2. Syllabus
• Ingredients of Concrete
• Cement- Chemical composition, hydration, heat of hydration,
hydrated structure, various types of cement, testing of cement as per
Indian standard.
• Aggregates-Function in concrete, classification, effect of geometry
• texture, strength, mechanical properties, moisture content, water
absorption, bulking of sand, deleterious substances, sieve analysis
various grading and grading requirements, sampling & testing as
per Indian Standards.
• Water- General Requirements & limiting values of impurities.
• Admixtures- Additives and admixtures, types, need and benefits
• Mineral admixture - Fly ash, silica fume, blast furnace slag, and
other pozzolanic materials.
• Chemical admixtures - Accelerator, retarder, water reducing,
elements, plasticizer and super-plasticizer, their functions and
dosage.
3. Concrete
• Concrete= Cement + Sand+ Aggregate+ Water+
Admixture+ Air
• The mixture of Cement and water is paste. The
function of paste is to bind sand and aggregate
particles by chemical process of hydration. It also
fills the voids between sand and aggregate particles.
• The strength of concrete depends upon the property
of cement, sand, aggregate, etc.
5. Composition of Concrete
• Concrete is composed of,
• Concrete= Cement + Sand + aggregate+ water+ admixtures +
air
• Cement: The funtion of cement is to bind the aggregates. It
also fills the void between sand and aggregate.
• Aggregate:
• The aggregate occupy about 75 % of the volume and hence
their influence on various properties of concrete is
considerable. Aggregates are generally cheaper than cement
and impart greater volume, stability, and durability to
concrete. The aggregate generally provides bulk to the
concrete.
6. Composition of Concrete
• Water: Water is required for carrying out chemical
reactions in cement. If the water content is less the heat of
hydration is not possible, hence the strength of concrete
will be reduced. If water content is in excess water will
cause undesirable capillary cavities and concrete becomes
porous.
• Admixtures: Admixtures is defined as a material other than
the basic ingredient of concrete mixed immediately before
or during mixing to modify some properties of concrete in
the fresh or hardened state.
• The use of admixtures like accelerators, retarders, air-
entraining agents, pozzolanic material, water proofing
admixtures etc.
9. Composition of Concrete
• The properties commonly modified using
admixtures are setting time, workability, air
entrainment, dispersion etc. The admixtures are
generally added in small quantity from 0.005 to
2 % by cement weight. Overuse of admixtures
have detrimental effect on the properties of
concrete.
• Air: The voids in the mass of concrete can be
classified into two groups
• Entrapped air
• Entrained air
10. Composition of Concrete
• Entrapped air: The entrapped air is the void
present in the concrete due to insufficient
compaction
• Entrained air: The entrained air is the
intentionally incorporated minute spherical
bubbles
16. Manufacturing Process of Portland
Cement
Raw material for
cement
Calcareous Materials
e.g. limestone
Chalk
marl
Argillaceous materials
e.g.
Clay
Shale
Calcareous: Composed of or containing calcium or calcium carbonate.
Argillaceous minerals: are minerals containing substantial amounts of clay-like
components . Argillaceous components are aluminosilicates, and more particularly clay
minerals such as kaolinite, montmorillonite-smectite, illite, and chlorite. Claystone and
shales are thus predominantly argillaceous.
17. Manufacturing Process of Portland
Cement
Calcareous Materials
e.g. limestone
Chalk
marl
Argillaceous materials
e.g.
Clay
Shale
22. Processes of Manufacturing
• Following are three distinct operations are involved in the
manufacture of cement.
• (i) Mixing of raw material
• (ii) Burning
• (iii) Grinding
• In the wet process, raw materials are mixed wet in required
proportions and slurry is formed. While in the dry process raw
materials are mixed in required proportions in dry form and dry
raw mix is formed. The remaining two operations, namely,
Burning, and Grinding are the same for both the processes.
• The correct slurry is fed into a rotary kiln from upper end. As the
slurry gradually descends, there is rise in temperature and small
lumps, known as nodules are formed.
