CHAPTER 2 LITERATURE REVIEW

2.1 URBANIZATION, WASTE AND COST OF BUILDING MATERIALS

There is a clear parallel between urbanization, generation of waste, and the growth of slums as well as the consistent increase in the cost of building materials. (Sridhar, 1996) defines waste is as any unavoidable material resulting from domestic activity or industrial operation for which there is no economic demand and which must be disposed of. The rapid expansion of city spaces and the activities of human beings within those spaces has ultimately led to the generation a lot of waste. According to data from the World Bank, humans generate 2 billion tons of waste per year, implying that each person can generate up to 1.2 kilograms of waste per day (Silpa, et al., 2021) and if current trends continue, this figure could rise to 2.2 billion tons by 2025, reaching 3.4 billion tons by the end of 2050 (Silpa, et al., 2021) For the purpose of comparison, the world’s population currently sits at about 7.9 billion (according to the most recent UN estimates elaborated by worldometer) which essentially translates to a horrific fact that there would possibly be 3 tons of waste for every human being every year! The massive increase in waste generation can be directly linked to urbanization, which can be defined as the process through which cities grow as higher and higher percentages of the population comes to live in the city (National Geographic Society, 2019)

According to the World Bank, up to half of the world's population already lives in some form of urban city, with that number anticipated to rise to 6 billion by 2041. (Silpa, et al., 2021) While urbanization comes with benefits like advancements in infrastructure and technology, employment opportunities, improvements in medical healthcare and facilities, high-quality education, and an overall improvement in living standards, it has also resulted in a number of health and environmental problems, particularly when not properly managed, such as high levels of pollution, poor health and living conditions, and an increase in the spread of communicable diseases.

But no matter how hard we might try to fight it, the world today is increasingly becoming urbanized. Unplanned urban sprawl is the major cause of ghettos and slums, resulting in the uncontrolled generation of waste as a result of inadequate and/or overburdened basic infrastructure like waste collection, sanitation systems, transport and worsening air pollution (United Nations Statistics , 2019). These regions often lack services like electricity, schools, toilets or running water and so diseases like cholera, dysentery and many others have become common (BBC, 2022). The victims within these regions who suffer from poor living conditions are often the poor like migrants and people who are low-income earners and cannot afford the cost of living within city areas but want to enjoy the services it provides and thus, settle around the surrounding areas in order to enjoy the benefits and access to various social amenities. However, due to a lack of proper planning and development, these regions often take on a life of their own resulting to the development of poor-quality planning and housing conditions. Aside from this, high cost led some to question those who reside these areas to utilize the cheapest available building materials or items that have been rejected due to flaws, resulting in the rise of "shanty towns".

United Nation’s estimate suggests that over 1 billion people are currently live in slums, ghettos or shanty towns; 80% of which can be attributed to mostly three major: sub-Saharan Africa (with a population of 238 million), Eastern and South-Eastern Asia (with a population of 370 million), as well as Central and Southern Asia (with a population of 227 million) (United Nations Statistics , 2019) However, as the global population expands, the promise of jobs and prosperity is a constant draw for people towards the urban environment. Most governments around the world have attempted to solve the problem of slums by eradicating them, with mixed results; though it may be preferable to repair these current places. They are an eyesore and reflect poorly on the city, influencing the ease with which diseases and poor health conditions spread.

The means of approaching this problem is of interest to this research; through self-help schemes -a type of informal program that enables people to help themselves and their neighbors to improve their homes (Gorvett, 2019) Residents are given building materials to use in constructing their own homes as part of self-help programs. People are given training and instruments to do this, allowing them to make use of the garbage disposed of, thus alleviating the problem of public waste caused by urban sprawl.

2.1.1 URBANIZATION AS A MAJOR CAUSE OF GLOBAL WARMING

There is a direct link between urbanization and global warming. Although human-based actions have a major role in global warming, the most significant of these is urbanization; particularly in this period of industrialization, digitalization, and fast-paced culture. (Rebecca , 2017)

In New York City, for example, the urban surface temperature is less intense and less frequent than in the adjacent non-urban regions (Bornstein, 1962-1982). Furthermore, (Eugenia & Ming, 2003) detected that urban expansion and other land use changes were responsible for half of the observed reduction in diurnal temperature. Between 1978 and 2000, China had tremendous economic expansion, resulting in an increase in the urban population from 18%to 39%, as well as an increase in the number of small towns from 2,176 to 20,312 and the number of cities from 190 to 663 (nearly double that of the world average during this period) as well as an increase of 0.05oC in the mean surface temperature (China Internet Information Center, 2004). Ultimately, national wealth is tied to the development of local cities, and no country has been able to maintain economic progress without dealing with the issues surrounding urbanization. The issue is figuring out how to deal with the consequences associated with it.

