Fly Ash Cement pva fibers Assignment PDF

Chapter 2
2- Fly ash, cement, PVA fibers and fine aggregate.
2.1- Fly Ash
2.1.1- Nature of fly ash and its production.
Fly ash is the named given to natural pozzolan, a “siliceous or siliceous-and-aluminous
material”. Fly ash is reacting with calcium hydroxide and acquired cementitous properties and
thus able to bind different materials/structure where it is applied and form a composite/ united
structure (Design and Control of Concrete Mixtures 2010). Fly ash is the ash generated after the
combustion of coal in thermal power industries for the generation of electricity. It is actually a
particulates matter, a air pollutant obtained as a byproduct of coal usage for which disposal is
also a problem. It will create various environmental problems. Disposal of fly ash if not using for
our fruitful purpose require a low lying area where it is disposed off. Digging pit is also required
in order to dig it underground. It’s a very costing process and hence not economical. So, best
alternative choices is rather than it disposed off it can be used as modern civil engineering
material and can be used for making bricks and improve one of more properties of cement. The
fly ash can also be used in construction industries various purposes viz. in mixing in cement to
change of one or more properties of it. Fly ash provides the various advantages over other
materials. The fire resistance properties of composite are greatly improved once mix fly ash in
that composite. The various advantages with application of fly ash are its cost are less, it’s a
environmental friendly which otherwise creates the various problem to the atmosphere,
application of fly ash increases the strength and It enable to conserve other natural resources and
material viz. conserve lime stone which is the major requirement in cement production
the procedure of production of fly ash is produced in the thermal power industries through the
following steps (Bremseth, 2010); Coal is the fossil fuel and the source of energy for generation
of electricity through thermal power plant. The coal is used to boil the boiler and thus steam is
produced. With the help of grinding mill coal is crushed and makes a fine powder. In the boiler,
this fine powder is feed where it is combusted with approx. temperature of 1500 degrees which

in turn produce heat. There are two mineral are present in coal, one is combustible and other is
non-combustible. While the combustible mineral burn and produce heat but non-combustible
minerals melts and fuses together in the furnace. These non-combustible minerals are separated
from the burning region with the help of exhaust chamber through the exhaust or passes through
flue gases. From the flue gases, these mineral is again separated through the cooling action. After
cooling, it forms the spherical glassy particles and settled. These glassy particles are known as
fly ash and collected by the means of mechanical and electrostatic precipitator.
2.1.2- Physical and chemical properties of fly ash.
Since the basic raw material through which fly ash is made is the coal, so the physical and
chemical properties are attained by the fly ash is totally depends upon the quality, nature of
prerequisite material coal, and how the coal are processed and operating condition of the furnace.
By the nature of coal we mean what are the constituents of coal and how pure the coal is? In
order to best efficiently use for different purposes, it is urged that the physical and chemical
properties of flyash are to be known. Based on physical and chemical properties, fly ash can be
used for making the flyash bricks or can be mix in cement to change one or more properties
required for different purposes.
Based on quality of coal, the chemical composition of fly ash would vary significantly. However,
the major constituent of the fly ash is always a Silicon dioxide (SiO2). As per Bremseth, 2010,
the chemical contents of flyash is governed by what the composition of different constituents
present in coal. Based upon the composition of calcium content, the fly ash is classify as class F
and class C. These classifications are given by American Society for Testing and Materials
(ASTM) C618-03. In case of class F, the percentage composition of calcium is less while in
class C it is high. Concerns of the quality, the quality of class C fly ash is good and can be used
for many purposes but class F have limited use. The reason is it contains various unwanted
mineral like sulphite and free lime (de Brito & Saikia, 2013). The table below shows the
chemical properties of fly ash (Gamage 2011).
Chemical Compound Low calcium fly ash
Class F
High calcium fly ash
Class C
Silicon dioxide (SiO2) 54.90 39.90
Aluminium oxide (Al2O3) 25.80 16.70

Iron oxide (Fe2O3) 6.90 5.80
Calcium Oxide (CaO) 8.70 24.30
Magnesium oxide (MgO) 1.80 4.60
Sulfur Trioxide (SO3) 0.60 3.30
Sodium oxide (Na2O) and
Potassium oxide( K2O)
0.60 1.30
The literature reviews revealed that Fly ash is in irregular to regular shape and size .The
diameters may vary range from 0.5 μm to 150 μm. As per Ramezanianpour, 2014, the size of Fly
ash is governed by the type of collector equipment and also by the source. The physical
properties of fly ash are presented in table below.
Properties --------
Specific gravity 2.3
Moisture content 19.75%
Fineness 0.001-0.6 mm
Maximum Dry density 1.53 g/cm3
Permeability 4.87×10-7 cm/s
Angle of internal friction 23°-41°
Cohesion 3-34 Kpa
Compression of index 0.15
Coefficient of consolidation 0.1-0.5 m2 per year
2.1.3- Effect of the fly ash on environment.
Fly ash is the ash generated after the combustion of coal in thermal power industries for the
generation of electricity. It is actually a particulates matter, an air pollutant obtained as a
byproduct of coal usage for which disposal is also a problem. It will create various
environmental problems. Disposal of fly ash if not using for our fruitful purpose require a low
lying area where it is disposed off. Digging pit is also required in order to dig it underground. It’s
a very costing process and hence not economical.
As per statistics, according to (Morrison, 2005), the combustion of coal in Australia for
generation of electricity through thermal power project generates around 12 million tonnes of fly

