1. Prof . Anand B. Kudoli
Assistant Prof.
Civil Department , PCCOER Ravet.
Basic information @ Cement.
2. Points to be cover
• Raw materials for production of cement.
• Composition of cement and their properties.
• Field Tests of Cement for Civil Engineers.
3.
4. Cement
• Cement is typically made of calcareous , Argillaceous and other
substances.
• Ingredients of Cement & their Proportions.
5. • Lime - Cao
Functions and Limitations of Cement Ingredients
6. • Lime or calcium oxide is the most important
ingredient of cement. It gives binding property. The
cement contains 60 to 67% of lime in it. It is
obtained from limestone, chalk, shale etc.
• Adequate quantity of lime in cement is helpful to
form the silicates and aluminates of calcium.
• If lime is added in excess quantity the cement
becomes unsound.
• If lime content is lower than the minimum
requirement then ultimately reduces the strength
of cement will reduce and also setting time of
cement will decrease.
8. Silica (SiO2
)
• Silica or silicon dioxide is the second largest
quantity of cement ingredients which is about 17
to 25%.
• Silica can be obtained from sand, argillaceous
rock etc. Sufficient quantity of silica helps for the
formation of di-calcium and tri-calcium silicates
which imparts strength to the cement.
• Excess silica in cement will increase the strength
of cement but at the same time setting time of
cement also increased.
9. Alumina forms a complex compound with silica and calcium . Mainly it controls the
setting time of cement. If large quantity of alumina present then it quickens the
setting time but weakens the cement.
10. 4.Iron oxide (Fe2
O3
)
• Iron oxide quantity in cement is ranges from 0.5 to 6%.It can
be obtained from fly ash, iron ore, scrap iron etc.
• The main function of iron oxide is to impart color to the
cement.
11. Magnesium oxide also imparts strength to the cement when mixed in small quantity.
The magnesium content shall not exceed 6 % by mass.
Excess magnesia makes the cement unsound.
Magnesia-(Mgo)
12.
13. Following instruments used to find chemical
composition of cement.
• Spectrophotometer.
• X-ray spectrometer.
• Electron microscope.
14. Field Tests of Cement for Civil Engineers
• Date of Manufacturing: As the strength of cement
reduces with age, the date of manufacturing of
cement bags should be checked.
• Cement Color: The color of cement should be
uniform. It should be typical cement color i.e. gray
color with a light greenish shade.
• Whether Hard Lumps are Formed: Cement should
be free from hard lumps. Such lumps are formed by
the absorption of moisture from the atmosphere.
15. • Temperature Inside Cement Bag: If the hand is
plunged into a bag of cement, it should be feel
cool inside the cement bag. If hydration reaction
takes place inside the bag, it will become warm.
• Smoothness Test: When cement is touched or
rubbed in between fingers, it should give a
smooth feeling. If it felt rough, it indicates
adulteration with sand.
• Water Sinking Test: If a small quantity of
cement is thrown into the water, it should float
some time before finally sinking.
16.
17.
18. process
• Excavation by pokland
• Transportation by dumpers.
• Stored in stack yard.
• By Conveyor belt sent to primary crusher.
• Secondary crusher to make fine ground limestone.
• Proper proportioning with other ingredients .
• Sent to grinding mill for proper mixing.
• Sent to pre heater for removing any moisture if present and
calcining.
• Sent to rotary kiln for heating at high temperature.
• Formation of clinkers . Then cooling of clinkers.
• Gypsum is added into clinkers and grinding is done to make
powder.
• Finally packing unit.
31. • High percentage of c3s and low percentage c2s
results in high early strength but also produces high
heat of generation as the concrete sets fast.
• The reverse combination of low c3s and high c2s
develops strengths very slow and generates less
heat and greater resistance to chemical attack.
• C4AF does not affect significantly. However it reacts
with gypsum accelerates the hydration of cement.
• Contribution in heat evolution - decreasing order -
c3A, c3s, c2s, c4AF.
• Contribution in strength development decreasing
order c3s c2s c3A c4AF
32. Heat of hydration
• The chemical reaction occurs when cement is mixed with
water called as heat of hydration.
• Unhydrous cement will not bind fine sand to coarse
sand.
33. • The reaction of cement with water is exothermic. The
reaction liberates a considerable quantity of heat. This
liberation of heat is called heat of hydration.
Different compounds hydrate at different rates and liberate different quantities of
heat. Fig. 1.3 shows the rate of hydration of pure compounds. Since retarders are
added to control the flash setting properties of C3A, actually the early heat of
hydration is mainly contributed from the hydration of C3S. Fineness of cement also
influences the rate of development of heat but not the total heat. The total quantity
of heat generated in the complete hydration will
37. Sulfate attack of concrete
• Sulfate attack of concrete is a complex process, which
includes physical salt attack due to salt crystallization
and chemical sulfate attack by sulfates from soil,
groundwater, or seawater. Sulfate attack can lead to
expansion, cracking, strength loss, and disintegration
of the concrete
38.
