Utilisation of
Waste Plastic Bags in
Bituminous Mix for
Improved Performance of Roads
Centre for
Transportation Engineering, Bangalore University, Bangalore, India [Unpublished]
Apr02
By
Prof. C.E.G. Justo Honorary Professor, Bangalore University Bangalore and
Dr. A. Veeraragavan Co-ordinator, Centre for Transportation Engineering,
Bangalore University, Bangalore - 560 0056
1. INTRODUCTION
The growth in various types of industries together with population growth has
resulted in enormous increase in production of various types of waste materials,
world over. The creation and disposal of non-decaying waste materials such as
Blast Furnace Slag, Fly-ash, Steel Slag, Scrap Tyres, Plastics, etc. have been
posing difficult problems in developed as well as in developing countries.
Considerable work has been done in various countries for the disposal of some of
these waste products and utilisation of some other products and there is a long
list of published literature dealing with different aspects of these challenging
problems(1). Attempts are still being made by various organisations and
researchers to find methods for effective utilisation of some of these waste
materials. Of these, the efforts to find useful applications of some of the
waste products in highway construction have given encouraging results (1). The
work done in India, particularly at the Central Road Research Institute (CRRI),
New Delhi on the use of waste materials like Fly-ash and Slag in road
construction is note worthy.
The use of thin plastic bags to pack and to carry various materials including
house hold articles has become a common practice all over the country. However
the disposal of the waste plastic bags in large quantities has been a problem
and is of great concern, particularly in big cities. The mixing up of these
waste plastic bags with other bio-degradable organic waste materials in the
garbage of the urban areas has been the main cause of the problem. Therefore
attempts are being made in some cities to limit or even to prohibit the use of
the thin plastic bags for packing and other common use, so as to control this
"undesirable waste material" from getting mixed up with the other
organic garbage.
In case it is possible to find useful application for the waste plastic bags,
there will be substantial scrap value for this waste product and therefore they
will be collected and sold by interested persons, instead of being littered or
thrown out in the dust bins or into the road side drains.
At the initiative of M/s K.K. Poly Flex Pvt. Ltd., a study on the possible
use of the processed plastic waste bags with the bituminous mixes was carried
out at the R.V. College of Engineering Bangalore. A group of students of B.E.
degree course in Chemical Engineering of this college under the guidance of the
concerned teaching staff carried out their final year project work for studying
the possibility of using of the processed plastic bags with bitumen and
bituminous mixes(2). As some encouraging results were reported in this study,
M/s K.K. Poly Flex Pvt. Ltd. later approached the Centre for Transportation
Engineering of Bangalore University with the request to carry out further
research studies on the effects of using the processed plastic bags with
bituminous mixes for road construction works. This company supplied the
processed plastic material and they also helped the Centre for developing some
additional facility to test the bituminous mix specimens under controlled
temperature.
2. USE OF RE-CYCLED PLASTICS AS ADDITIVES IN BITUMINOUS MIXES
It has been possible to improve the performance of bituminous mixes used in
the surfacing course of road pavements, with the help of various types of
additives to bitumen such as polymers, rubber latex, crumb rubber- treated with
some chemicals, etc. Some limited studies have been reported on the use of
re-cycled plastic, mainly polyethylene, in the manufacture of polymer - modified
asphalt cement or bitumen. According to Larry Flynn (3), re-cycled polyethylene
from grocery bags may be useful in asphaltic (bituminous) pavements, resulting
in reduced permanent deformation in the form of rutting and reduced low -
temperature cracking of the pavement surfacing.
Salah E. Zoorob (4) and Zoorob and Suparma (5) have shown that re-cycled
plastics composed predominantly of polypropylene and Low Density Polyethylene
can be incorporated into conventional asphaltic (bituminous) road surfacing
mixtures. Greater durability and fatigue life have been reported in these
modified mixes as compared to conventional mixes.
3. RECENT STUDIES ON THE USE OF PROCESSED PLASTIC BAGS IN BITUMINOUS
CONCRETE MIXES
3.1 General Findings
Laboratory studies were carried out at the Centre for Transportation
Engineering of Bangalore University on the possible use of the processed plastic
bags as an additive in bituminous concrete mixes(6). The material used in this
study was supplied by M/s KK Poly Flex (P) Ltd., Bangalore. The processed
plastic was used as an additive with heated bitumen in different proportions (
ranging from zero to 12 % by weight of bitumen) and mixed well by hand, to
obtain the modified bitumen.
The properties of the modified bitumen were compared with ordinary bitumen.
It was observed that the penetration and ductility values of the modified
bitumen decreased with the increase in proportion of the plastic additive, up to
12 % by weight. The softening point of the modified bitumen increased with the
addition of plastic additive, up to 8.0 % by weight.
