Architecture - First semester Building material unit 2 about the lime manufacturing and it uses.

1. UNIT – II
LIME

2. lime
 Types of lime
 Classification of lime
 Comparison between fat lime and hydraulic lime
 Manufacturing process slaking, Hardening –
Testing and Storage
 Lime putty
 Precautions in handling and uses of lime

3. What is LIME?
• The word lime refers to products derived from burnt (calcined)
limestone, such as quicklime and hydrated lime.
• Limestone is a naturally occurring and abundant sedimentary rock
consisting of high levels of calcium and/or magnesium carbonate,
and/or dolomite (calcium and magnesium carbonate), along with small
amounts of other minerals.
• It is extracted from quarries and underground mines all over the world.
• Lime and limestone products are among the oldest materials used by
humans for a very diverse range of applications.
• Today these products serve as an essential building block in every
industrial process.

4. lime
• The ancient romans used lime in building and road construction which continues to
the present day.
• In earlier days, lime has been made by heating limestone (calcium carbonate) to high
temperatures.
• This process known as calcining results in quick lime or calcium oxide.
• Hydrated lime (calcium hydroxide) is produced by reacting quicklime with
sufficient water to form dry white powder.
• While lime is one of the earliest industrial commodities known to man, its
production and uses have grown with the times, and it continues to be one of the
earliest building blocks of modern industry.
• Although, the cement has replaced lime to a great extent, yet in view of the rising
cost its quiet likely that lime will come into prominence again.

5. Lime cycle
• After processing, products derived
from limestone have the unique ability
to return to their original chemical
form.
• The lime cycle consists of first burning
of limestone to form quicklime.
Hydrated lime can then be produced
by adding water to the quicklime.
• Carbon dioxide in the atmosphere or
from industrial combustion processes
react with hydrated lime to convert it
back to limestone.
• This cycle of sustainability is called
the lime cycle.

6. Sources of Lime
 Lime is not generally found in nature in the free state but it is
obtained by burning one of the following materials:
• Limestone found in limestone hills
• Limestone boulders found in the beds of old rivers
• Kankar found below ground
• Shells of sea animals
 White chalk is pure limestone and kankar is an impure lime
stone.

7. properties of Lime
 Properties of good quality lime, which makes it suitable for
use as an engineering material are:
• Easily workable
• Provides strength to the masonry
• Possess good plasticity
• Offers good resistance to moisture
• Stiffens early
• Lime masonry proves durable due to low shrinkage in drying

8. Limestone
• Limestone is the most important and abundant sedimentary rock and is
formed by the compaction of the remains of coral animals and plants on the
bottoms of oceans around the world.
• Limestone is composed of the mineral calcite (calcium carbonate) and/or
the mineral dolomite (calcium and magnesium carbonate) along with small
amounts of other minerals.
• There are three distinct types of limestone which are defined by their
magnesium carbonate (MgCO3) concentrations:
 Dolomitic limestone consists of 35 to 46% magnesium carbonate
 Magnesian limestone consists of 5 to 35% magnesium carbonate
 High calcium limestone contains less than 5% magnesium carbonate.

9. Limestone
• Limestone is quarried or mined then crushed and screened to serve a
wide variety of applications including:
– pH adjustment (Ag-lime, water treatment)
– Formulated product filler (masonry cements, ready mix concrete,
asphalt and joint compounds)
– Raw material in the production of glass, pulp & paper, portland
cement and steel
– Production of stone blocks

10. Types and classification of Lime
LIME
QUICK LIME
SLAKED
LIME
HYDRAULIC
LIME
FAT LIME
CLASS C
CLASS B
CLASS A

11. Types and classification of Lime
 Quick lime: its obtained by calcination (i.e.,heating to redness) of comparatively
pure lime stone.
• Its amorphous in nature, highly caustic and possesses great affinity to moisture.
 Slaked lime (or hydrated lime): its obtained by slaking (i.e., combination of quick
lime with water) of quick lime.
• It has got the tendency of absorbing carbonic acid from the atmosphere in presence
of water and it’s a ordinary pure lime in white powder form.
 Fat lime (or high calcium lime or pure lime or rich lime or white lime): its obtained
from the pure limestone, shell and coral.
• It absorbs carbon dioxide when it is left in air, and gets transferred into calcium
carbonate.

