CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND
The pure water Sachet menace is common to all the markets, commercial centres and other controls of activities all over Rivers State and indeed Nigeria. The problem is essentially spawned by the growing business of packaging small quantities of water in sealed nylon for sale to the public, which began some years ago. But there is no well thought–out plan of what to do with the sachet after its contents has been consumed. The problem is further compounded by the improper waste disposal culture of Nigerians. Hence, many simply throw the sachets on the streets after consuming the water. The pure water sachets are categorized into solid waste.
Solid wastes are man’s unwanted material that cannot flow directly into the streams or rise immediately into the air. They are non-liquid, non-gaseous residue of our manufactories, construction, cooking, recreation, agriculture, industrial, and other activities that use and then discard materials. Included are Blast furnace slag, scrap tyres, plastics, metal cans glass abandoned automobiles, demolition rubbles, flyash, dewatered sewage sludge, and the garbage from our dining tables, etc. The numerical increase in these waste materials are attributable to the increased in population and poor waste management consciousness. Many of these waste (scrap tyres, glasses, plastics, etc.) produced today will remain in the environment for hundreds and perhaps, thousands of years if not properly managed.
Objections to the growing piles wastes in our environment commonly fell into five categories; public health, aesthetics, occupation of space, collection-processing cost, and degradation of natural resources, all of which represents form of economic costs since they will now or later detract from our opportunities to enjoy life. Solid wastes that are mishandled can harbor disease carrying agents, becomes air and water pollutants, and pose serious safety hazards both for the general public and for professionals engaged in waste collection and processing. The blockage of drains by these waste materials, especially plastic bags, and the resultant effects of flood is a serious matter of concern to the health of humans, as insects that cause disease breed in such environment. Solid wastes, irrespective of their generation mode, are visible and durable upon our landscape. Trash and garbage are sprinkled along highways. And open dumps used by municipalities contrary to accepted rules of public health and aesthetics provide eyesores and odours for nearby citizens. Besides being unsightly, waste occupy valuable space, especially now that agricultural awareness is being reawakened in Nigeria, it is necessary that scarce land be conserved as much as practicable. In light of this, open land fill dumping, pitfalls and land fill methods may be regarded as wasteful ventures in view of valuable agricultural land. Even when practiced, solid waste disposal should be aimed at maximizing of volume reduction prior to landfills to enhance the life span of fill.
The shift to the use of plastic and fibre substitutes in packaging and industries has continued to grow. As a result, most rural and urban solid waste contains significant qualities of non-compositing plastic waste. Nigeria is no exception to the changing trend in plastic waste composition in both rural and urban solid waste collection pools.
Furthermore, the Federal Government’s positive stride in the petrochemical sector has escalated the use of plastic material and subsequent generation of large quantities of plastic waste. Thus, if urgent and vigorous measure is not taken to avert the trend, the nation will be overwhelmed by plastic wastes of which they are non-decompositing. Incineration which seems to be better waste disposal method fails in handling plastic waste as toxic gas; hydrochloric acid (Hcl) and chlorine gas are emitted in the process. A waste plastic disposal method which eliminates contaminated combustion residues and maximizes solid waste volume reduction is pyrolysis. Essentially, pyrolysis is the thermal degradation of material (plastic) in the absence of air. Thus, this project “suitability of pellets produced from waste plastic bags as aggregate for asphalt cement concrete” seeks to drive at the back of pyrolysis to produce plastic pellets which are synthetic lights-weight aggregate.
Generally, highways and roads demand enormous amount of material for its construction. The necessity for earth- based –material creates impacts of resource depletion, environmental degradation and energy consumption. Waste materials can replace some of the natural materials used in highway construction; such alternative material protects the environment by conserving natural resource including the land from mining and landfills. Benefits also includes economic development opportunities and reduced pollution hazard.
Finally, haul cost is the single largest variable in determining the cost of aggregate in road construction; substantial amount of cost will be saved if a partial replacement is deviced for using pelletized plastic as aggregate.
1.2 DEFINITION OF PROBLEM
The use of thin plastic bags, to package and carry items including household article has become a common practice the world over. However, the disposal of these waste, plastic bags has been a problem and is of great concern, particularly in big cities, as many of these wastes produce today will remain in the environment for hundreds and perhaps thousands of years. The mixing up of these waste plastics bags with other biodegradable organic waste material in the garbage has been the main cause of the problem.
As a result of the poor management of waste in the developing countries leading to the excessive proliferation of waste plastic bags, there arose the need to recycle this waste into a useful product. One of such is in highway engineering, hence this study is geared toward investigating the suitability of pellet produce from waste plastic bags as aggregate for asphalt concrete.
1.3 OBJECTIVES OF STUDY
The objective of the study are as follows:
(i) To provide asphaltic concrete incorporating plastic aggregate as structural constituents.
(ii) To reduce plastic waste, thereby prolonging life span of landfills.
(iii) To investigate the effect of pellets in asphalt and recommend specification for their use as aggregate.
(iv) To investigate, using Marshall design method the effects of the waste plastic aggregate in asphaltic concrete
1.4 SCOPE OF WORK
The study assesses the stability and flow of asphaltic concrete involving partial substitute of pellets as coarse aggregate. Marshall design method was adopted to assess the effects of 0, 2, 4, 6, 8, 10 and 12 percent plastic pellet by weight of conventional coarse aggregate. Zero percent pellet content in the asphalt cement concrete is used as control.