2.1.2 URBANIZATION AND WASTE FROM CONSTRUCTION

These issues surrounding urbanization and growth of slums has also greatly influenced the demand for common construction materials such as cement, steel, sand, gravel and bricks and this is easily one of the most significant and relevant sustainability trends facing the world today. High cost of materials may occur as a result of a number of factors including but not limited to the lack of material, demand forecasts, security and environmental challenges and natural disasters however, the key reason that this research focuses on and probably the most important is the issue of rapid urbanization.

Concrete (which is made up primarily of cement, sand, gravel and water) in particular is probably the most common building element in modern architecture and an essential component to the development of resilient infrastructure. As the future marches ever closer, the construction industry is being forced to change as techniques and materials used in the past are now being seen as unsustainable and big contributors to global warming thereby requiring greater innovation on how to approach building materials for construction.

Virgin materials account for more than 15% of a building's energy use and carbon emissions, according to research. Furthermore, using virgin materials in construction materials depletes natural resources and increases carbon emissions (TheGreenAge, 2021). Concrete and masonry are the most common and possibly important components of construction. Concrete is utilized in the production of almost 30 billion tons of concrete used per year, and its demand is expanding faster than steel or wood (Springer Nature Limited, 2021). This is probably because of the strength concrete is able to possess. Concrete structures are generally preferred because of their resilience and has proven itself as a competent building material used extensively in buildings, bridges, roads and dams. However, concrete has a significant carbon footprint: the cement industry alone accounts for at least 8% of global emissions caused by humans, with the problem being that for every ton of Portland cement produced, one ton of CO2 is also produced.

In 2011, it was recorded that about 3.6 million tons of cement was used in the construction industry (Springer Nature Limited, 2021)

Typically, concrete is made through the mixture of sand, gravel, cement and water making it into molds before it dries. Despite the fact that the bulk of its constituents are environmentally favorable, cement is the most carbon-intensive component. Its manufacture entails heating a kiln with fossil fuels to temperatures above 1,400°C in order to heat a limestone and clay mixture (Edwards, 2022). Furthermore, for every ton of cement made, roughly 600 kilograms of CO2 are generated when limestone (calcium carbonate) is heated with clay (Springer Nature Limited, 2021) This process causes hazardous greenhouse gases to be discharged into the environment. Greenhousegases are gases that trap heat in the Earth's atmosphere (United States Environmental Protection Agency, 2022). They allow sunlight to travel through the atmosphere while preventing the heat that the sunshine produces from exiting. While there exist alternatives to cement such as according to Erica Van Tassel; slag and fly ash, cement production remains common and highly profitable. Also, these alternatives do not completely remove the carbon emission required in production but rather, reduce it.

Aside from the carbon generation involved in the production of cement, the influence of urbanization has led to an increase in its demand which has out balanced supply leading to an increase in cost price of materials thereby suffering urban planning process and building construction. It is an irreversible and ongoing force in industrialized and developing countries like Africa leading to the creation of slums and ghettos which are a prevalent urban phenomenon in developing countries. These regions, according to a 2003 United Nations global report on human settlement, are of low-quality dwellings, often built on valuable land, that allow poorer households to access communal areas like urban markets that otherwise would be unattainable.

The construction process as a whole also generates a lot of waste mostly through demolition and over estimation which then needs to be disposed of. While there are a lot of avenues for reusing these construction waste as they often do not pose a “real” environmental risk, a large amount still gets disposed of in landfill. It is estimated that 32% of landfill waste comes from the construction and demolition of buildings and 13% of products delivered to construction sites are sent directly to landfills without ever being used. This can be an expensive process, and ultimately factors into the increase in the cost of housing. Because construction is the largest business in many nations and the largest consumer of raw materials, the industry is a potential sector where plastic waste can be beneficially employed for numerous uses.