12. Types and classification of Lime
• When compared with quick lime, the volume of fat lime gets increased to about 2-
2.5 times.
• Its used for various purposes as white washing, plastering of walls, as a lime mortar
with sand for pointing in masonry work, as a lime mortar with surkhi for thick
masonry walls, foundations, etc.,
 Hydraulic lime (or water lime): The composition of hydraulic lime is different from
quick lime, it contains a definite quantity of clay which gives its hydraulic property.
• Hydraulic lime contains 70-80% of CaOH and 15-30% of clay.
• It has the capacity to set and harden even under water, where the quick lime cant be
used and hence its also known as water lime.
• Its obtained by burning the limestone containing rich clay or adding clay materials
to the limestone while burning.

13. Types and classification of Lime
• Depending upon the hydraulicity, its divided into feebly hydraulic, moderately
hydraulic and non-hydraulic lime.
– CLASS A – (Eminently hydraulic lime)
– CLASS B – (semihydraulic or moderately hydraulic lime)
– CLASS C – (non-hydraulic lime)
 CLASS A Lime (Eminently hydraulic lime): it contains about 25% clay content and
sets readily under water within a day or so.
• It slakes with difficulty
• The mortar and lime concrete prepared from this lime is very useful for construction
under water or in damp places.

14. Types and classification of Lime
 CLASS B Lime (Semi hydraulic or moderately hydraulic lime): it
contains about 15% clay and sets under water at a slower rate within a
week or so.
• The mortar and concrete prepared from this lime is strong and used for
superior type of masonry work.
 CLASS C Lime (Non-hydraulic lime): It contains about 7-5% clay and is
prepared from pure limestone.
• This slakes vigorously within a few minutes but doesn’t set under water.
• Its used for white washing and color washing.

15. Comparison of fat and hydraulic Lime
Item Fat lime Hydraulic lime
1.Composition Its obtained from comparatively pure
carbonate of lime containing only 5%
of clayey impurities
Its obtained from limestone
containing 5-30% clay and some
amount of ferrous oxide.
2.Slaking action i) Slakes vigorously and volume will
be increased to about 2-2.5 times the
quick lime
Slakes slowly and volume will be
increased slightly
ii) Slaking is accompanied by sound
and heat
Slaking is not accompanied by
sound and heat
iii) Sets slowly in presence of air Sets under water
iv) It absorbs carbon dioxide from air
and forms calcium carbonate
It combines with water and forms
crystals of hydrated tricalcium
aluminate and dicalcium silicate
3.Hydraulicity Doesn’t possess hydraulic property It possess hydraulic property
4.Color Perfectly white in color Its not as white as fat lime

16. Comparison of fat and hydraulic Lime
Item Fat lime Hydraulic lime
5.Strength Its not strong, hence it cannot be
used where strength is required
Its strong and can be used
where strength is required
6.Uses For plastering, white washing and
preparing mortar with sand or
surkhi,etc.,
For preparing mortar for thick
walls and damp places etc.,
 USES OF LIME
• Lime mortar: it has been extensively used in construction work from times
immemorial.
• Its used as a building medium in brick, stone and other masonry work as well as
for plastering and pointing
• Composition of the lime mortar for building work depends on:
- Type of masonry
- Location of the work
- Soil condition
- Condition of exposure to weather
- Weather condition under water(in case of hydraulic structures)

