NSCET E-LEARNING PRESENTATION 1/UNIT I Constituent Materials.pdf · Gupta.B.L & Amit Gupta, "Concrete Technology", Jain Book Agency, 2010. 2. Shetty,M.S, "Concrete Technology", S.Chand

NSCET E-LEARNING

PRESENTATIONLISTEN … LEARN… LEAD…

DEPARTMENT OF CIVIL ENGINEERING

Mr.R.Shanmugapriyan M.E.,

Assistant Professor

Nadar Saraswathi College of Engineering & Technology,

Vadapudupatti, Annanji (po), Theni – 625531.

CE 8404 – Concrete Technology

IInd YEAR / IVth SEMESTER

OBJECTIVETo impart knowledge to the students on theproperties of materials for concrete bysuitable tests, mix design for concrete andspecial concretes.

IntroductionSYLLABUS – LECTURE 01

Department of Civil Engineering, NSCET, Theni Page-5

UNIT I CONSTITUENT MATERIALSCement

• Different types

• Chemical composition and Properties

• Tests on cement-IS Specifications

Aggregates

• Classification

• Mechanical properties and tests as per BIS

• Grading requirements

Water

• Quality of water for use in concrete.


UNIT II CHEMICAL AND MINERAL ADMIXTURES

Chemical Admixtures like

• Accelerators

• Retarders

• Plasticizers

• Super plasticizers

• Water proofers

Mineral Admixtures like

• Fly Ash

• Silica Fume

• Ground Granulated Blast Furnace Slag and

• Metakaoline and their effects on concrete properties

UNIT III PROPORTIONING OF CONCRETE MIX

• Principles of Mix Proportioning

• Properties of concrete related to Mix Design• Physical properties of material required for Mix Design

• Design Mix and Nominal Mix

• BIS Method of Mix Design

• Mix Design Examples

Department of Civil Engineering, NSCET, Theni Page-03Department of Civil Engineering, NSCET, Theni Page-7

UNIT IV FRESH AND HARDENED PROPERTIES OF CONCRETE

• Workability

• Tests for workability of concrete

• Slump Test and Compacting factor Test

• Segregation and Bleeding

• Determination of Compressive and Flexural strength as per BIS

• Properties of Hardened concrete

• Determination of Compressive and Flexural strength

• Stress-strain curve for concrete

• Determination of Young’s Modulus.


UNIT V SPECIAL CONCRETES

• Light weight concretes

• High strength concrete

• Fibre reinforced concrete

• Ferrocement

• Ready mix concrete

• SIFCON

• Shotcrete

• Polymer concrete

• High performance concrete

• Geopolymer Concrete


TEXTBOOKS:

1. Gupta.B.L & Amit Gupta, "Concrete Technology", Jain Book Agency, 2010.

2. Shetty,M.S, "Concrete Technology", S.Chand and Company Ltd, New Delhi, 2003


REFERENCES:

1. Santhakumar,A.R; "Concrete Technology" , Oxford University Press, New Delhi,

2007

2. Neville, A.M; "Properties of Concrete", Pitman Publishing Limited,

London,1995

3. Gambir, M.L; "Concrete Technology", 3rd Edition, Tata McGraw Hill Publishing

Co Ltd, New Delhi, 2007

4. IS10262-1982 Recommended Guidelines for Concrete Mix Design, Bureau of

Indian Standards, New Delhi, 1998


Cement UNIT 01 - CONSTITUENT MATERIALS – LECTURE 02


CEMENT

Cement is mineral powder or substance, which are obtained by raw materials such asclay (Argillaceous) and lime (Calcareous). It is used to bind other materials likeaggregates in concrete.Cement is also known as Ordinary Portland cement (OPC) or Hydraulic cement

Active materials:

Cement and water

Inactive materials:

Fine and coarse aggregate

Coarse aggregate

Mortar (Fine aggregate

+Cement)

Aconcrete


CEMENT MANUFACTURING PROCESS

Manufacturing of cement is the process of making cement from raw materials suchas calcareous materials (Lime) and Argillaceous materials (Clay).There are three main operations involved in the manufacture of ordinary Portlandcement.

