This document summarizes research on producing artificial lightweight aggregate from industrial byproducts like fly ash. Fly ash was mixed with small amounts of cement and lime using a rotating drum pelletizer to form rounded pellets. Different mixtures were tested and the best mixture was found to be 47% fly ash, 47% lime, and 6% cement by weight. The pellets were water cured for 28 days. Tests found the fly ash aggregate to have properties suitable for concrete usage, including bulk density between 994-1189 kg/m3 and impact values between 27.92-31.91%. Producing artificial lightweight aggregate from industrial waste like fly ash provides an eco-friendly and cost-effective construction material.

1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 65-72 © IAEME
65
BASIC PROPERTIES OF ARTIFICIAL LIGHTWEIGHT AGGREGATE BY
USING INDUSTRIAL BY PRODUCT (FLY ASH)
1
Dr. V.BHASKAR DESAI, 2
A.SATHYAM
1
Professor, Dept. of Civil Engineering, JNTUA College of Engineering,
Anantapuramu – 515002, A.P.
2
Conservation Assistant Gr-I, Archaeological Survey of India, Anantapuramu Sub Circle,
Anantapuramu & Research Scholar, JNTUA College of Engineering, Anantapuramu – 515002, A.P.
ABSTRACT
In the recent past the utilization of the concrete is increasing in the construction industry
throughout the world. Presently this industry is facing shortage of natural granite aggregate due to
abundant usage of natural resources. Hence due to scarcity as well as rising cost of raw materials, the
concrete technologists must search for some alternate to the aggregate. In this study an attempt has
been made whether any artificially manufactured lightweight aggregate can be produced from
industrial by-products such as Fly ash or not. This led to the wide spread research on using viable
waste materials from industrial by products. Light weight aggregate has been the subject of extensive
research which affects the strength properties of cement concrete. The industrial by product such as
fly ash is a promising material to produce light weight aggregate. By adding small quantities of
binding materials like cement and lime to the industrial byproduct i.e. fly ash along with water in a
rotating drum pelletizer and by rotating it at certain angle about 12o
to 15o
, the rounded pellets can
be formed. The pelletized aggregates can be soaked in a curing pond for 28 days and afterwards they
can be used in concrete. The utilization of fly ash light weight aggregate is eco friendly and cost
effective.
Keywords: Light weight aggregate, Fly Ash, pellatization, cold bonded aggregates and coarse
aggregate.
INTRODUCTION
Fly ash that is collected directly from the electro static precipitators of Rayalaseema Thermal
Power Plant (RTPP) located at Muddanuru town of Andhrapradesh state, India has been used in the
present study. Fly ash is a finely divided residue resulting from the combustion of powdered coal
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2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
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and transported by the flue gases. It is referred as pulverized fuel ash. Fly ash is the most widely used
pozzolanic material all over the world. Fly ash was first used in large scale in the construction of
Hungry Horse dam in America in the approximate amount of 30 per cent by weight of cement. Later
on it was used in Canyon and Ferry dams etc. In India, Fly ash was used in Rihand dam construction
replacing cement up to about 15 per cent (Shetty 2005). Cement is the backbone for global
infrastructural development. The use of fly ash as aggregate in concrete not only extends technical
advantages to the properties of concrete but also contributes to the environmental pollution control.
In India alone, about 75 million tons of fly ash per year is produced, the disposal of which has
become a serious environmental problem. The effective utilization of fly ash in concrete making is
therefore, attracting serious considerations of concrete technologists and government departments
(Shetty 2005). In the recent times, the importance and use of fly ash in concrete has grown so much
that it has almost become a common ingredient in concrete, particularly for making high strength and
high performance concrete. The new Indian Standard on concrete mix proportions (IS 10262-2009)
has already incorporated fly ash as a supplementary material to cement. Extensive research had been
done all over the world on the advantages of fly ash as a supplementary cementitious material. High
volume of pelletized fly ash aggregate concrete is a subject of current interest across the globe.
