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INDUSTRIAL VISIT

REPORT

Submitted in partial fulfillment of the requirements

for the award of Bachelors of Technology in Civil Engineering from

University of Kerala

Presented By:

MOHAMMED SAJEEM A

Reg. No. 10417020

DEPARTMENT OF CIVIL ENGINEERING

TRAVANCORE ENGINEERING COLLEGE

OYOOR, KOLLAM - 691516

2014

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DEPARTMENT OF CIVIL ENGINEERING

TRAVANCORE ENGINEERING COLLEGE

OYOOR, KOLLAM

CERTIFICATE

This is to certify that this “INDUSTRIAL VISIT REPORT” is a bonafide record of

the work done by MOHAMMED SAJEEM A, VIII Semester (10417020), in partial

fulfillment of the requirements for the award of the Degree of Bachelors of

Technology in Civil Engineering from University of Kerala during the year 2014.

COORDINATOR HEAD OF THE DEPARTMENT

Ms. ANJANA ANAND A S Mrs. SREEJA JACOB

ASSISTANT PROFESSOR ASSOCIATE PROFESSOR

DEPT. OF CIVIL ENGINEERING DEPT. OF CIVIL ENGINEERING

TRAVANCORE ENGG. COLLEGE TRAVANCORE ENGG. COLLEGE

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ACKNOWLEDGEMENT

It is with great pleasure and learning spirit that we bringing out this industrial visit

report. We use this opportunity to express our heartiest gratitude to the support and guidance

offered to us from various sources during the courses and completion of the visit program.

We would like to extend our sincere gratitude to Mrs. Sreeja Jacob, Head of the

Department of Civil Engineering, for providing us the opportunity to undertake this industrial

visit.

We are very much thankful to our coordinator Ms. Anjana Anand A S, Assistant

Professor for sharing her wealthy knowledge.

We convey our sincere gratitude to all the engineers and labourers of Pee Kay steel

casting (P) Ltd. and Dura Tech RMC plant, Calicut for providing us valuable advice and

guidance during the industrial visit and also to all the staffs at Padmanabhapuram palace,

Thuckalay, Tamilnadu for the help and services they rendered.

Above all, we owe our gratitude to the Almighty for showering abundant blessings

upon us. And last but not the least we wish to thank our parents and our friends for helping us

to complete our industrial visit work successfully.

MOHAMMED SAJEEM A

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CONTENTS

1. INTRODUCTION

2. PADMANABHAPURAM PALACE

2.1 HISTORY

2.2 STRUCTURES

2.2.1 Poomukham

2.2.2 Mantrasala (Council chamber)

2.2.3 Thai Kottaram (Mother's palace)

2.2.4 Oottupura (Dining Hall)

2.2.5 Armoury and Watch Tower

2.2.6 Ambari Mukhappu

2.2.7 Indra Vilasam

2.2.8 Navarathri Mandapam

2.2.9 Natakasala (Hall of performance)

2.2.10 Four-storied central building (Uppirikka Maliga)

2.2.11 Thekee kottaram (Southern palace)

3. PEE KAY STEELS CASTING (P) LIMITED

3.1 THERMO MECHANICALLY TREATED BARS

3.2 MANUFACTURING OF TMT BARS

3.2.1 Raw Materials

3.2.2 Inspection of Raw Materials

3.2.3 Furnace

3.2.4 Roughing Mill

3.2.5 Cutter

3.2.6 Finishing Mill

3.2.7 TMT Quenching Box

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3.3 PROPERTIES OF TMT BARS

3.3.1 Advantages of TMT Bars

3.3.2 The grades of TMT bars

3.3.3 Applications of TMT bar

4. THE READY MIXED CONCRETE PLANT

4.1 MATERIALS REQUIRED FOR RMC

4.1.1 Aggregate

4.1.2 Cement

4.1.3 Admixture

4.1.4 Fly Ash

4.1.5 Water

4.2 EQUIPMENT REQUIRED

4.2.1 Batching Plant

4.2.2 Transportation Equipment: Transit Mixer

4.3MIXING PROCESS

4.3.1 Transit Mixed (Or "Truck-Mixed") Concrete

4.4 TESTS ON MATERIALS

4.4.1 Tests on Fine Aggregates

4.4.2 Tests on Coarse Aggregates

4.4.3 Test on Fresh Concrete

4.4.4 Test on Water

4.4.5 Test on Hardened Concrete

4.5 OPERATIONAL ASPECTS

4.5.1 Needs to be specified by Consumer for RMC

4.5.2 Information to be supplied by the Producer

5. CONCLUSION

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LIST OF FIGURES

1. THE SREE PADMANABHAPURAM PALACE

2. PADMANABHAPURAM PALACE GROUND FLOOR PLAN

3. THE CLOCK TOWER

4. PADMANABHAPURAM PALACE SECTION

5. EXTERIOR OF POOMUKHAM

6. INTERIOR OF MANTRASALA

7. CLOCK TOWER ELEVATION

8. JACKFRUIT WOOD PILLAR

9. MOTHER PALACE

10. EXTERIOR OF OOTTUPURA

11. INTERIOR OF OOTTUPURA

12. NAVARATHRI MANDAPAM

13. THEKEE KOTTARAM

14. PEE KAY STEEL CASTING (P) LTD. CALICUT

15. TMT MANUFACTURING PROCESS

16. BILLETS STACKED (GREEN COLOUR CODED)

17. FEEDING MECHANISM USED FOR PUSHING INGOTS

18. FURNACE

19. FURNACE EXIT

20. ROUGHING MILL

21. ALIGNMENT OF THE MOTOR, COUPLINGS, BEARINGS

22. DIFFERENT SLOTS

23. SHEARER OR CUTTER

24. PIECES OF ROD CUT FROM CUTTERS

25. FINISHING MILL

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26. THE SEQUENCE OF THE FINISHING MILL

27. TMT QUENCHING BOX

28. DURA TECH READY MIX CONCRETE PLANT, CALICUT

29. AGGREGATE STORAGE YARD

30. THE CAC ADMIXTURE USED AT DURA TECH

31. DURA TECH BATCHING PLANT, CALICUT

32. THE BATCHING EQUIPMENT AT DURA TECH

33. PROCESS CONTROL SYSTEM

34. TRANSIT MIXER, DURA TECH

35. HELICAL BLADES INSIDE TRANSIT MIXER DRUM

36. COMPRESSION TESTING MACHINE

37. CONCRETE MIXING DRUM

38. PYCNOMETER

39. SLUMP CONE

40. IS COURSE SIEVES

41. IS FINE SIEVES

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LIST OF TABLES

1. CHEMICAL QUANTITY USED FOR DIFFERENT GRADES OF

STEEL

2.

RE-BAR QUALITY AND CORRESPONDING STRENGTH

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1.INTRODUCTION

We were fortunate to visit three important civil structures or industries as a part of our

industrial visit of the final semester. With the aim of obtaining different and vast experience,

we selected industries based to three different sub branches of civil engineering. Our first

visit was to the Padmanabhapuram palace which is renowned for its architectural

appeasement. Secondly, Pee Kay steel castings (P) Ltd. helped us know things of

manufacture of steel bars, which is an integral part of structural mechanics. Our final visit to

Dura Tech ready mix concrete plant helped us acquire practical knowledge in the field of

concrete technology.

The Padmanabhapuram Palace is one of the best examples of traditional Kerala

architecture. Some portions of the sprawling complex are also the hallmark of traditional

Kerala style architecture. That’s exactly the reason why we visited the enchanted palace on

Aug.08th.2012 to learn the tremendous Kerala Architecture. The Padmanabhapuram Palace is

located in southern India, a region with high rainfall and a tropical climate. Founded by the

royal family of Travancore, adjoining the State of Kerala, the initial structures date from the

period 1400-1500, with other buildings added incrementally over time.

The purpose of industrial visit is to Pee Kay Steel casting (P) Ltd. Calicut on

Dec.27th.2013 was to learn the manufacturing process of TMT bars. Through this visit we

were able to know the manufacture of steel bars, materials used for it, their need and much

more. Pee Kay steel castings is a modern state-of-art foundry established in 1991. They

manufacture high quality steel castings made of carbon steel, alloy steel, stainless steel,

nickel based steel, duplex steel etc in various sizes and weight. They are also involved in

production of bars and rods of high quality as per Indian standard.

