Welcome to concrete technology, module 1 lecture
1. We shall be discussing about cement production and composition in this lecture. Of course, we start with, we will
just introduce concrete as a material, because is a coition concrete technology. So, general outline of our discussion will
be concrete material, components of concrete and also we will just mention concrete as a component. At the end, we will talk about
cement, the production process and its composition. Now, what is concrete? Perhaps you would have
seen concrete or also studied about it. Concrete is made up of components sachets, aggregation of stones, which we called
as aggregate embedded in cement mortar that is cement-sand mortar, in his hardened state concrete is aggregation of
stones or similar hard material embedded in what we call cement-sand mortar. The aggregates, aggregates in normal concrete
forms this skeleton matrix; it is about 60 to 65 percent by volume and rest all is 25 percent is a paste; now paste means cement
and water, that combines to paste. So, this aggregate when we talking of it is
the large aggregation of stones, sand etcetera etcetera put together. 1 to 2 percent words are usually there in normal concrete.
It is required that the aggregate shall be inert and strong, inert means should not be reacting with anything and it should be strong.
It should strong, so that it can carry the load. So, that it can carry the loads, so
that it can carry the concrete can which ten forces. Ingredients of concrete, therefore if you
look at the ordinary concrete or normal concrete it is made up by mixing inorganic material known as cement. I said cements and
water, so this is cement is one other component, water together with cement forms what is called paste and the naturals sand
or stone dust like something like this as we can see. Stone dust or naturals sand and
you know, in addition to that will have course
aggregate which quite often could be coarse stone or natural uncrushed stones themselves.
So, there for concrete is generally normal concrete or very conventional concrete is
made up of cement plus water plus water, this two makes paste, sand which are, which we
called as fine aggregate, could be sand or crushed stone powder. Then stones which forms are course aggregates. So, that is generally
the concrete normal concrete, generally the normal concrete. But modern concretes if you look at it, it
is not only this four components, but it has definitely two more components. So, modern engineered concrete has additional ingredients
other than the four components just mention, right? These are chemical admixtures, these are chemical admixtures
like they some of them are called accelerator, set retarders, water reducers etcetera. This ones are added to the concrete system
during production, in order to improve the performance of concrete, either in frustrate or in hardened state.
We will discuss about them later on in details. Mineral admixtures, this is the other kind
of material which goes into the concrete, sometimes even in cement making and this are
fly ash, silica fume, rice husk ash and other pozzolana or similar other material. So, as we can see modern concrete is not four
component material, but six components material. So, a modern engineered concrete is actually six components material
rather than four component material, rather then four component material, all right, okay? Chemical admixture admixtures as I mention,
therefore specific property performance enhancement. Specific property of performance an enhancement and mineral admixtures
they do improve long term strength and durability performance. So, therefore these two admixtures are must in
modern engineered concrete. Of course, manually produced concrete, non engineered concrete may not include this, but an engineered
concrete definitely includes this two item as well. Using this admixtures it has become possible to obtained high strength
materials, you know modern high strength and high performance concrete, right? You can design the concrete as you like, so this
is what the concrete is, this is what the concrete is. Now, there are lot of advantages and disadvantages
of concrete a few, the advantages are lower life cycle cost. It is relatively achieve material, right? I mean cheap, relatively
cheap and you know a material it is use for construction purpose is used in very huge quantity. Therefore it is a requirement
that a construction material be cheap and concrete of course is cheap. It has what we call, low life cycle cost. Now, life cycle
cost means not only that initial cost capital cost is low, initial production cost is low,
but its maintenance future, maintenance cost during
service life period is also low. It can be molded, you can mold into any shape
that you like. Concrete can be mold it, it can be molded to any shape that you like. It is robust it is robust what it means
is that, what we means mean is that, robustness, what we mean is that, were I need emissivity it can provide that emissivity.