17. Uses of Lime
 Plastering: Lime plastering serves the following functions
– To smoothen the surface of masonry
– To protect the masonry surface from weathering
– To cover unevenness of masonry
– To prepare surface for decorative purpose
 Whitewashing: It can be applied on both internal and external surface of
the wall as a finishing
• Apart from finishing purpose, white washed surface reflects away the
sun’s rays and reduces the heating effect.
 Lime concrete: In situations where quick setting and high strength are
not required, lime concrete serves as an economical substitute.
• It can be used for foundation, terraced roofing, flooring, etc.,

18. Uses of Lime
 Lime sand bricks: it is a pearl grey brick like dry pressed burnt clay brick.
• This can be used for low cost construction
• Its used as a chemical raw material in the purification of water and for
sewage treatment
 Following are the various uses of lime:
- Matrix for concrete
- Binding material in mortars for stoneware
- Plastering walls, ceilings, etc.,
- Flux in the manufacture of steel
- Stabilizer in the soil

19. Technical terms
• Calcination and quick lime:
– Calcination is the process of heating limestone to redness in contact
with air. Due to calcination, the moisture and carbon dioxide are
removed from the limestone and the remaining product is known as
lime. Its chemical composition is oxide of calcium (CaO). The
chemical reaction is as follows:
CaCo3 CaO + CO2
(Limestone) (Lime)
• The lime obtained by calcining pure limestone is called quick lime
(CaO). It has great affinity for moisture. Its amorphous (i.e.,not
crystalline) and highly caustic having no affinity for the carbonic acid.

20. Technical terms
• Lump lime: it’s the obtained lime in lumps after burning or
calcination in kilns.
• Fat lime: it’s the lime which has high calcium oxide content and
can set and become hard only in the presence of carbon dioxide
(from atmosphere). This type of lime is perfectly white in color.
• Hydraulic lime: Lime containing small quantities of silica, alumina
and iron oxide, which are in chemical combination with calcium
oxide and can set and become hard even in the absence of CO2 and
can set under water.

21. Technical terms
• Slaked lime/Hydrate of lime: its formed by the absorption of water by
quick lime and is the hydrated oxide of calcium, Ca(OH)2. The chemical
reaction is as follows:
CaO + H2O Ca(OH)2 + heat
(Quick lime) (Hydrated Lime)
• A dry powder obtained by treating quick lime with water, just sufficient
to convert the lime into calcium hydroxide is called hydrated lime.
• A plastic mass of lime which results from the slaked lime in the presence
of a sufficient quantity of water is called putty.
• A thin pourable suspension of slaked lime is called milk of lime.

22. Technical terms
• Slaking: it’s the process of chemical combination of quick lime with required
quantity of water for killing the heat and getting into powder form for use.
• Setting: it’s the hardening of lime which has been mixed to a paste with
water.its quite different from mere drying. In case of drying only the
evaporation of water takes place and that’s not the setting action.
• Hydraulicity: it’s the property due to which lime (or cement) will set in damp
places or under water or in thick masonry walls where there is no free access
of air.
• Hydraulicity is due to the crystallizing energy of the aluminates and silicates
of lime.
• Pure limestone (such as white chalk & marble) and also a commercial
mixture of limestone and sand don’t posses hydraulic property.

23. Manufacture of lime
• There are three operations involved in the manufacture of lime. They are:
– Collection of raw materials
– Burning of limestone
– Slaking of burnt lime
 Collection of raw materials:
– The required quality and quantity of limestone are collected and stacked in
sufficient quantity near the lime manufacturing unit for the continuous
production
– Pure limestone is used for manufacturing quick lime and its impure form may
be used for producing other types of lime. For fat lime impurities in limestone
should not exceed 5%. Kankar limestone (containing about 30% clay in the
form of alumina and silica and greyish iin color) is used for the preparation of

24. Manufacture of lime
 Burning of limestone: Limestone can be burnt either in clamps or kilns.
– For small quantity of limestone clamps can be used.
– Whenever the lime is desired intermittently or the supply of fuel is not
regular then the intermittent kiln can be used.
– Wood or charcoal can be used as a fuel in the continuous kiln.
• Clamps: For small quantity of limestone, burning is done in the clamp. On
a clear surface about 5 meters in diameter, layers of broken limestone and
fuel are laid to form a heap about 4 meters high.
– First and the last layers should be of the fuel. In case coal is used a fuel
it has to be well mixed with the limestone and laid in a heap.
– Sides of the heap, which incline slightly inwards, are plastered over
with mud to stop loss of heat.