Ready-mix concrete (RMC) is a ready-to-use material, with predetermined mixture of

Cement, sand, aggregates and water. RMC are manufactured in factory as per the

specifications of customers, at a centrally located batching Plant. Our industrial visit to Dura

Tech RMC Plant, Calicut on Dec.28th.2013 was to learn the advantages, the quality control in

the preparation of the concrete and the preparation procedure followed at the ready mix plant.

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2. PADMANABHAPURAM PALACE

Fig.2.1 the Sree Padmanabhapuram Palace

The Padmanabhapuram Palace is located in southern India, a region with high rainfall

and a tropical climate. Founded by the royal family of Travancore, adjoining the State of

Kerala, the initial structures date from the period 1400-1500, with other buildings added

incrementally over time. The palace’s present name was given to it in 1744 by Marthanda

Verma Maharaja, who was a devotee of Padmanabhan.

Comprised of edifices reflecting a variety of styles, the complex bears witness to the

socio-political influences prevalent at different moment in its history.

Entry to the palace compound is from the west, through a high door with a pitched

roof structure abutting it, typical of the Kerala region. A succession of courtyards formed by

buildings or simply wall becomes progressively more private in character until one reaches

the core of the complex, termed thai kottaram (literally, the generic mother), reputedly the

oldest building of the palace. It forms the centerpiece or focus of the entire palace compound,

corresponding in patterns to a manadala, the ancient Indian diagram of the cosmos. It is the

basic reference point in relation to which the location and opening of the other buildings have

been determined. Although the palace may seem to be without any rationale in the layout and

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disposition, one comprehends its organization the moment the esoteric rules governing its

design have been revealed. Thus, successive generations of builders in the palace complex

adhered to the rule laid down at the start.

Building science applied in the achievement of Padmanabhapuram involved a

combination of astronomy, astrology, mathematics, religious values, social moves, building

technology and magic. Such traditional building codes account for the overall cohesion in the

design.

Kerala is a region with abundant timber and excellent clay, used for tiles and bricks,

as well as laterite stone, granite and shell lime. While strict rules also existed for the

utilization of various materials and structural solutions, it was by far carpentry was the most

highly developed building art. Type of wood, their relative positions to one another, kinds of

functions to be served, and the types of wood determined by user’s place in the social

hierarchy were all specified in the traditional codes. Hence, one of the outstanding features of

Padmanabhapuram Palace is that these principles were faithfully followed over centuries.

Another significant quality of the buildings at Padmanabhapuram is the sensitive

handling of the light and atmosphere of repose created throughout. The aesthetics importance

of the palace might well be described as a subtle combination of sophisticated understatement

in design and a tactile celebration of material employed.

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2.1 HISTORY

Padmanabhapuram Palace is located in at Padmanabhapuram Fort, close to the town

of Thuckalay in Kanyakumari District, Tamilnadu, in India. It is about 20 km from Nagercoil,

and about 50 kilometers from Thiruvananthapuram, Kerala. The palace complex is inside an

old granite fortress around four kilometers long. The palace is located at the foot of the Veli

Hills, which form a part of the Western Ghats. The river Valli flows nearby. The palace was

constructed around 1601 AD by Iravi Varma Kulasekhara Perumal who ruled Venad between

1592 and 1609.It is believed that the Thai Kottaram was built in 1550. The maker of modern

Travancore Anizham Thirunal Marthandavarma (1706 -1758) who ruled Travancore from

1729 to 1758 rebuilt the palace in 1n around 1750. King Marthaanda Varma dedicated the

kingdom to his family deity Sree Padmanabha, a form of Lord Vishnu and ruled the kingdom

as Padmanabha dasa or servant of Lord Padmanabha. Hence the name Padmanabhapuram or

City of Lord Padmanabha. In the late 18th century, precisely in 1795 the capital of

Travancore was shifted from here to Thiruvananthapuram, and the place lost its former glory.

However, the palace complex continues to be one of the best examples of traditional Kerala

architecture, and some portions of the sprawling complex are also the hallmark of traditional

Kerala style architecture.

Fig.2.3 the Clock Tower

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2.2 STRUCTURES

The Padmanabhapuram Palace complex consists of several structures such as

Mantrasala; literal meaning, King's Council Chamber, Thai Kottaram; literal meaning,

Mother's Palace (It meant the mother's palace, where the mother of king resides) – believed to

have been constructed before AD 1550, Nataksala; literal meaning, the Hall of Performance,

or of Performing Arts, A four-storied building at the centre of the Palace complex, Thekee

Kottaram; literal meaning, the Southern Palace. The clock tower in the palace complex has a

300 year old clock, which still keeps time. A big hall now bare, which can accommodate

around 1000 guests, and where ceremonial feasts were held, on auspicious occasions. A

secret passage, now blocked, through which the king, his immediate family members, and

their entourage could escape to another palace, located several kilometers away in the event

of any emergency. Name of this palace is Charottu kottaram. A flight of steps leads to a

bathing pond, which has lost its freshness due to neglect and years of disuse. The structural,

architectural and functional features of which are explained below.

2.2.1 Poomukham

Fig.2.5 Exterior of Poomukham

It was here, the king entertained special guests. Built in the indigenous style of

Kerala, the entrance of this building is shaped as a triangle. On the wooden ceiling,

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ninety flowers have been carved. Each of them is marvelous and unique. Also do here

feature the rarest of the rare things like hanging brass lamp with a knight on horse-

back, a cot built of seven pieces of polished granite, a Chinese chair presented to the

king by Chinese merchants and the ‘Onavillu” presented to the king as tribute by the

land lords and chieftains of different clans during the onam festival. The ‘Onavillus’

are finest examples of the exquisite history of Kerala style of paintings.

2.2.2 Mantrasala (Council chamber)

Fig.2.6 Interior of Mantrasala

King’s Council chamber is the most beautiful part of the entire palace

complex. It has windows, with coloured mica, which keep the heat and the dust away,

and the interior of the council chamber remains cool and dark. Delicate and beautiful

lattice work can be seen all over the council chamber.

The floor is also beautifully done, with a fine and perfect finish. The floor is

dark and is made of a mixture of varied substances, including burnt coconut shells,

egg white and so on. The remarkable aspect is that this particular floor finish and

texture could not be duplicated in any other construction.

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The Manthrasala is a hall of considerable importance. Generally the term

‘Manthra’ refers to the administration of the kingdom. It was at this hall the king held

discussions with his ministers and prominent citizens and took important decisions.

The building displays a simplicity and purity of the styles of architecture. The wood

carvings across its beam and roof proclaim the expertise of the craftsmanship.

Manthrasala has only one projection and eleven number of ‘Kilivathil’. A Kilivathil is

a tiny window, the shutters of which are beautifully decorated with mirror work in

different hues. Chinese model sittings that adorn the Manthrasala are rich with

wonderful carvings. The floor of the Manthrasala is typical of the rare technology that

was in vogue.

2.2.3 Thai Kottaram (Mother's palace)

Mother’s palace, designed in traditional Kerala style, is the oldest construction

in the entire palace complex and is believed to be constructed around mid-16th

century. True to the traditional Kerala style, there is an inner courtyard, called

'nalukettu'. In the inner courtyard, sloping roofs from all four sided taper down. Four

pillars on four corners support the roof.

On the south-west corner of the mother’s palace, there is a relatively small

room, called the chamber of solitude or 'ekantha mandapam'. The chamber of solitude

has very beautiful and intricate wood carvings of every description all around. Of

particular interest is a pillar of single jackfruit wood, with very detailed and beautiful

floral designs.

Thai Kottaram also known as the ‘Dharbhakkulangara kottaram’, the Thai

kottaram is the oldest palace amongst the Padmanabhapuram palace complex. It was

built during the reign of Ravi varma Kulasekhara Perumal (A.D. 1592 to A.D. 1610).