For example, if I have a structure if I have a structure let us say I have a structures
like this and them already training wall. Now,
horizontal forces if acting is acting in to 8, then it must have sufficient resistance
again sliding. It should not slide, it should not
slide you know, it should not slide along this directions. It should not slide or it
should not avoid of turn because this forces will have
a tendency to causes it to overturn. So, it must have a sufficient resistance against
sliding, so resistance against sliding
sliding and over turning, that must be there. This you can get from concrete, this you can
get from concrete not for let us say, it is very difficult to make a retaining or dam
out of plastic. Let us say even steel you steel
you can, but steel is it is not very common. But concrete can provide this kind of concrete, can provide this kind of robustness,
concrete can provide robustness. You can design it for desire property, you can design it for desire property whatever property
you want, you can design it for that, it is a, it is a composite.
Now, a composite is a material as you know, is made up of number of material or ingradience,
which were combined together you know, when they are final material produce.
It has a property different than the original material use in his production. So, concrete is also a composite and composite
concrete you can design by braiding the proportion of ingradience or changing the ingradience themselves. You can design for
desire property, not of course very well versatiled but, quite well versatiled because it has got two weaknesses, it has got two weaknesses.
One it has got lower tensile strength and other it had got lower ductility.
Now ductility is a property by virtue of which the material exhibits a large amount of deformation
proir to failure and such large deformation ensures warning, prior to failure,
it does not fail suddenly. But particular system bounded by cementing material as in case of cement as we have seen. That it was
aggregates, which are bound together in a mortar matrix and if you go further the mortar itself is made of cement paste in which
we have sand, so concrete is a composite. First aggregates are and better then mortar matrix and in mortar sand is embittered
cement paste. If you go further down to final sizes, you will find cement paste itself, has got different solid components
as well as force etcetera etcetera. So, is a composite and its actually particulate
system bounded together. So, one can call concrete as a chemically combined ceramics also, chemically combined ceramic.
A composite is composite you know, and its actually composite if you look at it its composite form vary scale to scale. The scale
of structure it is almost a we quite an often assume it to be macro homogenizes. But if we go to slightly finer scale you will
find aggregate a mortar. You go to steel finer scale, you will find its is paste and sand, hardened concrete I am talking of. In the
paste itself there are different solids which will discuss some time later on.
So, it is composite and each scale its composite nature of the composite varies. And you know,
It becomes more and one complex as we go to the fines. Properties of the final
products actually is dependent on the micro level composite as well. Any way will talk about this sometime later on, but what
we on the stand, this is a particle its system bounded by the cementing material, such material do not show exhibit, do not exhibit
large ductility. They feel suddenly, so it is brittle. So, this are the two disadvantages, but it is quite at but advantages from other
point of view. Now, to take care of this accepts, we actually
put in steel rain for cement. You use rain force concreters a composite or pressured the concrete. Therefore when we use concrete
as a structural material, we really use it alone, accept for ingrabidi dam or massive structure, were we use mass concrete. Rain
force concrete or pressured concrete, which are again another form of composite, they are quite versatile and there we can
design them almost for whatever property we desire. So, that is why the statement and that is
why concrete is a most popular material in you know, in the are… In fact it is water,
the human being consumes possibly water and next
material is concrete. In fact cement is next to water consumed by human being, right? So, this are the very popular material
just because it has got all this advantages. So, concrete and concrete composite system,
some of which we will be discussing. Like it is not only one type of material, it is verity of material today. Modern concrete
there are verities and we can classify them something like this normal strength concrete, high strength or high performance
concrete, ultra high strength concrete or some composite special composite very high strength will discuss. Some of them at the
end of our you know, in the last module. Then fiber reinforced concrete, then they
something called densified with small particle, which will possible come into ultra high strength system. Macro defect free matrix,
which is again in ultra high strength system and reactive powder concrete which are again ultra high strength system. All this
will discuss in details, at the movement time I am just introducing to you the name of this concrete or cement based components, will
discuss about them at length sometime at appropriate time.