Tchobanoglous et al., 1993 define construction waste as relatively clean, heterogeneous building materials produced by diverse construction processes. Concrete, brick, asphalt, stones, bituminous mixes, coal tar, tar and sawdust are all generated at construction, demolition, and excavation sites (Burton-Hughes, 2019) While many of these wastes can readily be repurposed or recycled, they are disposed indiscriminately in many countries where recycling is not possible, posing a serious environmental threat.

Construction waste recycling is one technique to reduce the risk of construction waste. As a result, developing appropriate technologies to recycle these materials is critical. Sawdust, for example, may be used as an infill in bottle bricks (eco bricks), which would help to clean up the environment and reduce building waste. Aside from bottle-brick, they can be utilized as an aggregate in cementitious and asphalt mixtures, filler, insulation, and other construction materials in civil engineering. (Paul & Adewoyin, 2020)

2.1.3 URBANIZATION & HOUSING PROBLEMS IN THE DEVELOPING WORLD

The problems of housing in developing countries can mostly be attributed to urbanization and the result of rapid population growth outlined in the previous section. Housing is essential to man's well-being, survival, and health (Joia , 2017) and could easily serve as an indicator of the quality of living within a society. To be clear, the issues related to housing being discussed here is not limited to just the poor, but affects all classes across the society. This is mostly attributed to the highcostofbuildingmaterials, along with insufficient procedures and systems for land allocation, financing, mortgage institutions, and infrastructure. All of these causes have contributed to the lack of affordable houses, which has been defined by the World Health Organization (WHO) as housing that protects against diseases, accidents, and psychological and social stress. These housing problems often manifests in form of urban squalor and overcrowding, poor environmental conditions and a general lack of access to social amenities. Housing issues arise primarily as a result of an extraordinary urban population increase and slums, ghettos, and shantytowns are the result of housing shortages and overcrowding. Even in developed countries, the challenge has moved from scarcity to a lack of quality, affordability and, according to Freeman (2002) and Kotkin (2013), the difficulty of specific demographic groups accessing appropriate housing.

The problems with slums and ghettos are that aside from not being properly planned and laidout, their living conditions are often really poor. Since the dwellers cannot afford the planning requirements or the ever-increasing cost of building materials and the services required to build proper architecturally relevant dwellings, their houses are often of low quality, lacking the expected aesthetic appeal of modern buildings as well as the adjoining planning and services. They are often ripe with diseases, produce tremendous waste since the associated services cannot easily collect them for disposal and are constructed of low-grade and poor-quality materials which could adversely be affected by harsh weather conditions like excessive rain and landslides making them a danger to the inhabitants. According to a UN report, efforts to improve the living conditions of slum dwellers have been feeble and incoherent over the last decade. Slums have the highest concentrations of poor people with the worst shelter and physical environmental conditions and this problem is only expected to worsen as urbanization increases resulting in an increase in the total amount of waste generated globally is expected to increase significantly. Many municipal solid waste disposal facilities in low- and middle-income countries have become dumpsites, contributing to air, water as well as soil pollution of which 70% can be attributed to plastic waste (The World Bank, 2019).

There are basic things that can do to improve the quality of living in sprawled urban societies. One is to recognise that urbanisation is going to happen and employ the approach of recycling and by making use of the waste that is generated in the environment. Considering the enormous volume of construction work done annually and the huge number of plastics produced and the resulting waste generated each year, the issue of reusing the waste material by stuffing them with the waste littered within the same environment mostly through a build-it-yourself approach and by adapting the use of bottle-brick in construction is gaining attention. The problems surrounding waste could be lessened through this process of recycling within the building sector.

2.2 POLYETHYLENE TEREPHTHALATE (PET)

2.2.1 PET (POLYETHYLENE TEREPHTHALATE)

PET is sometimes abbreviated PETE is short for polyethylene terephthalate used in fibers for clothing, containers for liquids and foods, and thermoforming for manufacturing. (Lobke , et al., 2021) It is a transparent, robust, and lightweight plastic that's commonly used to package meals and beverages, particularly convenience-sized soft drinks, juices, and water. Plastic bottles made from PET are widely used for soft drinks (PET Resin Association, n.d.). Its use is widespread due to its strength, lightweight, non-reactive, easy to

Produce And Shatterproof Quality

(http://www.petresin.org/faq.asp). It is also relatively safe for food, beverage, personal care, pharmaceutical and other medical packaging. Its popularity of use for soda and bottle water packaging when compared to other materials like glass is mainly due to its lightweight as well as its and ease of production making which makes it relatively safe and easy to manufacture and transport when compared with other materials.