It was constructed in the traditional Nalukettu style. The Ekantamandapam’ –

The open verandah in this place contains the ‘Kannithoonu’, a ceiling supporting

pillar in one piece between base and capital carved with artistic affluence. Built of

jack fruit tree wood, it has the most exquisite carvings one will ever see. Carvings

have been done in the ethnic Kerala style. The ritualistic ‘Kalamezhuthu’ and other

ceremonies for the appeasement of goddesses were done in this prayer hall. The

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flooring of the hall which has withstood time attracts special attention. The tunnel

route connecting the Thai kottaram with the Charottu kottaram situated over one

kilometer away starts near the courtyard. It was used in times of war or danger to the

royal family. The drawings of Thai Kottaram are shown in fig.2.9.

Fig.2.8 Jackfruit wood Pillar

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2.2.4 Oottupura (Dining Hall)

Fig.2.10 Exterior of Oottupura

The kings of Travancore were known for their generous hospitality. Over 2000

people were served free meals in this grand dining hall on a daily basis. Each storey

of this two-storied building is built to accommodate one thousand people at a time.

The huge Chinese jars which were used to store pickles for the feast are exhibited in

the ground floor.

Fig.2.11 Interior of Oottupura

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2.2.5 Armoury and Watch Tower

During the days of royalty, these rooms were used as armory. The construction

of this building is such that it has more length and less breadth, without any windows

or ventilation facilities. There are only two entrances to the armory. At the modern

end there is the watch tower. Form this watch tower any movement in the near

surroundings can be detected. Thousands of different weapons stored here were

confiscated by the British army by order of Col. Macaulay. The rest of the weapons

and equipments are exhibited in the new museum.

2.2.6 Ambari Mukhappu

It was built for the kings to view chariot races (temple cars race) during

festivals and to appear before the public on special occasions. ‘Ambari’ is actually the

seat put on elephants’ back for safaris. The building has been constructed based on the

shape and structure of an ‘Ambari’. The ‘Ambari mukhappu’ is the crowning example

of the craftsmanship of Travancore wood carving.

2.2.7 Indra Vilasam

This building was constructed for accommodation of foreign tourists and

dignitaries coming to visit the king. Unlike other buildings, it has not been

constructed in ethnic Kerala style of architecture. The influence of foreign style of

architecture is evident in the structure of this building.

2.2.8 Navarathri Mandapam

King Marthanda varma built the Navarathri mandapam in 1744 A.D. Built of

solid rock, the building is 66 feet long and 27 feet wide. Famed for its unparalleled

architecture, breath taking beauty and intricate and exquisite carvings, the buildings

speaks of the rich cultural and artistic tradition. Various cultural programs were

conducted here, during the Navarathri festival. The dance floor has been polished to

mirror like perfection so much that it is known as ‘Kannadithara’ or mirror floor.

Separate rooms with ‘Kilivathil’ (Small wooden windows built in the wall) have been

made for the kings and his royal train to view the programs without being seen by the

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common public. Amongst the buildings of Padmanabhapuram palace complex, the

Navarathri mandapam is the only one made of stone.

Fig.2.12 Navarathri mandapam

2.2.9 Natakasala (Hall of performance)

This is a relatively new building, constructed at the behest of Maharaja Swathi

Thirunal, who reigned in Travancore from 1829 to 1846. He was a great connoisseur

of arts, especially music and dance. He himself composed music and has left a rich

legacy to classical carnatic music.

The Nataksala or the hall of performance has solid granite pillars and

gleaming black floor. There is a wooden enclosure, with peepholes, where the women

of the royal household used to sit and watch the performance.

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2.2.10 Four-storied central building (Uppirikka Maliga)

The four-storied building is located at the centre of the palace complex. The

ground floor houses the royal treasury. The first floor houses the King's bedrooms.

The ornamental bedstead is made of 64 types of herbal and medicinal woods, and was

a gift from the Dutch merchants. Most of the rooms here and in other parts of the

palace complex have built-in recesses in walls for storing weapons like swords and

daggers. The second floor houses the King's resting and study rooms. Here the King

used to spend time during fasting days. The top floor (called upparikka malika) served

as the worship chamber of the royal household. Its walls are covered with exquisite

18th century murals, depicting scenes from the puranas, and also few scenes from the

social life of the Travancore of that time. Ths top floor was supposed to be Sree

Padmanabha Swamy's room. This building was constructed during the reign of King

Marthandavarma. He was also designated as Padmanabha Dasa and used to rule the

Travancore kingdom as a servant of Sree Padmanabha Swamy.

2.2.11 Thekee kottaram (Southern palace)

The southern palace is as old as the ‘Thai kottaram’ (Mother's palace), which

would make it about 400 year old. Now, it serves as a heritage museum, exhibiting

antique household articles and curios. Collections of items give an insight into the

social and cultural ethos of that period.

Fig.2.13 Thekee Kottaram

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3. PEE KAY STEELS CASTING (P) LIMITED

From coarse and rocky iron ore to tough and shiny steel — the making of the magic

alloy is a fascinating journey that starts from the crust of the earth, involves complex

metallurgical reactions and processes, and demands technological expertise of a high degree.

Pee Kay steel’s Calicut plant, one of the major steel plant in India (production started in

1991), is today among the country’s largest integrated steel-making facilities, producing 6000

MT of steel every year. We walked through the modern Pee Kay Steel plant, much changed

from its original manifestation, to witness the birth of red hot molten steel in its multiple

forms and its casting as the radiant champion of industrial development.

Fig.3.1 Pee Kay Steel Casting (P) Ltd. Calicut

For more than 3,000 years, humans have known how to make tools, weapons and

ornaments from iron. Known as a metal of antiquity, iron is one of the building blocks of

modern civilization. Indeed, there was a time when iron was more valuable than gold.

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The basic process of making iron and its tougher alloy — steel — have not changed in

the last three millennia. First, the ore has to be found. Then it must be reacted with other

elements at very high temperatures. Third, the liquid steel must be collected and cast into

shape. And, finally, the steel must be treated to give it the properties needed for end use. Steel

is considered a green product because it is 100-percent recyclable and has an infinite life

cycle.

Untreated ore cannot be used to make steel as it reduces the quality of the metal.

Therefore, the raw iron ore is processed at the sinter (or processed iron ore) plant. The coal

used in the plant is cleansed of impurities in coke ovens. Conveyor belts carry metallic-

pellets and sinters — to the heart of the steel plant, the blast furnace. The blast furnace is a

six-storey tall reactor where the seemingly magical transformation of dark iron ore into

glowing hot liquid iron takes place. The ore is charged into the blast furnace along with

fluxes and limestone. Temperatures in the blast furnace reach up to 1,5000 0C and the

resulting metallurgical reaction converts iron oxide into molten iron. The blast furnace works

round the clock.

The red hot liquid metal produced in the blast furnace is collected in the hearth and

‘tapped’ on a near continuous basis through day and night. The process is called casting and,

typically, the steel plant does 10-12 casts in a 24-hour cycle. Pee Kay Steels has a number of

blast furnaces and most of these are operational. Hot metal or molten iron from the blast

furnace is transferred into vessels called torpedoes and transported on rail tracks to the LD, or

Linz Donawitz (named after the towns in Austria where the technology was commercialized),

shop. Here the molten iron is refined into steel using the ‘basic oxygen furnace’ method. One

dedicated to making steel for long products (used mainly in the infrastructure and

construction sectors) and two others for flat steel products (typically used in automobiles and

appliances).

At the LD shop the process begins with charging scrap into the furnace, where

temperatures reach 1,700°C. Large ladles, capable of holding 170 tonnes of liquid metal, pour

the molten iron into the furnace. A water-cooled lance is lowered into the furnace to blow in

pure oxygen. Iron ore (as coolant) and burnt lime and raw dolomite (as flux) are added from

the top. The oxygen removes carbon, silicon, sulphur and phosphorus content from molten

iron and converts it to steel, an alloy that is tougher than iron. One ‘heat’ (a cycle of

steelmaking) takes 45-50 minutes and produces an average of 158 tonnes of molten steel.

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The properties required for steel depend on the end use. And so, from every heat, a

sample of the molten steel is analyzed to see if it meets the requirement. If there is any

variation, a ‘correction blow’ is ordered. Once perfected to specification, liquid steel — still

aglow at about 1,630- 1,690°C — is tapped into a ladle car positioned under the furnace.

During tapping, Ferro-alloys and aluminum are added directly into the steel ladle for alloying

and deoxidization

This steel goes through further refining, depending on requirement, at the online

purging station, ladle furnace station or RH degasser. Ladles with a holding capacity of 160

tonnes carry the liquid steel to the continuous caster machines. Here the liquid steel finally

takes solid form and is shaped into what are called long products or flat products.

