BINDING MATERIALS · 2016. 9. 4. · cement was the prototype of the modern Portland cement. From then onwards, a gradual improvement in the properties and qualities of cement has

BUILDING MATERIALS AND CONSTRUCTION TECHNOLOGY BINDING MATERIALS

Compiled by: Prof. TARANATH S D 1

UNIT – II

BINDING MATERIALS

2.1. Cement

2.1.1. Introduction

Assyrians and Babylonians were perhaps the first to use clay as cementing material. In

ancient monuments, e.g. forts, places of worship and defence structures, stones have been

invariably used as a construction material with lime as the binder. Records show that

Egyptians have used lime and gypsum as cementing materials in the famous pyramids.

Vitruvius, a Roman scientist, is believed to be the first to have the know-how about the

chemistry of the cementitious lime. One of the most notable examples of Roman work is the

Pantheon. It consists of a concrete dome 43.43m in span. The calcareous cements used by the

Romans were either composed of suitable limestones burned in kilns or were mixtures of

lime and puzzolanic materials (volcanic ash, tuff) combining into a hard concrete. Vitruvius’s

work was followed by the researches made by M. Vicat of France. Joseph Aspedin of

Yorkshire (U.K.) was the first to introduce Portland cement in 1824 formed by heating a

mixture of limestone and finely divided clay in a furnace to a temperature high enough to

drive off the carbonic acid gas. In 1845, Issac C. Johnson invented the cement by increasing

the temperature at which the mixture of limestone and clay were burned to form clinker. This

cement was the prototype of the modern Portland cement. From then onwards, a gradual

improvement in the properties and qualities of cement has been made possible by researchers

in U.S.A., U.K., France and Germany.

2.1.2. Portland cement

It is a cementing material resembling a natural stone quarried from Portland in U.K.

Portland cement may be defined as a product obtained by finely pulverizing clinker produced

by calcining to incipient fusion, an intimate and properly proportioned mixture of

argillaceous and calcareous materials. Care must be exercised in proportioning the raw

materials so that the clinker of proper constitution may be obtained after burning.

2.1.3. Chemical composition of raw materials

The three constituents of hydraulic cements are lime, silica and alumina. In addition, most

cement contains small proportions of iron oxide, magnesia, sulphur trioxide and alkalis.

There has been a change in the composition of Portland cement over the years, mainly

reflected in the increase in lime content and in a slight decrease in silica content. An increase

in lime content beyond a certain value makes it difficult to combine completely with other

compounds. Consequently, free lime will exist in the clinker and will result in unsound

cement. An increase in silica content at the expense of alumina and ferric oxide makes the

cement difficult to fuse and form clinker.

The approximate limits of chemical composition in cement are given in Table below;



Oxide Function Composition (%)

CaO Controls strength and

soundness. Its deficiency

reduces strength and setting

time.

60 – 65

SiO2 Gives strength. Excess of it

causes slow setting

17 – 25

Al2O3 Responsible for quick

setting, if in excess, it

lowers the strength.

3 – 8

Fe2O3 Gives colour and helps in

fusion of different

ingredients

0.5 – 6

MgO Imparts colour and

hardness. If in excess, it

causes cracks in mortar and

concrete and unsoundness

0.5 – 4

Na2O +K2O

TiO2

P2O5

These are residues, and if in

excess causes efflorescence

and cracking

0.5 – 1.3

0.1 – 0.4

0.1 – 0.2

SO3 Makes cement sound 1 - 2

2.1.4. Composition of cement clinker The various constituents combine in burning and form cement clinker. The compounds

formed in the burning process have the properties of setting and hardening in the presence of

water. They are known as Bogue compounds after the name of Bogue who identified them.

Le-Chatelier and Tornebohm have referred these compounds as Alite (C3S), Belite (C2S),

Celite (C3A) and Felite (C4AF). The following Bogue compounds are formed during

clinkering process.

The principal

material

compounds in

Portland cement

Formula Name Symbol

Tricalcium silicate 3CaO.SiO2 Alite C3S

Dicalcium silicate 2CaO.SiO2 Belite C2S

Tricalcium

aluminate

3CaO.Al2O3 Celite C3A

Tetracalcium

alumina ferrite

4CaO.Al2O3.Fe2O3 Felite C4AF

The properties of Portland cement varies markedly with the proportions of the above

four compounds, reflecting substantial difference between their individual behaviour.

Tricalcium silicate is supposed to be the best cementing material and is well burnt

cement. It is about 25-50% (normally about 40 per cent) of cement. It renders the clinker

easier to grind, increases resistance to freezing and thawing, hydrates rapidly generating high

heat and develops an early hardness and strength. However, rising of C3S content beyond the

specified limits increases the heat of hydration and solubility of cement in water. The

hydrolysis of C3S is mainly responsible for 7 day strength and hardness. The rate of



hydrolysis of C3S and the character of gel developed are the main causes of the hardness and

early strength of cement paste. The heat of hydration is 500 J/g.

Dicalcium silicate is about 25-40% (normally about 32 per cent) of cement. It

hydrates and hardens slowly and takes long time to add to the strength (after a year or more).