2.2.2 PHYSICAL PROPERTIES POLYETHYLENE TEREPHTHALATE (PET)

Property Value

PET is a thermoplastic polymer resin made up of purified terephthalic and modified ethylene glycol monomers. In the polyester family, it is the most extensively utilized thermoplastic polymer resin. PET is a translucent, semi-crystalline, and semi-colorless resin in its native state. PET can be produced to be semi-rigid to rigid depending on how it is treated, and it is also lightweight. It works effectively as a gas and humidity barrier, and also an alcohol and solvent barrier. The characteristics of PET are high chemical resistance and have melting points approximately up to 260oc. PET is a thermoplastic that comes in two forms: amorphous and semicrystalline. The amorphous type of PET polymer has a high transparency but lower mechanical properties, such as tensile strength, as well as significantly lower sliding properties. ref book.

It has good creep strength, which makes it impact resistant, as well as low moisture absorption, dimensional stability, water resistance, and toughness (its strength to weight ratio is impressive), all of which make it ideal for applications which require complex parts and the highest levels of dimensional accuracy and surface quality. The material is virtually shatterproof, which improves its applicability in many conditions. PET has excellent temperature and dimensional stability due to its thermal characteristics (www.ensingerplastics.com).

In general, plastics are of two main types based on how they are manufactured. Thermosets, which are plastics that cannot be reformed once heated, meaning that they can’t be recycled and their shape can’t be repurposed or changed for another use. Thermoplastics on the other hand can have their bonds reversed and thus are recyclable and could have their shape changed to be reused for other purposes. Examples of these are soda bottles (which this research would concentrate on). surrounded by the triangular “chasing arrows” symbol and the acronym PET or PETE below the triangle. Only PET carries the #1 resin identification code (RIC) (Seaman, 2020).

2.3 PLASTIC WASTE AND GLOBAL WARMING

The wide range of outstanding properties plastics exhibit makes their application in society increasing ever-widening. However due to the linear nature of most modern cities, these plastics simply means that a large quantity of them are discarded carelessly after use. Today, millions of plastics are produced in the form of soda bottles popularized by drinks like Coke and Pepsi to be used once then discarded.

Approximately 80% of the estimated total 6.3 billion tons of plastics ever manufactured have been thrown, resulting in not only a massive waste of valuable resources, but also mismanaged waste that is the source of an ever-worsening environmental crisis (James, 2017). The ocean conservancy's annual September beach cleaning in over a hundred nations found plastic bottles and bottle caps to be the third and fourth most collected plastic garbage items (Parker, 2018). Because the materials used to produce this waste are of non-biodegradable components, it is believed that they can remain dormant in the environment for a long time without decomposing. The situation has become so dire that some countries like India banned the use of plastic bags in 2009 and later expanded that ban to include all plastic packaging and single disposable plastics although the ban is rarely enforced (Sampathkumar, 2019).

According to Jefferson, et al, 2009 there are two options for properly dealing with plastic waste: incineration, recycling and reusing. Incineration can be conducted to break down plastic to generate energy but the high temperature can produce high-calorie energy, where its combustion generates harmful gases which affect both human health and the environment (Jefferson , et al., 2009). Aside from that, the sheer volume of plastic waste and the rate at which it is produced makes recycling and incinerating them much more difficult and in truth, recycling could just be a gigantic placebo—from the fuel used to gather bottles to the energy used by recycling operations to the gases released into the atmosphere (Hutchinson, 2008). These methods are tedious, consume a lot of energy and involves the use of equipment that results in the production of carbon dioxide (CO2) and other dangerous greenhouse gasses that contribute to the effects of global warming that is witnessed especially today. “Global warming” refers to the long-term heating of the earth’s climate system monitored since the pre-industrial period (1850-1900) due mostly to human activities and fossil burning, which increases the heat trapping greenhouse gas levels within the Earth’s atmosphere (NASA's Jet Propulsion Laboratory , 2022). It refers to what is believed to be a trend where the earth’s temperature is increasing, attributed mostly to man-made activities through pollutants and ecological disturbances that cause more of the sun’s energy to be trapped within the atmosphere. (NASA's Jet Propulsion Laboratory , 2022).