25. Manufacture of lime
• A little opening at the top is provided for draught. The clamp is then fired at the
bottom.
• Disappearance of blue flame at the top is an indication of the burning of lime having
completed.
• The clamp is then allowed to cool down and pieces of quick lime are then
handpicked.
• Clamp burning of lime is uneconomical as the fuel consumption is more due to loss
of heat and as some lime powder is lost in fuel ash.
• Kilns: its for large quantity of lime, permanent structure of kilns are constructed.
A) Intermittent kiln: whenever the lime is desired intermittently or the supply of fuel is
not regular then the intermittent kiln will be used.
- This is the kiln in which the fuel is not in contact with the lime.

26. Manufacture of lime
- Big pieces of limestone are used to make a sort of arch on with which the
smaller pieces of limestone are loaded.
- Fire is lighted below the arch formed with big pieces of limestone.
- Its only the flame which comes in contact with the limestone.
- Burning should be gradual so that the stones forming the arch do not get
split.
- It normally takes two days to burn and one day to cool the charge.
B) Continuous kiln: wood or charcoal could be used as a fuel.
- Limestone or kankars free from earth or impurities are broken into small
pieces to about 5cm gauge.
- Alternate layers of 75mm stone and 6mm coal dust are fed into the kiln.

27. Manufacture of lime
- Top should be covered with mud, leaving a hole of 0.5 meter diameter in the center.
- Burning proceeds continuously and the kiln is not allowed to cool down.
- Burnt material is drawn out daily and fresh charge of stone and fuel is added from
top.
- Over burnt pieces are discarded whereas the under burnt ones are reloaded into the
kiln.
- Remaining material is slaked or ground in grinding mills for use.
 Precautions in burning of limestone:
- Before burning the limestone, they should be broken into suitable sizes.
- Quantity of fuel used should be carefully worked out.
- The limestone should be gradually heated (sudden heating may blow the stones to
pieces due to quick release of moisture and carbon dioxide)

28. Manufacture of lime
- The complete burning may be adjusted by the bright red color of the flame.
- Over burning and under burning of limestone should be avoided (over burnt or
under burnt stone doesn’t slake and its said to be dead lime).
 Slaking of lime: its the process of chemical combination of quick lime with
required quantity of water for killing the heat and getting into powder form for
heat.
- The process of adding water to quick lime is called slaking of lime. Its an important
process in rendering lime suitable for use and as such great care should be taken to
slake the lime.
- The lime should be slaked soon after its drawn from the kiln, preferably within a
week of its calcination.
- The burnt lime or quick lime can be slaked in the form of dry powder or in the
form of cream paste called putty.

29. Manufacture of lime
• The common methods employed for slaking are listed below:
i. Air slaking
ii. Basket slaking
iii. Platform slaking
iv. Tank slaking
i. Air slaking: Lime is spread over a non-porous platform, it absorbs moisture from
the air and slakes slowly into a powder form.
- This method is not suitable since complete slaking is not obtained.
ii. Basket slaking: In this method the quick lime is broken into pieces (size not more
than 50mm) and filled in a basket.
- The basket is then immersed in a clean water for few seconds.
- Then the basket is taken out and thrown on a platform in the form of a heap;
quick lime crumbles and falls into powder form.
- This method is suitable for slaking semi-hydraulic limes but not suitable for
other limes since complete slaking is not obtained.