Mixing of Raw Material:

•In this stage both raw materials are finely ground and mixed thoroughly in wet or dry process

•In Wet process both raw materials are washed and stored separately. Then mixed in wet state•In the dry mix

process, both materials are stored separately in dry state.

Burning:

•The raw mix is preheated before it goes into the kiln, which is heated by a flame that can be as hot as 2000 °C. The raw mix burns at 1500 °C producing clinker which, when it leaves the kiln, is rapidly cooled with air fans. So, the raw mix is burnt to produce clinker : the basic material needed to make cement.

Grinding

•The clinker and the gypsum are very finely ground giving a “pure cement”. Other secondary additives and cementitious materials can also be added to make a blended cement.

Storage, Packing, Dispatch

•The cement is stored in silos before being dispatched either in bulk or in bags to its final destination..


Cement Chemical composition and Properties

UNIT 01 - CONSTITUENT MATERIALS – LECTURE 02


Chemical Composition

During the burning process, the raw materials fused together and gives more complex

chemical compositions as follows;

Oxide Percent content

CaO 60-67

SiO2 17-25

Al2O3 3.0-8.0

Fe2O3 0.5-6.0

MgO 0.1-4.0

Alkalies (k2O, Na2O) 0.4-1.3

SO3 1.3-3.0


Chemical Composition

During the burning process, the raw materials fused together and gives more complex

chemical compositions as follows;

Oxide Percent content

CaO 60-67

SiO2 17-25

Al2O3 3.0-8.0

Fe2O3 0.5-6.0

MgO 0.1-4.0

Alkalies (k2O, Na2O) 0.4-1.3

SO3 1.3-3.0


Chemical CompositionFunctions of cement ingredient: (8marks)

Lime / Calcium oxide (Ca O): Controls strength and soundness. If it is reduced in quantity, the strength

and setting time will be decreased.

Silica (SiO2): Gives strength due to the formation of di-calcium and tri-calcium (C2S and C3S ) silicates.

If it is excess, causing slow setting.

Alumina (Al2 O3): Responsible for quick setting. It act as a flux and lowers the clinkering temperature.

If it is in excess, it lower the strength.

Iron oxide (Fe2 O3): Gives color and help in fusion of different ingredient of cement.

Magnesia (MgO): Gives color and hardness. If it is in excess, causes cracks and cement unsound.

Alkalies (K2O,Na2O): If it is in excess, causes alkali-aggregate reactions, efflorescence and discoloring.

[Note: alkali-aggregate reactions: aggregates having silica, it react with alkali’s and causes the

expansion and cracking in concrete]

Sulphur (SO3): A small amount is used to make sound cement. If it is in increase, causes unsound in

cement.

**[Soundness of cement: It refers to the ability of a hardened cement paste to retain its volume after

setting without delayed destructive expansion. ]Department of Civil Engineering, NSCET, Theni Page-13Department of Civil Engineering, NSCET, Theni Page-17

Chemical CompositionMajor compounds in cement:(8marks)

When water is added to the cement, the major compounds are developed. The identification of the

major compounds are based on R.H.Bogue’s research work, hence it is called Bogue’s compounds.

a) Tri Calcium Silicate (C3S) - 3CaO SiO2

b) Di Calcium Silicate (C2S) - 2CaO SiO2

c) Tri Calcium Aluminates (C3A) - 3CaO, Al2 O3

d) Tetra-Calcium Alumino Ferrite (C4AF) - 4CaO Al2O3 Fe2 O3

• C3S is formed with in a week, responsible for initial strength of concrete and contribute 50-60% of

strength.

• C2S is formed at last in the hydration process, responsible for later age strength [needed for bridge /

hydraulic structures]

• C3A is formed within 24 hours, responsible for initial setting time

• C4AF is also formed within 24 hours, responsible for heat of hydration


Hydration of cementUNIT 01 - CONSTITUENT MATERIALS – LECTURE 02


Hydration of cement When water is added to cement, ingredients of the cement react chemically with water and form

various complicated chemical compounds, this is called hydration of cement.