23. Processes of Manufacturing
• These nodules, reach to the burning zone, where the temperature is
about 1500 0C to 1700 0C. In the burning zone, calcinated product
is formed and nodules are converted into small hard balls, known
as clinkers.
• The size of clinkers varies from 3 mm to 20 mm.
• Clicker obtained from rotary kiln are finely ground in ball mills
and tube mills. A small quantity about 2 to 3 % of gypsum is added
to prevent flash-setting of the cement.
• The final ground cement is stored in silos. It is then weighted and
packed in bags by automatic machine.
• Each bag of cement contains 50 kg of about 0.035 m3 of cement.
24. Oxide Composition of Cement
• The raw material used for the manufacturing of
Ordinary Portland cement contains mainly lime,
silica, alumina, and iron oxide. These oxides interact
with one another in the kiln at high temperature to
form more complex compounds. The relative
proportions of these oxide compounds are
responsible for various physical properties of
cement. Rate of cooling and fineness of grinding also
affect the property of cement.
26. Oxide Composition of Cement
• IS 269-1989 Specifies the following chemical requirement
for 33 grade Cement:
27. Oxide Composition of Cement
• In Terms of Oxide Composition, a high lime content generally
increases the setting time and results in higher strengths. A
decrease in lime content reduces the strength of concrete.
• A high Silica content prolongs the setting time and gives more
strength.
• The presence of excess unburnt lime is harmful since it results in
delayed hydration causing expansion and deterioration of
concrete.
• Iron Oxide is not a very active constituent of cement, and generally
acts as a catalyst and helps the burning process. Owing to the
prescence of iron oxide the cement derives the characteristics grey
colour.
• Magnesia, if present in large quantities, (more than 5 %) causes
unsoundness,
• Alkali oxide (K2O, Na2O) if present in quantity more than 1%, leads
to alkali aggregate reaction, efflorescence and staining
28. Bogue’s Compounds
• As stated earlier the oxides present in the raw
materials interact with one another in the kiln
at high temperature to form more complex
compounds. The identification of the major
compound is largely based on the work of
R.H.Bogue. And other and so it is often
referred as ‘ Bogue’s Compounds’ or Bogue’s
Composition’.
29. Bogue’s Compounds
Name of Compound Formula Abbreviation
Tricalcium silicate 3 CaOSiO2 C3S
Dicalcium Silicate 2CaOSiO2 C2S
Tricalcium aluminate 3CaOAl2O3 C3A
Tetracalcium
aluminoferrite
4CaO.Al2O3.Fe2O3 C4AF
Bogue’s Compound Percentage by mass in cement
C3S 30-50
C2S 20-45
C3A 08-12
C4AF 06-10
30. Bogue’s Compounds
• In addition to four major compound there exists
minor compounds, such as MgO, TiO2, Mn2O3, K2O,
Na2O.
• Two of the minor compounds of interest are K2O,
Na2O, known as alkalies. They have been found to
react with some aggregates, the product of this
reaction causing disintegration of concrete, and also
have been found to affect strength of cement.
31. Bogue’s Compounds
• With The advancement of science and technology. It has
become possible to recognise and understand the micro
structure of the cement compound before hydration and after
hydration. The X-ray florescence method, the X-ray powder
diffraction method and use of powerful electron microscope
has helped to reveal the crystalline or amorphous structure of
the hydrated or unhydrated cement.
• Thornbohm and Lechatelier, also observed four different kind
of crystal in thin sections of cement clinkers. Thornbohm
called these four kind of crystals as alite, belite, Celite and
Felite. Thornbohm’s description of the minerals in cement
was found to be similar to Bogue’s compound. Hence,
Bough’s Compounds C3S, C2S, C3A, C4AF are sometimes called
in literature as Alite, Belite, Celite, and Felite.
32. Properties of Bogue’s Compounds
• The properties of Bouge’s are as under:
• C3S:
• It is responsible for early strength
• First 7 days strength is due to C3S
• It Produces more heat of Hydration
• A cement with more C3S content is better for cold weather
concreteing.
