EVALUATION OF GEOLOGICAL MATERIALS WITH PLASTIC ADDITIVES FOR THE PRODUCTION OF DURABLE PAVEMENT BLOCKS: CASE STUDY OF OFFA, NORTH CENTRAL NIGERIA

ABSTRACT

The  management  of  plastic  waste  (whose  generation  is  on  the  increase)  poses  a  great challenge to environmentalists owning to its non-biodegradability. The research project aims at using waste plastic materials as binding groundmass in place of cement thereby producing pavement blocks that are more durable and more failure resistant than the existing cement derived pavement blocks(whose water absorption rate  as well as moderate resistance to acidic condition is a major disadvantages). This also serves as a partial solution to the environmental and ecological challenges associated with the increasing use of plastics. Plastic wastes (PET and LDPE type) were melted at temperatures between   180˚C-250˚C and mixed in different proportions (by volume) with granite dust, sand and clay to produce sample paver blocks. The same mould was used to produce cement paver blocks. The sample blocks were subjected to Flexural test, acid test, test for compressive strength and water absorption test. Based on the four tests, comparison was drawn on plastic paver blocks against concrete paver blocks in terms of durability, corrosion resistance and viability. A fifth test (the oven test) was carried out on the plastic paver blocks to find out how much heat they could withstand before failing. Results obtained from both compressive and flexural tests showed higher strength and durability for plastic paver blocks against those made from cements. Results of water absorption test show abysmally low water absorption. The acid test shows that the plastic derived pavement blocks were more corrosion resistance than that derived from cement. The oven test shows that the blocks failed between 180˚C-220˚C. Based on these, it was be established that plastic paver blocks are more viable, failure resistant, cost effective and sustainable alternative to both cement paver blocks and asphalt paved roads.

CHAPTER ONE

INTRODUCTION

1.3 Background to the Study

Road networks that are of high quality are very important to the socio-economic development of any nation, especially the developing countries like Nigeria. The definition of a “road defect” includes any part of a road, highway, or construction site that does not meet the regulations for a safe road.

The causes of road failure in Nigeria as identified by many researchers include poor construction materials, poor design and specification, road usage, use of non professionals, poor drainage, geological and geotechnical factors (Aghamelu and Okogbue, 2011; Ofonime and Aniekan, 2005; Jegede, 2000;Adeyemi and Oyeyemi, 2000; Gidigasu, 1980).

The surface layer of the pavement structure is the most important layer as it is expected to provide the ultimate function of an economic, safe and comfortable riding surface to users, protecting the sub-structure layers (base, sub-base and subgrade) from infiltration of water and  other foreign  materials,  and  distribute stress  from  axle loads  satisfactorily to  layers beneath without compromising durability (Airey et al., 2002).

The nearness of the saturated zone to the land surface and the manner of fluctuation of this zone has direct effect on the geotechnical properties of the soil. These in turn influence the stability of engineering structures (like houses, bridges, dams and roads) (Brattebo & Booth, 2003).

Majority of the roads in Nigeria are asphalt paved roads. Their durability and frequent need for maintenance raises the question of cost effectiveness. Necessity they say is the mother of invention. Cement paved roads is becoming more popular in Nigeria, especially in Lagos state. Areas like Lekki and Victoria Island are adorned with roads made from cement paved blocks not because cement paved roads are less expensive but because they are more durable. This “invention” for roads in these waterlogged and sandy areas was born out of necessity. In reality, many private estates have employed the use of paving stones within their estates because of their relative ease of construction and maintenance. They also last longer. Roads in government schemes like the Lekki Scheme 1 and Scheme 2 have also been extensively made from paving stones.

Asphalt roads are expensive to construct, do not last long before they fail in spots and even more expensive to maintain in these areas where the water level can literarily be at the surface in the raining seasons.

The American Concrete Pavement Association (ACPA) did a 90-year comparative cost-life cycle analysis and found out that despite a 15% difference in initial investment on concrete pavement in comparison with asphalted road, the cost differential was over 230% more for the asphalted pavement.

Interlocking pavements are special dry mix precast pieces of concrete commonly used in exterior landscaping pavement applications. It is an attractive engineering and economical alternative  to  both  flexible  and  rigid  pavements  in  recent  times.  They  are  versatile, aesthetically attractive, functional, greener and cost effective and require little or no maintenance if correctly manufactured and laid.

Despite the huge prospects, two areas of concern are occasional failure due to excessive surface wear, variation in the strength of the blocks, disintegration resulting from alternating wet and dry conditions as well as attack of surface by acidic solutions.

In the face of depleting natural resources worldwide, generation of wastes from industrial and residential areas is on a steady increase. Sustainable development (being a core mandate of environmentalists) involves the use of non-conventional and innovative materials, and recycling of waste materials in order to compensate the lack of infinite reserve of mineral resources as well as management of waste.

The economic growth, geometric population growth and changing pattern of consumption are resulting in the rapid increase in the use of plastics in the world. The use of plastic materials has increased from 5 million tons in the 1950s to 100 million tons in the 2000s (Tuffour, 2016). Although, there is little research based information on the amount of plastic waste generated in Nigeria, a report in the BusinessDay Newspaper of January 3, 2019 states that Lagos is estimated to generate about 14 to 15 thousand tons of waste daily. Of that, roughly 30 percent is recyclable, and 50 percent of this is plastic. In essence, about 2,250 tons of plastic waste is generated in Lagos on a daily basis. This is a significant portion of the total waste generated.

The challenge of waste disposal has become one of the most serious environmental problems facing many cities in Nigeria (Amadi et al., 2012). Landfills are becoming scarce and the cost of building landfill sites are increasing. These results in open dump site burning (thereby causing great environmental pollution), blockage of drainages and waterways among other environmental challenges.