During hydration process, cement produces calcium hydrate silicate (C-H-S) and calcium

hydrate aluminate (C-H-A). These products are thick and sticky and it is called C-H-S / C-H-A

gel. This gel has adhesion properties and bind the aggregates together, also fill the voids between

sand and coarse aggregates.

The hydration process is not an instantaneous one. The reaction is faster in earlier age and

slower in later age. Complete hydration process can not obtain before one year (99% of concrete

strength can be obtained only at one year.

Heat of hydration: (2 marks)

The reaction of cement with water is exothermic. The reaction liberates a considerable amount of

heat is called heat of hydration.


Different types of CementUNIT 01 - CONSTITUENT MATERIALS – LECTURE 03


TYPES OF CEMENTBy altering the chemical compositions of the ordinary Portland cement (OPC), manytypes of cement can be obtained as follows;

1. Ordinary Portland cement (OPC)

2. Sulphate resistance cement

3. Low heat cement

4. Quick setting cement

5. Portland pozzolana cement (PPC)

6. High alumina cement

7. Colored cement

8. White cement

9. Air entraining cement

10. Hydrophobic cement

11. Expansion cement

12. Rapid hardening Portland cement


TYPES OF CEMENT

1. Ordinary Portland cement:

This is the most commonly used cement for all types of engineering works. Ordinary

Portland cement (OPC) is manufactured in different grades; the most common grades in India are

33, 43 and 53 grade. OPC is manufactured by burning lime stone and clay at very high

temperature range of 1400o C to1700oC and thereafter grinding (or) pulverizing it with gypsum to

retard the setting time.

Uses / Advantages:

a) Normally used for all kind of construction works

b) Widely used in residential construction where special type of cement properties is not

required


2. Sulphate resistance cement

Sulphate resisting cement is a type of Portland cement in which the amount of tri-calciumaluminates (C3A) is restricted to 5 %. The use of sulphate resistance cement is particularly beneficial insuch conditions where the concrete is exposed to the risk of deterioration due to sulphate attack ordirectly exposure to the soil.

Uses / Advantages:a) It is used in the construction of foundations and piles.

b) Basements and underground structures.

c) Sewage and Water treatment plants.

d) Chemical, Fertilizers and Sugar factories.

e) Food processing industries and Petrochemical projects.

f) Coastal works.

g) Also for normal construction works where OPC is used.

h) Construction of building along the coastal area within 50 km from sea.


3. Low heat cement

Low heat cement is produced by reducing the amount of tri-calcium aluminates (C3A) & di-

calcium silicate (C2S). This type of cement is used in mass constructions (like dams) and in high

wear resistance required area. In general, this type of cement is producing very minimum amount

of CO2 emission than OPC.

Uses / Advantages:

a) It is very much used in the mass Construction of dams,

b) Mass construction of marine structures

c) Hydraulic Engineering Concrete

d) Retaining wall construction


4. Quick setting cement

This type of cement is manufactured by reducing the amount of gypsum and adding small

amount of aluminum sulphate to accelerate setting time of cement. As the name suggests, it is used

where the works needs to be done quickly and when mixed with water starts to set in five minutes

and become hard like stone in just 30 minutes.

Uses / Advantages:

a) It is used in under water construction.

b) It is also used in rainy & cold weather conditions.

c) Where, quick strength is needed in short span of time.


5. Portland pozzolana cement (PPC)PPC is manufactured by adding pozzolanic materials such as fly ash, shales, clays etc. It

gains high compressive strength with age and it is affordable than other type of concrete.

Uses / Advantages:

a) Used in the hydraulic structures such as dam, canals, lining etc.

b) Mass concreting works such as foundation, tall building etc.

c) Construction of marine structures.

d) This cement has higher resistance to chemical attacks. Hence it can be used in

construction of industrial buildings

e) Used in the construction of water tightened structures (Water tank, retaining wall etc.)


6. High alumina cement

High-alumina cement is rapid hardening cement made by fusing at 1500 to 1600 °C a mixture of

bauxite and limestone in an electric furnace or in a rotary kiln. It also can be made by sintering at

about 1250 °C.

