2. INTRODUCTION
Definition: “Cement is a crystalline compound of
calcium silicates and other calcium compounds
having hydraulic properties” (Macfadyen, 2006).
3. History
Lime and clay have been used as
cementing material on constructions
through many centuries.
Cement was first invented by the
Egyptians. Cement was later
reinvented by the Greeks and the
Babylonians who made their mortar out
of lime. Later, the Romans produced
cement from pozzolana.
Romans are commonly given the
credit for the development of
hydraulic cement, the most
significant incorporation of the
Roman’s was the use of pozzolan-
lime cement by mixing volcanic ash
from the Mt. Vesuvius with lime.
Best know surviving example is the
Pantheon in Rome
In 1824 yoosuph Aspdin from
England invented the Portland
cement
4. Cements are considered hydraulic because of their ability to set and
harden under or with excess water through the hydration of the cement’s
chemical compounds or minerals
There are two types:
1. Those that activate with the addition of water
2. And pozzolanic that develop hydraulic properties when
the interact with hydrated lime Ca(OH)2
Pozzolanic: any siliceous material that develops hydraulic cementitious properties
when interacted with hydrated lime.
HYDRAULIC CEMENTS:
Hydraulic lime: Only used in specialized mortars. Made from calcination
of clay-rich limestones.
Natural cements: Misleadingly called Roman. It is made from
argillaceous limestones or interbedded limestone and clay or shale, with few
raw materials. Because they were found to be inferior to portland, most plants
switched.
Types of Cement
5. Portland cement: Artificial cement. Made by the mixing clinker with
gypsum in a 95:5 ratio.
Portland-limestone cements: Large amounts (6% to 35%) of ground
limestone have been added as a filler to a portland cement base.
Blended cements: Mix of portland cement with one or more SCM
(supplementary cemetitious materials) like pozzolanic additives.
Pozzolan-lime cements: Original Roman cements. Only a small quantity
is manufactured in the U.S. Mix of pozzolans with lime.
Masonry cements: Portland cement where other materials have been
added primarily to impart plasticity.
Aluminous cements: Limestones and bauxite are the main raw materials.
Used for refractory applications (such as cementing furnace bricks) and certain
applications where rapid hardening is required. It is more expensive than
portland. There is only one producing facility in the U.S.
6. TYPES OF PORTLAND CEMENT
Cements of different chemical composition & physical characteristics may
exhibit different properties when hydrated. It should thus be possible to select
mixtures of raw materials for the production of cements with various
properties.
In fact several cement types are available and most of them have been
developed to ensure durability and strength properties to concrete. It should
also be mentioned that obtaining some special properties of cement may lead
to undesirable properties in another respect. For this reason a balance of
requirements may be necessary and economic aspects should be considered.
1) Standard Types: these cements comply with the definition of P.C., and are
produced by adjusting the proportions of four major compounds.
2) Special Types: these do not necessarily couply with the definiton of P.C. & are
produced by using additional raw materials.
7. Standard Cements (ASTM)
Type I: Ordinary Portland Cement
Suitable to be used in general concrete construction when
special properties are not required.
Type II: Modified Portland Cement
Suitable to be used in general concrete construction. Main
difference between Type I&II is the moderate sulfate
resistance of Type II cement.
Type III: High Early Strength P.C.
Strength development is rapid.
Type IV: Low Heat P.C.
Generates less heat during hydration & therefore gain of
strengthis slower.
8. GEOLOGY (RAW MATERIALS)
The fundamental chemical compounds to produce cement clinker are:
Lime (CaO)
Silica (SiO2)
Alumina (Al2O3)
Iron Oxide (Fe2O3)
Fly ash: by-product of burning finely grounded coal either for industrial application or in
the production of electricity
Raw materials used in the production of clinker cement
9. 5 CHEMICAL REQUIREMENTS
When tested in accordance with the methods given in IS 4032, ordinary Portland
cement, 53 grade shall comply with the chemical requirements given in Table .
Chemical Requirements for Ordinary Portland Cement, 53 Grade
11. NOTES
1 In the event of cements failing to comply with any one or both the requirements of
soundness specified in the above table, further tests in respect of each failure shall be
made as described in IS 4031 (Part 3), from another portion of the same sample after
aeration. The aeration shall be done by spreading out the sample to a depth of 75 mm
at a relative humidity of 50 to 80 percent for a total period of 7 days. The expansion of
cements so aerated shall be not more than 5 mm and 0.6 percent when tested by Le
Chatelier method and autoclave test respectively. For 53-S grade cement, the
requirement of soundness of unaerated cement shall be maximum expansion of 5 mm
when tested by the Le-Chatelier method.
2 If cement exhibits false set, the ratio of final penetration measured after 5 minutes of
completion of mixing period to the initial penetration measured exactly after 20 seconds
of completion of mixing period, expressed as percent, shall be not less than 50. In the
event of cement exhibiting false set, the initial and final setting time of cement when
tested by the method described in IS 4031(Part 5) after breaking the false set, shall
conform to the value given in the above table.