Then there are something called polymer concrete, polymer modified concrete or polymer cement
concrete, self-compacting concrete and some more self-compacting concrete,
roller compacting concrete, some more more additional additional, once are self-compacting concrete, roller compacted
concrete etcetera. We will discuss them at a proper time, in
fact in generally we look, in generally we look at concrete, the binder scan be them
in our many binders like I said polymer concrete.
So, therefore it as also a not cement base composite, but its concrete of some type or polymer cement concrete were polymeric
material is added in almost like a admixture. So, you can have a difference type of binders because you can have a varieties of
cement as well the matrix is skeleton. I am talking of here it is a matrix is skeleton,
that can also vary and I can put varities of fiber reinforcement to obtain the composite. So, therefore concrete, there are
lot of choices, choice are available to me in terms of the binder, in terms of the matrix, in terms of the fiber. Like a is a
material, which has got this binder, this matrix and may be some here is a reinforcement because I can use varities of fibers in the
system. Will discuss about this special concrete some
time later on I mention. So, this is the just give an oval view of the concrete, before we start with the actual discussion of cement,
right? So, let us look at now cement. A little bit of history you see mankind use lime and silica for quite some time. In fact, first use of lime as a construction
material as reportedly in literature. You know, they actually found out one of the,
one of the article professor Iron Benthur, you know,
there, some were some of the people from Israel, they could craze. The first use of lime something to pre historic time possible
7000 years from now, lime was used as a construction material, right? If you look at roman civilization, they used lime and volcanic
ash, right? Because Italy there are volcanic cases available there and they used them.
So, lime an volcanic ash in medieval India people are use lime and surkhi, lime and surkhi.
Surkhi is a material which comes out from, when you burn the brake then there are
fine dust which settle downs below. You know, when you burn the brake, when you burn the brake when you burn the brake in
a kiln, so there is will be a fine dust, if this is the brake kiln let us say and find
dust will settle down at the bottom, this is called
surkhi. Then, lime and surkhi was using India also
largely as a binding material of stones to produce concrete like, concrete is a artificial stone. So, mesmery in mesmery contractors
or something of similar kind, so bind the stone, stone missionary lime will gives us use. Now, what is surkhi or volcanic ash?
If you look at if you look at volcanic ash or surkhi, they are nothing but clay I can
say, clay mineral heated to high temperature
and cooled rapidly, right? In fact cay you no volcanic ash
or surkhi and nothing but clay minerals
heated to high temperature
and cooled rapidly cooled rapidly
cooled rapidly. Now, what is ash chemically
or clay minerals? Essentially this are, essentially clay is
essentially clay is
silica alumina, some amount of iron etcetera etcetera magnesium all this, but main compounds are silica alumina. So,
what we are doing? You are heating up silica and alumina and then cooling rapidly is is also same formation of a more for silica
amaphor silica not crystalline amaphor silica and in amaphor material in crystalline material atoms are arranging regular order.
So, there at low ward potential energy, they are electively stable.
Amaphor material on the other hand atoms are all haphazardly arranged and it is resettable
can react. Provided physically this material is this material is fine, so that
large surface area is available for reaction. So, when it comes to surkhi or volcanic ash
this are clay material heated up and they cooled
rapidly. In fact they will some amount of emerged trade into it chemical energy trab into it. It forms a ore fast material and
if it fine and conduce of condition it can react and dissipate that chemical energy.
So, amaphor silica fine a more for silica can
react with lime
and can give you hard material, hard material solid hard solid like stone. And this is what was absorbs by you know this
is was utilized in Roman time or even in India, even in India. Now calcinations of lime together with silica obviously was next
step. So, in case of the earlier once, this this material volcanic ash were known as posalans, will come to that again sometime
later on. Now, this material together with lime in presence of water forms are hard mass, you know almost like stone. Say wards
a surkhi with lime and water forms hard mass, now this are reactive silica basically.