• C2S:
• The hydration of C2S starts after 7 days. Hence, it gives
strength after 7 days.
• C2S hydrates and hardens slowly and provides much of the
ultimate strength.
• It is responsible for the later strength of concrete.
• It produces less heat of hydration.
33. Properties of Bogue’s Compounds
• C3A:
• The reaction of C3A with water is very fast and may lead to
an immediate stiffening of paste, and this process is termed
as flash set.
• To prevent this flash set, 2 to 3 % gypsum is added at the
time of grinding the cement clinkers.
• The hydrate C3A do not contribute to the strength of
concrete.
• C4AF:
• C4AF hydrates rapidly.
• It does not contribute to the strength of concrete.
• The hydrates of C4AF show a comparatively higher
resistance to sulphate attack than the hydrates of C3A
34. Hydration of Cement
• When water is added to cement, ingredients of cement react
chemically with water and form various complicated
chemical compounds. The chemical reaction that takes place
between cement and water is reffered as hydration of cement.
• Anhydrous cement does not bind fine and course aggregates.
It requires adhesive property only when mixed with water.
• The silicates (C3S, C2S) and aluminates (C3A) aluminates of
cement react with water and form hydro silicates and hydro
aluminates. These products are thick and sticky. It is called
gel. Gel posses adhesive property and binds aggregate and
sand together. It also fill voids between sand and aggregate.
35. Hydration of Cement
• The hydration process is not an instantaneous
one. The reaction is faster in the early stage
and continious indefinately at a decreasing
rate. Complete hydration cannot be obtained
under a period of one year or more unless the
cement is very finely ground.
38. Water Requirement for Hydration
• Amount of water required for chemical reactions
with Portland Cement Compound is given below:
Major Compound % Water by Weight of Cement
C3S 24
C2A 21
C3A 40
C4AF 37
39. Water Requirement for Hydration
• It has been estimated that for C3S and C2S compounds, on an
average 23 % of water by weight of cement is required for
chemical reaction. Thus 23 % of water chemically combines with
cement and, therefore it is called bound water. A Certain Quantity
of water is inadequate to fill up the gel pores, the formation of gel
itself will stop and gel pores will not form. Gel water of about 15 %
by weight of cement is required. Therefore, a total 23 + 15= 38 % of
water by weight of cement is required for complete hydration. If
less than 38 % of water is used than complete hydration is not
possible as the volume available is insufficient to accommodate all
the product of hydration. Hence, Strength of Concrete will be
reduced.
• If more than 38 % of water is used, then the excess of water will
cause undesirable capillary cavities and concrete becomes porous.
40. Heat of Hydration
• The Reaction of Cement with water is exothermic. The
reaction liberates a considerable quantity of heat.
• The Quantity of heat (joules)/ gram of unhydrated
cement, evolved upon complete hydration at a given
temperature is defined as Heat of Hydration.
• The Temperature at which hydration occurs
significantly affects the rate of heat evolution, which is
of more importance than the total heat of hydration. In
ordinary Portland cement about 50 % of total heat is
liberated between 1 to 3 days, about 75 % in 7 days
and about 90 % in six months.
42. Setting and Hardening of Cement
Setting of Cement Hardening of Cement
Setting is the term used to describe
the stiffening of the cement Paste
Hardening refers to the gain of
strength of a set of cement paste
It refers to a change from a fluid to a
rigid state
It refers to formation of solid mass
possessing good compressive
strength.
The setting of Cement Starts after 30
minutes from the instant when water
is added to cement and compacted
within 10 hours
The process of hardening of cement
continues for a period more than 1
year.
To know the setting of cement, initial
setting time test and final setting time
test are conducted
To know the hardening of cement,
compressive strength test is
conducted.
