Proposal Draft 1

Title

Evaluation of Performance and Challenges of the Incorporation of Waste Plastics as a Bitumen Extender

1.0  Introduction 

This report has been developed in response to the request for proposals on developing solutions for engineering problems. This report aims at determining the suitability of using waste plastic materials as modifiers in bituminous road pavement construction.

1.1 Background information 

Plastics is a material that contains one or more organic polymers of large molecular weight, solid in its finished state and it also can flow under a specific state. It is durable and has a very slow process of degradation. Every vital sector of the economy starting from agriculture to packaging, automobile, electronics, building construction, communication sector has been virtually revolutionized by the application of plastic (Shrivastava & Vyas, 2019). Due to the industrial revolution, its large-scale production of plastic proved to be a cheaper and effective raw material. Around four percent of annual petroleum production is converted directly into plastics from petrochemical feedstock. As the manufacture of plastics also requires energy, its production is responsible for the consumption of a similar additional quantity of fossil fuels. 

Global production of plastic has been rising, statistics showed that global plastic production has increased significantly from 1.5 million tons in the 1950s to 368 million tons in 2019 (Tiseo, 2021) It is supported that 79% are not recycled and have eventually been released into landfills or disposed off in the natural environment (Geyer et al., 2017). In 1972,  plastic debris was revealed to be found in coastal waters (Carpenter & Smith, 1972). Plastic debris with sizes less than 5mm is termed Microplastic. Microplastic is formed under the influence of natural light, sea waves, temperature changes, and biodegradation (Singh & Sharma, 2008). Most microplastics are found to have formed from cumulates in a sedimentary manner on the seafloor (Aslam et al., 2020; Claessens et al., 2011). During the alleviation of waste plastic from land to ocean, plastics can lead to noxious ramifications on the environment, and even human health (Lambert & Wagner, 2017).  In addition, toxic chemicals were discerned to be released into the environment, insinuated that plastics waste is a source of toxic chemicals (Chen et al., 2019). 

Singapore is one of the world's most heavily populated countries, with a population of over 5.6 million people. Plastic bags and other single-use plastics has became very cheap and available in Singapore, a developed country with the seventh-highest GDP per capita. Single-use plastic has been part of the rapid urban Singapore lifestyle for more than three decades, with supermarkets and restaurants providing plastic bags, cups, and disposable cutlery (Koh, 2020). According to a report published by the Singapore Environment Council in 2018, Singapore uses three billion plastic bags every 12 minutes on average. (SEC, 2018). 

Figure 1: NEA Waste Statistic and Overall Recycling (NEA, 2018)

To combat the global plastic issue, Singapore has made numerous engineering and science advancements. For example, scientists from National University of Singapore and Singapore Institute of Manufacturing Technology have managed to turn polyethylene terephthalate (PET) bottles into an aerogel-like substance that has strong insulation and absorption. There is no lack of PET that could be recycled into an aerogel, with an estimated eight million tonnes of plastic waste entering the world's oceans per year. The aerogel, according to the researchers, can be used for a variety of purposes, namely thermal and sound insulation in structures and oil spill cleanup. When it comes to washing up oil, the aerogel fares up to seven times better than conventional commercial sorbents (Koh et al., 2018). Besides the discovery of converting plastic to aerogels, scientists from National Technical University (NTU) have managed to create a pathway that uses visible light, such as sunlight, to rapidly break down chemical bonds in plastics. Most recycling processes, which require heating and produce greenhouse gases as a by-product, which are less environmentally sustainable than this photochemical reaction (Leong, 2019).

In Singapore, environmentally friendly and sustainable projects have become the primary focus and concern. With the decline of natural resources around the world and the rise in solid wastes nationwide, construction projects can benefit from the use of plastic waste to improve the technical performance of asphalt mixes. Research has shown that plastic waste have been studied as an asphalt binder modifier with an optimum binder content of four to eight percent by mass. Lab tests revealed that blends containing 4% waste material had the best Marshall stability and the lowest flow, as well as being extremely resistant to permanent deformations (Hinislioglua S and Agar E., 2004). Many countries have reported utilizing recycled plastic as an aggregate extender, a bitumen extender, or a binder modifier in the manufacturing of concrete mixes. For instance, in 2012 plastic crate waste was used as a warm mixed asphalt wax additive in Vancouver, Canada (Ridden, 2015). In 2015, Rotterdam, Netherlands, revealed a proposal to manufacture recycled plastic fragments for infrastructure development (Darroch, 2015). In the United States of America, it was also evident that there is great interest in the use of recycled plastic in bituminous binders and asphalt mixtures. Whereby, the country will be testing a new paving material made mostly out of plastic waste (Alexa, 2019).

1.4 Problem Statement

Plastic has always been a global issue in terms of its waste and disposal. Main methods of disposal include burning and landfilling, which does not solve the problem, creating larger issues such as soil and air pollution. 

1.5 Purpose Statement

The purpose of this report is to propose to LTA (Land Transport Authority) the viability of incorporating plastic waste for the paving of roads, which will result in reducing the impact on the environment caused by the abundance of plastic in Singapore.

2 Proposed Solution

The team proposes a solution to incorporate plastic waste into the wearing layer of a flexible pavement. This layer consists of bitumen, which is the material that we are proposing to substitute. As the flexible pavement consists of a high percentage of bitumen, we are proposing to substitute 6-8% of it in the bituminous mix.