2.4 ENVIRONMENTAL EFFECTS OF PLASTIC WASTE

Our modern world has been altered by plastics. Plastic is one of the most disposable materials in the world today, and it is hard for any key area of the economy to function properly without it, from agriculture to packing and construction—the subject of this study. According to (Jefferson , et al., 2009), approximately 50% of plastics are used for these types of single-use disposable applications and 20% to 25% for long-term infrastructure such as pipes, cable coatings and structural materials and the remainder for durable consumer applications with intermediate lifespan, such as in electronic goods, furniture, vehicles, etc.

Since the 1950s, researchers estimate that more than 8.3 billion tons of plastic bottles have been manufactured, with around 60% of them ending up in the environment. According to data from world bank, the world has generated 242 million tons of plastic waste, which was equivalent to 12% of all municipal solid waste. Each minute, over a million plastic bottles were created in 2017 (The Guardian, 2017). Plastic production has soared from 2 to 380 million tons per year (approximately 20,000 plastic bottles are needed to manufacture one ton), making it the world's fastest-growing material. (European Environmental Agency, 2019)

The problem with plastic waste is that it a very long time to decompose in nature. Because of this, they cause problems whenever they are thrown in the environment. The clog drains thereby causing flooding. When burned, they release dangerous gases which could cause respiratory problems and warm the environment contributing to greenhouse gas. When consumed by animals they are deadly and they contaminate water bodies when dumped into the oceans

(United States Environmental Protection Agency, 2022). Plastic waste enters the environment through open dumping, burning and improper disposal in the water ways and even when it is collected, many countries lack capacity to properly dispose or process the waste. In 2017, Europe alone exported one-sixth of its plastic waste, largely to Asia (The Economist 2018).

2.5 PLASTIC WASTE CONSUMPTION

Post-consumer plastic waste generation across the European Union (EU) was 24.6 million tons in 2007 (Jefferson , et al., 2009). The table below shows a breakdown of plastic consumption in the UK during the year 2000, and its contributions to waste generation ref. This confirms that packaging is the main source of waste plastics although it is clear that other sources such as waste electronic and electrical equipment (WEEE) and end-of-life vehicles (ELV) are becoming significant sources of waste plastics.

Table 2 breakdown of plastic consumption in the UK during the year 2000

The chart below provided by (ourworldindata.org) shows the increase of global plastic production, measured in tonnes per year, from 1950 through to 2015. According to the chart, only 2 million tonnes of plastic per year was produced in 1950. However, by 2015, this number has risen by over 150% reaching 381 million tonnes. For context, this is roughly equivalent to the mass of two-thirds of the world population (Ritchie & Roser, 2022)and the number keeps rising.

In terms of countries, the United States produces the most plastic waste per capital in the world with the average American using up to 130.09kg of plastic waste per year (statista.com). They are followed closely by the United Kingdom, with an average individual there producing 98.66kg per year.

According to the data, even with poor disposal practices and little to no recycling developing countries like Nigeria is not on the list of top 20 countries that produce most plastic waste per capita worldwide. This might signify that the influence of recycling in these developed countries though intense, is quite minimal. Interestingly, the country with the most people produce 15.67 kilogrammes of plastic garbage per person. Some speculate that this is due to China's greater industrial and economic development. Another factor could be because until 2019, China was the go-to destination for countries wishing to recycle their plastic trash, which would have resulted in substantial rise in the quantity of plastic waste generated annually.

2.6 HOW TO DEAL WITH PLASTIC WASTE

The concept of using one world’s problem to solve another is a known philosophy, and with this, the research aims to look at ways to convert plastic waste bottles that have littered the environment into building blocks that can substitute masonry and hopefully, tackle environmental waste and housing shortage. While not an entirely new concept, the research aims to look in particular at the strength and thermal properties of plastic bottles while taking into account how the form and shape can possibly influence its strength. Because of the large-scale production that occurred following the industrial revolution and continues now, plastic is an effective raw material. Thus, while plastics cannot outrightly be banned, it could be reused in the construction industry as a feasible application. Versatility, lightness, hardness, and chemical, water, and impact resistance are all advantages of plastics. (New Life Plastics, 2022)

2.6.1 POTENTIAL OF PLASTICS IN CONSTRUCTION

There are two major global crises happening concurrently. The first is a housing shortage caused by supply chain problems, population growth, and shifts from where people live which has led to skyrocketing housing prices and record numbers of homeless people around the world. The second issue is pollution and global warming, and concerns about single-use plastics are growing. While single-use plastics have proven to be necessary in our daily use, there is an overload of trash filling our landfills and waterways. Fortunately, innovative organizations are seeking to solve these two problems.

