gives = 1. The degree of hydration can be measured in a few different ways, including x-ray measurements to determine how much of the minerals remain and loss on ignition measurements to determine how much bound water the paste contains. Another common method is to sum the amount of heat given off by the paste (as measured by thermal calorimetry and divide this value by the total amount of heat given off for complete hydration. The latter value will depend on the mineral composition of the cement. Another parameter that can be used to monitor the progress of hydration is the compressive strength. This is not a precise measure, since the strength depends on many

Figure 1-2: Results of a realistic digital model of cement hydration. Phases are color coded: Black=water (pores), Red = C3S, Blue = C2S, Yellow = C-S-H gel. a) Cement particles dispersed in water just after mixing. (Stage 1). b) 30% hydration, ~ 1 day (end of Stage 3). c) 70% hydration, ~ 28 days (Stage 4). (Images courtesy of NIST).


factors other than the progress of the chemical reactions, but it is very practical since the development of strength is the primary reason for using cement and concrete in the first place. Figure 1-3 shows the degree of hydration ( ), and the strength of a Type I OPC paste plotted as a function of time on the same graph. Note that the time is plotted on a log scale. From Figure 5-3 it can be seen that the degree of hydration and the strength track together, particularly at later times. This is because the strength of cement paste depends primarily on the amount of capillary porosity, and the amount of capillary porosity decreases in proportion to the amount of hydration that has taken place. This decrease occurs because the C-S-H gel phase (including its internal gel pores) occupies significantly more volume than the cement minerals it forms from.

In Figure 5-3 alpha has reached a value of 1 (complete hydration) after one year, but this will not always be the case, as many cement pastes will never reach full hydration. Depending on why hydration terminates, incomplete hydration may or may not be a bad thing. The final degree of hydration will depend on the w/c of the paste, the cement particle size, and the curing conditions. Hydration will continue at a slow rate during Stage 4 until one of the three following criteria is met: 1) All of the cement reacts. This is the situation shown in Figure 5-3. This indicates that the paste has a moderate or high w/c and was cured correctly. While it is the best possible outcome for the given mix design, it does not guarantee high quality concrete as the w/c may have been too high. If the cement contains some large particles, full hydration of these particles may not occur for years. However this is generally not the case

Figure 5-3: Typical development of the degree of hydration and compressive strength of a Type I Portland cement over time.


with modern cements. 2) There is no more liquid water available for hydration. If the cement has a w/c less than about 0.4, there will not be enough original mix water to fully hydrate the cement. If additional water is supplied by moist curing or from rainfall, hydration may be able to continue. However, it is difficult to supply additional water to the interior of large concrete sections. If the cement is improperly cured so that it dries out, hydration will terminate prematurely regardless of the w/c. This is the worst-case scenario, as the strength will be lower (perhaps significantly) than the value anticipated from the mix design. 3) There is no more space available for new reaction product to form. When the capillary porosity is reduced to a certain minimal level, hydration will stop even if there is unreacted cement and a source of water. This is the best possible outcome, and it is only possible if the w/c is less than about 0.4. Not only will the cement paste or concrete have a high strength, but it will also have a low permeability and thus be durable.

The term ‘Setting’ is used to describe the stiffening of the cement paste. Setting of cement refers to changes of cement paste from a fluid to rigid state. Setting differs from Hardening of cement.

The term ‘Hardening’ refers to the gain of strength of a set cement paste, although during setting the cement paste acquires some strength.

The setting characteristics of Portland cement paste are defined by initial set and final set. Initial set indicates the approximate time at which the paste begins to stiffen considerably. Final set roughly indicates the time at which the cement paste has hardened and can support some load.

Initial setting time indicates the beginning of the setting process when the cement paste starts losing its plasticity. Final setting time is the time elapsed between the moment water is added to the cement and the time when the cement completely lost its plasticity and can resist certain definite pressure.

These times of set are tested according to standardized procedures and have no special relationship to concrete setting behaviour. Setting types are affected by minor constituents in the cement such as alkalis and Sulphates, by fineness, water-cement ratio, ambient temperature and inclusion of mineral and chemical admixtures. Concrete generally sets more slowly than cement paste because of the higher water-cement ratios.


