S.R.V ENGINEERING COLLEGEDEPARTMENT OF CIVIL ENGINEERING

CE 6002 – CONCRETE TECHNOLOGYUNIT – I

CONSTITUENT MATERIALS

OUTLINE1. DEFINITION OF CEMENT2. MANUFACTURING PROCESS3. TYPES OF CEMENT4. GLOBAL SCENARIO5. EVOLUTION OF INDIAN CEMENT FACTORY6. Economic status 7. USES OF CEMENT8. TESTS9. Aggregates10.Classification of aggregates11.CHARACTERSTICS OF AGGREGATES12.AGGREGATE TEST

• The word Cement has come from the Roman word ‘Opus Caementicium’

• Cement is a binder, a substance that sets and hardens independently, and can bind other materials together.

• The most important use of cement is the production of mortar and concrete—the bonding of natural or artificial aggregates to form a strong building material that is durable in the face of normal environmental effects.

• Joseph Aspdin, a British stonemason, invented Portland cement way back in 1824. With this invention, Aspdin laid the foundation of today’s cement industry.

What Is CEMENT?

MANUFACTURING PROCESSCement is made out of limestone, shale, clay mined out of quarry close to the

plant.

The raw material is crushed, and then heated at temperature in excess of 1000

degree Celsius in rotating kiln to become clinker.

Clinker is then mixed with gypsum and ground to a fine powder to produce

final grade of cement.

The technology is a continuous process

At present 93% of cement production in India is based on modern and

environment-friendly dry process technology and only 7% of the capacity is based

on old wet and semi-dry process technology.

The cost of Cement is 29% energy; 27% raw materials; 32% labour and 12%

depreciation

MANUFACTURING PROCESS

TYPES OF CEMENT

•Ordinary Portland Cement (OPC)

•Portland Pozzolana Cement (PPC)

•Portland Blast Furnace Slag Cement (PBFS)

•Oil Well Cement

•Rapid Hardening

• Sulphate Resisting Portland Cement

•White Cement etc.

The basic raw materials used in the cement manufacturing process are limestone, sand, shale, clay, and iron ore.

GLOBAL SCENARIO•Today, it is estimated that there are around 1500 integrated cement production plants in the world.

•It is estimated that world cement consumption is to rise on an average between 3.6% and 4.8% per year in the coming years.

•Most of the growth is coming from Central and Eastern Europe and Asia, growth in mature markets also looks healthy.

•The share of the four largest firms account only for 23% of the overall demand.

•LAFARGE and CEMEX have become very strong global cement players.

EVOLUTION OF INDIAN CEMENT FACTORY•A Kolkata based company started manufacturing cement in 1889.

•In 1914, Indian Cement Company Ltd was established in Porbandar.

•In 1927, Concrete Association of India was set up to create public awareness on the utility of cement.

•In 1956, price and distribution system of cement industry came under government control.

•After the economic reform in 1980’s the government control on cement industry was liberalized.

•A great increase in demand of cement, has resulted India to become 2nd largest cement producer in the world after China.

ECONOMIC STATUSGrowth Rate

Investments

Exports

FDI and GDP

GROWTH RATE•India is the world’s second largest producer of cement with total capacity of 224 million tonnes as on April 2010.

•Indian Cement Industry comprises of 140 large and more than 365 mini cement plants.

•According to ACC cement report, Government’s continued thrust on infrastructure will help the cement to maintain an annual growth of 9-10% in 2010.

•With addition in the cement production, it is expected that cement production in India will reach 300 million tonnes in the coming years.

INVESTMENTS•Cement and gypsum products have received cumulative FDI of US$ 1708.69 million between April 2000 and March 2010, according to the Department of Industrial Policy and Promotion.

•Madras Cements Ltd is planning to invest US$ 178.4 million to increase the manufacturing capacity of its Ariyalur plant in Tamil Nadu to 4.5 MT from 2 MT by April 2011. •Shree Cement, plans to invest US$ 97.13 million this year to set up a 1.5 MT clinker and grinding unit in Rajasthan. Moreover, in June 2010, Shree Cement signed an MoU with the Karnataka government to invest US$ 423.6 million for setting up a cement unit and a power plant.