Studies were carried out on Bituminous Concrete (BC) mixes using 80 / 100
grade bitumen having average Marshall Stability Value (MSV) of 1100 kg at
optimum bitumen content of 5.0 % by weight of the mix. Further studies on BC
mixes were carried out using the modified binder obtained by the addition of
varying proportions of processed plastic bags (percentage by weight of bitumen)
with the conventional 80 /100 grade bitumen. The optimum modified binder content
fulfilling the Marshall mix design criteria was found to be 5.0 % by weight of
the mix, consisting of 8.0 % by weight of processed plastic added to the
bitumen. The average MSV of the BC mix using the modified binder was found to be
as high as 3312 kg at this optimum binder content, resulting in about three fold
increase in stability of the BC mix, which contains 4.6 % bitumen plus 8 %
processed plastic by weight of bitumen, i.e., 0.4 % processed plastic by weight
of the mix.
In order to evaluate the ability of the BC mix prepared with the
above-modified bitumen to withstand adverse soaking condition under water,
Marshall stability tests were conducted after soaking in water at 60 Co
for 24 hours. The average MSV of the BC mix with modified binder (using 8 %
processed plastic by weight of bitumen, as above) was found to increase by about
2.6 times of the mix with ordinary bitumen. Further laboratory studies carried
out on the BC mixes using this modified binder also indicated note worthy
increase in fatigue life under repeated application of loads.
Thus the laboratory investigations carried out so far at Bangalore University
have given highly encouraging results for the use of bituminous concrete mixes
in the surfacing course of road pavements by using this modified binder which is
prepared by the addition of 8.0 % of the processed plastic, by weight of
bitumen. 3.2. Advantages of Using Modified Bitumen with Processed Plastic as
Additive
i) The use of modified bitumen with the
addition of processed plastic, about 8.0 % by weight of bitumen, helps in
substantially improving the stability or strength, fatigue life and other
desirable properties of bituminous concrete mix, even under adverse
water-logging conditions. Therefore the life of the pavement surfacing
course using the modified bitumen is also expected to increase
substantially in comparison to the use of ordinary bitumen.
ii) The addition of 8.0 % by weight of
processed plastic for the preparation of modified bitumen results in a
saving of 0.4 % bitumen by weight of the mix or about 9.6 kg bitumen per
cubic metre (m 3) of BC mix. This results in a saving of about Rs.110 per
m 3 of BC mix based on the present cost of 80 / 100 grade bitumen, ( as of
June, 2001 ).
iii) The effective utilisation of the waste
plastic bags for the preparation of modified bitumen will result in
substantial increase in the scrap value for this other wise
"undesirable waste material", which are getting littered all
over the urban areas. These waste plastic bags will not therefore be
thrown out along with the garbage; instead they will get collected and
sold by the consumers themselves or other agencies, due to the attractive
scrap value.
4. NEED FOR FURTHER WORK
It is necessary to work out a project proposal to carry out further studies
on various aspects such as collection, processing and effective utilisation of
this waste material. To start with, such a study could be initiated in
Bangalore, with the following components :
i) Estimation of the types, quantity and
useful components present in the waste plastic materials in the city and
surrounding areas
ii) Methodology for collection and sorting out
the useful components of the plastic waste
iii) Methodology for processing the plastic
bags as required for use in the preparation of modified bitumen, including
cleaning, shredding and further processing of the plastic waste materials
iv) Identification of two or three
construction companies / entrepreneurs who could incorporate appropriate
mixing units in their bitumen boiler / hot mix plant to add and mix the
required proportion of the processed plastic additive
v) Carrying out further laboratory
investigations, construction of some test tracks and field studies on the
performance of pavements using the modified bitumen
vi) Working out relative economics of using
the modified bituminous mixes in road construction works, considering the
improved performance and increased service life of the pavement
vii) Preparation of specifications and
standards for the construction industry.
It is hoped that on completion of the above project, the plastic waste
materials will be put to effective use in road construction industry, resulting
in improved road pavements and also relief from the waste plastic materials
being littered all around urban areas.
5. SOME SELECTED REFERENCES
1. Robin L Schroeder, "The Use of Recycled
Materials in Highway Construction", Journal, Public Roads, Vol. 58, No.
2 (1994 )
2. Amjad Khan, Gangadhar, Murali Mohan and Vinay
Raykar, "Effective Utilisation of Waste Plastics in Asphalting of
Roads". Project Report prepared under the guidance of R. Suresh and H.
Kumar, Dept. of Chemical Engg., R.V. College of Engineering, Bangalore,
1999.
3. Larry Flynn, "Recycled Plastic Finds
Home in Asphalt Binder", Journal, Roads and Bridges, March 1993
4. Zoorob S.E. and Suparma, L.B.,
"Laboratory Design and Investigation of Proportion of Bituminous
Composite Containing Waste Recycled Plastics Aggregate Replacement
(Plastiphalt), CIB Symposiumon Construction and Environment Theory into
Practice, Sao Paulo, Brazil ( November, 2000 )
5. Zoorob, S.E., "Laboratory Design and
Performance of Improved Bituminous Composites Utilising Plastics Packaging
Waste", Conference on Technology Watch and Innovation in Construction
Industry, Belgium, Building Research Institute, Brussels, Belgium (April,
2000)
6. Research Work at the Centre for
Transportation Engineering, Bangalore University during the year 2000 - 2001
and the Seminar Report on "Study of the Effect of Plastic Modifier on
Bituminous Mix Properties" by V.S. Punith, II Semester, M.E. (Civil)
Highway Engg., Dept. of Civil Engineering, Bangalore University (March,
2001)
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