International Conference on Civil and Architecture Engineering (ICCAE'2013) May 6-7, 2013 Kuala Lumpur (Malaysia)
Utilization of Waste Products and By- Products
in Concrete: The Key to a Sustainable
Construction
Vasu Krishna1, Dr. Gajanan M Sabnis2*
these resources produces pollution and degradation of the
environment. Concrete Industries have a considerable impact
on the environment: they use large volumes of raw materials
that are extracted from the earth, their production consumes
large amount of energies and production of cement contributes
a lot to Greenhouse gas emission. Thus, utilizing the industrial
waste and by products in concrete can contribute towards
sustainable development and construction. Because of the
environmental and economical reasons, there has been a
growing trend for the use of industrial wastes or by-products as
a supplementary material in the production of the concrete [1].
There are several types of industrial wastes or by-products
which can be utilized in the concrete either as a replacement of
cement (or sand) or as an additive material. Some of these
wastes are Coal Fly Ash, Ground Granulated Blast Furnace
Slag, Metakaolin, Waste Glass, Plastics, Wood-ash etc.
Utilization of these wastes enhances the properties of the
concrete also.
Significant researches have been going on in various parts
of the world related to these subjects. Some waste products
have established their credential in their usage in concrete
while others are in progress for finding the potential
applications in concrete and construction industries.
Abstract— In the 21st Century, we have been using the natural
resources at a rate that cannot be sustained indefinitely. Exploiting
these resources and extent of energy used in their consumptions,
results degradation of our balanced ecological system in the form of
pollutants, wastes generation, heat sink effects in the cities etc.
Tremendous amount of waste materials and by-products like GGBS,
waste glass etc. is generated from the industrial sector. These
materials are difficult to dispose and cause serious environmental
problems. Morever construction sector also contributes a lot to the
emission of Greenhouse gases (GHG’s) besides consuming the nonrenewable natural resources. These environmental problems can be
resolved by utilizing the industrial wastes and by-products to create
beneficial construction materials. In addition use of these materials
resolves various environmental issues such as GHG’s emission,
construction wastes disposal etc. These materials also enhance the
mechanical and durability properties of the building material in
which they are added (like concrete). This research paper is the initial
step to bring forward the utilization of various industrial wastes and
by products in the concrete including their influence on the properties
of concrete. The paper has identified the different ways to
demonstrate the trend and the impact of such actions on the human
beings.
Keywords—
By-products, Properties, Utilization, Waste
materials.
1. Coal Fly Ash
I. INTRODUCTION
Fly ash also known as pulverized fuel ash, is the ash
precipitated from the exhaust of coal-fired power stations, it is
the most common artificial pozzolona. According to ASTM
C618-94a, Fly ash can be classified on the basis of coal from
which latter originates. Class F fly ash is the most common fly
ash derives from the bituminous coal. Sub-bituminous coal and
lignite result in high-lime ash, known as Class C fly ash.
I
NCREASING amount of industrial by products and Wastes
has become a major environmental problem. These by
products and wastes are not only difficult to dispose but they
also cause serious health hazards. The main aim of the
Environmental agencies and governments is to minimize the
problems of disposal and health hazards of these wastes and
by- products. The productive use of these materials is one of
the best ways to alleviate some of the problems of the solid
waste management. One of the key solutions is to utilize these
wastes in the concrete. But the question arises: why in
Concrete?
We all live in the world of finite natural resources. The
energy that we expend in extraction (or manufacturing) of
1.1 Influence on fresh properties
The main influence fly ash on fresh properties of concrete is
reduction in water demand and improving workability. For a
constant workability, the reduction in water demand of
concrete due to fly ash is usually between 5-15 % by
comparison with the controlled mix of the concrete [8].
Normally concrete mixtures with fly ash will require less water
per cubic meter for a given slump than a mixture without fly
ash.