The surkhi or the pozolone are the volcanic ash, so the reactive silica can react with
lime in ordinary temperature. But lime an silica if you combined them together and burn
it, then you know, that could give lies to a product, which can react with water itself because in lime surkhi reactions your
lime surkhi and water. Now, lime an surkhi put together heat them up and form into a compound, that can react with water to give
you seminal hard mass. So, that is the idea of cement. Actually the most commonly used cement is
called Portland cement patented by Joseph as paten in England in 19, 1824 and this when mixed with water hardens. Since, it s
mixed with water, it hardens we call it hydraulic cement. You know Portland died is a stone name and from that it got the name of
Portland cement, right? So, this is what? This is a cement, so therefore in this one basic raw material used in this manufacture
is calcium carbonate. The lime and the lime you know, the calcium carbonate which you can find in lime stone or chalk and silica
and alumina and iron found oxide found in clay or shale.
So, the difference here is you are putting them together and heating it up and do you
of course, some more is just a little bit of processing for the process will come to that
and in case of lime and surkhi or lime or pozolona lime and volcanic ash, you are actually used, using a reactive silica together
with lime get similar of products. So, Portland cement is this, ordinary Portland cement as we call it. It is actually produced
from lime and clay or shale. So, basically essentially you are using the silica alumina an iron present in clay or shale to get the
cement. There are two processes, well there are iron
say, there were they were one process called weight process, which is now not use much. So, you have to essentially mix up lime
and silica in a appropriate proportion and weight process was used were they were made into slurry and you know you get homogeny
mix of the two. So, in the wet process one would have got better homogeneity about 40 percent would have been the water,
in this slurry but then when you heated you have to drive over that water there for energy used his more.
In drive process in the technology improved in the second half of last century and there
for 90 and 80, so onwards you do not find in were process any more it is mostly
the dry process. So, modern practice is dry process, essentially what we got to do? You got to mix lime and silica or clay and glam
stone in an appropriate proportion and you got to grin them to fine size, grined them
to fine size and amount of grinding will of course,
depend upon the raw material. Generally granite up to 10 to 30 percent retained on 90 micron, sieve 10 to 30 percent retained
on 90 micron, sieve 10 to 30 percent retained on 90 micron, sieve and this homogenized then, then you mix them up grinned.
Then this is called row meal and this homogenized raw meal is introduced into the top of a pre
heater tower. This passes through a series of cyclones to precalciner as it is
called, passes through cyclone separator, cyclone sapper series of cyclone separators
to precaciner vessel. There it is subjected to flash heat, sudden
temperature rise of 900 degree centigrade in gas stream and some other carbon dioxide from the lime is given out because you know,
you know calcium carbonate is lime, which you heat to result in calcium oxide carbon dioxide. So, calcium carbonate some
of the carbon dioxide measured good lot of carbon dioxide is given of here. And this material then is allowed to entire
into a rotary kiln and then heated to 1500 degree centigrade which causes partial melting. The tumbling action of the kiln converts
into to granular material called clinker. So, this clinker because you know, it well melt. When you heat this material it will
melt form solids solutions and because of the tumbling action the form into granular material and this is called clinkers. So,
this is called OPC clinkers. The clinker in then cooled, so ground grinded with gypsum
to obtained ordinary Portland cement or portland
cement, portland cement. One issue is important write at the beginning, just let me introduced here.
Since, carbon dioxide is you no calcium carbonate brings down to calcium oxide pus carbon dioxide,
therefore you are producing carbon dioxide, in addition you are using
energy or heating. And when you use an energy for heating you might be using fossil fuel in some form other and people are actually
calculated there about point 7.4 to 1.25 or 26 turn of carbon dioxide which is produced, carbon dioxide is produce from one
turn of ordinary Portland cement production. So, that but on an average you can say that
one turn of OPC produces one turn of carbon dioxide, which will be an important points of discussions sometimes later on.