CHAPTER TWO
2.0 LITERATURE REVIEW
The performance of bituminous mixes used in surfacing course of road pavement is verified and improved with the aid of various types of additive to bitumen such as polymers, rubber latex, crumb rubber treated with some chemicals. Studies have been reported on the use of recycled plastic, mainly polyethylene, in the manufacture of polymer modified asphalt cement or bitumen. The center for Transportation Engineering Bangalore University contributed in the possible use of processed plastic bags supplied by M/s KK poly Flex (p) ltd, as additive ranging from zero to twelve percent by weight of bitumen to obtain a modified bitumen. The properties of the modified bitumen, when compared to ordinary bitumen, indicated that penetration and ductility value of the modified bitumen decreased with increase in proportion of the plastic additive up to twelve percent by weight. The softening point of the modified bitumen increased with the addition of plastic additive, up to eight percent by weight. Further studies carried out on the bituminous concrete mixes using 80/100 grade bitumen for both ordinary and modified bitumen resulted in the same optimum bitumen content of five percent by weight of the mix and largely deviated value of the average Marshall stability value (MSV) of 1100kg and 3312kg respectively, resulting in about three fold increase in stability of the bituminous mix in favour of the modified.
The addition of eight percent processed plastic has recorded tremendous saving of 0.4 percent bitumen by weight of the mix or about 9.6kg bitumen per cubic meter (m3) bituminous mix. Wami, E.N., Emesiobi, F.C and Ugoha, V.I.P. (2004) have confirmed the physical and mechanical qualification of pellets produced from waste plastic bags as coarse light weight aggregate with low water absorption capability attribute.
The need to involve waste plastic in bituminous mixes cannot be over emphasized. Larry Flynn (1993), opined that recycle polyethylene from grocery bags maybe useful in asphaltic pavements resulting in a reduced permanent deformation in the form of rutting and reduced low-temperature cracking of the pavement surfacing. Worried about the inconvenience/discomfort of this plastic waste material, the Lagos State Government (2006) initiated the purchase of four recycling machine worth N2.7 million each and a buy-back programme to combat the nuisance of improperly disposed nylon water sachet. S.E. Zoorob and Suparma (2000) have shown that recycling plastic composed predominantly of polypropylene and low density polyethylene can be incorporated into conventional asphalt road surfacing mixture achieving greater durability and fatigue life. Jew et al (2003), asserted that the use of polyethylene modified asphalt concrete mix displayed curious increases in both Marshall flow and Marshall stability values conversely, Hassani et al (2005) reported a decrease in flow value. Furthermore, Robert et al (1994) post that the improved properties of asphalt are as a result of the spread of long chain polymer molecules which creates an interconnecting matrix of the polymer through the bitumen. In Nigeria, Njiribeako (2003), developed a procedure for managing solid plastic waste as a large scale commercial venture and suggested the adoption of pyrolysis as an alternative to incineration of plastic waste materials. In the same direction, Ojolo et al (2004) carried out the pyrolysis of shredded plastic wastes and observed that 0.025dm3 of tar oil could be produced form 1kg of plastic waste leading to about 85.25 reduction in waste volume. Collins and Ciesielski (2003), carried out research on the use of recycled plastic in highway construction. The use of virgin polyethylene as an additive to asphaltic concrete is not new, however, two processes also use recycled plastic as asphalt cement additive, NOVOPHALT(R) and POLYPHALT(R). These two processes both use recycling low-density polyethylene resin, which is generally obtained from plastic trash and sandwich bags.
The Federal Highway Administration (1993) approved the use of guardrail offset block made of 100 percent recycled wood and plastic, although the initial cost is higher than the conventional block material, but it resist damage and deterioration better than the conventional material, thereby resulting in reduced overall life-cycle cost. Similarly, Horner (1993), a Carson City Nev company is marketing a noise wall that contains recycled tyres and plastic. The wall’s shell is made of a protruded thermosetting composite of polyester and glass and the fill section is made of ground, recycled plastic rubber tyres. Eng. (1993) of Alberta transportation and utilities initiated a research project on the use of recycled plastic fence and guardrail posts. These posts were purchased and distributed to districts throughout the province as alternatives to wood posts. The cost of these plastic fences and guardrail post was somewhat higher than for corresponding wood posts.
Research in the branch of using pelletized plastic as aggregate in asphalt cement concrete is entirely new and it holds a fortune for the construction industry.
REFERENCES
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American Association of State Highway and Transportation Officials, (1993): Sub-committee on Construction Quality, “Use of Waste Materials in Highway Construction”. Unpublished Report.
Amjad, K; Gangadhir, M. and Vinay, R. (1999): “Effective Utilization of waste plastic in Asphalting of Road, “Project Report Prepared under the guidance of R. Suresh and H. Kumar, Department of Chemical Eng, R.V-college of Engineering, Bangalore.
Collins, R.J. and Ciesielski, SK. (2003): “Recycling and Use of waste materials and By- products in Highway Construction” Unpublished Technical paper, Vol. 1 and 2.
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