43. False Set
• A phenomenon of abnormal premature stiffening (hardening) of
cement within a few minutes of mixing with water, is termed as false
set. It defers from flash set in that no appreciable heat is evolved, and
remixing the cement paste without addition of water restores
plasticity of the paste until it sets in the normal manner and without a
loss of strength.
• Some of the cause of false set are to be found in the dehydration of
gypsum when interground with too hot a clinker.
• False set can be due to the activation of C3S by aeration at moderately
high humadities. Water is adsorbed on the grains of cement and these
freshly activated surface can be combined very rapidly with more
water during mixing; this rapid hydration would produce false set.
• Another cause of false set may be associated with the alkalis in the
cement. During storage they may carbonate, and alkali carbonate
react with Ca(OH)2 liberated by the hydrolysis of C3S to form CaCO3.
This precipates and induce a rigidity of the paste.
45. Types of Cements
• Hydrophobic Cement
• Air Entraining Cement
• Masonry Cement
• Oil Well Cement
• Expansive Cement
• High Alumina Cement
• Concrete Sleeper Grade Cement
• Waterproof Cement
• Rediset Cement
• Very High Strength Cement
46. Types of Cements
• Ordinary Portland Cement (OPC):
• This is by far the most common cement in use: about 70 % of all
cement used in India is of the ordinary type.
• Prior to 1987, there was only one grade of OPC governed by IS
269: 1976 After 1987 higher grade of cement. The OPC was
classified into 3 grades as 33 grade, 43 grade, 53 grade. In modern
construction activities, higher grade cement have become so
popular that 33 grade of cement is almost out of the market.
• Although OPC are little costlier then low grade cement; they offer
many benefits like 10 – 20 % saving in cement consumption, faster
rate of development of strength and higher strength.
• OPC are generally recommended when there is no exposure to
sulphates in the soil or in ground water.
48. Types of Cements
• Rapid Hardening Cement (RHC) (IS 8041: 1990)
• As the name implies, it develops strength rapidly and therefore can be
called as high early strength cement. The rate of setting is same as that of
ordinary Portland cement.
• The strength of RHC at the age of 3 days is equal to the 7 days strength of
OPC with the same w/c ratio. The increased rate of gain of strength of
RHC is achieved by a higher C3S Content and by finer grinding of
clinker.
• The rapid gain of strength is accomplished by a high rate of heat
development and hence it should not be used in mass concrete
constructions like concrete gravity dam, concrete retaining walls.
• The Use of RHC is recommended in the following situations
• In pre-fabricated concrete construction
• For Road repair works
• Where form-work is required to be removed early for re-use elsewhere.
• In Cold weather concreting
• Wall Sealing
50. Types of Cements
• Extra Rapid Hardening Cement:
• This cement is obtained by intergrading calcium
chloride with RHC. The quantity of calcium chloride
should not exceed 2 %. It is necessary that the concrete
made by using extra rapid hardening cement should
be transported, placed, compacted, and finished within
20 min. The cement must be stored under dry
conditions and should generally be used within one
month of dispatch from the factory.
• This type of cement is suitable for cold weather
concreting. It is suitable where a very high early
strength is required.
52. Types of Cements
• Quick Setting Cement:
• This cement sets very early but does not gain strength
early. The early setting property is brought out by
reducing the gypsum content at the time clinker
grinding. Sometimes aluminum sulphate is added to
accelerate the setting process. It contains higher
percentage of C3A. It is required to be mixed, placed
and compacted very early.
• The use of quick setting cement is recommended
under the following conditions:
• Under Water Construction
• Grouting operations.
54. Types of Cements
• Low Heat Cement:
• The reaction of cement with water is exothermic and produces a
considerable quantity of heat. The rise in temperature in the
interior of a large concrete mass due to the heat of hydration. Can
lead to serious cracks.
• A low heat evolution is achieved by reducing the content of C2S
and C3A which are the compound evolving the maximum heat of
hydration and increasing C2S. For low heat cement the rate of gain
of strength is slow but the ultimate strength is the same as that of
ordinary Portland cement.