1
Vasu Krishna is a BTech.Civil Eng. Student, SRM University, DelhiNCR Campus, Ghaziabad (Email: [email protected])
2*
Dr Gajanan M Sabnis is a corresponding Author and Emeritus Professor,
Howard University, USA (Email: [email protected])
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International Conference on Civil and Architecture Engineering (ICCAE'2013) May 6-7, 2013 Kuala Lumpur (Malaysia)
1.2 Influence on hardened properties Increases the long
term strength
should be generally between 20-40 % of the total cementitious
material.
Although concrete mixtures containing fly ash tend to gain
strength at a slower rate than concrete without fly ash, the long
term strength (90 days and after) is usually higher [8]
Fig. 3 Expansion of the mortal in sodium sulphate soln. (Source:
CIRCA, Canada)
II. GROUND GRANULATED BLAST FURNACE SLAG (GGBS)
GGBS is a solid waste discharged by Iron and Steel
industries. It is a by-product for manufacture of pig iron and
obtained through rapid cooling by water or quenching molten
slag. Here the molten slag is produced which is
instantaneously tapped and quenched by water. This rapid
quenching of molten slag facilitates formation of “Granulated
slag. GGBS is processed from Granulated slag.
If slag is properly processed then it develops hydraulic
property and it can effectively be used as a pozzolanic
material. However, if slag is slowly air cooled then it is
hydraulically inert and such crystallized slag cannot be used as
pozzolonic material [6]. GGBS can be ground to a fineness of
any desired value but usually it is finer than Portland cement.
Increased fineness leads to increased activity at early ages [8].
Table given below shows the composition of GGBS:
Fig. 1 Effect of fly ash on compressive strength (Source: UNB,
Canada)
Pozzolonic reaction of fly ash is slow. The reactions of fly
ash are also affected by the properties of Portland cement with
which it is used [8].
Durability of fly ash Concrete
Since reaction of fly ash is slow in concrete, initially, the
concrete has higher permeability than controlled mix concrete.
However, with time, fly ash concrete exhibits very low
permeability. A concrete with 25% fly ash can have a
coefficient of permeability at least one order of magnitude less
than a concrete without fly ash. This leads to enhanced
durability as aggressive agents cannot attack the concrete from
within but are restricted to the concrete surface.
TABLE I
COMPOSITION OF GGBS (SOURCE: DUBEY, 2012)
COMPOSITION
PERCENTAGE
SiO 2
Al 2 O 3
Fe 2 O 3
CaO+MgO+P 2 O 5
SO 3
34.4
21.5
0.2
43.24
0.66
2.1 Influence on Fresh properties
The presence of GGBS in the concrete improves the
workability of the concrete. It improves the mobility of the
mix but cohesive also. This is due to surface characteristics of
the GGBS which are smooth and absorb little water during
mixing [8].Workability of the concrete mix containing GGBS
increases with the increase in surface are of the latter [9].
Fig. 2 Permeability of fly ash vs. controlled mix concrete (Source:
CIRCA, Canada)
Fly ash Concrete may contribute to the sulphate attack due
to presence of lime and alumina in the fly ash. However the
use of low lime fly ash (ASTM Class F) can increase the
sulphate resistance of the concrete. The content of the fly ash
2.2 Influence on Hardened Properties Strength evelopment
Concrete containing GGBS have long term strength
development (generally after 56 days or more). Because the
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International Conference on Civil and Architecture Engineering (ICCAE'2013) May 6-7, 2013 Kuala Lumpur (Malaysia)
initial hydration of GGBS is very slow. The progressive
release of alkalis by the GGBS, together with the formation of
Calcium Hydroxide by Portland cement, results in continuingreaction of GGBS over a long period [8]. Dubey et al [6]
reported that concrete containing GGBS up to 30% does not
show any increase in strength up to 28 days. Table shown
below can illustrate this:
TABLE II
EFFECT OF GGBS (UP TO 30%) ON THE COMPRESSIVE STRENGTH (SOURCE:
ATUL DUBEY, 2012)
Percentage of
GGBS
7 DAYS
14 DAYS
28 DAYS
0
5
10
15
20
25
30
21.0
3
20.
74
20.4
4
19.
85
18.
07
16.8
8
15.4
23.7
22.