Recycling technology has been a solution of choice in the developed countries. Many developing countries including Nigeria  are currently experiencing rapid urbanization and industrialization and as a result a lot of infrastructural developments could tap into turning their environmental problem (abundance of plastic waste) into a source of cheaper and more durable construction materials. Expanded polystyrene (EPS) based waste, High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Polyethylene Terephthalate (PET) waste bottles, polypropylene fibers and polyethylene bags have all been used in different forms by researchers in concrete (Kodua et al., 2018).

Plastic wastes pose a greater management challenge because of its non-biodegradability. They are  corrosion  resistant,  have  long  life,  maintenance  free  and  light  weighted.  All  these attributes that makes its waste management difficult could be exploited to replace cement as the binding material for aggregates in the production of paver blocks.

LDPE and PET plastic are major components of Municipal Solid Waste (MSW) could thus be melted and mixed with aggregates to produce more durable, cost effective, corrosion resistant pavement blocks. Polymer modified pavement blocks in essence could be the perfect alternative to the less durable asphalt pavement as well as the cement derived pavement blocks

1.4 Statement of Research Problem

Despite  the  fact  that  cement  derived  paver  block  roads  have  been  found  by  various researchers to be a better replacement to asphalt paved roads, there are shortcomings that needs to be addressed especially disintegration caused by extreme wetting and drying, as well as weakening by corrosion. These defects can be overcome by plastic derived paver blocks.

Unlike the biodegradable solid wastes, plastic wastes have a very low degrading pace, making it difficult for waste managers to deal with. Therefore the need for an efficient, effective, innovative and reliable method for managing plastic waste cannot be overemphasized. This waste management by recycling is a major plus for environmental Geologists There is need to innovatively address the shortcomings iterated on cement paved roads as well as partially taking care of environmental challenges posed by plastic wastes is equally a target of the present research.

1.3 Aim and Objectives

Aim

The research is aimed at producing failure resistant and durable pavement blocks for road construction, using plastic wastes as additives to clay, granite dust and sand.

Objectives

i.      To produce pavement blocks from plastic waste materials (LPDEs and PETs) mixed with three geologic materials (granite dust, sand and clay) in different proportions by volume (50:50; 40:60 and 30:70). Since these materials vary in porosity, permeability, shear strength and corrosion resistance (largely owing to their mineralogical composition)

ii.      To carry out flexural, compressive, water absorption, and corrosion test on sample pavement blocks produced from plastic waste.

iii.      To compare their engineering properties with pavement blocks produced from cement.

iv.          To determine the temperature at which pavement blocks made of plastic fails.

v.      To find out the suitability of plastic paver blocks as an alternative to cement paver blocks in the construction of durable roads, especially where low water absorption rate is desired to mitigate the water logging arising from near surface water table and base flow.

vi.      To  creatively  manage  plastic  waste  and  its  associated  environmental  challenges through its application in paver blocks production.

1.4 Study Area

1.4.1 Location, Extent and Accessibility

The study area is Offa municipality, Offa local government area of Kwara State. The area lies between  latitudes  8°6’43”N  and  8°8′10’’N  and  longitudes  4°43′00′′E  and  4°44′0′′E  and Covers a landmass of about 17 Km2. It is accessible through Ajasse-Oshogbo trunk ‘A’ road from either Oshogbo or Ilorin, both being capitals of Osun and Kwara states respectively. It is also accessible through rail, as the Lagos-Jebba rail line passes through the town. The train station situated in the town served as the terminus before the extension of the rail line to Kano. Offa has a population of about 180,000 inhabitants.

1.4.2 Relief and Drainage

It has elevations of between 440m to 440m above sea level. The runoffs and streams are drained by Rivers Oyun and Afelele.

1.5 Scope of the Study

The  study  area  is  about  17km2.  The  study  area  (lying  between  latitudes  8°6’43”N  and 8°8′10’’N, and longitudes 4°43′00′′E and 4°44′0′′E) would be mapped. A cross section profile of the area would be produced from the geological map. The work will attempt a fair appraisal of the performance of asphalt paved roads, the causes of its failure and reasons why it will be better to shift to the use of cement pavement blocks for building roads in Nigeria. The work will also try to evaluate the performance of plastic derived paver block as better road builder than the cement derived paver block.

In this research work, LDPE (like plastic grocery bags, squeezable bottles and sachet water nylons) and PET bottles were collected, washed and shredded into flakes, melted and then used to replace cement completely. Clay, granite dust and sand were mixed with the melt in different proportions by volume, so as to have concise engineering properties of the varying mix  ratios. The same mould was used to  produce cement paver blocks too.  Established fundamental and empirical laboratory tests such as compressive strength, acid, water absorption, and flexural tests were carried out on the sample blocks, so as to compare the engineering properties of the various plastic derived blocks to the cement derived blocks. Oven tests were carried out on the plastic derived blocks to determine the heat condition that will make each sample block to fail. The Acid test would also be carried out to compare the corrosion resistance ability of both the plastic derived and cement derived paver blocks.

1.6     Justification of the Study

Since Lagos State as the economic capital of the country has taken the lead in road construction using paver blocks, there is the likelihood of other states doing the same. Hence the urgent need to find solutions to the shortcomings of cement paver blocks.

The study will also reduce plastic waste menace and its associated hazards in the environment.  These dual objectives can be achieved by replacing cement paver blocks with plastic paver blocks.

Several studies have been carried out in countries such as Egypt, India, Australia and U.S.A where plastic wastes have been converted to other products. Sadly, Nigeria has very few research efforts as well as published academic work in this direction, hence the need for the present study.

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