• The use of low-heat cement is recommended in the following
situations:
• Mass Concrete Construction
• Where it is necessary to produce resistance to sulphate attack.
• Hot weather concreting.
56. Types of Cements
• Sulphate Resisting Cement (IS 12330:1988)
• Ordinary Portland Cement is susceptible to the attack
of sulphates, in particular to the action of magnesium
sulphate. Sulphates react both with the free calcium
hydroxide in set cement to form calcium sulphate and
with hydrate of calcium aluminate to form calcium
sulphoaluminate, the volume of which is about 227%
of the volume of the original aluminates. Their
expansion within the framework of hardened cement
paste results in cracks and subsequent disruption. This
phenomenon is known as sulphate attack.
58. Types of Cements
• Sulphate resisting cement is very similar to OPC except the
quantity of C3A which is the least stable compound is strictly
limited to about 5 %. The low C3Acontent and comparatively
low C4A content in sulphate resisting cement give it a high
strength but the early strength is low. The heat of hydration is
not much higher than that of low heat cement.
• The use of Sulphate resisting cement is recommended under the
following conditions
• Concrete to be used in marine conditions
• Concrete to be used in the construction of sewer treatment
plant.
• Concrete used for fabrication and basement where soil is
infested with sulphates.
• Concrete to be used in the construction of chemical industry.
59. Types of Cements
• Super Sulphated Cement:
• This cement is manufactured from well-granulated slag and hard
burnt gypsum together with 1 to 2 % of Portland cement the
mixture is ground finer than that of Portland cement. Its setting
action is different from the other cements and admixtures should
not be used with it. If used with R.C.C work a minimum cover of 35
mm is necessary. It should not be mixed with either ordinary
Portland cement or high alumina cement since the action will be
different. It is highly resistant to chemical attack. It cured in air, the
surface gets softened by atmospheric CO 2. Hence, minimum 3
days of water curing is preferable.
• The use of super sulphated cement is recommended under the
following conditions:
• In foundations, where chemically aggressive condition exists.
• In marine works.
• RCC pipes likely to be used in sulphate bearing soils.
• Mass Concreting.
60. Types of Cements
• Portland Pozzolana Cement (IS 1489:1991):
• Portland Pozzolana Cement is manufactured by intergrading
of OPC clinker with 15 to 35 of pozzolanic material. The
pozzolanic materials used for manufacturing of Portland
Pozzolana Cement (PPC) are fly ash and claimed clay. The
pozzolanic material are essentially a siliceous or aluminous
material which itself possessing no cementations properties,
which will. In finely divide form and in the presence of
water, react with calcium hydroxide, liberated in the
hydration process, to form compounds possessing
cementations properties.
62. Portland Pozzolana Cement
(IS 1489:1991)
• The hydration of C3S and C2S produce considerable quantity
of Calcium hydroxide [Ca(OH)2], which is by are large and
useless material from the point of view of strength or
durability. if such useless mass could be converted into a
useful cementations product, it considerably improves quality
of cement.
• Ca(OH)2 + fly ash or claimed clay + water C-S-H (Gel)
• It is important to note that the addition of pozzolana does not
contribute to the strength at early ages, but gives later
strength similar to OPC. However, in India there is an
apprehension in the minds of the users to use the PPC for
structural works. If PPC is manufactured by using right type
of reactive pozzolana, it will not in any way inferior to OPC
63. Types of Cements
• Advantages of PPC:
• It is economical, as costly clinker is replaced by cheaper pozzolanic
material.
• Pozzolanic material converts soluble Ca(OH)2 into insoluble cementations
products. Hence, durability and permeability of concrete are improved.
• It generates low heat of hydration.
• As the flyash is finer and of lower density, the bulk volume of 50 kg bag is
slightly more than OPC therefore OPC gives more volume of mortar than
OPC.
• Uses of PPC:
• For Hydraulic Structures
• For marine structures
• For mass concrete structures like dam, bridge piers, and raft foundation.
• For sewer and sewage disposal works etc.