There are 2 types of abnormal setting behaviour that should be mentioned.

1. False Set: This refers to the rapid setting that occurs without the liberation of much heat. Plasticity can be regained by further mixing without the need to add more water, and thus is not a problem where concrete is

mixed for long periods (ready-mixed concrete). Increasing mixing time when possible will help to reduce a false set problem.

2. Flash Set (or quick set): This behaviour is accompanied by the liberation of considerable heat. The plasticity of the mixture cannot be regained with additional mixing or water.

Hydration of C3S: C3S on reaction with water produces C-S-H and calcium hydroxide, CH, (also known as Portlandite). The hyphens used in the C-S-H formula are to depict its variable composition: CSH would imply a fixed composition of CaO.SiO2.H2O. C/S ratios in C-S-H vary from 1.2 to 2.0, and H/S ratios vary between 1.3 and 2.1.

Tricalcium silicate + water -> calcium silicate hydrate + lime + heat

2C3S + 6H → C3S2H3 (C-S-H) + 3CH (calcium hydroxide) + 120 Cal/gm

The C-S-H is very poor crystalline and non-stoichiometric phase. C-S-H phase is the main binder in the hardened Portland cement paste and also main contributor of compressive strength development at least up to 7 days.

Hydration of C2S: The kinetics and hydration mechanism for C2S are similar to those of C3S, except that the rate of reaction is much slower. The hydration products are the same except that the proportion of CH produced is about one-third of that obtained on hydration of C3S.

Dicalcium silicates + water -> calcium silicate hydrate + lime

2C2S + 4H → C3S2H3 (C-S-H) + CH (calcium hydroxide) + 62 Cal/gm


Like in the reaction of C3S Calcium silicate hydrate (CSH) contribute to the strength of the cement paste. The reaction generates less heat and proceeds at a slower rate, meaning that the contribution of C2S to the strength of the cement paste will be slow initially. This compound is however responsible to the long-term strength of Portland cement.

The principal hydration product is C3S2H4, calcium silicate hydrate, or C-S-H (non-stoichiometric). This product is not a well-defined compound. The formula C3S2H3 is only an approximate description. It has amorphous structure making up of poorly organized layers and is called glue gel binder. C-S-H is believed to be the material governing concrete strength. Another product is CH - Ca(OH)2, calcium hydroxide. This product is a hexagonal crystal often forming stacks of plates. CH can bring the pH value to over 12 and it is good for corrosion protection of steel.

Hydration of C3A: The initial reaction of C3A with water in the absence of gypsum is vigorous, and can lead to “flash set” caused by the rapid production of the hexagonal crystal phases, C2AH8 (H = H2O) and C4AH19. Sufficient strength is developed to prevent continued mixing. The C2AH8 and C4AH19 subsequently convert to cubic C3AH6 (hydrogarnet), which is the thermodynamically stable phase at ambient temperature. Typically, gypsum is added to retard this reaction, though other chemical additives can be used.

The reaction products formed on reaction of C3A in the presence of gypsum depend primarily on the supply of sulfate ions available from the

CSH Calcium Hydroxide(CH)


dissolution of gypsum. The primary phase formed is ettringite (C6AS3H32) (S = SO3). Ettringite is the stable phase only as long as there is an adequate supply of soluble sulfate. A second reaction takes place if all of the soluble sulfate is consumed before the C3A has completely reacted. In this reaction, the ettringite formed initially reacts with the remaining C3A to form a tetracalcium aluminate monosulfate-12- hydrate known as monosulphate or monosulfoaluminate (C4A SH18).

C3A + CH + 12H → C4AH13 (In absence of gypsum)

Tricalcium aluminate + gypsum + water → ettringite + heat

C4AH13 + 3CS H2 (Gypsum) + 26H → C6AS3H32 (Ettringite) + 207 Cal/gm

Tricalcium aluminate + ettringite + water → monosulfate aluminate hydrate

2C3A +3C6AS3H32 + 22H → 3C4ASH18,(Calcium monosulfoaluminate Hydrates)

Both the monosulphate and C4AH13 are hexagonal plate type phases.