Because with the concerns of global warming and green house gas emission, carbon dioxide is one of the green house gases along
with water vapor and methane etcetera etcetera. This issue has become very very important that cement produces carbon dioxide,
a greenhouse gas. therefore OPC clinker consumption should be minimize or it should be use as judicially as possible. So,
that so at the beginning itself I just one point out here, which will be discussing sometime later at some appropriate of time,
right? Diagrammatically look at this product process
diagrammatically if we look at this production process you will have lime stone coring may be some other raw material you
might be adding as flaxes things like that to control the clinker formation temperature clay or shale this is the other one and this
together both of will be grinded and bended to get in an uniform mix of the two. All this are mix together to get a final blend, which
I can stored somewhere, have I raw meal, raw meal which I can feed now to the pre heater or pre calsyner, were I have like slices
cyclones, it will get heated. Followed by some other carbon dioxide, we
removed. After the pre heater, pre heating then it will go to the kiln kiln burning kiln were once the product is form this will mixed
with gypsum and grinded by you no finish by grinding. So, this is what the production process of cement clinker looks
like, right? This can be then stored, this can be then stored in a proper ate manner. If we look at the kiln where, you know, the
feed enters this is d hydrations zone ,were water will move out if there is in free water at 50 degree to 100 degree centigrade. At
600 centigrade clay decomposes, right? All exist gasesgo out through this, so therefore water vapor will move out along this directions.
The heat is supplied from here through by warning process, you know? There the burner, so through you actually supply the
heat. This zone is summer here is 1500 degree centigrade, this in clam a little bit, so that an this rotor nickel.
So, its rotate at 600 centigrade clay will the compose, then lime stone d composes. This
is the calcinations of lime stone will take place in this zone of 600 to about 1200 1300
degree centigrade and this decomposition of lime stone results in carbon dioxide, w hich will go a with the exhaust gas. Then
formation of C 2 S or another compound in the cement clinker that take place. C 3 s forms at somewhat higher temperature. This
is called clinkering zone and then you cool it, the clinker goes out cool to about 60 degree centigrade also. Then later on you
can mix up with gypsum very amount of gypsum and grind it, grind it. So, therefore if I summaries the cement production
process, cement is produce by burning calcium carbonate form found in lime stone or chalk, right? Found in lime stone
or chalk and silica alumina and iron oxide found in clay or shale at about 1500 degree centigrade 14, 1500 degree centigrade. The
material centers and partial refuse to form clinkers. The clinker is cooled and ground to a fine powder with some gypsum, resulting
in ordinary Portland cement. Well, one important point is at a India is
the second largest producer of cement after China at the moment. In fact we we you know, we have being second large producers
cement for quite some time, lot of infra structure you know, construction going on. All across China and India producing the maximum
amount of cement now. In fact cement is again I said next material after water which is consume by human being and
of course, India contributes to a large chunk in this production of cement. So, what is that the production process is all about
cement productions, let us see the composition. Now, if you if you we can quickly understand, that there will be calcium oxide
calcium oxide because calcium carbonate bound to form to calcium oxide. Obviously I will have Si O 2 and other materials
available in clay, right? Fe 2 O 3 and some fluxes, which are added, so they will also be there. So, the oxide main oxides composition,
it would be alkenes of course, alkenes. Then other impurity etcetera that will be there are magnesium oxide. That it
usually then they controlled some of them come from the ingradience raw materials and some come through the process and then
the oxide composition oxide composition are controlled depending upon the performance of the cement that you desire,
right? So, carbon dioxide from the lime stone is
liberated while burning, therefore calcium oxide and Si O 2 would be there and approximate composition limits of the ordinary
Portland cement if you look at it. Generally calcium oxide it would be, calcium oxide would be 60 to 67 percent. Silicon oxide
Si O 2 is 17 to 25 percent aluminum oxide is 3 to 8 percent. Iron oxide is should be Fe 2 O 3 or Fe 2 O 3, the 3 should be subscript
0.5 to 0.5 to 6. This is controlled, alkalis 0.2 to 1.3 percent.