[*Sintering: Process of compacting and forming a solid mass of material by heat or pressure

without melting it to the point of liquefaction]

Uses / Advantages:

a) This cement is used in construction of refineries, factory or other workshop type structure

b) Used in Sewage structures

c) Used where acid resistance structures are needed


7. Colored cement

Colored cement is manufactured by mixing color pigments (5 - 10%) with OPC. As the name

suggests, It is used where colored cements required for any aesthetic purpose. Chromium Oxide

gives Green color. Cobalt gives blue color. Iron oxide gives brown color.

Uses / Advantages:

a) These are wildly used for finishing of floor, external surface, plastering wall, colored tiles.

b) Used in construction of swimming pool, garden path, tennis courts etc.

c) Used in the construction of artificial marble


8. White cement

This cement is white in color. This cement is free from coloring ingredients such as iron oxide,

magnesium oxide, chromium oxide. This cement in burned by oil, and is very costlier than other

type of cements.

Uses / Advantages:

a) It is used for floor finishes, plaster works, pointing of brick and stone works

b) Used in the manufacturing of precast stone and tiles, aerodromes marking, traffic kerb and

bridge rails.

c) Used as a base coat before painting

d) Used to cover the hairline cracks on concrete surface to give smooth finish


9. Air entrained cement

Air entraining cement produced by mixing small amount of air entraining agent (Polymer based

chemicals). Generally, this air entraining agents are used to introduce a tiny bubbles in the

concrete. It is used to fill up the gap in concrete which are produced by excessive amount of

water during casting.

Uses / Advantages:

a) Used in frost resistance concrete (resistance to freezing and thawing)

b) Air entrained concrete has less tendency to bleed, it is considerably more plastic than

ordinary concrete, and it generally shows less segregation.


10. Hydrophobic cement

This type of cement is manufactured by mixing admixtures like petrolatum, napthalene soap

which forms layer and act as water repellent. It is useful in wet climatic conditions and

Useful when cement is stored for longer duration in wet climatic conditions.

11.Expansion cement

Expansive Cement is formed from the reaction of tri calcium aluminate (C3A) with Calcium

Sulphate (C2SO4). As the name suggests, it expands and increases in volume while settled.

Used to avoid the shrinkage of concrete.

Uses / Advantages:

a) Used in repair works (to create a bond with old concrete surface)

b) Used in Hydraulic Structures


12. Rapid hardening Portland cement (RHPC)RHPC manufactured by combining lime stone (finely ground) and shale at high temperature. This

type of cement is used where high strength is needed to be achieved quickly.

Uses / Advantages:

a. It is used where formwork has to be removed as early as possible in order to reuse it.

b. It is used where high early strength is required.

c. It is generally used for constructing road pavements, where it is important to open the road

to traffic quickly.

d. It is used in industries which manufacture concrete products like slabs, posts, electric poles,

block fence, etc.

e. It is used for cold weather concreting

[The main disadvantage of the rapid hardening cement is costlier than other type of cement]

Department of Civil Engineering, NSCET, Theni Page-

33

Tests on cement.UNIT 01 - CONSTITUENT MATERIALS – LECTURE 04


TEST ON CEMENTIn order to check the quality of cement the following tests may be used;

Testing of cement can be brought under two categories:

Field testing

a) In the cement bag, there should not be any visible lumps and the color should be

greenish grey.

b) Thrust your hand into the cement bag. It must give you a cool feeling.

c) Take a pinch of cement and feel between the fingers. It should give a smooth and not

a gritty feeling.

d) Take a handful of cement and throw it on a bucket full of water, the particles should

float for some time before they sink.

e) Take about 100 grams of cement and a small quantity of water and make a stiff

paste. Put it on a glass plate and slowly take it under water in a bucket. After 24

hours the paste should retain its original shape


Laboratory testingThe following tests are conducted in the laboratory:

1. Fineness test

2. Soundness test

3. Setting time test

4. Strength test


1. Fineness test

The fineness of cement has an important properties of cement and is responsible to

a) The rate of hydration

b) Rate of gain of strength

c) Rate of evolution of heat

The fineness of cement can be obtained by sieve test;

Sieve test:

To determine fineness of cement and particle size of cement.

Sample size – 100gms; sieving period – 15 minutes.

The standard sieve size used is 90 m.