Hydration of C4AF: The ferrite phase (C4AF) reacts in a similar fashion to the C3A but more slowly. One important difference is that some of the aluminum in the reaction products is substituted for iron. The amount of substitution depends on many factors including the composition of the C4AF and the local conditions in the paste. The heat of hydration of this phase is 420J/gm. A convenient way to represent these reactions is-

Ferrite + gypsum + water → ettringite + ferric aluminum hydroxide + lime

C4AF + 3CSH2 + 3H → C6(A,F)S3H32 + (A,F)H3 + CH

Ferrite + ettringite + lime + water → garnets

C4AF + C6(A,F)S3H32 + 2CH +23H → 3C4(A,F)SH18 + (A,F)H3

where (A,F) indicates aluminum with variable substitution of iron, and (F,A) indicates iron with variable substitution of aluminum. The (F,A)H3 is an amorphous phase that forms in small amounts to maintain the correct reaction stoichiometry. Because of the substituted iron, the main reaction products are not pure ettringite and monosulfoaluminate, although they have the same crystal structure. Instead, cement chemists have given them the names AFt and AFm, respectively, where the m indicates monosulfate (one sulfate ion) and the t indicates trisulfate.

Ettringite


Schematic Of Cement Hydration:

Hydration of cement phases:

Although the basic reaction mechanisms and theories on the hydration of the pure phases pertain to the phases in cement, there are some significant differences. A schematic of the initial hydration reactions up to the time of set is illustrated in Fig. 1.


:

Gypsum is added to the cement primarily to retard the hydration of the aluminate and ferrite phases. The effectiveness of the gypsum depends on the rate at which the relevant ionic species dissolve and come in contact with each other.

Without gypsum, C3A reacts very rapidly with water:

C3A + 6 H → C3AH6

The reaction is so fast that it results in flash set, which is the immediate stiffening after mixing, making proper placing, compacting and finishing impossible.

With gypsum, the primary initial reaction of C3A with water is:

C3A + 3 (C S H2) + 26 H → C6A S 3H32

The 6-calcium aluminate trisulfate-32-hydrate is usually called ettringite. The formation of ettringite slows down the hydration of C3A by creating a diffusion barrier around C3A. Flash set is thus avoided. Even with gypsum, the formation of ettringite occurs faster than the hydration of the calcium silicates. It therefore contributes to the initial stiffening, setting and early strength development. In normal cement mixes, the ettringite is not stable and will further react to form monosulphate (C4A S H18).


EFFECTIVE WASTE UTILIZATION

Now a days waste materials of industry is a headache to everyone. So

utilization of this waste materials is very necessary. Cement industry is

gives us the ample scope of utilizing huge amount waste materials of Steel

plant and thermal power plant and other industry. This waste materials can

be used as a raw materials or additives of manufacturing cement. The

following waste materials can be used in cement industry-

1. USE OF BLAST FURNACE SLAG:

Slag is a huge waste materials produced in iron blast furnace of Steel Plant.

Cement industry effectively using this blast furnace slag. This slag contains

the essential constituents of cement like Ca0= 43% SiO2=25% and

Al2O3=17%. Slag can be mixed with Portland Clinker with a percentage of

25-70 to manufacture Portland slag cement.

Benefits: Use of slag in cement gives a huge benefits –

Use of slag not only reduces the production cost by reducing the use

of Clinker but also it reduces the production of CO2 indirectly.

Using slag Portland slag is manufactured which have a very high

potential in term of strength because its strength development

increases exponentially with respect to time up to years.

It also utilises the huge waste product of steel plant reducing the

disposal cost.

2. USE OF Fly Ash:

Fly Ash is very hazardous materials for environment which is a huge

amount of Thermal Power plant on burning of coal. It stays in the

atmosphere as a suspended particular matter creating Aspiration Problem

to the human being. This huge amount of fly ash can be utilized for

manufacturing Portland Pozzolana Cement. It can be used as an additives

with Portland cement clinker with a percentage of 15-35% to make PPC

cement. Fly Ash is a huge amount of Silica, Iron and alumina content which

is essential constituents of cement. So it can be used to make cement very

effectively.