PET recycled plastic bottles have gained appeal as a building material in recent decades, according to Azhdarpour et al. (2016). Plastic as a material is versatile and could be easily adapted to as a major component in building materials thanks to a number of its properties. There are a variety of ways in which it could be used and a variety of instances in which it might be better than conventional materials. Its use might range from being an insulating material, to plumbing, sinks, and of course, as bricks – which is the main focus of the research. Characteristically, plastics no matter the form or shape they are in are made up of small, granular pieces known as microns that are between 5 to 10 microns (0.005 to 0.01mm) large (National Ocean Service, 2021). It can be a chemically resistant, ductile, stable, and fire-resistant material, as earlier mentioned. Most polymers are susceptible to UV light and distort when exposed to high temperatures, such as those found in the sun. With a growing body of research on concrete and mortars containing Polyethylene Terephthalate (PET) waste aggregates, use of rice husk and plastics application as a composite in concrete, aggregate replacement in concrete, investigation in water-cement ratios of such concrete with PET bottles, and even sometimes for soil stabilization, their re-use in the construction industry has been considered (Nwosu-Obieogu, et al., 2016). Despite extensive research into the use of plastic bottles as an additive to traditional construction materials, there is much confusion about whether either bottle can be used for potential construction applications, and there appears to be little research into classifying such solutions to any extent.

The use of empty vessels in construction is not exactly a novel idea, and can be traced back to as far as ancient Rome where structures with empty amphorae embedded in concrete in order to reduce concrete usage and lighten the load of upper structures (Rowland, 2013). William F. Peck erected the first bottle home in more modern times in Tonopah, Nevada, in 1902, utilizing 10,000 beer bottles. This was quickly followed by one erected by Tom Kelly in Rhyolite, Nevada, which began to crack in 1954, almost 50 years after it was constructed under the scorching heat of the sun. Despite the fact that it is made of bottles, I believe that a study of this structure would provide me with insight into how a sustainable structure similar to this might function (Kim, Wisniewski, & Baker, 2019). Bottle home construction has continued since then, with more instances making headlines all around the world. ( WHITE CANVAS DESIGNS, 2010). Ecological House, constructed a house from 8,000 bottles, comprising of toilets, and a solar water heating system, which was completed in November 2002. When wet, the green roof can weigh up to 30 tonnes, and it has been supported by the walls alone. It is the world's first house made entirely of PET bottles, with no cement used in the construction process.

2.6.2 CHALLENGE OF USING PLASTIC (PET) IN CONSTRUCTION

The technique of filling plastic-bottles with waste or earth commonly now commonly called bottle-bricks was first pioneered by German Architect - Andrias Froese - in South America between the year 2000 and 2001, where PET plastic bottles were installed within walls with the aid of mortars in order to shape the building as reported by (Sina & Amani , 2016) The filler content in these plastic bottles was made up of natural materials such as mud, sand, soil, or landfill waste. The program has recovered and reused over 300,000 PET bottles, in over 50 construction projects in Honduras, Columbia, and Bolivia. Countries like Nigeria, South Africa, Norway, the Philippines, and India were among the first countries to implement the technology. (Muyen, et al., 2016) Once stuffed with soil, the plastic containers can then act as bricks and can be used in place of traditional bricks in walls and pillars. These walls can come in a variety of shapes and sizes, as well as different orientations. Froese also tested the strength properties of his bricks, finding that when filled with the weakest infill materials, such as sand, the walls of his plastic bottles can withstand up to 4.3 N/mm2 (Muyen, et al., 2016).

Since then, innovative citizens worldwide have been making and using Eco bricks as building materials. Other eco-pioneers that have helped to develop the practice include Alvaro Molina, the founder of the Ometepe Bilingual School, who began filling plastic in order to maintain the island’s delicate eco-systems and construct school classrooms by re-purposing plastic trash.

Greyton, a town in the western cape, is often recognized as the first town to use Eco bricks in south Africa for community gardens and local schools. In 2010, Ecobricks.org founder Russell Maier and collaborator Irene Bakisan developed a curriculum guide of simplified and recommended practices called the vision Eco brick construction guide, to help local schools integrate Eco bricks into their curriculum (Maier & Himawati, 2019). The organization now offers training and inspiration through its Facebook page, Eco bricks: Plastic Solved.