The % residual (retained) of cement on 90 m sieve shall not exceed 10%.

Sieve used for determining Fineness of Cement


2.Soundness test

DETERMINATION OF SOUNDNESS

Lechatelier Test IS 4031 (Part 3 ) – 1988

To determine the soundness or unsoundness of cement due to presence of free lime only.

The expansion of cement paste specimen in Lechatelier mould shall not exceed 10mm.


3. Initial Setting time testInitial setting time test (Vicat Apparatus) IS : 4031 (Part 5) – 1988

(Reaffirmed 2000)

To determine the time required by cement paste to loss its plasticity.

The Vicat apparatus is used to determine initial setting time of cement where the

penetration of the needle in the cement paste kept in Vicat mould (40 mm height)

shall be in a range of 33 to 35 mm from the top.

It shall not be less than 30minutes(≥30min) for normal cement, 60 minutes for

low heat cement and 5 minutes for rapid hardening cement.


3. Final Setting time test (cont…)Final setting time of cement (Vicat Apparatus)

The time required by cement paste to gain the proper shape and becoming hard considering

from the instant of adding water is called final setting time.

i.e., the time elapsing from the instant of adding water to the cement and the instant when

paste becomes hard (solid) is known as final setting time which is determined by Vicat

apparatus where the enlarge needle should not penetrate the specimen of cement.

Final setting time shall not exceed 10hrs for normal cement, 30 minutes for rapid hardening

cement.


4. Strength test

Compressive Strength Test (IS : 4031(Part 6):1988)

To determine compressive strength of cement where the

specimen is made up of 1:3 (cement : sand) proportion i.e. 185 gm cement and

555gm sand or 200gm cement and 600gm sand.

The specimen is tested under compression machine at an age of 1 day, 3, 7 and 28

days.

The compressive strength of rapid hardening cement at 1 day curing shall not be

less than 16 MPa and at an age of 3 days it shall not be less than 27.5 MPa.


IS SpecificationsUNIT 01 - CONSTITUENT MATERIALS – LECTURE 04


Grade of CementThe Bureau of Indian Standard (BIS) has classified ordinary Portland cement

(OPC) in three different grades. The classification is mainly based on the compressive

strength of cement -sand mortar cube at 28 days. The Grades are

a) 33 Grade cement

b)43 Grade cement

c) 53 Grade cement

The Grade number (33, 43 and 53) indicates the minimum compressive strength of

cement sand mortar cube in N/mm2 at 28 days.


Physical and chemical properties of 33, 43 and 53 grade of cement / concrete

Physical properties Grade of cement

33 43 53

Minimum compressive strength at 28 days (N/mm2) 33 43 53

Fineness-minimum specific surface area (m2/kg) 225 225 225

Initial setting time (minimum) 30 min. 30 min. 30 min.

Final setting time (maximum) 600 min. 600 min. 600 min.

Soundness (expansion) in mm 10 10 10

Autoclave test for MgO, percent, maximum 0.8 0.8 0.8

Chemical Properties

Loss on ignition (%) 5 5 4

Insoluble residue (%), maximum 4 2 2

Magnesia MgO (%), maximum 6 6 6

SO3 (%) , maximum for C3A>5 percent 2.5 2.5 2.5

Lime saturation factor (LSF) 0.66-1.02 0.66-1.02 0.8-1.02

Ratio, A F,minimum 0.66 0.66 0.66


GENERAL PROPERTIES OF CEMENT

a) It is an excellent binding material.

b)It gives strength to masonry.

c) It gives good plasticity.

d)It gives a good resistance to moisture.

e) It is easily workable. Hence less workmanship is needed

f) It hardens quickly after addition of water.

g) It gives good bonding property to the concrete.


Effect of Water/cement ratio on strength of concrete

• The water–cement ratio is the ratio of the weight of water to the weight of cement used in a

concrete mix.

• A lower ratio leads to higher strength and durability, but may make the mix difficult to work with

and form.

• Workability can be resolved with the use of super plasticizer.

• Higher workability leads the segregation and bleeding


Aggregates and its Classification



Aggregate

The aggregate is a relatively inert material and it imparts volume stability.