It imparts resistance to chemical attack. Raising of C2S content renders clinker harder to

grind, reduces early strength, decreases resistance to freezing and thawing at early ages and

decreases heat of hydration. The hydrolysis of C2S proceeds slowly. At early ages, less than a

month, C2S has little influence on strength and hardness. While after one year, its

contribution to the strength and hardness is proportionately almost equal to C3S. The heat of

hydration is 260 J/g.

Tricalcium aluminate is about 5-11% (normally about 10.5 per cent) of cement. It

rapidly reacts with water and is responsible for flash set of finely grounded clinker. The

rapidity of action is regulated by the addition of 2-3% of gypsum at the time of grinding

cement. Tricalcium aluminate is responsible for the initial set, high heat of hydration and has

greater tendency to volume changes causing cracking. Raising the C3A content reduces the

setting time, weakens resistance to sulphate attack and lowers the ultimate strength, heat of

hydration and contraction during air hardening. The heat of hydration of 865J/g.

Tetracalcium alumina ferrite is about 8–14% (normally about 9 per cent) of cement. It is

responsible for flash set but generates less heat. It has poorest cementing value. Raising the

C4AF content reduces the strength slightly. The heat of hydration is 420 J/g.

2.1.5. Manufacture of cement

Calcareous and argillaceous raw materials are used in the manufacture of Portland

cement. The calcareous materials used are cement rock, limestone, marl, chalk and marine

shell. The argillaceous materials consist of silicates of alumina in the form of clay, shale,

slate and blast furnace slag.

From the above materials, others like lime, silica, alumina, iron oxide and small quantities

of other chemicals are obtained. Cement can be manufactured either by dry process or wet

process. Dry process:

The dry process is adopted when the raw materials are quite hard. The process is slow

and the product is costly. Limestone and clay are ground to fine powder separately and are

mixed. Water is added to make a thick paste. The cakes of this paste, which contain about 14

per cent of moisture, are dried and are charged into rotary kiln (Fig. 2.1). The product

obtained after calcination in rotary kiln is called clinker. The clinker is obtained as a result of

incipient fusion and sintering at a temperature of about 1400°- 1500°C. Because ferric oxide

has lower melting point than the other oxides, it acts as a flux. Aeration of cement clinker,

which is commonly practised to slake free lime, also causes absorption of some moisture and

carbon dioxide. Absorption of moisture tends to decrease the setting where as that of carbon

dioxide accelerates setting. The clinker is cooled rapidly to preserve the metastable

compounds and their solid solutions — dispersion of one solid in another — which are made

as the clinker is heated. Clinker is then cooled and ground in tube mills (Fig. 2.2), where 2-

3% of gypsum is added. Generally, cement is stored in bags of 50 kg. The purpose of adding

gypsum is to coat the cement particles by interfering with the process of hydration of the

cement particles. This retards the setting of cement.



Fig. 2.1. Schematic diagram of modern cement plant

Wet process:

The operations in the wet process of cement manufacture are mixing, burning and

grinding. The crushed raw materials are fed into ball mill (Fig. 2.2) and a little water is

added. On operating the ball mill, the steel balls in it pulverize the raw materials which form

slurry with water. This slurry is passed to silos (storage tanks), where the proportioning of the

compounds is adjusted to ensure desired chemical composition. The corrected slurry having

about 40 per cent moisture content is then fed into rotary kiln (Fig. 5.4) where it loses

moisture and forms into lumps or nodules. These are finally burned at 1500-1600°C. The

nodules change to clinker at this temperature. Clinker is cooled and then ground in tube mills.

While grinding the clinker, about 3 per cent gypsum is added. The cement is then stored in

silos from where it is supplied. A flow diagram of manufacturing cement by wet process is

shown in Fig. 2.2.

Fig. 2.2. Ball mill



Comparison of Wet and Dry Process: The chief advantages of the wet process are the low

cost of excavating and grinding raw materials, the accurate control of composition and

homogeneity of the slurry, and the economical utilization of fuel through the elimination of

separated drying operations. On the other hand the longer kilns, essential in the wet process,

cost more and are less responsive to a variable clinker demand than the short kilns which can

be used in the dry process.

2.1.6. Different types of cement and uses

Cements of unique characteristics for desired performance in a given environment are

being manufactured by changing the chemical composition of OPC or by using additives, or

by using different raw materials. Some of the cements available in the market are as follows.

Rapid Hardening Portland cement (IS: 8041):

It has high lime content and can be obtained by increasing the C3S content but is

normally obtained from OPC clinker by finer grinding (450 m2/kg). The basis of application

of rapid hardening cement (RHC) is hardening properties and heat emission rather than

setting rate. This permits addition of a little more gypsum during manufacture to control the

rate of setting. RHC attains same strength in one day which and ordinary cement may attain

in 3 days. However, it is subjected to large shrinkage and water requirement for workability

is more. The cost of rapid hardening cement is about 10 per cent more than the ordinary

cement. Concrete made with RHC can be safely exposed to frost, since it matures more

quickly.

Properties: Initial setting time 30 minutes (minimum)

Final setting time l0 hours (maximum)

Compressive strength

1 day 16.0 N/mm2

3 day 27.5 N/mm2

Uses: It is suitable for repair of roads and bridges and when load is applied in a short period

of time.