ash every years. From which 60 % is dumped in low lying areas. However by doing so may
cause various enormous environmental problems including promoting air, water, and land
pollutions. Some of the problems are contamination of ground water and ground pollution, fog/
smog, asthma, inhalation problems etc.
So, best alternative choices is rather than it disposed off it can be used as modern civil
engineering material and can be used for making bricks and improve one of more properties of
cement. The Fly ash can be used in manufacturing fly ash brick which is the substitute for
tradition brick. The fly ash can also be used in construction industries various purposes viz. in
mixing in cement to change of one or more properties of it. By application of fly ash in civil
engineering construction, at one side we can dimishes the problem of waste flyash disposal and
at the same time we can mitigates the negative effect of global warming due to less emission of
carbon-dioxide which otherwise emits excessively due to production of cement in various stages
through lime stone. Now to some extent, flyash replace cement and hence safe our scarce
resources like lime stone. Fly ash provides the various advantages over other materials. The fire
resistance properties of composite are greatly improved once mix fly ash in that composite. The
various advantages with application of fly ash are its cost are less, it’s a environmental friendly
which otherwise creates the various problem to the atmosphere, application of fly ash increases
the strength and It enable to conserve other natural resources and material viz. conserve lime
stone which is the major requirement in cement production
2.1.4- Australian Experiences with Fly Ash.
Australia started the usage of fly ash in concrete since 1950 after carrying out various extensive
research and laboratory experiments in Western Australia on the potential use of fly ash in
concrete. The experimentation concluded that there is no any big difference in the strength
parameters of concrete made out of either of fly ash or Portland cement and practically have the
will have same strength. However the strength gained by 6 month latter by the flyash based made
is the same as that of concrete made by portland cement.
So from that time the Australia got an innovative substitute material over cement and fine
aggregates and hence can be used as a partial replacement of either cement or fine aggregates.
Since inception in Australia, there is increase in the usage of flyash for different purposes either
for making flyash brick or in cement to change of one or more properties. It can be used as a

supplementary cementitous material and can be used for partial replacement of fine
aggregate/sand and cement (Ash Development Association of Australia 2009). Some
researcher(Gamage,2011) revealed that if 25 to 30 percentages of cement can be replace by fly
ash, then there is no any big change in the properties of end product means have had attained
same strength. Other researchers revealed that it is also possible to replace up to 60% of cement
from flyash then also attained the same strength properties by final good but in this time we need
to add some admixtures and followed a proper curing method.
The aim of this research lays on to find the optimum fly ash /cement ratio that can be used in
concrete mix.
Besides fly ash can be used in various civil engineering application viz. premixed concrete,
precast concrete, concrete masonry, etc. It is due to its basic properties of pozzalanic action. And
also can be used for making flyash bricks.
2.3- Cement
2.3.1- Nature of cement and its production.
Cement exhibits both cohesive and adhesive properties. These properties can be used to make the
bond between different materials and then forms a composite unit. Cement is used for making
the concrete. Concrete is the homogeneous mixture of cement, coarse aggregates, fine
aggregates, and water. In concrete or otherwise, cement acts as binding material which binds
coarse aggregates (ballast), fine aggregates (sand) after reacting with water and set out in a rigid
mass. Cement is also used in finishing work like plastering, neat cement punning, brick work,
ashlars masonry work, roofing, flooring, and footing work etc. The usage of cement as a civil
engineering material is not limited and scope is very beyond high. In cement, generally
ordinary/normal portland cement is one which can be widely used. Due to similarity in color
(color being white grey lime stone) and its quality when it hardens as Portland stone, its name is
given as Portland cement. The cement production procedure is summarized below.
Firstly the limestone is quarried. By using explosive materials, the rocks are blasted from the
ground and we get limestone/raw materials in rock form (Glenn Hegar, 2005). These raw
materials are then transported to the plant.