The aggregate provide about 75% of the body of the concrete and hence its

influence is extremely important.

An aggregate should be of proper shape and size, clean, hard and well graded.

It must possess chemical stability and it must exhibit abrasion resistance.


Classification of AggregateI. Classification Based on Size

a. Fine aggregates:

It is the aggregate, which is passes through a 4.75mm IS sieve and retained on 0.7 mm. The fine

aggregate may be natural sand, crushed stone sand or crushed gravel sand. According to IS 383-1970,

there are four grading zones of the fine sand, Zone I, Zone II, Zone III and Zone IV.

b. Coarse aggregates:

The aggregates, most of which are retained on 4.75mm IS sieve are termed as coarse aggregates.

The coarse aggregates may be Crushed stone, Uncrushed gravel and Partially crushed stone or gravel.

[*Sometimes combined aggregates are available in nature consisting of different fractions of fine and

coarse aggregates, which are known as all in aggregate.]


Classification of AggregateII. Classification Based on Shape

a. Rounded aggregate:

The aggregate with rounded particles (river or sea shore gravel) has minimum voids ranging from 32 to

33%.

It gives minimum ratio of surface area to the volume, thus requiring minimum cement paste to make

good concrete.

The only disadvantage is that the interlocking between its particles is less, and hence the development of

the bond is poor, making it unsuitable for high strength concrete and pavement.


b. Irregular aggregates:

The aggregate having partly round particles (pit sand and gravel) has higher percentage of voids ranging

from 35 to 38 %.

It requires more paste for a given workability.

The interlocking between particles, though better than that obtained with the rounded aggregate, is

inadequate for high strength concrete.


c. Angular aggregates:

The aggregate with sharp angular and rough particles (crushed rock) has a maximum percentage of voids

ranging from 38 to 40%.

The interlocking between particles is good, providing a good bond.

The aggregate requires more paste to make workable concrete of high strength.

The angular aggregate is suitable for high strength concrete and pavements subjected to tension.


d. Flaky and elongated aggregates:

An aggregate is termed flaky when the ratio of least dimension (thickness)

to the mean dimension is less than three-fifth (0.6).

The particle is said to be elongated when the ratio of greatest dimension (length) to the mean dimension

is more than nine-fifth (1.8 times).


III. Classification based on unit weight

a. Normal weight aggregates:

The commonly used aggregates i.e. sand, gravel, crushed rocks such as granite, basalt, sandstone (sedimentary) and limestone.

It has specific gravities between 2.5 and 2.7 produce concrete with unit weight ranging from 23 to 26 kN/m3

The compressive strength at 28 days between 15to 40 MPa are termed Normal weight aggregate.

b. Heavy weight aggregates:

Heavy weight concrete is produced from heavy weight aggregate, which is more effective as a

radiation shield.

The unit weight of concrete varies from 30 to 57 kN /m3.

The specific gravity is varies from 4 – 6.8

Example: Baryte (Gs = 4 to 4.6), Ferrophosphorus (Gs = 5.8 to 6.8), Haematite (Gs = 4.9 to 5.3)

and Magnetite (Gs= 4.2 to 5.2)


c. Light weight aggregates:

The light weight aggregates have unit weight up to 12 kN /m3.

These aggregates are obtained from pumice, volcanic cinder, Diatomite, blast

furnace slag, fly ash etc,.

The weight of concrete (structure) is reduced to a great extent and it

provides better thermal insulation and improved fire resistance.


Physical propertiesUNIT 01 - CONSTITUENT MATERIALS – LECTURE 05


Physical Properties of Aggregates

The physical properties of aggregates are;

1. Shape

2. Size

3. Color

4. Texture

5. Gradation

6. Fineness modulus


Effect of aggregate properties on concretei. Particle Size, Grading and Dust Content

Well-graded sands tend to have lower water requirements than single-sized sands

and increasing dust contents tend to increase the water requirement of sands.

ii. Particle Shape

It is fact that sands with well-rounded particles will be less water and make more

workable concrete than sands with flaky, elongated particles. However, the strength

is undesirable. Aggregate with angular shape, will give moderate water and high

strength to concrete by good interlocking characteristics.

iii. Particle Surface Texture

In general, sands with a rough surface texture will have a higher water requirementthan sands with smooth particle surfaces.


v. Fineness Modulus

The fineness modulus (FM) is a numerical index of fineness, giving some idea of the

mean size of the particles present in the entire body of the aggregate.