High Alumina Cement (IS: 6452):

This is not a type of Portland cement and is manufactured by fusing 40 per cent

bauxite, 40 per cent lime, 15 per iron oxide with a little of ferric oxide and silica, magnesia,

etc. (Table 5.5) at a very high temperature. The alumina content should not be less than 32%.

The resultant product is ground finely. The main cement ingredient is monocalcium

aluminate CA which interacts with water and forms dicalcium octahydrate hydroaluminate

and aluminium oxide hydrate.

The dicalcium hydroaluminate gel consolidates and the hydration products crystallise.

The rate of consolidation and crystallisation is high leading to a rapid gain of strength. Since

C3A is not present, the cement has good sulphate resistance.

Properties: It is not quick setting: initial setting time (minimum) is 30 minutes, even up to 2

hours. The final setting time should not exceed 600 minutes. It attains strength in 24 hours,

high early strength, high heat of hydration and resistance to chemical attack. Compressive

strength after one day is 30.0 N/mm2 and after 3 days it is 35.0 N/mm2. After setting and

hardening, there is no free hydrated lime as in the case of ordinary Portland cement. The

fineness of the cement should not be less than 225 m2/kg. The cement should not have

expansion more than 5 mm.



Uses: It is resistant to the action of fire, sea water, acidic water and sulphates and is used as

refractory concrete, in industries and is used widely for pre-casting. It should not be used in

places where temperature exceeds 18°C.

Supersulphated Portland Cement (IS: 6909)

It is manufactured by intergrinding or intimately blending a mixture of granulated

blast furnace slag not less than 70 per cent, calcium sulphate and small quantity of 33 grade

Portland cement. In this cement tricalcium aluminate which is susceptible to sulphates is

limited to less than 3.5 per cent. Sulphate resisting cement may also be produced by the

addition of extra iron oxide before firing; this combines with alumina which would otherwise

form C3A, instead forming C4AF which is not affected by sulphates. It is used only in places

with temperature below 40°C.

Water resistance of concretes from supersulphate Portland cements is higher than that

of common Portland cements because of the absence of free calcium oxide hydrate. In

supersulphate Portland cements the latter is bound by slag into calcium hydroaluminates of

low solubility and calcium hydrosilicates of low basicity, whereas concretes from Portland

cement carry a large amount of free calcium oxide hydrate which may wash out and thus

weaken them. Supersulphate Portland cement has satisfactory frost and air resistances, but it

is less resistant than concrete from Portland cement due to the fact that hydrosilicates of low

basicity show greater tendency to deformation from humidity fluctuations and resist the

combined action of water and frost less effectively.

Properties: It has low heat of hydration and is resistant to chemical attacks and in particular

to sulphates. Compressive strength should be as follows:

72 ± 1 hour ≮ 15 N/mm2

168 ± 2 hours ≮ 22 N/mm2

672 ± 4 hours ≮ 30 N/mm2

It should have a fineness of 400 m2/kg. The expansion of cement is limited to 5 mm.

The initial setting time of the cement should not be less than 30 minutes, and the final setting

time should not be more than 600 minutes.

Uses: Supersulphated Portland cement is used for similar purpose as common Portland

cement. But owing to its higher water-resisting property, it should be preferred in hydraulic

engineering installations and also in constructions intended for service in moist media. RCC

pipes in ground water; concrete structures in sulphate bearing soils, sewers carrying industrial

effluents, concrete exposed to concentrated sulphates of weak mineral acids are some of the

examples of this cement. This cement should not be used in constructions exposed to frequent

freezing-and-thawing or moistening-and-drying conditions.

Sulphate Resisting Portland Cement (IS:12330): In this cement the amount of tricalcium

aluminate is restricted to on acceptably low value(< 5). It should not be mistaken for

supersulphated cement. It is manufactured by grinding and intimately mixing together

calcareous and argillaceous and/ or other silica, alumina and iron oxide bearing materials.

The Materials are burnt to clinkering temperature. The resultant clinker is ground to produce

the cement. No material is added after burning except gypsum and not more than one per cent

of air-entraining agents are added.



Properties: The specific surface of the cement should not be less than 225 m2

/kg. The

expansion of cement is limited to 10 mm and 0.8 per cent, when tested by Le-chatelier

method and autoclave test, respectively. The setting times are same as that for ordinary

Portland cement.

The compressive strength of the cubes should be as follows.

72 ± 1 hour ≮ 10 N/mm2

168 ± 2 hours ≮ 16 N/mm2

672 ± 4 hours ≮ 33 N/mm2

It should have a fineness of 400 m2 /kg. The expansion of cement is limited to 5 mm.

The initial setting line of the cement should not be less than 30 mm and the final setting time

should not be more than 600 mm.

Uses: This cement can be used as an alternative to order Portland cement or Portland

pozzolana cement or Portland slag cement under normal conditions. Its use however is

restricted where the prevailing temperature is below 40°C. Use of sulphate resisting cement is

particularly beneficial in conditions where the concrete is exposed to the risk of deterioration

due to sulphate attack; concrete in contact with soils or ground waters containing excessive

sulphate as well as concrete in sea water or exposed directly to sea coast.