ASTM broadly classifies fly ash into two classes. Class F and class C. Class F Fly ash is normally
produced by burning anthracite or bituminous coal and has pozzolanic properties only. Class C Fly
ash is normally produced by burning lignite or sub-bituminous coal and can possesses pozzolanic as
well as cementitious properties (Shetty 2005).
In the present investigation an attempt has been made to use the fly ash as the basic
ingredient in the preparation of artificial light weight aggregate using lime and cement as binders.
One of the common techniques for producing the light weight aggregate is agglomeration technique.
In agglomeration technique the pellet is formed in two ways either by agitation granulation or by
compaction. The agitation method is not taking any external force rather than the rotating force. With
the increase in the dosage of water in the binder the cohesive force of the particles would increase.
Sintering or autoclaving or cold bonding are three different processes which are adopted for
hardening of green pellets.
Here attempts have been made to make pellets of fly ash with various proportions of lime and
cement mixing with water. Pelletization of fly ash is done by using a rotating drum with fixed blades
with adjusting inclination from 12o
– 15o
. The percentage of binder content is taken by the weight of
fly ash.
Plate 1. Drum pelletizer Plate 2. During the formation of fly ash aggregate

3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 65-72 © IAEME
67
Plate 3. Fly ash aggregate in green state
LITARATURE REVIEW
Artificial light weight aggregates can be formed by different processes like autoclaving or
cold bonding or sintering (Bijen, 19861
; Baykal and Doven, 20002
; Mangialardi, 20013
). Research
studies show better results on usage of various waste products for the manufacture of artificial light
weight aggregates, some of which are sewage sludge (Cheeseman and Virdi, 20054
; Mun, 20075
),
mining residues, heavy metal sludge (Su-Chen Huang et al., 2007)6
, bottom ash (Geetha and
Ramamurthy, 20107
). Some of the parameters that need to be considered for the efficiency of
production of pellets are speed of revolution of pelletizer disc, moisture content, angle of pelletizer
disc and duration of Pelletization (HariKrishnan and RamaMurthy, 2006)8
. An angle of 55o
is
maintained as per a previous study which gives better pelletization efficiency and good grading of
pellets (Manikandan and Ramamurthy, 2007)9
. High rate of hydration can be achieved with larger C-
S-H gel formation (Mehmet Gesoglu et al., 2007)10
. Though class C fly ash has Cao content for
better binding property, the usage of Ca(OH)2 improves the efficiency and reduces the duration and
binder dosage in pelletization (Geetha and Ramamurthy, 2010)11
. The addition of silica fume at 5 to
15% in the LWC can improve the strength properties while, replacements of 10% fly ash instead of
cement in concrete can decrease strength as compared to without fly ash (Shannag, 2011)12
. From the
literature available very limited work is reported on the manufacture and usage for structural
application of fly ash based light weight aggregate concrete.
CONSTITUENT MATERIALS
The constituent materials used in the present investigation for making artificial light weight
aggregate are; as follows.
Fly Ash
Fly ash consists of very vitreous particles with a surface area around 8.20 m2
/gm when
measured by nitrogen absorption techniques with particles approximately 100 to 150 times smaller
than the cement particles. Because of its extreme fineness, it is an effective pozzolanic material and
is used in concrete to improve its properties. It has been found that Fly ash improves compressive
strength, bond strength, abrasion resistance and reduces permeability.

4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
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Cement
Ordinary Portland cement of Ultra-tech 43 grade with specific gravity of 3.07 is used as
binder. Initial setting and final setting times are 60 minutes and 420 minutes respectively.
Lime
Locally available lime used is as another binder.
Water
Locally available potable water which is free from concentration of acids and organic
substances has been used in this work for mixing and curing.