The fineness modulus =

iv.Water Absorption

All aggregates absorb water to a greater or lesser degree. The higher the water

absorption the higher the water requirement will be, but the water absorbed into the

aggregate will not affect the effective water: binder ratio or the strength. It will

however lead to rapid slump loss if absorption is excessive, say >1% by mass. In

general it is preferable to avoid concrete aggregate properties with water absorptions

of more than 1 or 1.5% by mass


According to IS 2386-1963, the sieves that are to be used for the sieve analysis of the

aggregate for concrete are 80mm, 40mm, 20mm, 10mm, 4.75mm, 2.36mm, 1.18mm,

600m, 300m and 150m.

For example, a fineness modulus of 6 can be interpreted to mean that the sixth sieve,

i.e. 4.75 mm is the average size.

The value of fineness modulus is higher for coarser

aggregate and lower for fine aggregate.

Limitations:

The FM for fine sand = 2 - 3.5

The FM for coarse aggregate = 5.5 - 8

[Note: higher FM, the mix will be harsh and if on the other hand gives a lower FM, it produces

an uneconomical mix]


Worked Example: (Take 5000 g sample)

Aggregates Sieve size Weight retained(g)Cumulative weight

retained (g)

Cumulative %

retained (g)

Coarse aggregates

80mm 0 0 0

40mm 250 250 5

20mm 1750 2000 40

10mm 1600 3600 72

Fine aggregates

4.75mm 1400 5000 100

2.36mm 0 5000 100

1.18mm 0 5000 100

0.6mm 0 5000 100

0.3mm 0 5000 100

0.15mm 0 5000 100

Sum = 717


FINENESS MODULUS (cont..) Therefore,

fineness modulus of coarse aggregates = sum (cumulative % retained) / 100

= (717/100) = 7.17

Fineness modulus of 7.17 means, the average size of particle of given coarse

aggregate sample is in between 7th and 8th sieves, that is between 10mm to 20mm.


Grading requirementsUNIT 01 - CONSTITUENT MATERIALS – LECTURE 06


Gradation of aggregates Gradation refers to the particle size distribution of aggregates.

The gradation of coarse aggregate plays an important role

in workability and paste requirements.

The gradation of fine aggregate affects the workability and finishing ability of

concrete.

Types of gradation:

1. Well graded

2. Poor / Uniform graded

3. Gap graded


Gradation of aggregates (Cont..)

1. Well graded

Incorporates a combination of particles of many sizes. Hence, it has Low void

content, Low permeability and High stability but increases the particle surface

area. This is the preferred gradation for making a good concrete.



2. Poor / Uniform graded

All particles are of same size. It produces a large volume of voids irrespective of

particle size. Hence the paste requirement for this concrete is high.



3. Gap graded

This involves grading in which one or more sizes are omitted. It has low

stability, moderate voids content and permeability than well graded aggregate.

This type of concrete is generally used for architectural or aesthetic purposes.


Mechanical properties and tests as per BIS



1. Crushing strength (IS2386-Part-4)

• It is the mechanical properties of aggregates

• Ascertained by aggregate crushing value

• It gives a relative measure of the resistance of an aggregate to crushing under a gradually applied compressive load

• For this test, 12.5 mm passed and 10 mm retained aggregates are used

• Surface dry condition aggregates are filled intothe standard cylinder with three layer of 25 blows

• Compressive force is gradually applied upto 40 tons in 10 minutes time

• The crushed aggregates are sieved in 2.36 mm sieve

Then aggregate crushing value = B/A x 100where, A- Weight of sample and B- weight of retained aggregate in 2.36 mm sieve.

[Crushing value should not higher than 45%]


1. Crushing strength (test set up)


2. Impact strength test• It is the another mechanical properties of aggregates

• Ascertained by aggregate impact value

• It gives a relative measure of the resistance of an aggregate to sudden shock or impact

• For this test, 12.5 mm passed and 10 mm retained aggregates are used

• Surface dry condition aggregates are filled into the test cylinder with three layer of 25 blows

• Filled cylinder is placed in impact testing machine Then,15 blows are given to the cylinder using

14 kg weight hammer.