In 2014, while in Guatemala, environmental activist Susana Heisse encouraged Eco bricking as a building technique and solving excess plastic challenges faced in Lake Atitlan communities (Hopkins, 2014) . Since then, the open-source development of Eco brick technology and awareness has spread throughout the world, with Eco bricks being used as sustainable, alternative building materials in the Philippines, Indonesia, South Africa, Zambia, Thailand, Perum Mexico, and the United States.

The challenge of bottle-bricks is that if they’re going to last, they would have to be made to some sort of standards, which would be dependent mostly on the type of in-fill material stuffed into it. The bottles must also be stuffed really tight from the very bottom to the top, which on its own, takes a lot of concentration and physical hard work. Filled bottles have to reach a minimum weight to make them acceptable. If a bottle is not full enough, it won’t stand any pressure and would collapse and break down. There are also the issues that might be related to how the bricks are arranged, the type of foundations and concrete mixes used.

Eco-bricks represent a different approach to waste management. However, their biggest disadvantage is that irrespective of their use, they are still plastics and like all plastics, they do not decompose. If they melt, they release gases that are harmful to human health and the environment.

2.7 CASE STUDIES

In 2015, research was conducted to examine the thermal and structural response of walls by comparing dry sand, saturated sand and an empty plastic bottle. The PET pieces were subjected to unconfined compressive stacking employing a compression machine of 3000 kN capacity and of an accuracy of 0.10 kN.

In addition, the thermal examination was done by enacting the simulated models of the three brick work squares on ECOTECT computer program – software used to calculate building’s energy consumption by simulating its context within the environment. Thermally, similar to the second case study, the plastic air-filled bottles show more improved thermal insulation characteristics than the traditional masonry construction, which could work as a thermal insulation material.

According to (Khaled, et al., 2020), parallel research was published in Malaysia, which compared the performance of plastic bottle walls filled with brick to sand-filled bottle walls. The strength of the brick-filled bottle walls was three times that of the sand-filled bottle walls although the sand-filled bottle wall system was strong enough to pass for the minimum permitted strength and as a result, in terms of thermal comfort, plastic bottle bricks could substitute regular bricks in Malaysian buildings.

In Egypt, researchers contrasted traditional bricks and masonry with plastic bottle blocks using energy simulation software on two sample rooms fitted with both materials in a similar study focusing on the thermal performance of sand filled plastic bottle walls. On-site measurements of the rooms' energy efficiency were also taken. The average temperature in the brick room was greater than in the plastic bottles room, according to the findings. However, the relative humidity in the plastic bottles room was greater. Similar research was carried out in a number of other emerging countries, including, Bangladesh, India, and several Arab nations however this research would focus on those conducted in Nigeria.

2.7.1 FIRST CASE STUDY

There is a general idea of the high strength of PET bottles that makes them bullet proof and earthquake resistance has been floated around for a long time although there is very little research that can adequately support these claims. Despite the fact that building walls with plastic bottles instead of traditional construction materials has been done successfully in the past, the industry and research focused on the structural and thermal response of plastic bottles were not taken seriously until a few years ago.

In the Nigerian city of Kaduna, an engineer and director of a non-governmental organization, Developmental Association of Renewable Energies in Nigeria (DARE), Mr. Yahaya Ahmed, designed and built a house entirely of plastic bottles. A total of 14,800 sand-filled plastic bottles were used as bricks in the house, which consists of three rooms, a toilet, and a kitchen. The house bottles were linked at the neck by an intricate network of strings.

He stated that the structure was 20 times stronger than brick buildings and that it could last for over 300 years if designed correctly. It is also fireproof, bulletproof, earthquake-resistant, and can adapt to all forms of changes in the climate, desertification, and deforestation, according to him. The interior of the building maintains a temperature of 64o Fahrenheit all year round. His motivation behind this was to “reduce the volume of plastic that is polluting our environment and causing diseases and other disasters” (Premium Times, 2021). Mr. Ahmed explained the house's shape, saying that a circular shape is the most practical for bottle houses. "The circular shape gives the walls strength while also giving them a very beautiful and attractive aspect."