30. Manufacture of lime
iii. Platform slaking: Its usually carried out on clear, dry, masonry platform.
- Large lumps of quick lime are broken to less than 50mm size. They are spread in a
150mm thick layer on the platform and water is then sprinkled over it.
- The lime slakes and gets into powder form.
- During the water sprinkling, the heap of lime is turned over no more water is used
than that required for the lime to retain its powder form.
- Slaked lime is then screened through a sieve of 3 meshes to a cm to remove
unburnt lumps, unslaked material or other foreign matter.
- Screened lime can be used for the preparation of mortar.
iv. Tank slaking: Two brick-lined tanks are normally required to be constructed.
- One of the tank is generally constructed at ground level and is 45 cm deep, the
other tank is made adjacent to the first tank but at a lower level below the ground
usually 60 to 75cm deep.

31. Manufacture of lime
- The tank at the ground level is partly filled with water and sufficient quicklime is
added gradually to fill up the tank to about half the level of water.
- It may be noted that lime should always be added to water and not water to lime.
- The lime is then stirred properly and no part of lime is allowed to get exposed above
water.
- As the lime slakes with the evolution of heat, the temperature of water will begin to
increase and water begins to boil.
- Thus, when the required temperature (85o C to 98o C) for slaking is reached, additions
of lime and water are made in small quantities with constant stirring so as to maintain
the temperature.
- The lime in the state of suspension (or the milk of lime) is then allowed to pass through
a sieve of 3 meshes to a cm flow into the second tank built at lower level.
- The particles of lime settle down and water gets partly evaporated and partly absorbed
in ground and the remaining surplus water is removed.

32. SLAKING NATURE OF LIME
• Finding the slaking nature of lime:
– For finding the slaking nature, put two or three lumps of lime
or an equal amount in case of granular lime in bucket.
– Add sufficient water to barely cover the lime and note how
long it takes for slaking to begin (when the lumps start
crumbling).
– If the slaking begins in less than 5 minutes, the lime is quick
lime
– If it takes from 5 – 30 minutes, it’s a medium slaking
– If it takes above 30 minutes, it’s a slow slaking.

33. hardening of lime
• There are three types of hardening of lime. They are:
a. Carbonate hardening
b. Hydrate hardening
c. Hydro silicate hardening
a. Carbonate hardening: Two simultaneous processes takes place in
lime mortar or concrete from slaked lime
- The mixed water evaporates and calcium oxide hydrate
crystallizes out of its saturated water solution.
- Calcium carbonate is formed in accordance with the reaction
Ca(OH)2 + +CO2 + nH2O CaCO3 + (n+1)H2O
The crystallization process of calcium oxide hydrate is very slow.

34. hardening of lime
• Evaporation of water causes fine particles of Ca(OH)2 to stick together
and form large Ca(OH)2 crystals.
• The rate of CaCO3 formation is significant only in the presence of
moisture. A film of calcium carbonate appearing on the surface of the
mortar during the initial period of hardening, prevents the penetration of
carbon dioxide into the inside layers, and because of this carbonisation
process, which is very intensive in the presence of a sufficient amount of
carbon dioxide stops almost entirely.
• The more intensive is the evaporation of water, the quicker is the
crystallization of calcium oxide.

35. hardening of lime
b) Hydrate hardening: it’s a gradual conversion of lime mortar and concrete mixes
from ground unslaked lime into a rock like hard body.
- First, lime dissolves in water to give a saturated solution, which over saturates
rapidly because water is absorbed by the remaining unslaked grains.
- Rapid and strong over saturation of a mortar, prepared from unslaked lime
results in formation of colloidal masses, which appears because calcium oxide
hydrate formed by mixing lime with water.
- Colloidal calcium hydrate coagulates into a hydrogel which glues the grains
together.
- As water is partly sucked in by the deeper layers of grains and partly evaporates,
the hydrogel thickens and increase the strength of the hardening lime.
- As slaking lime hardens, crystallization of calcium oxide hydrate increases its
strength.