PELLETIZATION PROCESS
The different types of pelletizer machines were used earlier to make the pellets such as disc
or pan type, drum type, cone type and mixer type. Here, in this pilot study, fly ash aggregates are
made by cold bonded technique with drum type pelletizer. Pelletizer of 60 cm in diameter and 90 cm
depth with a rotating speed of 40 rpm is used in the process of pelletization (Plate 1). Pelletization is
a technique that enables the formation of rounded balls or pellets with a mean diameter usually
ranging from 5 mm to 25 mm. The desired grain size distribution of an artificial light weight
aggregate is by means of agglomeration process (Plate.2). The Pelletization process is used to
manufacture light weight coarse aggregate. With drum type pelletizer small grains are formed
initially and subsequently size gets increased. Different trial mixes are made with different contents
of fly ash, lime, cement and water to get the best proportion. Moisture content and angle of drum
influence the size growth of pellets. Fly ash and the binders are mixed well in advance initially for 2
minutes in the drum pelletizer and then water is sprayed in to it. Spraying should be done carefully to
make sure that the water has been sprinkled not in the same place to avoid balling. The fresh pellets
formed are then kept at room temperature for a day to attain initial strength and then water cured for
28 days. The usage of calcium hydroxide gives better initial strength to the pellets which helps in
easy handling. The dosage of binding agents is more important for making the aggregate. Initially
some percentage of water is added in the binders and remaining water is sprayed during the rotation,
because while rotating the drum pelletizer without water the fly ash and binders (Lime & Cement)
tend to form lumps and do not ensure increase in the distribution of particle size (Plate 2). The pellets
are formed approximately in duration of 6 to 7 minutes. After 24 hours of drying under shade the
pelletized aggregates are soaked in curing pond for cold bonded curing.
TABLE 1. Chemical Composition of Fly Ash and Lime Supplied By Manufacturer
Constituent of Chemical Composition
Material
SiO2 CaO Al2O3 Fe2O3 MgO LOI Na2O K2O
TiO2
Fly ash
56.88 3.62 27.65 6.28 0.34 4.46 0.19 0.27
0.31
Lime
0.50 70.00 < 0.40 -- 0.60 + 93.00 -- --
--

5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 65-72 © IAEME
69
TABLE 2. Physical Properties of Fly Ash As Supplied By the Manufacturer
Property Fly ash
Specific Gravity 2.17
Grain size distribution
Silt fraction (%) 94.50
Clay fraction (%) 5.50
Atterberg Limits
Liquid limit (%) 29.00
Plastic Limit (%) NP
Plasticity Index (%) NP
Compaction characteristics
Optimum moisture content (%) 23.80
Max. dry density (KN/m3
) 13.30
Surface area (m2
/gm) 8.20
NP: Non Plastic
EXPERIMENTAL WORK
The bare fly ash aggregate are porous and to improve the strength of pellets, the binder
materials like cement and lime powder are added. In this investigation totally 12 no of mixes are
tried for arriving at the control mix by changing the proportion of ingredients i.e. pozzolanic
materials, lime and cement by trial and error method. Different trails made are presented in table 3.
Hardening of the pellets is done by cold bonding. The fresh pellets formed are then kept at room
temperature for a day to attain initial strength and then water cured for 28 days. Autoclaving and
steam curing methods are less effective to improve the properties of aggregate as compared to
normal water curing method. The curing is more important to enhance the aggregate strength. Hence,
a normal water curing method is adopted. The corresponding physical properties of mixes obtained
are presented in table 4. Finally, the mix proportion in percentage, 47:47:6 i.e. pozzolanic Material:
lime: cement is adopted for further work. By decreasing the binding material i.e. cement and lime the
pellets at 28 days curing period become powder and they have lost the shape. The properties such as
impact and crushing strengths are also decreased with the decrease in the binding material. For FA12
these proportion are found to be the better.
PHYSICAL PROPERTIES OF LWA
The physical characteristics of the artificial lightweight aggregate produced by pelletization
process are given in Table 4. The moisture content and amount of binder can affect the size of fly ash
aggregate thus formed. The fineness of the fly ash gives the better pelletization efficiency compared
to the other powders. The average particle size of fly ash is smaller than average particle size of port
land cement.