3 By agreement between the purchaser and the manufacturer, transverse strength test
of plastic mortar in accordance with the method described in IS 4031(Part 8) may be
specified. The permissible values of the transverse strength shall be mutually agreed to
between the purchaser and the supplier at the time of placing the order.
4 Notwithstanding the compressive and transverse strength requirements specified as
per the above table, the cement shall show a progressive increase in strength from the
strength at 72 hours.
12. Limestone deposits are mainly extracted by bench mining in which holes are
charged with ammonium nitrate and fuel oil explosive and blasted
The rock is excavated with front end loaders (10 m3
capacity) and loaded into
70 to 90 tons haul trucks and then transported to the primary crusher
Marl and chalk normally do not require blasting.
A trend is to use in pit moveable primary crushers and belt conveyors to
transport the rock to a fixed secondary crusher, thereby reducing the number
of trucks and haulage distance
Underground mining of limestones is not typical, in the U.S one plant obtains
its limestone from underground operation, using room and pillar mining
method.
Clay and shale normally extracted using front end loaders and loaded into
haul trucks.
When they occur as overburden the clays and shales not used are stored and
often reused for reclamation in the mined out areas of the quarry
MINING METHODS
14. THE CEMENT MANUFACTURING PROCESS
1. BLASTING : The raw materials that are used to manufacture cement (mainly limestone and clay) are
blasted from the quarry.
Quarry face
1. BLASTING 2. TRANSPORT
3. CRUSHING AND TRANSPORTATION : The raw materials, after crushing, are
transported to the plant by conveyor. The plant stores the materials before they are
homogenized.
Quarry
3. CRUSHING & TRANSPORTATION
2. TRANSPORT : The raw materials are loaded into a dumper.
crushing
conveyor
dumper
storage at
the plant
loader
15. THE CEMENT MANUFACTURING PROCESS
1. RAW GRINDING : The raw materials are very finely ground in order to produce the raw mix.
1. RAW GRINDING
Raw grinding and burning
2. BURNING
2. 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.
conveyor Raw mix
kiln
cooling
preheating
clinker
storage at
the plant
Raw mill
16. THE CEMENT MANUFACTURING PROCESS
1.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.
1. GRINDING
Grinding, storage, packing, dispatch
2. STORAGE, PACKING, DISPATCH
2. STORAGE, PACKING, DISPATCH :The cement is stored in silos before being dispatched either in
bulk or in bags to its final destination.
clinker
storage
Gypsum and the secondary additives are
added to the clinker.
silos
dispatch
bags
Finish grinding
17. TESTS
• The sample or samples of cement for test shall be taken as described in 10 and shall
be tested in the manner described in the relevant clauses.
• Independent Testing
If the purchaser or his representative requires independent tests, the samples shall
be taken before or immediately after delivery at the option of the purchaser or his
representative, and the tests shall be carried out in accordance with this standard on
the written instructions of the purchaser or his representative.
The manufacturer shall supply, free of charge, the cement required for testing.
Unless otherwise specified in the enquiry and order, the cost of the tests shall be
borne as follows:
a) By the manufacturer, if the results show that the cement does not comply with the
requirements of this standard, and
b) By the purchaser, if the results show that the cement complies with the requirement
of this standard.
After a representative sample has been drawn, tests on the sample shall be carried
out as expeditiously as possible.
REJECTION
12.1 Cement may be rejected if it does not comply with any of the requirements of this specification.
12.2 Cement remaining in bulk storage at the factory, prior to shipment, for more than six months, or
cement in bags, in local storage such as, in the hands of a vendor for more than 3 months after
completion of tests, may be retested before use and may be rejected if it fails to conform to any of the
requirements of this specification.
18. Uses
Main use is in the fabrication of concrete and mortars
Modern uses
Building (floors, beams, columns, roofing, piles, bricks, mortar, panels, plaster)
Transport (roads, pathways, crossings, bridges, viaducts, tunnels, parking, etc.)
Water (pipes, drains, canals, dams, tanks, pools, etc.)
Civil (piers, docks, retaining walls, silos, warehousing, poles, pylons, fencing)
Agriculture (buildings, processing, housing, irrigation)
USES
19. Cement used for railway sleepers shall additionally
satisfy the following chemical/mineralogical requirements and shall
be designated as 53-S grade:
• Magnesia, percent by mass, Max 5.0
• Tricalcium aluminate content percent by mass, %, Max 10.0
• Tricalcium silicate, percent by mass, Min 45.0
Note – The tricalcium silicate content (C3S) is calculated by the formula:
C3S = 4.07 CaO - 7.60 Si02 - 6.72 Al203 - 1.43 Fe203 - 2.85 SO3
20. FINENESS OF CEMENT
As hydration takes place at the surface of the cement particles, it is the
surface area of cement particles which provide the material available for
hydration. The rate of hydration is controlled by fineness of cement. For
a rapid rate of hydration a higher fineness is necessary.