64. Types of Cements
• Portland Slag Cement: (IS 455:1989)
• This type of cement is made by intergrading Portland Cement
Clinker, Gypsum and granulated blast furnace slag. The
quantity of blast furnace slag mixed with Portland clinker
will range from 25 to 65 %. Blast furnace slag is a waste
produce consisting of a mixture of lime, silica, alumina
obtained in the manufacturing of pig iron. The slag can also
be used together with limestone as a raw material for the
conventional manufacture of Portland Cement resulting in
clinker which when grouped gives Portland Slag Cement.
• The Portland Slag Cement (PSC) has low heat of hydration
and better resistance to chlorides, sulphates or alkalis and
acidic water. Therefore it can be used in marine works.
66. Types of Cements
• Advantages of PSC:
• Low Heat of Hydration
• Better resistance to Chloride, Sulphate, Alkalis.
• Low permeability
• Good resistance to acidic waters.
• Refinement of pore structure.
• Uses of PCS:
• For mass concreting works
• For marine work.
67. Types of Cements
• Colored Cement (White Cement) IS 8042: 1989
• The Grayish color of Portland is due to the presence of Iron Oxide. The
Process of manufacturing of white cement is the same as that of Portland
cement but the amount of iron oxide is limited to less than 1 %. The kind
of limestone required for manufacturing white cement is only available
near Jodhpur in rajastan. The raw material used are high purity lime
stone (96 % CaCO3 and less than 0.07 % iron oxide)
• For manufacturing of various colored cements either Grey Portland
Cement or White Cement is used as a Base. With the use of Grey cement
only red or brown cement can be produced. Colored cement consists of
Portland Cement with 5 -10 % of pigment. For proper mixing of pigment,
it is usual to grind pigment and cement clinkers together.
• The following are the use of White/ Colored Cement:
• To fill joints of Glazed tiles in W.C. Bathrooms, kitchens etc.
• To fill joints in flooring.
69. Types of Cements
• Hydrophobic Cement (IS 8043:1991):
• Hydrophobic Cement is obtained by adding water repellant
file forming substances such as oleic acid, stearic acid and
boric acid to OPC clinkers at the time of grinding. The
water-repellant film formed around each grain of cement,
prevents the entry of atmosphere moisture and reduces the
rate of deterioration of the cement during long storage,
transport or under unfavorable conditions. The film is
broken out when the cement and aggregate are mixed
together at the mixer exposing the cement particles for
normal hydration.
• The film forming water-repellant substance will entrain
certain amount of air in the body of concrete which will
improve the workability of concrete.
70. Types of Cements
• Air entraining cement is made by mixing a small amount of an air-
entraining agent with OPC clinkers at the time of grinding. The
main air-entraining agent used are:
• Alkali salts of wood resins.
• Calcium salts of glues and other proteins.
• Animal and vegetable fats, oils etc.
• Bleaching Powder.
• Hydrogen Peroxide, Aluminum Powder..
• The air entraining agents may be used in powder or in liquid forms
to the extent of 0.025 – 1.0 percent. Air-entraining agents will
produce at the time of mixing, tiny discrete non-coalesceing air
bubbles in the mass of concrete which will modify the properties of
plastic concrete with respect to workability, segregation and
bleeding. It will modify the properties of hardened concrete with
respect to resistance in frost action and reduction in density.
• This Cement is used to produce light weight Concrete.
72. Types of Cements
• Masonry Cement: (IS 3466: 1988):
• Ordinary Cement, when used in masonry, gives a
harsh mortar and because of the sucking of water by
masonry, often results in poor bond. To avoid this,
masonry cement is now used which is made of
Portland Cement Clinkers, limestone, gypsum and
air-entraining agent.
• The masonry cement should be workable, adhere to
the surface help the grinding and the plasticity,
workability and the water retentive property. It
reduces shrinkage too.