Portland Slag Cement (IS: 455):

It is manufactured either by intimately inter-grinding a mixture of Portland cement

clinker and granulated slag with addition of gypsum or calcium sulphate, or by an intimate

and uniform blending of Portland cement and finely ground granulated slag. Slag is a non-

metallic product consisting essentially of glass containing silicates and aluminosilicates of

lime and other bases, as in the case of blast-furnace slag, which is developed simultaneously

with iron in blast furnace or electric pig iron furnace. Granulated slag is obtained by further

processing the molten slag by rapid chilling or quenching it with water or steam and air. The

slag constituent in the cement varies between 25 to 65 per cent.

Properties: The chemical requirements of Portland slag cement are same as that of 33 grade

Portland cement. The specific surface of slag cement should not be less than 225 m2

/kg. The

expansion of the cement should not be more than 10 mm and 0.8 per cent when tested be Le

Chatelier method and autoclave test, respectively. The initial and final setting times and

compressive strength requirements are same as that for 33 grade ordinary Portland cement.

Uses: This cement can be used in all places where OPC is used. However, because of its low

heat of hydration it can also be used for mass concreting, e.g., dams, foundations, etc.

Low Heat Portland Cement (IS: 12600):

To limit the heat of hydration of low heat Portland cement (LHC), the tricalcium

aluminate component in cement is minimised and a high percentage of dicalcium silicate and

tetracalcium alumino ferrite is added. The heat of hydration should not be more than 272 and

314 J/g at the end of 7 and 28 days respectively. The rate of development of strength is slow

but the ultimate strength is same as that of OPC. To meet this requirement, specific surface of

cement is increased to about 3200 cm2/g.

Properties: Less heat is evolved during setting low heat Portland cement. When tested by Le

Chatelier method and autoclave test the expansion should not be more than 10 mm and 0.8%,

respectively. The minimum initial setting time should not be less than 60 minutes, and the

final setting should not be more than 600 minutes.



The compressive strength should be as follows.

72 ± 1 hour ≮ 10 N/mm2

168 ± 2 hours ≮ 16 N/mm2

672 ± 4 hours ≮ 35 N/mm2

Uses: It is most suitable for large mass concrete works such as dams, large raft foundations,

etc.

Portland Puzzolana Cement (IS: 1489 (Part – I):

It is manufactured by grinding Portland cement clinker and puzzolana (usually fly ash

10-25% by mass of PPC) or by intimately and uniformly blending Portland cement and fine

puzzolana. Puzzolana (burnt clay, shale, or fly ash) has no cementing value itself but has the

property of combining with lime to produce a stable lime-puzzolana compound which has

definite cementitious properties. Free lime present in the cement is thus removed.

Consequently, the resistance to chemical attack increases making it suitable for marine

works. The hardening of Portland puzzolana cement consists in hydration of Portland cement

clinker compounds and then in interaction of the puzzolana with calcium hydroxide released

during the hardening of clinker.

Properties: These have lower rate of development of strength but ultimate strength is

comparable with ordinary Portland cement.

Compressive Strength

72 ± 1 hr ≮ 16.0 N/mm2

168 ± 2 hrs ≮ 22.0 N/mm2

672 ± 4 hrs ≮ 33.0 N/mm2

The initial and the final setting times are 30 minutes (minimum) and 600 minutes

(maximum), respectively. The drying shrinkage should not be more than 0.15% and the

fineness should not be less than 300 m2

/kg.

Uses: It has low heat evolution and is used in the places of mass concrete such as dams and in

places of high temperature.

Quick Setting Portland Cemnt:

The quantity of gypsum is reduced and small percentage of aluminium sulphate is

added. It is ground much finer than ordinary Portland cement.

Properties: Initial setting time = 5 minutes

Final setting time = 30 minutes

Uses: It is used when concrete is to be laid under water or in running water.

Masonry Cement (IS 3466):

The Portland cement clinker is ground and mixed intimately with pozzolanic material

(flyash or calcined clay), or non-pozzolanic (inert) materials (limestone, conglomrates,

dolomite, granulated slag) and waste materials (carbonated sludge, mine tailings) and gypsum

and air entraining plasticizer in suitable proportions.

White and Coloured Portland Cement (IS :8042):

It is manufactured from pure white chalk and clay free from iron oxide. Greyish

colour of cement is due to iron oxide. So, the iron oxide is reduced and limited below 1 per

cent. Coloured cements are made by adding 5 to 10 per cent colouring pigments before



grinding. These cements have same properties as that of ordinary Portland cement and are

non-staining because of low amount of soluble alkalis. Sodium alumino fluoride is added

during burning which acts as a catalyst in place of iron.

Properties: Loss on ignition of white cement is nil. The compressive and transverse strength

of this cement is 90 per cent of that of 33 grade ordinary Portland cement.

Uses: These cements are used for making terrazzo flooring, face plaster of walls (stucco),

ornamental works, and casting stones.

Air Entraining Cement:

Vinsol resin or vegetable fats and oils and fatty acids are ground with ordinary

cement. These materials have the property to entrain air in the form of fine tiny air bubbles in

concrete.

