1. Full Paper
©2012ACEE
DOI:02.ADCS.2012.1.
Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012
506
Effect ofUse ofRecycled ConcreteAggregates in
BituminousConcreteSurfaceCourse
Gurukanth S1
, Donal Nixon D’souza2
, Avinash Babu S3
, Vivek A K4
and Dr.Srikanth M Naik5
1
UG Student, Department ofCivil Engineering, MSRIT, Bangalore, India.
Email: guru_kanth@hotmail.com
2
UG Student, Department ofCivil Engineering, MSRIT, Bangalore, India.
Email: donalnixon@gmail.com
3
UG Student, Department ofCivil Engineering, MSRIT, Bangalore, India.
Email: avinashbabu123@gmail.com
4
UG Student, Department ofCivil Engineering, MSRIT, Bangalore, India.
Email: vivekakannan15@gmail.com
5
Professor, Department ofCivil Engineering, MSRIT, Bangalore, India.
Email: srikanth_naik@yahoo.com
Abstract—India has a road network of over 4.32 million
kilometres as of 2011, the third largest road network in the
world. However, qualitatively Indian road network are a mix
of modern highways, narrow paved roads & unpaved roads. As
of 2008, 49% i.e. 2.1 million kilometres of Indian roads are
paved. India plans to spend approximately 70 billion USD by
2013to modernize its road network. Several projects like
Pradhan Mantri Grama Sadak Yojana (PMGSY) have been
initiated by Government of India to upgrade rural roads to
black top surface roads.
Aggregates form a bulk of the material required for
bituminous concrete pavements. Aggregate being a natural
material is being fast consumed and is causing a shortage of
resources required for rapid infrastructure development. Also
on the other side with the new trends in construction industry
there is a generation of solid waste in the form of demolished
structures. Cement concrete being a non biodegradable
element is a challenge to dispose.Generally demolished
concrete ends up in landfills. However with new environmental
regulations and limited space available, concrete disposal has
been a major environmental challenge.Today, science and
technology has a responsibility of innovating new trends which
are both economical and ecofriendly. Old demolished concrete
structures can be recycled to obtain recycled aggregate (RA).
This can be used along with the natural aggregates effectively
in various infrastructure need so that we attain a balance
between demand and supply of construction material thereby
reducing the impact on nature.
The present investigation aims in the strength variation
of bituminous concrete surface course in which recycled
aggregates are used in partial or full replacement of natural
aggregates. Marshall’s method is used to study the strength
variations in bituminous concrete surface course with
replacement of natural aggregates with recycled aggregates.
It was found that replacement of natural aggregates by recycled
aggregates upto 20% is possible in bituminous concrete surface
course without significant impact on the strength
characteristics. However there is an increase in the binder
content for which there is a need to study the economic value
of the replacement.
Keywords— Bituminous concrete surface course, Recycled
aggregate, Marshall’s method.
I. INTRODUCTION
Aggregate form a major portion ofthe pavement structure
and they form the prime material used in pavement
construction. Aggregates have to bear stresses occurring
due to the wheel loads on the pavement and on the surface
course they have to resist wear due to abrasive action of
traffic. These are used in pavement construction in cement
concrete, bituminous concrete and other bituminous
construction and also as granular base course underlying
the superior pavement layers.
Most of the road aggregates are prepared by crushing
natural rock. Natural materials are of limited availabilityand
its quantities are declining rapidlycreating an acute shortage.
It is estimated that 750 million cum of aggregate would be
required for achieving the targets of the road sector [1].
Researchers are looking for alternative materials for highway
construction which are economical and ecofriendly. Concrete
recycling is becomining an increasinglypopular waytoutilize
the aggregate left behind when structures and roadways are
demolished [2]. In the past, this rubble was disposed off in
landfills, but with more attention being paid toenvironmental
concerns, with existing woes of solid waste management
system and an aim towards sustainable development.
Re-utilization or recycling seems to be an attractive
alternative and an important strategyfor management ofsuch
waste which could flourish as a good business, if done in a
proper manner. For further utilization of recycled aggregates,
a proper study needs to be done for its use in the construction
and infrastructure projects. Recycling of concrete not only
allows the reuse of the rubble, but also helps in conserving
the natural resources, reducing the construction costs.
Recycled aggregates (RA) can be obtained from crushed
concrete rubble (from C & D wastes) comprising of crushed
and uncrushed parent aggregate coated with mortar and small
pieces of hardened mortar.
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2. Full Paper
©2012ACEE
DOI:02.ADCS.2012.1.
Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012
506
II. RECYCLING OF CONSTRUCTION AND DEMOLITION WASTES
Wastes arising from construction and demolition (C & D)
constitutes one of the largest streams in many countries. It
has been estimated that approximately 180 million tons of
construction and demolition wastes are produced every year
in the European Union. Germanyis the leading producer ofC
& D waste with 77 million tons followed by United Kingdom
with 30 million tons. It is estimated that the construction
industryin India generates about 10-12 million tons ofwaste
annually [3]. Demolished building waste contains cement
concrete, bricks, cement plaster, steel, stone, timber, piping,
electrical fixtures, panels and glass. Minor components like
steel, piping and electrical components goes to the scrap
yard where as bulk material like concrete ends up in landfills
and land reclamation sites.