8
22.6
6
22.
36
19.
5
18.5
1
16.7
4
26.9
25
24.5
9
22.
29
20.
88
20.7
4
Fig 5: Drying shrinkage of ggbs concrete with 0 to 180 days. (Source:
Neville, 2012)
Concrete containing GGBS are highly resistance to chloride
penetration. Table shown below shows the test results of
chloride penetration of the GGBS cement mortars:
TABLE III
CHARGES PASSED IN COULOMBS (SOURCE: FAPOHUNDA, 2010)
MIX
W/C Ratio
23.C
OPC
0.4
0.5
4700
9800
12000
13000
Slag
0.4
0.5
1300
1700
1500
2200
18.8
1
It is found that concrete containing 20-60% GGBS does not
achieve the desirable strength after 28 days of curing, where
similar or higher long term strength are obtained with that of
normal PC concrete. The proportions of GGBS and Portland
cement influence the development of strength of the resulting
concrete. For the highest medium term strength, 50% of GGBS
in the cementitious material has been used. But the early
strength is comparatively lower than with same content of
cementitious material consisting of Portland cement only.
50.C
The GGBS enhances durability of concrete is because of its
dense micro-structure and due to the pore space filled with CS-H rather than in Portland- cement- only paste. Due to this
Sulphate Resistance of GGBS concrete is much better than
ordinary cement concrete [8]. However to be effective, the
content of GGBS must be at least 50% by mass of the total
cementitious material (preferably 60-70%).
III. WASTE GLASS
It is estimated that about 7 % of the total solid waste
generated each year in USA consist of only waste glass [7].
Definitely for the entire world, it would be much more. But
unlike many of the other constituents, it does not decay and is
a permanent and often hazardous pollutant. Common glass
contains about 70% SiO 2 and others including Al 2 O 3 , CaO,
MgO etc. Crushed glass particles are generally angular in
shape and may contain some elongated and flat particles. The
degree of angularity and the quantity of flat and elongated
particles depends on the degree of crushing. Recycling glass
from the municipal solid waste stream for use as a raw material
in new glass products is limited because of the high cost of
collection and processing of waste glass (WSDTED, 1993). In
addition, during collection and handling of waste glass, high
percentage of glass breakage limit the quantity of glass that
can be actually recycled. Several Researches has been made to
utilize the waste glass in the concrete. The glass can either
used as aggregate (coarse/fine) or as a partial replacement of
cement. But the flat elongated particle shape of crushed glass
Fig 4: Compressive strength of GGBS concrete of various
percentages (Source: Neville, 2012)
Durability
The value of Drying Shrinkage of Concrete containing
GGBS are always much smaller than the Portland cement
concrete. Figure given below shows the test result of drying
shrinkage of concrete:
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International Conference on Civil and Architecture Engineering (ICCAE'2013) May 6-7, 2013 Kuala Lumpur (Malaysia)
However if waste glass are used as a Coarse aggregate
(10mm-20mm), the strength obtained are comparatively less
than the ordinary mix. Nevertheless, most of the values exceed
the minimum specified value for structural plain concrete.
and the physical and chemical nature of the surface do not
normally make crushed glass a very suitable for any type of
concrete. However, given an economic or environmental
incentive to dispose of the material, technical problems need
not necessarily prevent its successful utilization as aggregate.
3.1 Influence on fresh properties
Whether used as coarse or fine aggregate, waste glass
reduces the workability of the concrete mix. Using a high
proportion of waste glass decreases the slump value due to its
poor geometry. Waste Glass aggregate has sharper and angular
shape which results in less fluidity [7].