Properties: Minute voids are formed while setting of cement which increases resistance

against freezing and scaling action of salts. Air entrainment improves workability and

water/cement ratio can be reduced which in turn reduces shrinkage, etc.

Uses: Air entraining cements are used for the same purposes as that of OPC.

Calcium Chloride Cement: It is also known as extra rapid hardening cement and is made by

adding 2 per cent of calcium chloride. Since it is deliquescent, it is stored under dry

conditions and should be consumed within a month of its dispatch from the factory.

Properties: The rate of strength development is accelerated; a higher percentage of calcium

chloride causes excessive shrinkage. Strength gained after 1 day is 25 per cent more and after

7 days about 20 per cent more than the ordinary Portland cement.

Uses: It is very suitable for cold weathers.

Water Repellent Cement (IS: 8043):

It is also called hydrophobic cement. A small amount of hydrophobic surfactants such

as stearic acid, boric acid or oleic acid is mixed with the ordinary Portland cement during

grinding of clinker. These substances are added in amounts of 0.1 to 0.5% of the weight of

cement in terms of dry admixtures. These acids form a thin (monomolecular) film around the

cement particles which prevent the entry of atmospheric moisture. The film breaks down

when the concrete is mixed, and the normal hydration takes place.

When concrete is being prepared, hydrophobic admixtures plasticize the mix and

contribute to the formation of uniformly distributed fine pores in concrete as it hardens and

thus enhance its frost resistance. Hydrophobic cement also features greater water resistance

and water impermeability.

Properties: The specific surface of hydrophobic cement should not be less than 350 m2/kg.

The average compressive strength should not be less than

72 ± 1 hour ≮ 15.69 N/mm2

168 ± 2 hours ≮ 21.57 N/mm2

672 ± 4 hours ≮ 30.40 N/mm2

The weak points of hydrophobic cement are its small strength gain during the initial

period because of the hydrophobic films on cement grains which prevent the interaction with

water, but its 28-day strength is equal to that of ordinary Portland cement.



Uses: It is most suitable for basements and for making water tight concrete.

Water Proof Cement:

It is manufactured by adding strearates of Ca and Al and gypsum treated with tannic

acid, etc. at the time of grinding.

Properties: It is resistant to penetration of water.

Uses: Water retaining structures like tanks, reservoirs, retaining walls, swimming pools,

bridge piers, etc.

2.2. Mortar

2.2.1. Introduction

Building mortars are mixtures used for the jointing of bricks, stones, blocks, etc. Mortar

may be defined as a paste (capable of setting and hardening) obtained by adding water to a

mixture of fine aggregates such as sand and binding material, e.g., clay, gypsum, lime or

cement or their combinations. The pyramids of Egypt have been built with clay-gypsum,

gypsum-lime and lime mortars. Indians have used lime mortar for monumental structures

such as Taj Mahal and forts. In the years that followed, if was found that burning limestone

with clayey substance produced hydraulic lime of high water-resistant properties. Lime with

a still higher content of clay led to the manufacture of Roman cement. In 1824 Portland

cement appeared; today it is considered to be the strongest binding material for making

mortar.

2.2.2. Different types and their properties

Cement mortar:

Cement mortar can be prepared by mixing cement, sand and water in desired proportions.

Portland cement and blast furnace slag cement form excellent mortars for walls built with\

bricks, stones and large blocks. Puzzolana Portland cement and sulphate-resisting cement

form mortar which is used for constructions exposed to aggressive and waste waters. Cement

mortars are used for plastering, rendering smooth finishes and damp proof courses.

The mix proportions of cement mortar are given in Table 2.1.

S.No. Type of Work Cement Sand

1 Masonry 1 4-5

2 Plastering (a) Interior

(b) Exterior

1

1

4

5-6

3 Pointing 1 1-3

4 Reinforced brick work 1 3

5 Foundation 1 3-4

Preparation: Small quantities of mortar are mixed manually; mechanical mixers may be used

for large quantities.

For manual mixing,_sand is sieved, cleaned with water to remove dirt and dust and dried.

This dry sand is laid uniformly, on a pucca platform, over which cement is uniformly spread.

The whole mass is then thoroughly mixed with spades till it becomes uniform in colour. A



depression is then made in the middle of the mix and required quantity of water is added. The

dry mix from the sides is moved and placed on the edges of the depression formed till the

water is completely absorbed by the mix. The wet mix is then worked with spades to give a

uniform consistency to the mortar.

For mechanical mixing_ the calculated quantity of cement, sand and water are fed into

the cylindrical container of the mixer. A rotar with blades, inside the container, rotates and

thoroughly mixes the ingredients.

Precautions: Cement mortar should be of uniform and workable consistency. It should be

consumed within 30 minutes from the instant of adding water to the mix. The bricks, stones

and blocks should be fully saturated in water before laying. The masonry and plastered or

pointed surface should be kept completely wet by sprinkling water for at least 7 days.

Lime mortar: Lime mortar is made by mixing lime, sand and water. Lime used for mortar may be

fat lime (quick or hydrated lime) or hydraulic lime. Fat lime has high calcium oxide content.