Concrete and masonry waste can be recycled by sorting,
crushing and sieving into recycled aggregates. These
recycled aggregates can be used to make concrete for road
construction and building material. Recycling of concrete
and masonry waste is verywell done in developed countries
like U.K., USA, France, Denmark, Germanyand Japan.
According to a study commissioned by Technology,
Information, Forecasting and Assessment Council (TIFAC),
70% of the construction industry in India is not aware of
recycling techniques. However work on recycling of
aggregates has been done at Central Building Research
Institute (CBRI) Roorkee.
Aggregates from concrete can be easily recycled by
crushing the concrete in a rock crusher after removing all the
reinforcement. The crushed concrete is sieved in a mechanical
sieve and sorted out. The recycled aggregates are then
washed to remove all dust and fine particles.
III. LITERATURE REVIEW
Rapid industrialization and urbanization in the late 80’s
created a great boom in the construction industry of India,
this caused a rapid decline of natural aggregates causing a
serious shortage of raw materials. This initiated research in
the field of recycling and reusing of waste materials in the
construction industry. However research was more focused
on using recycled aggregates in cement concrete mixes
[2][4][5][6]. The findings from the recent experimental
investigation showed that for recycled aggregates (RA),
physical properties namely the specific gravity and bulk
density are relatively low and water absorbtion is high in
comparison with that of the natural aggregates (NA).
The quality of old adhered mortar in governing the
increase or decrease in value specific gravity and water
absorbtion. The size and quantity of old adhered mortar
enveloping the recycling aggregate increases with the
increase in the strength of parent concrete due to relatively
higher bond between the aggregate and low density mortar
phase. Therefore, results show that the higher quantity of
mortar adhering to the recycled aggregate lead to higher
reduction in specific gravityof the recycled aggregate which
in turn results in reduced quantity of coarse aggregate to be
used in recycled aggregate concrete (RAC) [6][7][8][9]. Also
it was observed that the water absorbtion value was
significantlyhigh [5][7] for recycled aggregate which maybe
due to the type and maximum size of the parent aggregate
used in parent concrete, strength of the parent concrete [7]
and due to mortar phase having higher porosity than that of
the aggregate phase in recycled aggregate [7][9].
In the pavement sector, recycled aggregates have used
from ReclaimedAsphaltic Pavements (RAP)in hot mixasphalt
(HMA) since 1980 [10]. This has generally been used by
various state transport agencies in the United States. The
use of RAP also decreases the amount of waste produced
and helps to resolve the disposal problems of highway
construction. In 1996, it was estimated that about 33% of all
asphaltic pavements in the United States was recycled into
HMA [11]. In 2001, the Illinois department ofTransportation
(IDOT) used 623,000 tons of RAP in highway construction
and anticipates increasing its use in the near future [12]. After
more than 30 years since its first trial in Nevada and Texas, it
appears that the use of RAP will not only be a beneficial
alternative in the future but will also become a necessity to
ensure economic competitiveness of flexible pavement
construction.
Recycled aggregates obtained from demolished building
waste material can be effectively utilized for base and sub
base construction of road projects [13]. Use of recycled
aggregates in sub base can reduce the construction cost by
40% [14]. However no work has been done on the use of
recycled aggregates in bituminous concrete surface course.
IV. MATERIAL USED
A. Aggregate
Natural aggregates used in the studywere obtained from
local quarry in Yelahanka, Bangalore North. Aggregate
passing 20mm sieve was used and its physical properties are
given in table (I). Rock dust available in the quarry was used
as filler material. Recycled aggregate was obtained from the
demolished waste concrete from the demolished old medical
blockof M.S.Ramaiah Medical College, Bangalore, which was
around 30 years old at the time of demolition.
Only concrete was used and no brick masonry was used.
Concrete beams and slabs of the demolished material were
broken down with the help of a jackhammer drill to remove
reinforcements.The concrete was then crushed in the crusher
to obtain recycled aggregates. The aggregates were washed
in running water to remove impurities and later soaked for
24hours before drying at room temperature. Powdered mortar
obtained from demolished material is used as filler material.
Material passing 20mm is used and its physical properties
are given in table (I).
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3. Full Paper
©2012ACEE
DOI:02.ADCS.2012.1.
Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012
506
TABLE I. PHYSICAL PROPERTIES OF THE AGGREGATES USED
B. Bitumen
The type of bitumen plays a very important role in the
performance of bituminous concrete mixes. For all studies
conducted paving grade bitumen [VG-10] is used. Physical
& engineering properties of bitumen are given in table (II).