• The crushed aggregates are sieved in 2.36 mm sieve

Then aggregate impact value = B/A x 100

where, A- Weight of sample B- weight of retained aggregate in 2.36 mm sieve.

[Crushing value should not higher than 45%]


2. Impact strength test (test set up)


3. Abrasion test (Los angeles test)

• Select the grading to be used in the test such that it conforms to the grading to be used

in construction

• Choose the abrasive charge balls depending on grading of aggregates.

• Place the aggregates and abrasive charge on the cylinder and fix the cover.

• Rotate the machine at a speed of 30 to 33 revolutions per minute with uniform speed.

• The machine is stopped after the desired number of revolutions and material is

discharged to a tray.

• The entire stone dust is sieved on 1.70 mm IS sieve.

• The material coarser than 1.7mm size is weighed correct to one gram.


3.Abrasion test (Los angeles test)

Abrasion Value = (W1 – W2 ) / W1 X 100

Where,

Original weight of aggregate sample = W1 g

Weight of aggregate sample retained = W2 g

Weight passing 1.7mm IS sieve = W1 – W2 g

[Note: Abrasion value should not more than 16%]


3. Abrasion test (Devals test)

• Select the grading to be used in the test such that it conforms to the gradingto be used in construction

• Choose the abrasive charge balls depending on grading of aggregates.

• Place the aggregates and abrasive charge on the devals cylinder and fix thecover.

• Rotate the machine at a speed of 30 to 33 revolutions per minute withuniform speed up to 10,000 revolutions and then stopped.

• The entire stone dust is sieved on 1.70 mm IS sieve.

• The material coarser than 1.7mm size is weighed correct to one gram


3. Abrasion test (Devals test)

Devals abrasion Value = (W1 – W2 ) / W1 X 100

Where,

Original weight of aggregate sample = W1 g

Weight of aggregate sample retained = W2 g

Weight passing 1.7mm IS sieve = W1 – W2 g

[Note: Abrasion value should not more than 16%]


Water and its Quality for use in concrete.



Water for concrete• Water is the most important material for construction, especially for making

concrete.

The purpose of water in concrete are

• It distributes the cement evenly.

• It reacts with cement chemically and produces calcium silicate hydrate (C-S-H)

gel which gives the strength to concrete.

• It provides for workability, i.e., it lubricates the mix.

Hence, for construction, quantity and quality of water is as important as cement.


Water for concrete (Cont..)As water quantity goes up in a mix (ill effect), the following are the effects:

•Strength decreases

•Durability decreases

•Workability increases

•Cohesion decreases

•Economy may increase at the expense of quality and reliability.


Quality of water for concrete (IS10500:2012)

• Water used for mixing and curing should be free from oil, acid and alkali, salts

and organic material.

• It should be potable and concreting generally requires a value purer than that of

drinking

• Whenever there is uncertainty in quality, water should be tested before use.

• Even chlorine added for city water supply will affect concrete if used carelessly

without proper testing and treatment.

• If well water is used for construction, it must be tested for impurities.


Quality of water for concrete (cont.)

• Chlorides: They can cause corrosion of steel reinforcement, can acceleratesetting. The water used may be contaminated with chlorides because ofseawater, some admixtures, salts or deliberate chlorination for disinfections.

• Sulphates: They reduce long-term strength levels.

• Organic matter: Their effects on concrete are variable. If an alga is present,water should not be used. It will affect the setting and strength development.

• Sugar: It will retard setting time. Too much may ‘kill' the concrete (theconcrete will never set).

• Wastewater: It should never be used in construction. Water for curing shouldbe as pure as water for mixing concrete.


THANKS!Does anyone have any questions?

Documents

NSCET E-LEARNING PRESENTATION 1/UNIT I Constituent Materials.pdf · Gupta.B.L & Amit Gupta, "Concrete Technology", Jain Book Agency, 2010. 2. Shetty,M.S, "Concrete Technology", S.Chand