Its hardening depends on loss of water and absorption of carbon dioxide from the atmosphere

and possible recrystallisation in due course. Hydraulic lime contains silica, alumina and iron

oxide in small quantities. When mixed with water it forms putty or mortar having the

property of setting and hardening under water.

Slaked fat lime is used to prepare mortar for plastering, while hydraulic lime is used for

masonry construction and are most suitable for construction of chimneys and lightly loaded

superstructure of buildings. The mix proportions of lime mortar for various types of works

are given in Table 2.2.

Table 2.2. Mix Proportions

Sl. No. Type of lime Lime Sand Fineness

modulus of

sand

Type of work

1 Fat Lime 1-2

1-5

2-3

2-3

2-3

2-3

Plastering

Pointing

2 Hydraulic 2-3 1.5-2.5 1.5-2.5 Masonry

Lime mortars have plasticity and placability, good cohesion with other surfacings and

little shrinkage. They harden and develop strength very slowly continuously gaining strength

over long period. Fat lime mortars do not set but stiffen only as water is lost by absorption

(by masonry units) and evaporation. The gain in strength is a very slow reaction of lime with

carbon dioxide absorbed from air.

Preparation:

Hand mixing: Lime and sand in required quantities are placed on an impervious floor or in a

tank (Fig. 2.3). The constituents are thoroughly mixed dry by turning them up and down with

spades. Water is added and mixing is done again with spades till mortar of uniform colour

and consistency is obtained.

Fig. 2.3. hand mixing of lime mortar



Mill mixing: Mills used for preparing lime mortars in undeveloped countries may be a

chakki or ghanni run by bullocks (Fig. 2.4) while a pan mill (Fig. 2.5) is used in developed

countries. In the case of ghanni the required quantity of ingredients in the form of putty is put

in the trench and grinding for 100 to 200 revolutions is carried out by moving stone roller.

The operation takes about 2 to 3 hours for each batch of mix; the time required in a Pan mill

is much less.

Fig. 2.4. Ghanni run by bullocks

Fig. 2.5. Pan mill

Precautions: Lime mortar or putty should be kept moist till use and in no case its drying is

allowed. The mortar made of hydraulic lime should be consumed within one day and that

with fat lime within 2-3 days.



Surkhi mortar: It is prepared in the same way as lime mortar, with surkhi replacing sand. Surkhi

should be ground to pass through 4.75 mm sieve and about less than 15 per cent through 150

micron sieve. Sand is also mixed sometimes. The mix proportions of surkhi mortar are given

in Table 2.3.

Table 2.3. Mix proportions

Sl. No. Type of mortar Lime Surkhi Sand Type of work

1 Surkhi 1 2 - Masonry and foundation

2 Lime-surkhi 1 1 1 Masonry and foundation

Lime – cement mortar:

Also known as guarded mortar or gauged mortar is made by mixing cement and

lime. The advantages of lime-cement mortar are increased water retentivity, workability,

bonding properties and frost resistance. The mortar gives good and smooth plaster finish and

is used in buildings.

Preparation: For low lime content, cement and sand are first mixed dry. Lime putty is

dissolved in water and added to the dry mix. The mix is then worked thoroughly with spades

till uniform consistency is obtained. For high lime content lime cement mortar is made in the

mills; lime and sand are first mixed separately in the form of paste for the entire day’s

requirement. Then cement is mixed with lime mortar in batches to be consumed in an hours

time. The mix proportions of lime-cement mortar are given in Table 2.4.

Table. 2.4. mix proportions

Sl. No. Location Ratio (by volume)

Cement Lime Sand

1 Outside wall 1 1 6

1 2 9

2 Inside wall 1 2 9

1 3 12

Mud mortar: They are the cheapest type of mortar prepared with locally available ingredients and

are used for masonry works, surfacing floors and plastering wall surfaces in low cost houses.

To improve resistance to rain water, the plastered surfaces are sometimes sprayed with

bituminous material.

Preparation: The top 150 to 200 mm layer of earth is removed and the clay nodules dug from

the ground are wetted and allowed to mature for a day or two. Some fibrous material such as

cow dung is added which prevents the shrinkage cracks. The ingredients are then kneaded

well and mixed thoroughly.

Special mortars:

Some of the mortars intended for use under special circumstances are as follows:

Mortars for filling joints between Prefabricated Reinforced Concrete Components are

prepared with Portland cement and quartz sand with a mobility of 70 to 80 mm. The grade of

the mortar should be same as that of the concrete and in no case less than M-10.



Cement-sand and cement paste injection mortars intended for filling grooves inside

prestressed concrete components should have a grade not less than M-40 grade or more is

preferred. Sulphite-alcohol vinasse or naphetene soap is added in amounts up to 0.2 per cent

of the weight of cement to reduce viscosity.

Packing mortars used for packing oil wells these mortars may be of cement-sand, cement-

loam and cement-sand-loam. Slag Portland cement, puzzolana and sulphate resisting cements

are used for aggressive water and packing Portland cement when water pressure is expected.

These mortars should have high homogeneity, water resistance, predetermined setting time,

adequate water yield under pressure and ability to form soil water-proof plugs in cracks and

voids of rocks. Cement-sand-loam mortar with 5 per cent calcium chloride is especially

suitable for tunnelling.