73. Types of Cements
• Oil Well Cement( IS 8229: 1986):
• In drilling of oil wells, cement is used to seal off the
annular space between steel casing and rock strata
and also to seal off any other fissures or cavities in the
rock strata.
• The desired properties of oil well cement can be
obtained in two ways, by adjusting the compound
composition of cement (to have very little C3A) and by
adding retarders to ordinary Portland cement.
Retarders prevent quick setting and retains the slurry
in mobile condition to facilitate penetration to all
fissures and cavities.
75. Types of Cements
• Expansive Cement:
• Concrete shrinks while getting due to loss of free water.
This is known as drying shrinkage. The important property
of expansive cement is that it suffers no overall change in
volume on drying. Such type of cement is made by using
an expanding agent and stabilizers very carefully,
Generally about 8-20 parts of the sulphoaluminate
clinkers are mixed with 100 parts of the Portland cement
and 15 parts of the stabilizer
• Uses of expansive Cement are:
• Grouting anchor bolts.
• Grouting machine foundation.
• Grouting prestress concrete ducts.
76. Types of Cements
• High Alumina Cement (IS 6452:1989):
• High alumina cement is obtained by fusing or
sintering of limestone and bauxite. It is also
known as aluminious cement or aluminate
cement. It has good resistance to attack of
gypsum bearing water and chemical attack. This
cement is very different in its composition and
also in some properties from Portland cements so
that its structural use is severally limited but the
concreting techniques are similar.
78. Types of Cements
• Concrete Sleeper Grade Cement (IRS-T 40: 1985):
• This Cement is a special high strength cement
manufactured as per specification laid down by the
ministry of Indian Railway under IRS –T 40:1985.
The use of this cement is restricted to the production
of railway sleepers. It is very fine ground cement
with high C3S content. No accelerating agent are
added. This cement can be used for prestress
concrete.
79. Types of Cements
• Waterproof Cement:
• This cement is manufactured by adding
waterproofing compounds like calcium
separate, aluminum separate and gypsum
treated with tannic acid to ordinary Portland
Cement at the time of clinker grinding.
• It is used for waterproofing of terrace, water
tanks, W.C. bathrooms etc.
81. Types of Cements
• Rediset Cement:
• Associated Cement Company (ACC) of India have developed a
cement, which could yield high strengths in a matter of hours,
without showing any retrogression of strength. It is known as
rediset Cement.
• Importance properties of Rediset Cement:
• Its Initial Setting time is about 8 to 10 minutes
• It liberates more heat of hydration
• The sulphate resistance is very poor.
• Application of Rediset Cement:
• Repairs of Concrete roads and pavements
• Quick removal of forms in precast concrete product industry
• Slip formed Concrete construction
• Paslletisation of iron ore dust.
83. Types of Cements
• Very High Strength Cement:
• Very High Strength cement is required for special application like
repairs of air fields runways. Launching pads, expressway
pavement repair etc. This cement can be manufactured by different
ways under different names as follows:
• High early Strength Cement: This can be achieved by using lithium
salts as accelerators. It gives very high strength with a marginal
reduction in later strength.
• Magnesium Phosphate Cement (MPC): This cement can be used for
rapid repair of damaged concrete roads and airfield pavements.
• Pyrament cement: Some Cement Companies in USA have developed
very high strength cement under a trade name pyrament cement. It
is a blended Hydraulic Product. No Chlorides are added.
• The Associated Cement company in collaboration with R & D
engineers, Dighi, Pune have developed similar very high strength
for repair of air field pavements
84. Field Testing of Cement
The following field tests are necessary to perform, to ascertain the
quality of cement at site.
• Open the bag and take a good look at the cement. There should be no
visible lumps.
• The colour of the cement should be greenish grey
• When hand is inserted in cement bag it should feel cool.
• Take a pinch of cement and feel between fingers. It should give a
smooth feeling and not a gritty feeling.
• Take a handful of cement and throw it on a bucketful of water, the
particles should float on water for some time before they sink.