39. Laboratory tests on cement
• Fineness test of cement.
• 1- By dry seiving.
• 2- Air blaine Air permeability apparatus.
• Consistency limit test.
• Initial and final setting time test.
• Compressive strength test.
• Soundness test of cement.
41. Functions of Aggregates .
• They act as a structural filer material in concrete.
• They provide strength to the concrete.
• They help in increasing durability of concrete.
• They decrease the amount of shrinkage that
could occur in concrete.
• They reduce the amount of cement paste
required.
42. Alkali Aggregate Reaction
• Some of the aggregate obtained from opaline,
chalcedonic cherts, siliceous limestone,
rhyolites, andesite contain reactive silica.
• This silica reacts with alkalis present in the
cement like Na2o and K2o , which will form a
alkali- silicate gel . This gel is responsible for
unlimited swelling in concrete structures.
• Due to unlimited swelling it increases internal
pressure and subsequent disruption of the
cement paste.
44. Factors promoting the Alkali- Aggregate
Reactions
• Reactive type aggregate .
• High alkali content cement. - keep less than
0.6%
• Availability of moisture
• temperature changes .
45. Control of Alkali- Aggregate Reaction
• Selection of non reactive aggregate.
• By using low alkali cement.
• By using corrective admixture such as pozzolanas.
• By controlling moisture condition and
temperature.
• By controlling void space in concrete.
46. Grading of aggregate
• The particle size distribution of an aggregate is
done by sieve analysis i.e. called as grading of
aggregates.
• The particle size distribution of a mass of
aggregate should be such that the smaller
particles fill the gap between the larger particles.
• The proper grading of an aggregate produced
dense concrete which reduces the amount of sand
and cement paste.
• Consistency of grading of aggregate helps to
ensure uniform quality of concrete.
47. Sieve Analysis
• Sieve analysis is the operation of dividing a
sample of aggregate fractions , each fraction
consisting of particles between specified
limits
• The sieve analysis determines the particle size
distribution in a sample of aggregate.
• The sieves used for Sieve Analysis of CA are-
4.75mm, 10mm,20mm, 40mm, 80mm .
• For FA- 2.36mm,1.18mm, 600,300,150
microns.
52. Types of grading.
• Continuous grading – minimize the volume of
voids but increases the size of surface area.
• It is preferred for concrete mix.
• Uniform grading – all particles are of same
size.
• It produces large volume of voids.
63. Properties of harden concrete depends
on
• Compressive strength.
• Durability
• Impermeability
• Dimensional changes.
64. Compressive strength
• It is very important property of concrete.
• It is defined as the ability to resist compressive
stress without failure.
• In some situations, other strengths of
concrete are play a important role those are
flexural and tensile strength.
65. Factors Affecting Strength of concrete.
• Water cement ratio.
• Gel space ratio
• Aggregate size
• Properties of ingredients
• Effect of age of concrete.
66. Water cement ratio.
• The compressive strength of concrete is primarily
depends upon w/c ratio. Lower the w/c ratio,
higher is the compressive strength and vice versa.
• Water cement ratio is defined as , it is the ratio of
wt of water / wt of cement added during mix
formation.
• Water cement generally expressed in volume of
water required per 50kg cement bag.
• Concrete achieves its strength due to chemical
reaction hydration.
67. Gel – Space Ratio
• Gel –space ratio is the better approach than Abram’s
law , as it takes into account the following five factors
mentioned which are also responsible for strength of
concrete.
• Degree of hydration of cement.
• Chemical and physical properties of cement.
• Temperature at which hydration takes place.
• Air content in case of air entrained concrete etc.
• Effective w/c ratio, formation of fissures due to
bleeding.
68. • The gel-space ratio is the ratio of hydrated
cement paste to the sum of hydrated cement
and of the capillary pores.
x= volume of gel/ space available
= Vhc/ Vhc + Vcp
Where x= gel- space ratio.
Vhc= volume of hydrated cement gel
Vcp= volume of the capillary pores.
69. Maturity of concrete.
• Increase in strength of concrete is not only depends
upon curing period of concrete , but also on the
temperature at which concrete is cured.
70.
71.
72.
73.
74. Other strengths
• Bond strength - it is measure of adhesion
between concrete and steel. when steel is
embedded in concrete it is called bond
strength.
• It can be increased by using –
• High strength concrete.
• Low w/c ratio.
• Using deformed bars.
75. Green concrete
• Concrete which is made from concrete wastes
that are eco-friendly are called as “Green
concrete”.