EXPORTS•During 2007-08, the export of cement from India touched the 2.16 million tonnes mark. However during 2008-09, the cement export from India stood at 1.46 million tonnes. 

•In spite of seeing fall during 2008-09, the export segment of the industry is expected to grow again on account of various infrastructure projects that are being taken up all over the world. India has an immense potential to tap markets of Middle East and South East Asia

•The negative ACGR (Annual Compound Exponential Growth Rate) of -5.52% in control period has seen ACGR of 35.35% in decontrolled and opened up economy

FDI AND CONTRIBUTION OF GDP•The industry occupies an important place in the national economy because of its strong linkages to other sectors such as construction, transportation , coal and power.

•The cement industry is one of the major contributors to the exchequer by way of indirect taxes.

•100% FDI is permitted in the cement industry.

•It contributes approximately 1.3% of GDP and the industry is employing over 0.14 million people

USES…•Production of Concrete

• Construction Purposeo Building (Floors, Beams, Columns,

Roofing)o Transport (Roads, Pathways, Crossings,

Bridge)o Water (Pipes, Drains, Canals)o Agriculture (Irrigation, Housing)

TESTING OF CEMENTS1. Field testing2. Standard consistency test 3. Fineness test4. Soundness test5. Strength test

FIELD TESTING TESTOpen the bag and take a good look at the cement, then it should

not contain any visible lumps. Colour of cement should be greenish grey.Should get cool feeling when thrusted.When we touch the cement, it should give a smooth &not a

gritty feeling.When we throw the cement on a bucket full of water before it

sinks the particles should flow.When we make a stiff paste of cement & cut it with sharp

edges & kept on a glass plate under water there wont be any disturbance to the shape& should get strength after 24hours.

STANDARD CONSISTENCY TEST The standard consistency of a cement paste is defined as that consistency which will permit a Vicat plunger having 10 mm diameter and 50 mm length to penetrate to a depth of 33-35 mm from the top of the mould.

USE:Used to find out the percentage of water required to

produce a cement paste of standard consistency. This is also called normal consistency (CPNC).

PROCEDURE

PROCEDURE•For first trial, take about 500gms of cement & water of 24%by weight of cement.

•Fill it in Vicat’s mould with in 3-5min.

•After filling, shake the mould to expel air.

•A standard plunger, 10 mm diameter, 50 mm long is attached and brought down to touch the surface of the paste and quickly released.

•Note the reading according to depth of penetration of the plunger.

Conduct trials continuously by taking different water cement ratios till the plunger penetrates for a depth of 33-35mm from top.This particular percentage is known as percentage of water required to produce cement paste of standard consistency.This is usually denoted as ‘P’.

SETTING TIME TESTAn arbitraty division has been made for the setting

time of cement.

Initial setting time &

Final setting time.

INITIAL SETTING TIMEThe time elapsed between the moment that the water

is added to the cement, to the time that the paste starts losing its plasticity.

Normally a minimum of 30min has maintained for mixing & handling operations.

It should not be less than 30min.

FINAL SETTING TIMEThe time elapsed between the moment the water is

added to the cement, and the time when the paste has completely lost its plasticity and has attained sufficient firmness to resist certain definite pressure.

It should not exceed 10hours.So that it is avoided from least vulnerable to damages

from external activities.

SIEVE TESTPROCEDURE:

•Take correctly 100grams of cement on a standard IS sieve No.9

•Break down the air-set lumps & sieve it &weigh it.

•This weight shall not exceed 10% for ordinary cement.

•Sieve test is rarely used.

SOUNDNESS TEST It is very important that the cement after setting shall not undergo any

appreciable change of volume.

This test is to ensure that the cement does not show any subsequent expansions.

The unsoundness in cement is due to the presence of excess of lime combined with acidic oxide at the kiln.

This is due to high proportion of magnesia & calcium sulphate.

Therefore magnesia content in cement is limited to 6%.

Gypsum 3-5.

STRENGTH TEST

This is the most important of all properties of hardened cement.

Due to excessive shrinkage and cracking the strength tests are not made on heat cement paste.