3. USE OF BOTTOM ASH GENERATED IN CAPTIVE POWER PLANT AS

A ALTERNATIVE RAW MATERIALS :

The generated fly Ash from Thermal power plant could

be effectively used for cement for cement manufacturing

but the bottom Ash generated are being Coarser in

nature not conforming to IS 3812:2003 could not be used for same

purposes. But the disposal of this huge bottom ash is a serious hazard to

the environment that consumes millions or rupees towards the cost of

disposal. On various investigation and research it was found that the

bottom ash is alumino-silicate materials equivalent to natural clay/shale

which is commonly been used as a minor component of raw mix in

manufacturing cement clinker. On successful raw mix design and

subsequent burn ability studies it was found that this bottom ash can be

used as a component of raw mix.

Benefits-

i. Utilization of bottom ash for manufacturing Portland

cement directly reduces the environmental pollution and

reduces the use of natural resources like clay, Shale.

ii. The Bottom ash being a fine materials consumes less

electrical power for achieving required fineness during

grinding in the mill and saves electricity.

4. USE OF CINDER GENERATED IN REFRACTORY GAS PRODUER

PLANT AS AN ALTERNATIVE RAW MATERIAL.

In gas Producer plant Cinder is generated as a waste

materials which is difficult for disposal. Cinder

contains Silicate materials equivalent to that of a

natural Clay/Shale which is commonly been used as

a raw materials in raw mix design. So some quality

of cinder can be used for raw mix design for the

manufacture of Portland cement.


5. UTILIZATION OF PHOSPHOGYPSUM.

Phosphogypsum is huge waste from fertilizer

industry. Cement industry able to use this

chemical gypsum for grinding with clinker to

manufacture Portland cement.

1. UTILIZATION OF NON-MAGNETIC CHAR AS AN ALTERNATE FUEL.

As a drive for saving natural resources and gainful utilization of waste

many cement plant has taken initiative to use non-magnetic char of

sponge iron plant as an alternative fuel in the Kiln as a replacement of

non-renewable fossil energy like coal.

Benefits:

i. Saving of normal coal mix which gives a substantial amount of

cost benefit.

ii. This initiative also helps in preserving the eco system by

avoiding the use of prime land for dumping these hazardous

wastes.

KILN with tertiary air ducts are more difficult to control since these

kiln contain two distinct and separate combustion processes that must

be closely controlled independently.

The kiln exit gases are being passed through PH section and are not

being by passed or vented directly. This might cause recycle and

accumulation of alkali leading to troubleshoot building and ring

formation. Fortunately, this problem is not being encountered in OCL

AT present.

Huge amount of CO2 production during calcination reaction.


OCL India Limited has taken many steps to improve the qualitative as well

as quantitative aspect of its product. It follows the ISO manual 9001. It has

a fully systematic approach. Each and every work which is done has a

unique format and steps. Functions are also distributed among the

employees. It has taken steps for continuous monitoring of the processes.

The different developments taken through the years are listed below:

Up gradation of the quality of chemical gypsum for use as set controller.

Development of ternary and quaternary blended cement for improved quality and performance.

Development of X-Ray Diffraction method for real time estimation of Slag/Fly ash content in blended cement.

Development of high strength hollow Fly ash blocks using wastes from our captive mines, cement & refractory units.

Use of industrial waste like Cinder, Non-magnetic Char, Slag, Bottom Ash as alternate raw material and fuel.

Use of waste wood chips, bags, waste paper, waste oil as alternate fuel.

OCl India Ltd.

www.google.com

www.wikipedia.org

www.understanding-cement.com

IS-4031: Methods of physical tests for hydraulic cement.

IS-4032: Methods of chemical tests for hydraulic cement.

http://iti.northwestern.edu/

F.M.Lea, “Chemistry of cement and concrete”, Fourth edition, 2004. Taylor H.F.W., 1997, cement chemistry, second edition, Thomas Telford, London . Dalmia Institute of Scientific and Industrial Research.

http://www.google.com/

http://www.wikipedia.org/

http://www.understanding-cement.com/

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