The long products are processed at the wire mill to produce wire rods and bars. Pee

Kay Steels makes a range of long products, including TMT bars. Flat steel is further

processed at the hot rolling mill or cold rolling mill, depending on end use. Cold rolling mills

have a continuous galvanizing line and produce the galvanized steel used in the automotive,

engineering and appliances sectors.

3.1 THERMO MECHANICALLY TREATED STEEL BARS

By adopting thermo mechanically treatment process higher strength of TMT bars is

obtained. In this process, steel bars get intensive cooling immediately after rolling. When the

temperature is suddenly reduced to make surface layer hard, the internal core is hot at the

same time. Due to further cooling in atmosphere and heat from the core, the tempering takes

place. This process is expected to improve properties such as yield strength, ductility and

toughness of TMT bars. With above properties, TMT steel is highly economical and safe for

use. TMT steel bars are more corrosion resistant than Tor steel.

The full form of TMT is Thermo Mechanical Treatment; in this the steel bars are

passed through a specially designed water-cooling system. After the bars pass, the outer

surface of the bars solidifies while the core remains hot. This creates a temperature gradient

in the bars. After the intensive cooling, the bar is exposed to air and the core re-heats the

quenched surface layer by conduction, therefore tempering the external marten site. When the

bars are taken out of the cooling system, the heat flows from the core to the outer surface,

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further tempering of the bars, which helps them attain higher yield strength. The resulting

heat-treated structure imparts superior strength and toughness to the bars.

The pre-determined cooling of the bar periphery transforms the peripheral structure to

marten site and then annealed through the heat available at the core. The peripheral and core

temperature difference finally equalizes at around 600 degree C and the resultant bar

structure is of tempered marten site at the periphery and of fine-grained ferritepearlite at the

core. Generally speaking, the resultant soft core forms about 65-75 per cent of the area

(depending upon the desired minimum yield strength) and the rest is the hardened periphery.

The equalizing temperature together with the final rolling temperature is the most important

parameter to achieve the required mechanical properties. Finally, when the bar is discharged

on to the Cooling Beds, the remaining austenite transforms into a very fine-grained pearlite

structure.

After this process of thermo mechanical treatment, a dark etched peripheral rim of

tempered marten site and a grey core of ferrite pearlite get formed. The tempered marten site

surface layer is very hard while the microstructure of the core is a very fine-grained ferrite

and pearlite which is quite soft. The result is a structure with a 6 high yield strength combined

with high ductility. Hence from the above data it is seen that the sudden quenching is the key

role in hardening the steel bars. The pressure of the water jets on the hot molten bars

determines the thickness of the marten site structure and is controlled for the required

hardness.

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3.2 MANUFACTURING OF TMT BARS

Fig.3.2 TMT Manufacturing Process

Let us have a thorough review about the entire manufacturing process in a brief

manner. Just like the schematic shown above there are different stages in the manufacturing

of the TMT bars. It shows stage by stage development from the raw material and gradually

how the finished product is emerged.

Now the first stage is handling the ingots and billets. They are the raw materials for

the TMT bars. They are unloaded from the truck and placed in stacks and are in line with the

next batch ready to be processed further. Various color coding is already done based on their

type. They are always placed in order as to reduce lead time. There are few minor differences

between ingots and billets which will be later discussed in greater detail. The ingots then fed

into the furnace and are softened to a red hot ingot which is later on fed into the roughing mill

which considerably decreases the diameter of the ingot and gradually brings it closer to the

final required diameter and then leading its way to the intermediate mill to further decrease

the diameter. Finally the finishing mill comes into play where the final dimensions are

obtained. Note that the rod is still red hot after emerging from the finishing mill and enters

into the TMT quenching box where the pressure of water is set and the rod is hardened. In the

31

final stage the rod is placed on the cooling bed and then at last they are stacked together and

are ready for dispatch. Thus this brief summary gives us a proper foundation how the TMT

bars are manufactured.

3.2.1 Raw Materials

The raw materials used in production of TMT bars are of two types. They are

Ingots and Billets. The ingots have a structure similar to a trapezoid. It is like a cuboid

structure but with a little taper included at the sides. This makes the area of one side

of ingot bigger than the other end. These ingots are manufactured by casting process

with either iron ore or iron scrap at a furnace plant. The iron ore or scrap metal is

melted in the furnace and poured in vessels and after cooling the ingots are taken out

of the vessels. The ratio metals used to make the ingots depend upon the order. There

are 5 standard ratios that all ingot furnaces follow. Every ratio has a colour allotted to

it and after manufacturing the ingot are marked with that color so that there is no

margin of error. There are certain specifications given to the ingots. They have certain

optimum sizes at which they are available. Basic ingot size varies from 52 to 60

inches ingot length is used for TMT production 3 types based on the breadth and

height of ingot which are,

3⅟4 X 4⅟4 inches

3⅟2 X 4⅟2 inches

4 X 5 inches

The ingots and billets are almost similar but billets have better finish and there

is less chance of blow holes being present inside within. The final product obtained by

using billets have better finish when compared to the ingots. Billets are more refined

raw material which has less chance of blow holes and smooth surface finish.

13 Billets have no standard color coding or a standard ratio. They are entirely made as

on order. But after manufacturing the billets are supplied with a Heat number (a test

certificate) which elaborates the ratios of metals used and order size. The dimensions

of billets are almost similar to the ingot. The cross section area of a billet is

125.Average mass per length 3.1kg per inch in length.

32

As we know that there is a specific color coding for each ingot based on the

carbon percent present in the ingot. This helps in better handling of raw materials as

well as final product. The color allotted is given below,

Below 18 – white paint

18 to 20 – blue paint

21 to 23 – green paint

24 to 26 – Yellow paint

27 to 30 – orange paint

Above 30 – red paint

Fig.3.3 Billets stacked (Green Colour coded)

3.2.2 Inspection of Raw Materials

The incoming material is inspected visually at the initial stage before it

unloaded. The QA person tags yellow ribbon to the material which indicates the

material is for Inspection. After inspection based on the C% the respected Ribbon

colors will be issued. The stacked is done based on the color Code. The ingots are

identified by lot number, color Code is issued based on the C%. Billets don’t have any

standard color coding but they are tested and coding is done by the company itself.

33

There is a heat number mentioned on Billets which is evidenced to the

Chemical Composition. Before feeding there is a procedure of inspection where there

is a series of chemical tests done which determines the percentage of Carbon,

Sulphur, Phosphorous and Manganese.

The presence of carbon affects the strength where 30 is the maximum.

The presence of sulphur and phosphorous gives more strength where the

Maximum allowable level is 0.060%

3.2.3 Furnace

After quality testing, the ingots are ready to be fed in the furnace. It is

necessary for the ingots to have a high temperature for the rolling process through the

rollers. This is where the furnace comes to play. The ingots are fed into the furnace

wherein they are constantly heated for 4 hours. The material, on exit is suitable to

undergo Rolling. The furnace generates heat energy by the combustion of coal gas,

which is produced in a coal gas plant located nearby. The furnace has three process

namely feeding, Heating, Ejection.

The feeding of the raw material into the furnace is done with the help of

conveyer rollers. The ingots are placed on the conveyer rollers manually; tongs are

used in the positioning onto the conveyor system, which transports the raw material to

the feeding bed. Once the ingots are stacked one after the other on the feeding bed,

they are pushed into the pre-heating chamber of the furnace with a mechanism which

consists of a worm gear pushing the ingots into the furnace. This mechanism is also

controlled manually by a person due to discontinuity in feeding.

34

Fig.3.4 feeding Mechanism used for pushing ingots

Fig.3.5 Furnace

Fig.3.6 Furnace exit

35

The Heating Chamber or furnace is the chamber where the ingots are made

molten, which makes it feasible to pass it through the rollers. The furnace is a fuel

consuming chamber which works on coal gas. The furnace has a total of 8 burners.