Standard sand is used for finding the strength of cement.

aggregatesAggregates are inert materials which are mixed with binding material such as cement or lime for manufacturing of mortar or concrete. Aggregates are used as filler in mortar and concrete and also to reduce their cost.

classification

(1) Fine aggregates

(2) Coarse aggregates

Fine aggregatesAggregates whose particles pass through 4.75 mm IS sieve are termed as fine aggregates. Most commonly used fine aggregates are sand (pit or quarry sand, river sand and sea sand) and crushed stone in powdered form, how ever some times sukhi and ash or cinder are also used.

a) sand: It consists of small angular or rounded grains of silica depending upon the source from which it is obtained. It is classified as:

(i) Pit or quarry sand

(ii) River Sand

(iii) Sea Sand

(i) Pit or quarry sand

It is found as deposited in soil and is to be excavated out. Its grains are generally sharp or angular. It should be free from organic matter and clay. It is usually considered to be the best fine aggregate for use in mortar and concrete.

(ii) River SandIt is obtained from the banks and beds of rivers. It may be fine or coarse. Fine sand obtained from beds and banks of rivers is often found mixed with silt and clay so it should be washed before use. But coarse sand is generally clean and excellent for use especially for plastering.

(iii) Sea Sand

It consists of fine rounded grains of brown colour and it is collected from sea shores or sea beaches. Sea sand usually contains salts and while using that in mortar, etc, causes disintegration of the work in which it is used. In R.C.C work these salts will attack reinforcement if salt content is high. These salts may cause efflorescence. It should be used locally after thorough washing.

b) Crushed stone:It is obtained by crushing the waste stones of quarries to the

particular size of sand. Sand obtained from by crushing a good quality stone is excellent fine aggregate.

Mortar made with this sand is usually used in ashlar work (good quality of work).

Coarse aggregatesAggregates whose particles do not pass through 4.75 mm IS are termed as coarse aggregates. Most commonly used coarse aggregates are crushed stone, gravel; broken pieces of burnt bricks,etc.

a) sand:It is an excellent coarse aggregate and is obtained by crushing granite, sand stone or grained lime stone and all types of stones. Crushed stones are used for the construction of roads and railway tracks, etc.

b) gravel:It is an other very good coarse aggregate. It is obtained from river beds, quarries and sea shores. The gravel obtained from sea shores should be well washed with fresh water before use in order to remove the impurities which may be clay, salts ,silt,etc. It is commonly used in the preparation of concrete.

C) BROKEN PIECES OF BRICKS:It is also a good artificial source of coarse aggregates. It is obtained by breaking well burnt bricks. It is generally used in lime concrete at places where aggregates from natural sources are either not available or are expensive. It can be used at places where low strength is required. It should be watered well before using it in the preparation of concrete. It is commonly used for mass concrete in foundations and under floors.

GOOD QUALITIES OF IDEAL AGGREGATE:(1) It should consist of natural stones, gravels and sand or in various combinations of these materials.(2) It should be hard, strong and durable.(3) It should be dense, clear and free from any coating.(4) It should be free from injurious vegetable matters.(5) It should not contain flaky (angular) and elongated pieces.(6) It should not contain any material liable to attack steel reinforcement in case of reinforced concrete.

CHARACTERSTICS OF aggregates

a) COMPOSITION:Aggregate containing the constituents which generally react with alkalies in cement cause excessive expansion, cracking of concrete mix, should never be used. Suitability of aggregates should be judged either by studying its service history or by laboratory tests.

B) SIZE AND SHAPE:The size and shape of the aggregate particles mainly influence the quantity of cement required in a concrete mix and ultimately economy of the concrete. For the preparation of economical concrete, one should use largest coarse aggregates feasible for the structure.

TEST’S OF aggregatesa) CRUSHING TEST :

The aggregate crushing value gives a relative measure of resistance of an aggregate to crushing under a gradually applied compressive load. The aggregate crushing strength value is useful factor to know the behaviour of aggregates when subjected to wear.

B) IMPACT VALUE:The aggregate impact value gives a relative measure of the resistance of an aggregate to sudden shock or impact. The impact value is some times used as an alternative to its crushing value.

C) ABRASION VALUE:The aggregate abrasion value gives a relative measure of resistance of an aggregate to wear when it is rotated in a cylinder along with some abrasive charge.

THE END……