• Take about 100 gms of cement, add some water and prepare a stiff
paste. From stiff paste, pat a cake with sharp edges. Put it on a glass
plate and slowly take it under water in a bucket. The shape of the cake
should not be disturbed, while taking it down to the bottom of the
bucket. After 24 hours the cake should retain its original shape and at
the same time it should also set and gain some strength.
86. Storage of Cement
The following points should be observed while storing Cement.
• Bagged Cement should be stored in waterproof shed with non porous walls
and floors.
• The plinth level should be well above ground level.
• Number of opening like doors, windows and ventilator should be minimum
and kept tightly shut.
• Drainage should be provided if necessary to prevent accumulation of water in
the vicinity of the shed.
• Cement should be kept 30 cm away from walls.
• To reduce air circulations no gap is desirable between rows of cement bags.
• In moist area cement bags should be placed on wooden planks kept above
floor.
• Old bags should be used first for beams and slabs casting use fresh bags.
• Once the cement has been properly stored it should not be disturbed until it is
to be used. The practice of moving and restacking the bags, exposes fresh
cement to air.
88. Physical Properties of Portland
Cement
• The important physical properties of cement are:
• Fineness
• Standard Consistency
• Initial and final setting time
• Compressive strength
• Soundness
89. Physical Properties of Portland Cement
• Fineness:
• The fineness of a cement is a measure of the size of the particle of
cement, and is expressed in terms of specific surface of the cement.
Since the hydration starts at the surface of the cement particles, it is
the total surface area of cement that represents the material
available for hydration. For a given weight of cement, the surface
area of cement is more for a finer cement than for a coarser
cement. The finer the cement, the higher is the rate of hydration as
more surface area is available for chemical reaction. This results in
the early development of strength. Moreover, fine cement bleeds
less than coarse one.
• Fineness of cement can be determined by two tests:
• By Sieve Test
• By Air Permeability Test
90. Fineness of cement can be determined by two tests
Sieve Test
Air Permeability Test
Air Permeability Test
Sieve Test
91. Physical Properties of Portland Cement
• Standard Consistency Test:
• The Standard consistency of cement paste is defined as
that consistency which will permit a Vicat Plunger
having 10 mm diameter and 50 mm length to
penetrate to a depth of 33 to 35 mm from the top of
the mould of 40 mm height.
• The standard consistency of the cement paste is some
time called as normal consistency test. The standard
consistency parameter is used to determine, initial
setting time, final setting time, soundness of cement
and compressive strength of cement.
93. Physical Properties of Portland Cement
• Initial and Final Setting Time
• When the cement is mixed with water to make a soft paste, it
becomes gradually less plastic and finally becomes a hard mass. In
this process of setting, a stage is reached when the cement paste is
sufficiently rigid to withstand a definite amount of pressure. The
time to reach this stage is termed as setting time. The setting time is
divided into 2 parts, namely initial setting time and final setting
time.
• The period elapsing between the time when water is added and the
time at which the cement paste start loosing plasticity is termed as
Initial Setting Time.
• The period elapsing between the time when water is added to the
cement and the time at which the cement paste completely loose its
plasticity is termed as final setting time.
• For ordinary Portland cement Initial setting time is 30 min and
final setting time is 600 min (10 Hrs).
95. Physical Properties of Portland Cement
• Compressive Strength Test: Compressive strength is one
of the important properties of cement. Cement mortar (1:3)
cubes having an area 50 cm2 are used for the determination
of compressive strength of cement.
• The test is carried out as per IS 4031 (Part VI): 1988
97. Physical Properties of Portland Cement
• Soundness Test:
• Undesirable expansion of some of the constituents of
cement after setting is known as unsoundness.
• The unsoundness in cement is due the presence of excess
of free lime, magnesia, and calcium sulphate
• The unsoundness of cement may be reduced by:
• Limiting the magnesia content to less than 6 %
• Through mixing
• Fine grinding
• Allowing the cement to aerate for several days.
• Two main tests for determining soundness are Le Chatelier
Test and the Auto Clave Test.