3.2 Influence
Development
on
Hardened
properties
Strength
It is stated that smaller is the size of the glass, the higher the
strength of the concrete. Modhera C.D. et al [10] showed that
strength of the concrete increases with the percentage in
replacement of the cement by the glass fines but up to certain
limit only. Table given below can illustrate this:
Fig 7: Waste glass as a replacement of coarse aggregate (Source:
Johnston)
(Note: size of the crushed glass is about 19mm)
TABLE IV
WASTE GLASS AS A REPLACEMENT OF CEMENT (SOURCE:
MODHERA, 2012)
Waste glass
Strength (N/mm2)
Percentage
0
27.33
5
28.87
10
30.08
15
31.85
20
33.86
25
30.82
30
35
40
Durability
Expansion is one of the major drawbacks concerned with
concrete containing waste glass. Several studies report that all
concrete with glass aggregates had always expanded and
cracked. Several publications state that expansion of cement
concrete containing mixed waste glass aggregate was due to
reaction between glass aggregate and alkalis from cement, like
traditional ASR [7]. However, it is found that use of low alkali
Portland cement does not reduce the expansion of concrete
made with crushed glasses. The expansion of concrete
containing glass aggregate is due to the imbibition of water by
its corrosion product N-C-S-H. In traditional ASR, reactive
silica reacts with alkalis in the cement to form N-C-S-H, which
adsorb water and cause expansion [3]. It is also found that
concrete containing waste glass are not much resistant to
Sulphate attack. Figure 8 shows the effect of Sulphate attack
on waste glass concrete
24.44
22.72
19.25
Figure given below explains the effect of size of glass waste
on the strength of the concrete:
Fig 8: Sulphate resistance of concrete, Controlled vs. glass powder
mix (Source: NBMCW, May 2012)
However according to Siddique, mineral additives (Silica
fumes, fly ash, glass powder) can reduce the expansion of the
concrete and improves the durability of concrete. Also size of
Fig 6: Effect of glass size on strength (Source: Siddique, 2010)
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International Conference on Civil and Architecture Engineering (ICCAE'2013) May 6-7, 2013 Kuala Lumpur (Malaysia)
the waste glass controls the expansion. The finer the particle
size, the lesser will be the expansion.
MK increases the Sulphate resistance of the concrete structure.
Khatib and Wild [14] evaluated the effect of MK on the
sulphate resistance of the mortar. Cement was replaced with 0,
5, 10, 15, 20 and 25% of Metakaolin. The specimens were
tested for sulphate attack (using 5% of Sodium Sulphate soln.).
It was observed that expansion decreased systematically with
increase in MK content.
Metakaolin reduces the chloride ion permeability of the
concrete structures. According to Poon et al [15], the amount
of chloride charges passing through MK concrete are lower
than the control. Also at higher w/b ratio, MK is more
effective than SF in improving the resistance of concrete to
chloride ion penetration.
IV. METAKAOLIN
Metakaolin (MK) is a pozzolonic material and is
manufactured from kaolin clay, which is a fine, white, clay
mineral that has been traditionally used in the manufacture of
porcelain. It is silica based product that, on reaction with
calcium hydroxide, produces CSH gel. It also contains
alumina. MK is a very fine material and is about 99.9% finer
than 16µm. Major constituents of MK are SiO 2 and Al 2 O 3.
4.1 Influence on Fresh properties
Workability of the concrete decreases with the inclusion of
MK and decrease in workability increases with the
replacement level. Brooks and Johari [14] reported the slump
and setting times of concrete containing 0, 5, 10 and 15% MK.
The results are given in the table below:
TABLE VII
CHARGE PASSED (COULOMBS) THROUGH SAMPLES (SOURCE: POON ET AL,
2006)
W/B
Mix
3D
7D
28D
Ratio
TABLE V
WORKABILITY OF MK CONCRETE AND CEMENT (SOURCE: BROOKS & JOHARI,
2001)
Percent of Replacement
Compressive Strength
(MPa)
0
87.0
5
91.5
10
104
15
103.5
0.30
0.50
4.2 Influence
on
Hardened
PropertiesStrength
Development
Compressive strength of concrete increases, if the MK is
replaced up to 30 %.[16]. It also contributes to the high early
age strength development. Table given below shows the
strength development of concrete containing MK
Slump
(mm)
Initial Setting
Time (Hours)
Final Setting
Time (Hours)
OPC
MK5
MK10
MK15
100
30
20
5
5
6.42
6.98
6.45
7.7
8.82
9.42
9.31
2461
1327
417
406
1060
567
2451
1244
347
395
945
445
1035
862
199
240
665
360
0%
5%MK
10%MK
20%MK
5%SF
5312
4215
1580
751
3156
4054
3765
1247
740
2067
2971
2079
918
640
1641
10%SF
3140
1877
1233
V. . WOOD ASH
The enormous amount of wastes produced during wood
processing operations in many countries provides challenging
opportunities for the use wood wastes as a construction
material. The physical and chemical properties of wood ash
depend upon several factors such as species of wood,
combustion temperature etc. The average particle size of wood
ash is about 230 µm [9]. The major chemical components
present in wood ash are SiO 2 , CaO, and Fe 2 O 3 . Wood ashes
have very less and slow pozzolonic activity however from
strength point of view, they are quite satisfactory.