However,
• Higher fineness requires higher grinding (cost).
• Finer cements deteriorate faster upon exposure to atmosphere.
• Finer cements are very sensitive to alkali-aggregate reaction.
• Finer cements require more gypsum for proper hydration.
• Finer cements require more water.
Fineness of cement is determined by air permeability methods. For
example, in the Blaine air permeability method a known volume of air is
passed through cement. The time is recorded and the specific surface is
calculated by a formula.
Fineness is expressed in terms of specific surface of the cement (cm2
/gr).
For OPC specific surface is 2600-3000 cm2
/gr.
21. SETTING
Setting refers to a change from liquid state to solid state. Although, during
setting cement paste acquires some strength, setting is different from
hardening.
The water content has a marked effect on the time of setting. In
acceptance tests for cement, the water content is regulated by bringing
the paste to a standard condition of wetness. This is called “normal
consistency”.
Normal consistency of O.P.C. Ranges from 20-30% by weight of cement.
Vicat apparatus is used to determine normal consistency. Normal
consistency is that condition for which the penetration of a standard
weighed plunger into the paste is 10mm in 30sec. By trial & error
determine the w/c ratio.
In practice, the terms initial set&final set are used to describe arbitrary
chosen time of setting. Initial set indicates the beginning of a noticeable
stiffening & final set may be regarded as the start of hardening (or
complete loss of plasticity).
22. Factors Affecting Setting Time
• Temperature & Humidity
• Amount of Water
• Chemical Composition of Cement
• Fineness of Cement (finer cement, faster setting)
Abnormal Settings
False-set
Flash-set
Flash-Set: is the immediate stiffening of cement paste in a few minutes after
mixing with water. It is accompanied by large amount of heat generation
upon reaction of C3A with water.
Gypsum is placed in cement to prevent flash-set. The rigidity can not be
overcome & plasticity may not be regained without addition of water.
Amount of gypsum must be such that it will be used upto almost hardening.
Because expansion caused by ettringite can be distributed to the paste before
hardening. More gypsum will cause undesirable expansion after hardening.
23. False-Set: is a rapid development of rigidity of cement paste without
generation of much heat. This rigidity can be overcome & plasticity can be
regained by further mixing without addition of water. In this way cement
paste restores its plasticity & sets in a normal manner without any loss of
strength.
Probable Causes of False-Set:
1) When gypsum is ground by too hot of a clinker, gypsum may be
dehydrated into hemihydrate (CaSO4.1/2H2O) or anhydrate (CaSO4). These
materials when react with water gypsum is formed, which results in
stiffening of the paste.
2) Alkali oxides in cement may carbonate during storage. Upon mixing such
a cement with water, these alkali carbonates will react with
Ca(OH2) (CH- Calcium Hydroxide) liberated by hydrolysis of C3S
resulting in CaCO3. CaCO3 precipates in the mix & results in false-set.
24. SOUNDNESS OF CEMENT
Soundness is defined as the volume stability of cement paste.
The cement paste should not undergo large changes in volume after it
has set. Free CaO&MgO may result in unsound cement. Upon hydration
C&M will form CH&MH with volume increase thus cracking.
Since unsoundness is not apparent until several months or years, it is
necessary to provide an accelerated method for its determination.
1) Lechatelier Method: Only free CaO can be determined.
2) Autoclave Method: Both free CaO&MgO can be determined.
25. STRENGTH OF CEMENT
Strength tests are not carried out on neat cement pastes, because it
is very difficult to form these pastes due to cohesive property of
cement.
Strength tests are carried out on cement mortar prepared by
standard gradation (1 part cement+3 parts sand+1/2 part water)
PP
1
” 1
”
• σt=P/1in2
• Difficult test procedure
26. 2) Flexural Strength (tensile strength in bending):
• σf=(M*C)/I
• M:maximum moment
• I:moment of inertia
• C:distance to bottom fiber
from C.G.
P
L
4c
m
4c
m
C
27. 3) Compression Test:
i) Cubic Sample ii)Flexural Sample after it
is broken
P
P
σc=P/A
4cm
4cm
4cm
σc=P/A
A=4x4
28. Packing
9.1.1 The cement shall be packed in any of the following bags:
a) jute sacking bag conforming to IS 2580,
b) double hessian bituminized (CRI type),
c) multi-wall paper sacks conforming to IS 11761,
d) polyethylene lined (CRI type) jute,
e) light weight jute conforming to IS 12154,
f) HDPE/ PP woven sacks conforming to IS 11652,
g) jute synthetic union bags conforming to IS 12174, or
h) any other approved composite bag