Initially the raw materials as mentioned above are crushed, screemed & stockpiled. After these
are mixed with definite proportions to obtain raw mix which can be done either through dry (dry
mixing) or by water (wet mixing). Prepared raw mix is then fed into the rotary kiln and burn by
raising the temperature to 1300-1600 0C, we then get the output which is known as clinker which
is about 0.15-5cm in diameter. This Clinker is then cooled & stored, which is subsequently
ground with adding gypsum (3-6%) to adjust setting time, the result is the cement. This cement is
then packed and ready for market and marketing
The Portland cement is classified as Standard types and special types. The standard cement is
used for general building purposes while the special types are used for special purpose of use of
cement is special conditions of our requirements. Depending upon the usage in different
environmental conditions some oxide/compounds are decreases while other increases in making
the cement.
2.3.2- Chemical properties of cement
The major oxides present in the cement are CaO, SiO2, Al2O3, and Fe2O3. It contributes to
about 90% volume of cement. The percentage composition of different constituents of
portland cement are presented in the table (Gamage 2011).

2.3.3- Health and environment effects of cement productions.
The real sustainable development can be achieved only by adopting the sustainable technology.
Today’s, sustainability of cement is the topic of debates amongst the various playing
actors/experts. Some think that the use of cement in constructional industries is sustainable as
there is no any other alternative substitute over cement. At the same time, other experts think that
use of cement creates the health and environmental degradation problem and hence it’s not
sustainable.
a) Non-sustainability issue: Portland cement is not an eco friendly product. Its product process is
one of the causes of greenhouse gas emissions which promote the global warming. Production of
cement required the lime stone and thus scarce lime stone are depleted day by day which is the
issue of concern today. In production process of cement, the various gases viz. sulphur dioxide,
nitrogen oxide and carbon monoxide are emitted to the atmosphere. These gases are reacted with
the atmospheric vapour and may result acid rain. Once the acid rain fall upon the land may
damage our agricultural land and various health problems viz. breathing, reduce the oxygen

transport through hemoglobin, lung diseases, asthama, breathing problems etc. are associated
with these gases, and acid rain
Sustainability Issue: Ash generated in Cement manufacturing utilized in Brick making called as
Fly-ash brick and also in blended cement, Generate a large scale employment for the local,
regional, global people. Infrastructure development is also enhanced with the growth of such
plants. Few important benefits may include FDI, large scale technology transfer and
development. Indirect Benefits includes literacy, life style improvement and Better transportation
facilities with the development of railways, roads and ports. The industry may help in developing
the socio- economic status of the local people and the area by an efficient Corporate Social
Responsibility Plan.
Hence If properly used, cement is seems as a viable in construction industries.
The chemical composition of cement is tabulated below
 Table 2.1 Chemical properties of fly ash and Portland cement.
Chemical Compound Low calcium fly ash
Class F
Cement
Silicon dioxide (SiO2) 54.90 22.60
Aluminium oxide (Al2O3) 25.80 4.30
Iron oxide (Fe2O3) 6.90 2.40
Calcium Oxide (CaO) 8.70 64.40
Magnesium oxide (MgO) 1.80 2.10
Sulfur Trioxide (SO3) 0.60 2.30
Sodium oxide (Na2O) and
Potassium oxide( K2O)
0.60 0.60
2.6.2- Environment implication of fine Aggregate.
If we see in past, the river sand was only considered as a fine aggregates and can be used in
making concrete. Due to excessive extraction of sand from the river, it started to degrade the
rivers. As a result due to mining operation in the river, it lowers the river/stream bottoms and
may leads to the problem of bank erosion. It causes the deepening of rivers due to unrestricted

exploitation of sand from river bed and then saline-water intrusion from nearby sea. Due to
continue extraction of sand, it indirectly increases the level of sea water. Besides, sand mining is
also threatened to various civil engineering structure viz. bridges, river banks and nearby
structures. Directly or indirectly, more extraction of sand from river bodies can damage our
environment.
Due to various issues, constraints and challenges, there is a need to search alternative over fine
aggregates replacement and still the research is going on (Gonçalves, 2007).
References:
i) Noushini. A. (2012), Effect of Polyvinyl Alcohol Fibre and Fly Ash on Flexural Tensile
Properties of Concrete, 22nd Australian Conference on the Mechanics of Structures and
Materials,
ii) Joseph. A., K.,(2017),Mechanical Properties and Shear Strengthening Capacity of High
Volume Fly Ash-Cementitious Composite, IOP Publishing, Materials Science and Engineering,
310
iii) K. Kaviya(2015),Utilisation of Fly Ash and Fibre in Concrete, Indian Journal of Science and
Technology, Vol 8(32),
iv) Erxia Du(2017), Mechanical Property Test of Polyvinyl Alcohol (PVA) Fiber Reinforced
Concrete, Journal of chemical engineering transactions, vol.62
v) http://www.buddyrhodes.com/pva-fiber-recs-15/