TABLE VI
28 DAYS TEST RESULT OF MK CONCRETE (SOURCE: BROOKS AND JOHARI,
2001)
Mix
0%
5%MK
10%MK
20%MK
5%SF
10%SF
5.1 Influences on Fresh Properties
Strictly speaking, Wood ash reduces the workability of the
concrete whatever the percentage of replacement is. Udoeyo et
al [4] reported the slump test of concrete containing different
percentages (5, 10,15, 20, 25 and 30 by weight of cement) of
waste wood ash used as an additive in concrete. The values of
slump were 62,8,5,2.5,0,0,0 mm for concrete containing 0, 5,
10, 15, 20, 25 and 30% wood ash. It is evident from the results
that wood ash concrete mixes exhibited less workability than
that of plain concrete of same water cement ratio.
The higher surface area Metakaolin yielded the highest
strength and the fastest rate of strength gain. The positive
influence of the Metakaolin fineness on compressive strength
was more apparent at the later ages (i.e. 7 days or more).
Furthermore, the 3 days strength at 10% and 15% Metakaolin
replacement are large than the 28 d strength without
Metakaolin, confirming that Metakaolin has a pronounced
influence on early strength [16].
Durability
Sulphate attack is one of the most aggressive deteriorations
that affect the long-term durability of concrete structures.
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International Conference on Civil and Architecture Engineering (ICCAE'2013) May 6-7, 2013 Kuala Lumpur (Malaysia)
[7]
5.2 Influence
on
Hardened
propertiesStrength
Development
Udeoyo et al [4] determined the compressive strength of
concrete made with various percentage of waste wood ash.
They reported that compressive strength generally increased
with the age but decreased with the increase in wood ash
content. A possible explanation for this trend is that wood ash
acts more like filler in the matrix than as a binder. However
there is a improvement in strength of wood ash concrete (up to
20% replacement level) after 90 days. This is due to weak
pozzolonic activity and fine filler effect.
[8]
[9]
[10]
[11]
[12]
[13]
Durability
Naik [12] investigated the drying shrinkage of concrete
mixture made with wood ash. Wood ash percentage was 5, 8
and 12. He concluded that mix containing more wood ash has
more drying shrinkage. However there is not much effect on
the wood ash concrete due to freezing and thawing.
[14]
[15]
[16]
VI. CONCLUSIONS
1. Utilization of Industrial waste and by-products can
contribute to sustainable development.
2. Fly ash improves the workability of the concrete, but
results in higher strength than normal concrete later. This
property is useful in mass concrete.
3. GGBS improves the workability of the concrete mix. Up
to 30% GGBS does not show much improvement in
strength but more than 30% significant long term strength
is developed.
4. Metakaolin decreases the workability of concrete. It
increases the strength of concrete especially after 7 days.
Metakaolin up to 15% is sufficient to increase the strength
and durability.
5. Waste glass reduces the workability of the concrete. Glass
fines can increase the strength but up to certain percentage
of replacement of cement only. Durability of concrete
containing waste glass can be affected due to expansion.
6. Wood ash lowers the workability of the concrete. Strength
is also lowered with increase in percentage of the wood
ash. However wood ash concrete is not much affected by
freezing-thawing.
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[2]
[3]
[4]
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