There is a preheating zone, which leads to the intermediate zone ultimately leading to

the final zone. The gas plant is where the coal gas is produced. There is a pipeline

system which leads the gas to the burners. The peak temperature in the furnace goes

up to 1200°C. The gas is streamlined to vary the temperature. Lot of precaution is

taken as there is immense heat in proximity to the furnace. The furnace interior is

made of refractory bricks to withstand the high temperatures. There are also certain

doors at the side for inspection during maintenance. There is another controller near

the exit of the furnace to guide the red hot ingots outside of the furnace and position

them onto the rollers; leading them to the rolling mill.

The fig.3.5 shows the structure of the furnace. Several pipelines can be seen at

the entrance of the furnace, for exhaust. The pipes present near the burners Consist of

the gas fuel pipeline. The doors or gates present at the side are used for inspection or

to replace the refractory bricks during maintenance.

After heating, the ingot is ready for the roughing mill. Authorized personnel

are stationed at various nodal points to navigate the heated raw material from the

Furnace to the Roughing mill. The exit door is opened by the person who removes the

ingot. The furnace exit is shown in fig.3.6 the gate opens when an ingot is ready to be

rolled and the rollers in the path provided; carry the heated ingot onto the roughing

mill. This describes the process involved in the furnace.

36

3.2.4 Roughing Mill

Just after the ingot comes out of the furnace it is slowly led to the roughing

mill. The roughing mill is the first mill among the three mills present there. The mills

are operated with a high capacity motor. There is a gear reduction of ratio 1:6 to

provide the necessary torque required for rolling. The roughing mill is where there is

very slight elongation and gradually decreases in diameter and this is the main

function of the roughing mill. There are three sets of rollers present in the roughing

mill.

Fig.3.7 Roughing Mill

This figure shows the entire set of the roughing mill. There are three sets of

rollers and each set has three rollers placed one over each other. Now the hot ingot is

moved into the first roller. A single roller is something like described below,

The single motor shaft is transmitted to three shafts through the distributer.

The sequence of the alignment of the motor, couplings, bearings are as shown in the

figure below.

Fig.3.8 Alignment of the Motor, Couplings, Bearings

37

Fig.3.9 Different slots

Here is the order of the layout of the roughing mill. “C” stands for coupling

and “B” stands for bearing. While entering the first set of the roughing mill it roles at

about seven times at the same roller in different slots. The different slots are shown in

fig.3.9 which are the gray parts and the molten ingot passes through these slots and

then manually put back into the next slot and after 7 times in the first set of rollers it

moves through the guide way which leads it to the second set of rollers and again

leading it through the third roller and then the roughing mill is over. The roughing

mill is where most of the elongation is done and the area cross section gradually

decreases and the length increases. But the ingot is still in the molten state and it

continuously moves on to the next rollers through the guide ways. The motor used for

the roughing mill has a capacity of 800HP. enough power has to be produced to as the

shaft power has to be divided among three shafts.

3.2.5 Cutter

After the roughing mill it moves through the guide ways which are mostly

made of cast iron and these guides also provide an open top just in case the rod

expands and comes out of the guide. The guide ways are sometimes placed with a

cone which decreases miss alignment. These guide ways helps the tip of the red hot

rod to enter into the next roller that is the intermediate mill. This is the automated part

of the mill which does not need the manual method of feeding like in the roughing

mill. Hence there are front and back cutters which remove the front and back tip of

the hot rod as to allow proper entering into the next mill.

Here the cutter blade is visible it moves in a to and fro motion and as the red

hot rod is still soft it easily shears it. These shearers are sensory activated and are

automated. The sheared waste pieces are put aside as scrap. They usually fall beside

38

the cutter itself and are removed during maintenance. In fig.3.11 the cut pieces are

shown laying aside. These pieces actually fly off when they are cut. Shearing is easy

as the rod is red hot and still not fully hardened. This helps in easy shearing of these

pieces. The front and back tips of the rod are cut to enable it to freely pass through the

next roller.

Fig.3.10 Shearer or cutter

Fig.3.11 Pieces of rod cut from cutters

After every roller there is increase in the length of the rod which results in

bending or misalignment while entering into the roller. For that reason there are some

special cones placed while entering into the roller shown in the figure below. These

cones help the rod to enter in and align properly and go into the allocated grove in the

roller. Without this it may result in the slipping or entering into the wrong grove.

These are usually made of cast iron and are long lasting. They are made in such a way

so it would be easy while changing or removing the setup.

39

3.2.6 Finishing Mill

Fig.3.12 Finishing Mill

The finishing mill is the main roller where the required dimension is obtained.

The rollers are made with precision and in such a way that the exact dimension can be

obtained. Quality is of great importance, since the manufactured products are graded

and approved by the ISI. This gives the company an edge over its competitors. The

finishing mill also facilitates for the brand imprint to be put onto the rod. The picture

shows the finishing mill. The last three rollers of the finishing mill are placed inline.

Separate motors are used for each roller. The motors can also been seen coupled to the

rollers with shafts and universal joints. Just before entering the finishing mill, two

pinch rolls are placed to improve the speed and then, the red hot feed subsequently

enters the roller through a Shearer. The shearer is placed in such a way that the force

of the rod itself removes its tip. The schematic below describes the entrance of the

finishing mill.

The final dimensions of the TMT steel bar are achieved by finishing rollers.

The rods, after passing through the finishing rollers; are still soft due to high

temperature. There is a special guide way present after the finishing rollers which

leads the rods to the TMT quenching box. The conic shaped guide way helps in the

alignment of the rods while movement to prevent torsion. Before the finishing mill

there is a Shearer which cuts the edge suitably, to enter the finishing mill. The

sequence of the finishing mill is shown in fig.3.13

40

Fig.3.13 The sequence of the finishing mill

41

3.2.7 TMT Quenching Box

One of the most important parts of the plant is the TMT box where the

hardening takes place. Water is sprayed on the red hot rod to reduce the temperature

abruptly which results in the hardening of the outer surface of the rod. The amount of

hardening depends on the pressure of the water from the nozzle. This fig. shows the

quenching process. Various pipes can be seen which carry water and several gauges

are present for the measurement of water pressure. The pipes in blue show the

passage, through which hot rod passes. The rods are made to fall on the cooling bed

after the TMT treatment, but the speed of the rods is too high due to the motor power

and various pinch rolls. Hence to reduce the speed before the rod on exit, a breaker is

used. It reduces the speed of the incoming rod. The breaker provides safety to the

labor and prevents accidents. The finished products are then organized for Dispatch.

Fig.3.14 TMT quenching box

42

3.3 PROPERTIES OF TMT BARS

3.3.1 Advantages of TMT Bars

Better Safety of structures: because of higher Strength combined with higher

Ductility.

Easy working at site: owing to better Ductility and Bend ability. Pre-welded

meshes can be made to eliminate manual binding at site. Reduces construction

and fabrication time.

Resists fire: Unlike Tor steel/ CTD Reinforcement bars, TMT bars have high

thermal stability. They are the preferred choice when elevated temperatures of

400-6000 C may be encountered (Chimneys, fires).

Resists corrosion: The TMT process gives the bar superior strength and

anticorrosive properties. Controlled water-cooling prevents the formation of

coarse carbides, which has been cited as the main cause for the corrosive

nature of common bar. Another reason for better corrosion resistance is the

absence of surface stresses caused by the cold twisting process.

Formability: Due to very high elongation values and consistent properties

throughout the length of bar, TMT rebars have excellent workability and

bendability.

Earthquake resistance: The soft ferrite-pearlite core enables the bar to bear

dynamic and seismic loading. TMT bars have high fatigue resistance to

Dynamic/ Seismic loads due to its higher ductility quality. This makes them

most suitable for use in earthquake prone areas.

Malleability: TMT bars are most preferred because of their flexible nature

Fine welding features: TMT rebars (having low carbon content) can be used

for butt and other weld joints without reduction in strength at the weld joints.

Bonding strength: External ribs running across the entire length of the TMT

bar give superior bonding strength between the bar and the concrete. Fulfils

Bond requirements as per IS: 456/78 and IS: 1786/85.

Cost-effective: A high tensile strength and better elongation value gives you

great savings, Reduced Transportation Costs.