S O 3 is 1 to 3 percents. This are the oxide compositions of cements, this are limits actually given typical limits of oxides given
you know, when most of the codes all over the world the ordinary Portland cement will have this kind of limits of oxides. Now, this oxides actually found in solid solution
forms and compound while you no clinkers formation occurred within the kiln, because they are partially melt, the compound
main compounds, those are present in cement are recognized as you know this are the solid solutions, they are this compound
3 Ca O Si O 2 2 Ca O Si O 2, 3 Ca O l 2 O 3 and 4 Ca O Al 2 O 3, Fe 2 O 3 etcetera, etcetera. 4 Ca O Al 2 O 3 Fe 2 O 3, this is
combined, this together etcetera. These compounds we, the names will come to them, but before that since this are the compounds
and you can see their complex compound actually, complex oxides. So, therefore we do not write instrument chemistry we write
do not write them, time an again. 2 Ca O Si O 2.
We abbreviate them, so oxides are actually abbreviated in cement, chemistry or in discussion
with us to cement and Ca O abbreviate as C, Si O 2 we abbreviate as S,
Al 2 we abbreviate as A and Fe 2 O 3 are abbreviates as F. Well some more abbreviations are something like this, all
those is retained here, but sometimes it might be using it H 2 O, we abbreviate as H, H 2 O we abbreviate as H. So, the compound water
abbreviations. Similarly, S O 3 we abbreviate as abbreviate as S bar because S is already there, so we abbreviate as S bar.
So, this will comes sometimes later on, right? Now, if I use this abbreviations, then this
compound this compound can be a retain, this compound can be retain as C 3 S, this compound can be written as C 3 S, this compound
can be written as C 2 S. So C 3 3 3Ca O tri calcium silicate, tri calcium silicate we call it. Di calcium we call it, d icalcium
silicate I will come to the name, name I have not really mention to you.
Tri calcium aluminates, we call it C 3 A and this is called tetra calcium aluminous ferried
C 4 AF tetra calcium aluminous ferried and that is C 4 AF, all right? So, this is
the abbreviated form of the compounds and now on words will be using mostly this and surly not this kind of compound functions
this. So, let us see the name nomenclature, main
compound in Portland cement tri calcium silicate this is this, then we abbreviate as C 3 S. We also the mineral name is alite. So,
it is a mineral logical name is alite. D I calcium silicate it is a mineral logical name
is belite and it is 2 Ca O Si O 2 or C 2 S, so
alite and belite. Tricalcium aluminate is 3 Ca O, Al 2 O 3 or 3 Ca.
It is mineral name is aluminate, the bue colour signifies the mineral name, but its compound
name is tri calcium aluminate. Tetracalcium aluminoferrite, so tetracalcium
alumino ferrite C 4 AF is abbreviation and is mineral name is ferrite. So, alite and belite of the two compound, which has got
silica and aluminate and ferrite of the compounds were there are alumina and iron present iron an alumina present. Well, it is important. Then you control the
properties of the cement because there are performance will depend upon, I mean properties of the control the composition
of the cement because performance depend upon the compound composition. We will see that, each compound actually behaves differently
than the others. Although it is possible is very difficult to actually identify directly C 3 S, C 2 S etcetera in cement if
you take cement identifying directly other microscope or something or separating usually it is not easy. Although, you can
identify them through, lets us say techniques analytical chemical techniques.