DISCUSSION OF TEST RESULTS
Properties of Fly Ash Aggregate
The shape and texture of aggregate affect the fresh properties of the concrete. Fly ash
aggregate is rounded in shape while natural aggregate is angular in shape (Plate 3). Rounded

6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 65-72 © IAEME
70
aggregate promotes workability of concrete while the angular nature of natural aggregate gives a
better bonding property. The basic tests on FA12 fly ash aggregate are conducted and the properties
are compared with those of natural aggregate. Also the properties such as aggregate crushing
strength, aggregate abrasion value and water absorption for FA12 in addition to the basic properties
of mixes like fineness modulus, specific gravity, bulk density and aggregate impact value are also
studied to know the better proportion for further studies and the values are presented in table 4. From
this table it can be observed that the properties of FA12 aggregate are satisfactory.
Table 3. Different Percentages of Constituent Materials in Pelletized Aggregate
Mix
Designation
Fly Ash (%) Lime (%) Cement (%)
Water % age WRT
(FA+LIME+CEMENT) by weight
FA1 95 0 5 20.50
FA2 90 0 10 20.50
FA3 85 0 15 20.50
FA4 77 19 4 23.00
FA5 74 18 8 23.00
FA6 70 18 12 23.00
FA7 65 32 3 25.50
FA8 63 31 6 25.50
FA9 61 30 9 25.50
FA10 49 49 2 25.50
FA11 48 48 4 25.50
FA12 47 47 6 25.50
Table 4. Properties of Fly Ash Aggregate with Lime and Cement as Binding Materials for
Different Mixes
Mix
Designation
Fineness
Modulus
Specific
Gravity
Bulk Density in Kg/m3
Aggregate impact
valueLoosest
state
Densest
state
FA1 2.48 1.42 994 1189 31.91
FA2 3.07 1.70 1022 1189 27.92
FA3 3.50 1.60 1078 1244 26.45
FA4 3.72 1.62 967 1078 31.25
FA5 4.69 1.63 994 1094 27.66
FA6 4.08 1.74 1050 1189 25.49
FA7 3.78 1.72 922 983 27.92
FA8 4.88 1.74 972 1016 27.25
FA9 4.44 1.70 1033 1089 24.44
FA10 4.25 1.86 889 967 27.91
FA11 4.85 1.76 967 1022 27.08
FA12 4.69 1.70 1000 1056 24.20

7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 65-72 © IAEME
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Table 5. Properties of Fly Ash Aggregate Compared With Locally Available Granite Aggregate
of Fa12 Mix
Sl.No Properties of aggregate
Locally available granite
aggregate
Pelletized Fly
Ash Aggregate
1 Aggregate Impact value in % 15.50 24.20
2 Aggregate Abrasion value in % 3.54 31.70
3 Specific Gravity 2.68 1.70
4 Water Absorption in % 0.70 15.00
5 Bulk Density in Kg/m3
1620 1056
6 Fineness Modulus 4.23 4.69
CONCLUSIONS
The following conclusions are made from the above study, which are applicable to the materials used
and range of parameters studied.
• Fly ash is not a waste material; and it can be effectively used in concrete either as artificial
aggregate fillers, replacement for fine aggregate or for making fly ash aggregate.
• The overall studies conducted by various researchers have shown that the artificial light
weight fly ash aggregate produced by pelletization can be an effective aggregate in concrete
production.
• For achieving maximum pelletization efficiency, the dosage of binders and moisture content
varies with type of binder used.
• The efficiency of pelletization depends on the speed of the pelletizer, angle of the pelletizer
and the type of binder added along with the fly ash.
• No dought, In the near future the depletion of the natural resources for aggregate can be
suitably compensated by the artificial aggregate such as fly ash aggregate.
• The potential applications of light weight aggregate are more phenomenal in terms of the
usage as new construction materials.
• It is observed that the specific gravities of coarse aggregates corresponding to mixes from
FA1 to FA12 are influenced by the properties of fly ash, lime and cement etc.
• Also the bulk densities, Impact values of fly ash aggregate are influenced by the proportion of
fly ash, lime cement etc.
• The important properties such as impact value and abrasion value are found to be within the
allowable limits for the recommended set of fly ash pellets.
• From the limited experimental study, it is concluded that the FA 12 mix is considered as
better proportion on overall basis.
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3. Mangialardi, T., 2001, Sintering of MSW fly ash for reuse as a concrete aggregate, Journal of
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