Damp proofing mortars are prepared using high grade sulphate-resisting Portland cement or

sulphate-resisting puzzolana cement as binding material and quartz sand or sand from

crushed solid rock. An approximate composition of the mortar is 1:2.5 or 1:3.5. Water proof

seams and joints are made from damp-proofing mortars prepared with expanding cement.

Sound – absorbing mortars are prepared with Portland cement, slag cement, lime or gypsum

as binding material, caustic magnesite and single-size fraction sand (3.5 mm) from light

weight porous materials such as pumice, cinders, ceramsite, etc. They have a bulk density of

600- 1200 kg/m3 and used as sound absording plaster to reduce the noise level.

Fire shielding mortars are used for setting refractory bricks in the furnace linings where the

temperature is too high for ordinary mortars. Aluminous cements and finely powdered fire

bricks in the ratio 1:2 give excellent fire resisting mortars. Its trade name is Accoset 50.

X-ray Shielding mortars: Heavy mortars of bulk density over 2200 kg/m3 are required for

plastering walls and ceilings of X-ray cabinets. The binding materials are Portland cement

and slag cement, and the aggregates are from heavy rocks in the form of sand (up to 1.25

mm) and dust. Admixtures containing light weight elements (hydrogen, lithium, cadmium)

are added to enhance the protective properties.

2.3. Concrete

2.3.1. Introduction

Concrete a composite man-made material, is the most widely used building material in

the construction industry. It consists of a rationally chosen mixture of binding material such

as lime or cement, well graded fine and coarse aggregates, water and admixtures (to produce

concrete with special properties). In a concrete mix, cement and water form a paste or matrix

which in addition to filling the voids of the fine aggregate, coats the surface of fine and

coarse aggregates and binds them together. The matrix is usually 22-34% of the total volume.

Freshly mixed concrete before set is known as wet or green concrete whereas after setting

and hardening it is known as set or hardened concrete. The moulded concrete mix after

sufficient curing becomes hard like stone due to chemical action between the water and

binding material. It would be impossible to discuss all the aspects of this material in few

pages and the discussion is confined to the general characteristics and quality tests necessary

for its use by civil engineers and architects.



2.3.2. Grades of concrete

The cement concrete is specified by proportions of different ingredients, e.g., 1 (cement) :

1.5 (fine aggregate) : 3 (coarse aggregate). It is presumed that by adhering to such perspective

specifications satisfactory performance may be achieved. The usual mix proportions of

cement concrete are given in Table 2.5. Here, M refers to the mix. This type of concrete mix

is also known as nominal mix. Conventional nominal mix proportions have limited

significance, since the quantity of fine aggregate is fixed irrespective of the cement content,

water-cement ratio and the maximum size of aggregate to be used. The proportions of

materials of nominal mix concrete as given in Table 2.5 are prevalent in field. However, IS:

456 restrict its use only up to M-20 grade. Table 2.5. mix proportions of cement concrete

Grade of concrete M10 M15 M20 M25

mix. proportions 1:3:6 1:2:4 1:11

2:3 1:1:2

Perspective characteristic strength 10 15 20 25

2.3.3. Properties of concrete

Important properties of concrete are;

a) It possesses a high compressive strength.

b) It is a corrosion resistance material and atmospheric agent has no appreciable

effect on it.

c) It hardens with age the process of hardening continues for a long time after the

concrete has attained sufficient strength. It is this property of cement concrete

which gives it a distinct place among building materials.

d) It is more economical than steel.

e) It binds rapidly with steel and as it is weak in tension, the steel reinforcement is

placed in cement concrete at suitable places to take up the tensile stresses. This is

termed as the reinforced cement concrete or simply as R.C.C.

f) Under the following two conditions, it has a tendency to shrink:

1. There is initial shrinkage of cement concrete which is mainly due to the loss

of water through forms, absorption by surfaces of forms etc.

2. The shrinkage of cement concrete occurs as it hardens. This tendency of

cement concrete can be minimized by proper curing of concrete.

g) It has a tendency to be porous. This is due to the presence of voids which are

formed during and after its placing. The two precautions necessary to avoid this

tendency are as follows:

1. There should be proper grading and consolidating of the aggregates.

2. The minimum water-cement ratio should be adopted.

h) It forms a hard surface, capable of resisting abrasion.

i) It should be remembered that apart from other materials, the concrete comes to the

site in the form of raw materials only. Its final strength and quality depend entirely



on local conditions and persons handling it. However the materials which concrete

is composed may be subjected to rigid specifications.

2.3.4. Types of concrete and their uses

Types of concrete with applications for different structural components like

beams, columns, slabs, foundations are explained here. Special concrete with uses.

Light weight concrete

One of the main advantages of conventional concrete is the self weight of

concrete. Density of normal concrete is of the order of 2200 to 2600. This self weight will

make it to some extend an uneconomical structural material.

1. Self weight of light weight concrete varies from 300 to 1850 kg/m3.

2. It helps reduce the dead load, increase the progress of building and lowers the

hauling and handling cost.

3. The weight of building on foundation is an important factor in the design ,

particularly in case of weak soil and tall structures. In framed structure , the beam

and column have to carry load of wall and floor. If these wall and floor are made

of light weight concrete it will result in considerable economy.