TABLE II. PHYSICAL PROPERTIES OF BITUMEN
Bituminous mixes with varying dosages of binder bitumen
are prepared. For different dosages of bitumen content 3
specimens are prepared and average values are taken.
Marshall Test is conducted as per IRC specification and the
stabilityofthe mix is assumed. Theoptimum amount ofbinder
is arrived at considering i)maximum stability ii)maximum
density iii) median of designed limits of percent air voids in
total mixture (4%).
Figure 1. Marshall Mould
Graphs of Marshall stabilityv/s percentage bitumen, flow
value v/s percentage bitumen, unit weight v/s percentage
bitumen, percentage air voids in the mixture v/s percentage
bitumen and percentage air voids filled with bitumen v/s per-
centage bitumen are plotted for different mixes tounderstand
the effect of replacement of natural aggregate with recycled
aggregate in bituminous concrete surface course.
TABLE III. IRC SPECIFIED GRADATION OF AGGREGATE FOR BITUMINOUS CONCRETE
SURFACE COURSE [15][16][17]
TABLE IV. DETAILS OF THE MIXES TRIEDV. TESTING PROGRAM
All materials used for the investigation are subjected to
basic material testing to evaluate engineering and physical
properties. Marshall Test is used to evaluate the effect of
recycled aggregate in bituminous concrete surface course.
The gradation used for testing is given in table (III) which is
specified by IRC. Rothfutch’s method is used to obtain
aggregates of desired gradation. Seven different mixes were
tried C, M1, M2, M3, M4, M5, M6. The amount of natural
aggregate was replaced by recycled aggregate in different
proportions. The table (IV) gives in detail the quantity of
natural and recycled aggregates in the mixture.
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©2012ACEE
DOI:02.ADCS.2012.1.
Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012
506
VI. ANALYSIS OF TEST RESULTS
TABLE V. MARSHALL’S TEST RESULT FOR MIX C
TABLE VI. MARSHALL’S TEST RESULT FOR MIX M1
TABLE VII. MARSHALL’S TEST RESULT FOR MIX M2
TABLE VIII. MARSHALL’S TEST RESULT FOR MIX M3
TABLE IX. MARSHALL’S TEST RESULT FOR MIX M4
TABLE X. MARSHALL’S TEST RESULT FOR MIX M5
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©2012ACEE
DOI:02.ADCS.2012.1.
Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012
506
TABLE XI. MARSHALL’S TEST RESULT FOR MIX M6
Figure 2. Marshall Stability v/s percentage bitumen
Figure 3. Flow v/s percentage bitumen
Figure 4. Unit weight v/s percentage bitumen
Figure 5. % voids in total mix v/s percentage bitumen
Figure 6. %voids filled by bitumen v/s percentage bitumen
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6. Full Paper
©2012ACEE
DOI:02.ADCS.2012.1.
Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012
506
TableXII. Marshall Properties Of Different Mixes At Optimum
Bitumen Content
Figure 7. Percentage loss in Marshall Stability with increase in
replacement of natural aggregates
TABLE XIII. DESIRED MARSHALL MIX DESIGN CRITERIA FOR BITUMINOUS
CONCRETE [IRC]
Figure 8. Percentage increase in bitumen content with increase in
replacement of natural aggregates
DISCUSSION & CONCLUSION
By implementing this technology, the amount of waste
materials finding their way into landfills will be reduced
through usage of recycled aggregate. This will therefore
reduce the amount of quarrying therebyextending the life of
natural resources thereby preventing the environmental
degradation.
Using recycled aggregates in the construction ofbituminous
concrete surface course is economically feasible.
From table (I) containing the test results of the properties
of the aggregates, it is apparent that all values are within the
permissible limits prescribed for each test with the exception
of water absorption, which appears to be higher than the
limits. This is mainlydue to the residual mortar coating to be
found on the recycled aggregates which enhances water
absorption.
From table (II) containing the test results of the bitumen
(VG-10) used, it is apparent that all values are within the
permissible limits prescribed for each test.
Recycled aggregates are found to be inferior to the natural
aggregates
With increase in recycled aggregate content, the Marshall
Stability decreases.
With increasein recycled aggregatecontent, optimum binder
content increases.
With increase in recycled aggregate content, dry densityof
bituminous concrete decreases.
Air voids in mix is found higher in mixes containing more
recycled aggregates.
The efficiencyofvoids getting filled with bitumen decreases
with increase in recycled aggregate content.
From figure (2) to figure (6), it can be observed that the
behaviour of the materials byvarying percentage increase in
bitumen content and replacement of natural aggregates,
shows uniform curve characteristics regardless of the mix.
As per table(XIII) recycled aggregates can be effectively
replace natural aggregates by 20% as there is no significant
reduction in Marshall stability & no large increase in binder
content.
Flowvalueat OBCreduces with higherreplacement ofnatural
aggregates by recycled aggregates.
However, fatigue behaviour & durability studies need to be
conducted before implementation.
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©2012ACEE
DOI:02.ADCS.2012.1.
Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012
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