43

3.3.2 The grades of TMT bars

The grades of TMT bars are nothing but the various compositions the TMT

bars are made off. These compositions determine the various characteristics of TMT

bars such as malleability, hardness, etc. The following table shows the chemistry of

the steel used for the production of TMT bars:

Table 3.1 Chemical Quantity used for different grades of steel

In the production of TMT bars the carbon is restricted to below 0.20% for

imparting better ductility and bend-ability and to ensure better weld-ability. The

carbon equivalent of the steel is controlled by the addition of Manganese (from 0.50%

to 1.0% depending on the grade of the TMT bar being produced. In case of production

of corrosion resistant TMT bars, corrosion resisting elements are suitably added in the

steel.

Re-bar Quality

Table 3.2 Re-bar Quality and corresponding strength

44

3.3.3 Applications of TMT bar

TMT bars find wide applications in different spheres:

General purpose concrete re-enforcement structures

Bridges

Flyovers

Dams

High rise buildings

Industrial structures

Concrete roads

Underground structures

45

4. THE READY MIXED CONCRETE PLANT

Ready Mix Concrete (RMC) is a specialized material in which the cement aggregates

and other ingredients are weigh-batched at a plant in a central mixer or truck mixer, before

delivery to the construction site in a condition ready for placing by the builder. Thus, `fresh'

concrete is manufactured in a plant away from the construction site and transported within the

requisite journey time. The RMC supplier provides two services, firstly one of processing the

materials for making fresh concrete and secondly, of transporting a product within a short

time.

Fig.4.1 Dura Tech Ready mix concrete plant, Calicut

It is delivered to the worksite, often in transit mixers capable of mixing the

ingredients of the concrete just before the delivery of batch. This results in a precise mixture,

allowing specialty concrete mixtures to be developed and implemented on construction sites.

The second option available is to mix the concrete at the batching plant and deliver the mixed

concrete to the site in an agitator truck, which keeps the mixed concrete in correct form.

In the case of the centrally mixed type, the drum carrying the concrete revolves

slowly so as to prevent the mixed concrete from "segregation" and prevent its stiffening due

to initial set. However, in the case of the truck-mixed concrete, the batched materials (sand,

46

gravel and cement) are carried and water is added just at the time of mixing. In this case the

cement remains in contact with the wet or moist material and this phase cannot exceed the

permissible period, which is normally 90 minutes.

The use of the RMC is facilitated through a truck-mounted 'boom placer' that can

pump the product for ready use at multi-storied construction sites. A boom placer can pump

the concrete up 80 meters.

RMC is preferred to on-site concrete mixing because of the precision of the mixture

and reduced worksite confusion. It facilitates speedy construction through programmed

delivery at site and mechanized operation with consequent economy. It also decreases labour,

site supervising cost and project time, resulting in savings. Proper control and economy in use

of raw material results in saving of natural resources. It assures consistent quality through

accurate computerized control of aggregates and water as per mix designs. It minimizes

cement wastage due to bulk handling and there is no dust problem and therefore, pollution-

free.

Ready mix concrete is usually ordered in units of cubic yards or meters. It must

remain in motion until it is ready to be poured, or the cement may begin to solidify. The

ready mix concrete is generally released from the hopper in a relatively steady stream through

a trough system. Workers use shovels and hoes to push the concrete into place. Some projects

may require more than one production run of ready mix concrete, so more trucks may arrive

as needed or additional batches may be produced offsite and delivered.

However there are some disadvantages of RMC to, like double handling, which

results in additional cost and losses in weight, requirement of go downs for storage of cement

and large area at site for storage of raw materials. Aggregates get mixed and impurities creep

in because of wind, weather and mishandling at site. Improper mixing at site, as there is

ineffective control and intangible cost associated with unorganized preparation at site are

other drawbacks of RMC. There are always possibilities of manipulation; manual error and

mischief as concreting are done at the mercy of gangs, who manipulate the concrete mixes

and water cement ratio.

47

4.1 MATERIALS REQUIRED FOR RMC

4.1.1 Aggregate:

Aggregates are the important constituents in concrete. They give body to the

concrete, reduce shrinkage and effect economy. Earlier, aggregates were considered

as chemically inert materials but now it has been recognised that some of the

aggregates are chemically active and also that certain aggregates exhibit chemical

bond at the interface of aggregate and paste. The mere fact that the aggregates occupy

70-80 per cent of the volume of concrete, their impact on various characteristics and

properties of concrete is undoubtedly considerable. To know more about the

aggregates which constitute major volume in concrete.

Fig.4.2 Aggregate storage yard

Aggregates are divided into two categories from the consideration of size

Coarse aggregate

Fine aggregate

The size of the aggregate bigger than 4.75 mm is considered as coarse

aggregate and aggregate whose size is 4.75 mm and less is considered as fine

aggregate.

48

Sampling procedure for aggregates used in concrete:

Collect the aggregate sample from different locations at different depths

from the site immediately after unloading the aggregates from the trucks.

Collect the samples at least from 10 to 15 locations.

Thoroughly remix the sample collected from various places & depths of

the trucks or from the stocks.

Make a cone from the sample.

Flatten the cone sample to form a circle of uniform thickness.

Divide the cone in to four equal quarters.

Discard any two diagonally opposite segment of quartered sample.

Collect the remaining sample & remix.

Take this remixed aggregate for testing.

The material so sampled only should be taken for testing. The Indian standards

recommend sampling the aggregates as above. However it recommends collecting

samples from different sub lots which are not practical as it takes long time to build

up the lots at site. Hence the method suggested above may be conveniently adopted at

site.

4.1.2 Cement

Cement is a binder material which sets and hardens independently, and can

bind other materials together. Cement is made up of four main compounds tricalcium

silicate (3CaO SiO2), dicalcium Silicate (2CaO SiO2), tricalcium acuminate (3CaO

Al2O3), and tetra-calcium aluminoferrite (4caco Al2O3 Fe2O3).tetra-calcium

aluminoferrite (4CaO Al2O3 Fe2O3). In an abbreviated notation differing from the

normal atomic symbols, these compounds are designated as C3S, C2S, C3A, and

C4AF, where C stands for calcium oxide (lime), S for silica and A for alumina, and F

for iron oxide. Small amounts of uncombined lime and magnesia also are present,

along with alkalis and minor amounts of other elements.

49

4.1.3 Admixture

The role of admixture is ready mixed of concrete is same as that in normal

concrete. However, admixture used in RMC is modified to meet the requirement of

pumpable concrete and other properties of concrete. The types of admixture used in

RMC are generally termed as Super plasticizers.

Fig.4.3 The CAC Admixture used at Dura Tech

The history of admixture is as old as history of concrete. There are several

types of admixture available in market. But few admixtures namely Plasticizers and

Super plasticizers are of recent interest. These of admixture were initially developed

in Japan and German around 1970. IN India use of admixture was recognized after

1985.In 1990 admixture started to gain Importance after introducing Ready Mixed

Concrete. The importance of admixture was further recognized after revision on of IS:

456 - 1978. The earlier versions of IS 456 have permitted to use w/c ratio as high as

0.65 in RCC works. The Revised IS 456-2000 has Restricted the w/c ratio to 0.55 for

mild exposure and 0.50 for moderate exposure ,0.45 for severe and very severe

exposure and 0.40 for extreme weathering conditions. The restriction on w/c ratio has

made the use of admixture all the more compulsory ingredient of concrete.

50

Admixture is used in RMC are of following types:

Chemical admixture

Mineral admixture

Chemical and mineral admixture

In RMC admixture mainly perform the following functions:

Increasing workability

Accelerate or retard the setting time of concrete.

Reduce segregation and bleeding in concrete.

Improve pump ability.

4.1.4 Fly Ash

Fly ash is a by-product from coal-fired electricity generating power plants.

The coal used in these power plants is mainly composed of combustible elements

such as carbon, hydrogen and oxygen (nitrogen and sulphur being minor elements),

and non combustible impurities (10 to 40%) usually present in the form of clay, shale,

quartz, feldspar and limestone. As the coal travels through the high-temperature zone

in the furnace, the combustible elements of the coal are burnt off, whereas the mineral

impurities of the coal fuse and chemically recombine to produce various crystalline

phases of the molten ash. The molten ash is entrained in the flue gas and cools

rapidly, when leaving the combustion zone (e.g. from 1500°C to 200°C in few

seconds), into spherical, glassy particles. Most of these particles fly out with the flue

gas stream and are therefore called fly ash. The fly ash is then collected in

electrostatic precipitators or bag houses and the fineness of the fly ash can be

controlled by how and where the particles are collected. Fly ash use improves

concrete performance, making it stronger, more durable, and more resistant to

chemical attack. Fly ash use also creates significant benefits for our environment.