36. hardening of lime
b) Hydro silicate hardening:
- When lime – sand mixtures are treated by high-pressure steam (8-16 atm)
corresponding to temperature between 175 and 200oC, lime and silica interact in
the autoclave and form calcium hydrosilicate which ensures high strength and
durability.
- In the autoclave method of hardening lime – sand materials, lime does not play
the part of a binding material, whose hydration and carbonisation gives rise to a
stony body of required strength at usual temperatures.
 Lime putty: Its obtained by adding hydrated lime to water, stirring to the
consistency of a thick cream and allowing it to stand and mature for a period
of about 16 hours in the case of non-hydraulic lime before using. The putty
so obtained should be protected from drying out.

37. testing of limestone
• Tests which are generally performed on limestone are:
– Physical tests and
– Chemical tests
• Physical tests(properties): These tests are based on the texture, appearance, color &
odour of limestone.
– Limestone except crystalline variety used in the lime and cement trades are
amorphous in texture
– Deposits of chalk and fat limes have white or whitish brown or grey color.
– Magnesia limestone are very hard and heavy
– A good hydraulic limestone has white bluish grey; yellow or brown color.
– It has a compact texture with an irregular dull fracture. The freshly fractured
surface of hydraulic limestone gives a clayey form and an earthy smell

38. testing of limestone
• Chemical tests: There are three chemical tests. They are:
– Heat test
– Hydraulic test-slaking
– Acid test
a) Heat test: This test is usually carried out in open and the temperature should be
maintained at 1500o C approximately.
– The limestone disintegrates by giving CO2
– Due to removal of CO2 from sample it loses its weight and this loss in weight
gives an indication of the presence of CaCO3 in the sample.
– For every loss in weight of 44 parts there must be 56 parts of lime by weight.
b) Hydraulic test- slaking: when quick lime is brought into contact with water it
hydrates and this process is said to be slaking.
– During slaking considerable amount of heat is released due to which quick lime
crumbles to powder.

39. testing of limestone
- If the slaking is vigorous it indicates that the quantity of calcium content is high. In
hydraulic lime the slaking action is very slow.
c) Acid test: The purpose of this test is to assess the classification and calcium-
carbonate content of lime.
- Place a teaspoon of powdered lime in a test tube and pour dil.HCL into it, stir the
contents well with a glass rod and leave the test tube with the contents for 24 hours.
- If the effervescence is in abundance, it indicates high percentage of calcium
carbonate.
- If the content of calcium carbonate is less, there will be less effervescence and more
formation of residue; this indicates that the limestone is impure or hydraulic.
- The formation of thick gel, which will not flow even when the test tube is turned
upside down , shows eminently hydraulic lime.
- If the gel is not quite thick and tends to flow when the test tube is tilted, it indicates
feebly hydraulic lime.
- Absence of gel indicates non-hydraulic or fat lime.

40. storage of lime
- The quick lime soon after delivery, should be slaked or run into putty otherwise it
will deteriorate when stored.
- The deterioration is caused due to the action of the atmospheric moisture in the
unslaked limes, which causes it air slaked.
- The lime thus attacked loses a great deal of its useful properties and is considered
unsuitable for sound construction.
- Lime can be safely stored in the form of lime putty for a maximum of 14 days and
must be consumed within this period.
- If unslaked lime is to be stored for a short period of time, it should be piled up and
covered with a blanket of lime powder to exclude moist air.
- In case of storing of lime for a long period cannot be avoided, it should be stored in
closed store houses properly insulated against the penetration of moisture from the
atmosphere and from the ground below.
- Hydrated lime can be safely stored for considerable time without deterioration if the
bags are kept in a dry place.

41. Precautions in handling of lime
• While handling lime, the following precautions should be taken:
- As the dust from hydrating lime may be irritating, so goggles for eyes,
respirators for nose and throat protection should be used.
- Skin protecting cream may be provided to the workers as quick lime particles
may cause burn on skin.
- To avoid skin cracks oils can be used
- Fresh water facility should be provided in the working premises