4. Light weight concrete have low thermal conductivity.( In extreme climatic

condition where air condition is to installed the use of light weight concrete with

low thermal conductivity is advantageous from the point of thermal comfort and

low power consumption.

5. Only method for making concrete light by inclusion of air. This is achieved by a)

replacing original mineral aggregate by light weight aggregate, b) By introducing

gas or air bubble in mortar c) By omitting sand fraction from concrete. This is

called no – fine concrete.

6. Light weight aggregate include pumice, saw dust rice husk, thermocole beads,

formed slag. Etc

7. Light weight concrete aggregate exhibit high fire resistance.

8. Structural lightweight aggregate’s cellular structure provides internal curing

through water entrainment which is especially beneficial for high-performance

concrete.



9. lightweight aggregate has better thermal properties, better fire ratings, reduced

shrinkage, excellent freezing and thawing durability, improved contact between

aggregate and cement matrix, less micro-cracking as a result of better elastic

compatibility, more blast resistant, and has better shock and sound absorption,

High-Performance lightweight aggregate concrete also has less cracking, improved

skid resistance and is readily placed by the concrete pumping method

a) Aerated concrete is made by introducing air or gas into a slurry composed of

Portland cement.

b) No fine concrete is made up of only coarse aggregate , cement and water.

These type of concrete is used for load bearing cast in situ external walls for

building. They are also used for temporary structures because of low initial

cost and can be reused as aggregate.

High density concrete

1. The density of high density concrete varies from 3360 kg/m3 to 3840 kg/m3.They

can however be produced with density upto 5820 kg/m3 using iron as both fine

and coarse aggregate.

2. Heavyweight concrete uses heavy natural aggregates such as barites or magnetite

or manufactured aggregates such as iron or lead shot. The density achieved will

depend on the type of aggregate used. Typically using barites the density will be in

the region of 3,500kg/m3, which is 45% greater than that of normal concrete, while

with magnetite the density will be 3,900kg/m3, or 60% greater than normal

concrete. Very heavy concretes can be achieved with iron or lead shot as

aggregate, is 5,900kg/m3 and 8,900kg/m

3respectively.

a) They are mainly used in the construction of radiation shields (medical or

nuclear). Offshore, heavyweight concrete is used for ballasting for pipelines

and similar structures

b) The ideal property of normal and high density concrete are high modulus of

elasticity , low thermal expansion , and creep deformation

c) Because of high density of concrete there will be tendency for segregation. To

avoid this pre placed aggregate method of concreting is adopted.

d) High Modulus of Elasticity, Low thermal Expansion ,Low elasticity and creep

deformation are ideal properties.



e) The high density. Concrete is used in construction of radiation shields. They

are effective and economic construction material for permanent shielding

purpose.

f) Most of the aggregate specific gravity is more than 3.5

High Performance Concrete

This mix has the following main properties:

High strength.

High workability.

High durability.

Ease of placement.

Compaction without segregation.

Early age strength.

Long-term mechanical properties.

Permeability.

Density.

Heat of hydration.

Toughness.

Volume stability.

Long life in severe environments.

High strength concrete mix can be prepared with careful selection of

ingredients and optimization of mix design.

High workability is attained by super plasticizers, they lower the water cement ratio to

0.25 which is the amount required only for hydration process.

High durability is attributed to fly ash and silica fume which modify the e mineralogy

of the cement; it enhances the compatibility of ingredients in concrete mass and

reduces the CH amount. Fly ash also causes ball bearing effect increasing workability.

The admixtures are 20-25% fly ash of partial replacement of cement and rest 70% is

Ordinary Portland Cement.

As it is not usually durable against freezing and thawing so air entrained agents can

also be utilized.

Properties of high performance concrete mix

Strength of high performance concrete ranges from 10000 psi - 15000 psi

Water cement ratio can be reduced to 0.25

Uses:

The high performance concrete is widely adopted as following;

a) High rise buildings



b) Towers

c) Tunnels

d) Long spanned bridges

e) Piers

f) Highway concrete

g) Precast concrete

Self-Compacting Concrete

The concrete where no vibration is required. The concrete is compacted due to its own

weight. It is also called self-consolidated concrete or flowing concrete. It can be also categorized

as high performance concrete as the ingredients are the same, but in this type of concrete

workability is increased. This self-consolidating concrete is characterized by:

Extreme fluidity as measured by flow, typically between 650-750 mm on a flow table,

rather than slump (height).

No need for vibrators to compact the concrete.

Placement being easier.

No bleed water, or aggregate segregation.

Uses and Applications of Self Compacting Concrete:

1. It is used in location unreachable for vibrations. e.g. underground structure, deep wells or

at bottom of deep sea.

2. SCC can save up to 50% in labor costs due to 80% faster pouring and reduced wear and

tear on formwork.



References:

1. “Building Materials” by S.K. Duggal

2. “Building Construction” by Rangwala

3. Concrete Technology by M.S. Shetty

4. Google images.

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BINDING MATERIALS · 2016. 9. 4. · cement was the prototype of the modern Portland cement. From then onwards, a gradual improvement in the properties and qualities of cement has