The size of fly ash ranges from 1.0 to 100 micron & the average size is around

20 microns. It is found that particle size below 10 microns contributes towards early

Development of strength (7& 28 days). The particle size of fly ash between l0 & 40

microns Contributes towards the development of strength between 28 days & 1 year.

The particle size above 45 microns does not contribute towards development of

51

strength even after 1 year and for all practical purpose they should be considered only

as sand.

The fly ash is generally used in the concrete in the following ways.

As partial replace for cement.

As partial replacement for sand.

As simultaneous replacement for both cement and sand.

It is found that fly ash replacement from l0 to 30% increases the development

of Strength up to 3 month or even more depending on the fineness of fly ash & its

reaction with Calcium hydroxide released during primary hydration of cement.

Addition of fly ash as per replacement of cement improves the workability of

concrete for the same water content. This means that the water content can be reduced

for fly ash based concrete. This reduced water cement ratio to some extent can offset

for initial gain of Strength can range from 10 to 25 % of the difference in strength

between the strength of Normal concrete & fly ash concrete.

Fly ash as a partial replacement for sand is uneconomical and sometimes it is

inevitable in pumping concrete especially when coarser types of fine aggregates are

used in concrete. It is also found that partial replacement of fly ash marginally

increases the strength Concrete due to filler effect in the initial stages and due to

pozzolanic action in 28days.Simultaneous use of fly ash as a partial replacement of

cement and sand is good Proposal to increase strength, workability & pump ability of

concrete.

52

4.1.5 Water

The pH value of water should be in between 6.0 and 8.0 according to IS 456-

2000.

Effect of Mixing Sea Water in Concrete

The sea Water generally contains salinity of about 3.5% in which about 80% is

sodium chloride. Many researchers have been conducted to study the corrosion

problem of steel Embedded in concrete where sea water is used as mixing water in

concrete nevertheless the Indian standard is adamant & do not permit using sea water

for mixing or curing in reinforced Concrete constructions, but allows for using of sea

water only for PCC work that too under unavoidable circumstances.

Quality of Water for Curing Concrete Members:

Generally the water that is fit for mixing of water in concrete is also fit for

curing. However where appearance is important, water containing impurities which

cause stains should not to be used. The most important elements that cause stains in

the concrete are iron, and organic matters. It is also found that even sea water also

causes stains in concrete. Hence water containing iron, organic matters and also sea

water should not be used for curing of concrete when appearance is also set as criteria

for the acceptance of concrete.

Quality of Water for Curing Concrete Cubes:

The water that is fit for mixing and curing of water for concrete is also fit for

curing of cubes which are cured under water. However the curing water should not to

be allowed to remain in stagnant condition in water tanks for long time. As a

guideline the water tanks shall be cleaned twice a week or when ph value of water

reaches a value more than 9. The cleaned Water tanks shall be refilled with fresh

water every time.

The cleaning of water is necessary to remove algae and fungus materials

developed inside the water tanks which otherwise alters the setting and strength

gaining properties of Concrete. The low results of such cubes may call for in situ tests

resulting in consequential Delay of the project.

53

4.2 EQUIPMENTS REQUIRED

4.2.1 Batching Plant

The principal functional elements of every stationary concrete production

Plant comprises of the following:

Storage of materials - Silos, containers and bins

Batching arrangement

Measuring and recording equipment

Mixing equipment

Control systems

Electrical, hydraulic and pneumatic drives

Conveying systems (belt / screw conveyors)

Fig.4.4 Dura Tech Batching Plant, Calicut

Storage of Materials

i) Cement - Cement is generally stored in silos. The loading of cement is done with

the help of pneumatic blower systems either installed on bulk carriers or a separate

system available at the plant. If baggage cement is used then the cement is loaded

using a compressed air loader and a splitter unit.

54

Cement is weighed separately, and is transported from the silo into a mechanical or

electro mechanical weigher by means of a screw conveyor.

ii) Water - Water is generally stored in tanks located close to the plant. It is accurately

measured by a water gauge and microprocessor controlled system. The modern plants

have new litronic MFM 85 moisture recorders. These recorders actually measure the

moisture present in sand while the entire batch flows past. A recording unit calculates

the average moisture value of the sand and passes on the information to the batching

control unit to allow corrective action to be taken. The system operates to an accuracy

of as low as 0.2% relative moisture.

Consistency of the mix is generally checked by visual observation later confirming it

with a workability test like the slump test. However, in modern plants consistency of

the concrete mix is checked by a remote recording system which is automatic, easy

and more accurate.

If concrete is very dry (stiff) the electrical resistance of the batch is measured and if

the concrete is wet the motor output is measured.

Accurate maintenance of the workability (consistency) of one cubic meter batch of

concrete may depend on as little as one litre or less of water. It is scarcely conceivable

that such a production process could be controlled without actually measuring the

workability and later correcting the consistency.

iii) Aggregates - The storage of aggregates is done in various way depending on the

type of plant.

There are basically three types of plants generally in use.

Vertical Production Plant - In this the aggregates are stored above the batching and

mixing elements, in one or more silos. These plants are not suitable for relocation at

short intervals of time. As the aggregates are stored in silos it is relatively easy to

protect the aggregates from very low temperature in winter period.

Horizontal Production Plant

They can be again broadly classified into four types

Star pattern aggregate storage

Storage in tall silo

Storage in pocket silo

Inline aggregate storage silos

55

The star bin storage of aggregates is most popular in India mainly because of climate

conditions. The aggregates can be stored exposed to ambient temperature in different

compartments forming a star type pattern. A storage capacity of up to 1500 CuM is

possible in this type. The star pattern aggregates are stored in four to six

compartments. They are bulked at a 45 degree flow angle against the batching plant's

bulkhead and partition wall of the compartments using a boom type dragline loader.

The drag-line operations are either fully manual, semi automatic or fully automatic.

Fully automatic dragline loader system operator.

The star bin type plant requires more space and as the aggregates are stored in open

they heat up at high ambient temperatures and freeze at very low temperatures. These

types of plants are not suitable in extreme weather conditions.

In silo type storage additional investment for loading equipment such as hopper,

bucket elevator or conveyor belt plus rotary distribution are required. They have large

active storage (up to 500 CuM) in a small areas. Loading is fully automatic,

aggregates are well protected in extreme climatic conditions and storage is very clean.

Batching Arrangements

Batching is the process of measurement of specified quantities of cement,

aggregates, water and admixture, i.e., ingredients of concrete in correct proportion.

The batching arrangement should control and store the materials. For that aggregate

bins provided for storing aggregate and Silos tanks for storing cement and

cementitious materials

Fig.4.5 the Batching Equipment at Dura Tech

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Batching Process

Volumetric batching - Not desirable except for small non engineered jobs

Weigh Batching (Mass basis, IS456:2000)

Components of a Batching Plant

Aggregate bins for various types of aggregates.

Feeding mechanisms such as scrappers, conveyors or hoists etc. to transfer

aggregate to scales (balances).

Balance and measuring system.

Cement silos and a conveyor screw or bucket conveyor.

The storage tank for water and water measuring system.

Dispenser for chemical (liquid) admixture.

Mixing Arrangements

There are various types of concrete mixers used on the concrete production

plant. The two basic types are free fall mixers and power mixers. Most of our

indigenously manufactured plants have free fall mixer. Free fall mixer consists of a

rotating drum with blade fixed on the drum's interior. As the drum rotates, the

material inside is lifted and dropped. The drum is loaded and emptied by changing the

direction of rotation, dropping a flap or tipping it.

Most of the imported plants have power mixer. The power mixer sets in

motion the materials positively. The materials get thoroughly mixed by rotating arms.

These mixers have shorter mixing time; give better homogeneity, consistency and

strength to the concrete. Besides, they have better facility for inspection.

If mixing is to be done on difficult concrete mixes, additional agitator is

provided. The pan type mixer with additional agitator or two agitators is claimed to be

far in advance of any if other mixer. Using additional agitators almost halves the

mixing time. The additional agitator is driven by a separate hydraulic system and can

be set to any speed between 0 to 200 revolutions per minute.