Now, there properties would be governed by the the properties are governed by properties
are governed by composition of C 3 S, C 2 S etcetera, etcetera. Now, therefore there
are some control ratios lime saturation factor is one of them, lime saturation is factor is one of them, silica ratio and alumina
ratio are the two others. So, we shall see that how they control? Lime saturation factor is defined in this manner. This is
the calcium oxide, divided by 2.8 S Si O 2 1.2 A 0.65 F expressed usually as percentage. So, lime saturation factor is nothing but
the ratio of calcium two some factor multiply you know, some 2.8 multiple by the silica content 1.2 multiple by alumina and n 0.65
by multiply by the iron Fe 2 O 3 expressed at percentage.
Silica ratio is divided by S plus F plus F and alumina ratio is a by F. Now, how do that
matter? If the lime saturation factor is greater than 100, you have some lime which
will remain un combined free lime. So, it is more than 100 percent, right? This lime saturation factor more than 100 percent, then
it results in free lime, un combined lime will be there; calcium oxide, because there now too much lime in this system and it cannot
react. So, they will remain as un reacted, so therefore
the you no compound composition of oxide that is present proportion of oxide is various oxide, there is are very, very important.
Now, generally it is maintain from 95 to 98 percent, lime saturation factor it is maintain 95 to 98 percent. Higher silica ratio
means more C 3 S, so higher this means more C 3 S less C 3, C 2 S and obviously C 3 A. So, if you have high silica by you no
silica ratio you will get more of this compound less of C 3 A and obviously less of C 2 S as well as you shall see.
Higher alumino ratio means higher C 3 A. So, higher supposing I control this proportions
then I can control this oxide composition, I should be able to control the
compound composition in cement and that would result in different performance. So, depending upon performance or type of cement
I want to obtained, I can control this controlling, control ratios, in order to get appropriate compound composition also compound
composition also is cement calculated. From oxide composition by and equation called Bogue’s equations. Bogue’s
equations this is an empirical, we have determining. This is what it is C 3 S amount is given as
4.07 C minus 7.60 S minus 6.72 A, 1.43 F and 2.85 this is S O 3, A bar S O 3, this is S
O 3 this is S O 3, so from this you can find
out how much you will be the… So, if you no oxide composition, then you can find out the C 3 S composition and approximately, approximately
using this are Bogue’s empirical equation. C 2 S is obtain as 2.87 S that Si O 2 content minus 0.754 C 3 S. So, if you
first calculate this, then from the C 2 S. C 3 A quantity you can find out from 2.65 aluminum oxide and 1.69 higher oxide.
C 4 A F is found order 3.04 S. S of course, is S O 3 as I mention. So, if you calculate
the compound composition from oxide composition, then C 3 S typical something
like 54.1 percent. Generally this is observes C 3 S, 10.8 percent. If you take 60, if you know, 65 percent from the oxide composition,
which I have given earlier, earlier I have given from that, if you calculate out you can calculate out to find the C 3 S miht come
around 54.1 C 3 S might come were there C 4 AF will be there. Then minor compounds etcetera etcetera. So, you can obtained
the compound composition from oxide composition, using Bogue’s equations. This diagram shows you at different stages
what are the Si O 2 AF etcetera, like this is lime stone. then the shale. They mix together as 80 20 proportion that comes to
the meal, then the raw feat to the pre heater and to the kiln final product is the opposite of 65 percent of calcium oxide, 3
percent alumina 5.6 and S 20.9 percent. So, this shows the stages, have various stages the composition of the oxide composition mixture
at various stages. This is a face diagram, in fact if we see
with temperature the proportion by weight, then to start with I got lime here. This is
low quartz right and the clay minerals iron oxide.
Now, S by temperature increases the water has gone out 600, 800 centigrade, carbon dioxide as gone up. So, mass would
have reduced, total mass would have reduced and C 4 A formation would have started here, C 4 A formation would at started here.