2.7.2 SECOND CASE STUDY

There have been very few researches that adequately document and support these claims of strength in particular. In order to prove this, a transdisciplinary research carried out by the Institute of Energy and Sustainable Development, DeMonfort University, Leicester, UK in conjunction with the school of Engineering and Applied Science, Aston University, Birmingham, Leicester School of Architecture, De Montfort University, Centre for Global Learning,

Education and Attainment, Coventry University, UK, The Global EMIT Project, Rugby, UK, Department of Mechanical Engineering, Ahmadu Bello University, Zaria, Nigeria, Engineering and Physical Sciences Research Institute, De Montfort University, Leicester, UK, LE1 9BH, School of Chemical Engineering, University of Birmingham, Birmingham UK. B15 2 TT, School of Engineering, Plymouth University, Plymouth PL4 8AA and Awonto Konsolts, Abuja, Nigeria.

Their goal was to address globalization concerns by building resources and capacity for the construction of inexpensive homes in low-income areas in Nigeria using repurposed materials such as PET plastic bottles, thereby reducing the tremendous damage to the environment that these bottles create. In order to replicate real-world scenarios, they intentionally made use of plastic bottles with a wide range of deformations which in theory should affect their maximum strength. They carried out a number of experimental studies in order to classify the thermal, mechanical and structural properties.

Thermal

A test wall was built to characterize the thermal properties of PET, one made of water-filled bottles and the other consisting of sand-filled bottles. The results showed that the water-filled bottles provided significant thermal benefits over the sand-filled bottles, however at the cost of some strength. This finding is comparable to that of (Wang, Tian et al. 2013), who investigated the utilisation of water in a thermal storage wall.

Strength

In order to understand the strength characteristic of PET bottles, tests were carried out under various loading conditions. The results showed that PET bottles filled with water had a strength of about 1.4kpa, while those filled with sand had a strength of about 25kpa. A similar test to this was carried out by (Taaffe, O’Sullivan et al. 2014) who obtained a strength of 35kpa by filling PET bottles with compressed plastic bags. It needs to be noted that the compressive strength of cement block is 25mpa, which is still a times stronger than the compressive strength of typical PET used in this research.

Summary Of The Results They Obtained

property value

Compressive strength of water bottles 1.4 kPa

Compressive strength of sand bottles 25 kPa

Their study looked into the feasibility of employing repurposed materials in construction, like plastic bottles and waste materials. Experimentation revealed that filling some bottles with water provided significant thermal comfort improvements, albeit at the sacrifice of strength. Further structural testing revealed that panels produced from plastic bottles filled with sand had a yielding load of 25.30 kN on average. The study found that using a user-cantered, co-creation methodology and collaborating with local experts resulted in a solution (a prototype home) that was more functional and long-lasting.

Their most obvious environmental conclusion is that using waste local building materials has a positive impact, especially in low- and middle-income countries. The research revealed that, given the right motivations, different members of the community can assist in waste management activities such as preventing farmers from incinerating agricultural waste and picking up plastic trash. Another environmental impact stemmed from the building's selfsufficiency; measures were taken to reduce the environmental footprint, such as improving thermal comfort. Construction waste will be substantially minimised when using plastic bottles instead of traditional bricks because they are non-brittle. This also means that if the wall is damaged, they can be reused. As a result, the environmental impact is minimised not only during the construction phase, but also throughout its life cycle.

2.8 CONCLUSION

The literature was combed over in order to determine the impact of urbanization on the generation of waste, rise of slums and shanty towns, the cost of construction materials, and its impact on global warming. Research Question 1 is addressed in the literature review by demonstrating the impact of industrialization on plastic trash output, particularly in developing nations. Before the United Nations added plastic to the Basel Convention in May 2019, developed countries could hide their waste problem by outsourcing the majority of their plastic waste to developing countries, which is one of the reasons why plastic waste management issues are more visible in these countries.

Within the context of Research Question 2, housing and global warming on the other hand are considerably more pressing challenges, particularly in poor countries. The cost of living in cities in Europe and North America is significantly fairer by comparison because income in these countries is not proportional to the cost of housing. This literature analysis also shows how plastics are used in construction projects all around the world, lending credence to the idea of repurposing plastic trash to create houses.

From the case studies, it is identified that despite having a far lower compressive strength of 670 KN/m2 than the 3670 KN/m2 of traditional masonry, plastic bottles can nevertheless be used as suitable construction units for partition walls or as load-bearing walls for roof slab types. It is also apparent that the thermal evaluation and its comparative performance against conventional wall typologies is not well investigated.