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Control Systems

Almost all imported production plants offer automatic systems for control

functions. These are required for better quality control, higher economy and superior

working conditions. Fully automatic plant control systems with multiple inputs for up

to 120 mixes or template control system are usually housed in a container or control

room of the plant. Micro processor controlled production plants represent the state of

the art in the developed countries.

Fig.4.6 Process Control System

These controls are operated from main desk. It also has material availability

monitor and printer plus an additional batching monitor. The entire plant can be

operated by just one person. Microprocessor control besides having fully automatic

running facility offers number of additional features like statistical data recording and

processing, a printer unit, moisture adjustment arrangement, customer address,

memory etc.

All you need to do is push the required mix template into the slot and press the

"start" button and the control system does the rest. Aggregate and cement weighment,

moisture correction, overrun correction and additive weighment are done accurately

to give the concrete mix of desired strength and workability. The built in trouble

shooting programs are most valuable and have a high reliability factor. Even upto

1500 mixes of different types can be stored along with names and addresses of the

consumer and other data which is required to be stored in the computer for operation

of the plant. The mix data with quantity can be if required printed by the printer which

is very useful for invoicing the consumer for the concrete supplied to them.

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4.2.2 Transportation Equipment: Transit Mixer

There are developments taking place all over the world for different types of

concrete equipments. However, the transit mixer is one of the most .popular

equipments out of several modes available. In India too, a number of transit mixers

are in use all over the country which are mainly mounted on Indian truck chassis. The

mixer drum is either manufactured in India or is improved. However, in general, the

hydraulic system is improved.

4.3 MIXING PROCESS

Thorough mixing of the materials is essential for the production of uniform concrete.

The mixing should ensure that the mass becomes homogeneous, uniform in colour and

consistency. There are three methods adopted for mixing Ready Mix Concrete.

4.3.1 Transit Mixed (Or "Truck-Mixed") Concrete

While ready mixed concrete can be delivered to the point of placement in a

variety of ways, the overwhelming majority of it is brought to the construction site in

truck-mounted, rotating drum mixers. Truck mixers have a revolving drum with the

axis inclined to the horizontal. Inside the shell of the mixer drum are a pair of blades

or fins that wrap in a helical (spiral) configuration from the head to the opening of the

drum. This configuration enables the concrete to mix when the drum spins in one

direction and causes it to discharge when the direction is reversed.

To load, or charge, raw materials from a transit mix plant or centrally mixed

concrete into the truck, the drum must be turned very fast in the charging direction.

After the concrete is loaded and mixed, it is normally hauled to the job site with the

drum turning at a speed of less than 2 rpm.

Since its inception in the mid-1920, the traditional truck-mixer has discharged

concrete at the rear of the truck. Front discharge units, however, are rapidly becoming

more popular with contractors. The driver of the front discharge truck can drive

directly onto the site and can mechanically control the positioning of the discharge

chute without the help of contractor personnel.

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Fig.4.7 Transit Mixer, Dura Tech

Fig.4.8 Helical Blades inside Transit Mixer Drum

Currently, because of weight laws, the typical truck mixer is a 7 to 8.5 m3.

The drums are designed with a rated maximum capacity of 63% of the gross drum

volume as a mixer and 80% of the drum volume as an agitator. Generally, ready

mixed concrete producers, load their trucks with a quantity at or near the rated mixer

capacity. Fresh concrete is a perishable product that may undergo slump loss

depending on temperature, time to the delivery point on the job site, and other factors.

Water should not to be added to the mix unless the slump is less than that

which is specified. If water is added, it should be added all at once and the drum of

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the truck mixer should be turned minimum of 30 revolutions, or about two minutes, at

mixing speed.

The ASTM C 94, Specification for Ready Mixed Concrete, indicates that the

concrete shall be discharged on the job site within 90 minutes and before 300

revolutions after water was added to the cement. The purchaser may waive this

requirement, when conditions permit.

In certain situations, air-entraining, water reducing, set-retarding or high-range

water reducing admixtures may need to be added to concrete prior to discharge to

compensate for loss of air, high temperatures or long delivery times. The ready mixed

concrete producer will assist the purchaser in such circumstances.

4.4 TESTS ON MATERIALS

4.4.1 Tests on Fine Aggregates

Sieve Analysis

Specific Gravity (Pycnometer Method)

Bulk Density Test

Absorption Test

4.4.2 Tests on Coarse Aggregates

Sieve Analysis

Specific Gravity Test

Aggregate Impact Value Test

Bulk Density Test

Water Absorption Test

Flakiness Index Test

Elongation Index Test

4.4.3 Test on Fresh Concrete

Slump Test

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4.4.4 Test on Water

pH Value

Chloride

Sulphite

Nitrite

4.4.5 Test on Hardened Concrete

Compressive Strength

Flexure Strength

Fig.4.9 Compression Testing Machine Fig.4.10 Concrete Mixing Drum

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Fig.4.11 Pycnometer Fig.4.12 Slump Cone

Fig.4.13 IS Course Sieves Fig.4.14 IS Fine Sieves

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4.5 OPERATIONAL ASPECT

4.5.1 Needs to be specified by Consumer for RMC

The following needs to be specified very clearly:

Characteristic strength or grade (N/mm2)

Target workability or slump in mm required at site

Exposure conditions for durability requirements

Maximum water to cement ratio

Minimum cement content

Maximum aggregate size

Type of cement

Mineral admixture and its proportion (Kg/m3)

Maximum aggregate size

Rate of gain of strength (for formwork removal or prestressing etc.)

Maximum temperature of concrete at the time of placing (in extreme climatic

conditions or in case of massive concrete pours)

Type of surface finish desired.

Method of placing

Rate of supply desired to match the placing and compaction speed planned at

site.

Quantity of concrete required.

Lift and lead of concrete transportation and placement at site.

Frequency of concrete testing

Details of materials and their required tests.

Permeability tests required (if any)

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Placing of concrete in formwork to be under scope of RMC supplier (if

required)

Permissible wastage

Mode of measurement.

4.5.2 Information to be supplied by the Producer

The RMC supplier must provide the following information to the consumer if

and when requested:

Nature and source of each constituent material including the name of the

manufacturer in case of branded products like cement, admixtures etc.

Proportion of quantity of each constituent per CuM of fresh concrete.

Generic type of the active constituent of the chemical admixture and its solid

content.

Chloride content in all constituent materials.

Compatibility of cement and chemical/mineral admixtures.

Compatibility of admixtures with one another when more than two types of

admixtures are proposed.

Initial and final setting time of concrete when admixture is used.

Details of plant and machinery (capacity CuM/hr), storage (CuM) availability,

type of facilities to dose admixtures, type of moisture measurement

arrangement, type of mixer, rated capacity (CuM/min.) of the mixer.

Availability of number of transit mixers and their capacities.

Details of last calibrations done on various weighing /dosing equipments

Testing facilities available at RMC plant

Capacity and type of concrete pump and placing equipment available (if

required)

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5. CONCLUSION

By visiting the Sree Padmanabhapuram Palace we were able to grasp lots of

information about the traditional Kerala architecture in detail. The significant quality of the

buildings at Padmanabhapuram is the sensitive handling of the light and atmosphere of

repose created throughout. The aesthetics importance of the palace might well be described as

a subtle combination of sophisticated understatement in design and a tactile celebration of

material employed.

Steel is a product of a large and technologically complex industry having strong

forward and backward linkages in terms of material flows and income generation. TMT Bars

are re rolled bars from Ingots/Billets. The finished product TMT bars are of Fe 415 & Fe 500

Grade steel bars. TMT bars have proven record in resisting loss of strength at high

temperatures as experienced during fires. These bars are corrosion resistant. TMT Bars can

be described as new generation-high strength steel having superior properties such as weld

ability, strength, ductility and tensile strength, which meet the highest international quality

standards.

The concrete quality produced in RMC plant is highly consistent with low deviation

order. It provides a high degree of overall strength of hardened concrete and the performance

of the structure at a later date. RMC operations are highly mechanized and fully controlled

through electronic controls and hence reduce the probability of errors in various operations. It

is also environment friendly and brings down pollution due to dust at construction can also be

accelerate with the use of RMC. The use RMC in civil construction is widely adopted

throughout the world.