This low quartz changes to high quartz and here free lime started producing from about 700 degree or 600 you no below 700 some
were close to 700 because lime would have broken down, calcium carbonate had broken down, carbon dioxide have gone,
so free lime would have gone. As I go further C 4 A formation could occur
around 1000, 1100 or 1200 degree centigrade. C 2 this this would be this is quartz they will change, this are in some liquid
states which will solid if I later on. Belite forms here and alite finally, forms around
1400 degree centigrade, which we showed earlier
also. That about 1400 degree centigrade C 3 S is formed. That is alite is form, the alite forms earlier and C 4 A forms much earlier
at around 700 800 centigrade. So, this is the production and composition of cement. Next is, you see when cement reacts water
it produces heat. It is in exothermic reactions because philosophically, we can understand this will occur we have heated
this material up lime and silica I mean clay and you know, lime stone. Therefore, finally the product that is form, it is heated
and produce high temperature. Now, this product will have some chemical energy logged up in to it because we have given energy
to it. Therefore it will have tendency to react and it reacts with water, because that is we have seen that lime and surkhi,
you know reacts with water. Similarly, now we have producing for the raw
material of lime and silica and this material the clinker grinded together with gypsum y gypsum. I will come to that some
time later on, it will react with water, readily react with water it will readily with water, right? So, because it has got some
chemically energy logged up its chemical potentially high, it will readily react with water and give a those energy, so the reaction is
exothermic. Reaction of exothermic and the process, the reaction process we call it hydration process because you know, hydration
because it at if water. Simply it have the water, so it is a hydration in chemistry.
We call it hydration process were water simple is reacting, right, getting added, so this
hydration. Now, in the process of hydration of cement, hydration of cement heat is, heat
ambulation takes place. So, heat of hydration occurs and if you see heat of hydration of this pure compound C 2 S C 3 S etcetera,
we will find that C 4 C 3 A has got does highest value Jules per gram 867 or in calorie per gram is 207. C 4 C 3 A has got
next highest as 502 Jules per gram and this is got 419 this has got least.
So, the one which is which gives out maximum heat, will have a tendency to react in the
beginning, earlier. It will react, because it has a highest tendency to react. So, C
3 A has got highest tendency to react with water, C 3 S will have next highest tendency
to react with water. This is a small compound,
but this has a next tendency and this is the compound which will have list tendency to react with water. So, this is what it is,
so heat of hydration is important from that point of view. And we will use this quickly if we look now
cement, the elements those are presents are oxygen, silica, calcium, aluminum and iron. Components oxides are calcium oxide
Si O 2 Al 2 Fe 2 O 3 alkalis etcetera, etcetera. Then cement compounds is a form from next stages C 3 S, c 2 S, C 3 A C 4 A
F and from this by combination of this, we formed various kind of Portland cements. Then this reacts and from some products which
will discuss in a next lecture, right? So, summaries this, what we have discuss today.
First of all we actually introduced concrete as a material and of course, together with it cement based composites. Because concrete
is one material, but today concrete is very, very versatile with cement based composite. There are many of them, many varieties
as I mention earlier. So, we actually summaries them, you no introduced them by name only not gone into the details.
We also explain we also looked into that concrete is a composite made up of difference material
and the properties of final product, is different than that. Also, we
stayed that it is composite and depends upon the level at which you doing. So, multi level composite it is at the highest level of course,
micro homogenizes, as we go should becomes a composite next level final level it still becomes composite etcetera, etcetera.
Then we looked into the cement production process. We looked into the concrete material looked
into the cement a production process, right? So, we looked into components of the concrete as well natural aggregates cements
and cements is you know, other, other material and water and mixtures. Then we looked into a cement production process, and
then we looked into composition of cement. We will next follow, will next follow up, in the next lecture we look into the process
of reaction of cement with water, which we call it as hydration products, hydration process. That products its form
both in physical changes that occurs, because that cement and water when in whet together it forms of plastic paste and when
its solidifies as the reaction progresses, and then we look into the product that is
form hidden products in the next class, right?
So, thank you very much.