Technical Report Draft 1

1. Introduction

1.1 Background

Singapore named the “The Garden City’’ as it is one of the greenest countries in Asia. Thus, Singapore has been emphasizing on waste management as Singapore’s only remaining landfill is Semakau landfill. Semakau landfill is predicted to be filled by the year 2035. Singapore’s population is growing at a staggering rate every year from 4,027.9 million in 2000 to 5,612.3 million in 2017. An increase of 1584.4 million in the past 17 years.The increase in population eventually leads to the incline of solid waste generation. In 2016, there were 7.81 million tonnes of waste being produced as compared to the 7.67 million tonnes in 2015. There is an increase of 140,700 tonnes. Similarly, if this rapid increase in waste generation continues, the landfill would be filled up before the expected year.

National Environment Agency (NEA) conducted several surveys about the different waste type, waste disposed, and waste recycled, waste generated and recycling rates in 2016. Plastic waste is one of the main contributing waste in Singapore as it has one of the highest amount of waste generated and the lowest recycling rate. Examples of plastic waste are takeaway containers, plastics utensils, plates, and cups. In 2016, 822,200 tonnes of plastic waste was being generated, however, only 7% of it was recycled. The remainder is incinerated and then sent to the landfill. The recycling rate of plastic waste cannot keep up with the increase in plastic waste. This causes more and more plastic waste to be sent to the landfill.

In addition, NEA is urging our local construction industry to investigate the usage of recycled and waste materials. Plastic waste can be recycled and be made into other products like carbon nanotubes and different chemical fuel. However, it is not fully utilized due to the difficulties in collecting and sorting plastic waste.

Samwoh Corporation has been carrying out research on repurposing waste materials and incorporating them into concrete. The project team sees the potential of using plastic waste as aggregates in concrete and is going to focus on promoting the possibility of incorporating plastic waste into concrete.

1.2 Problem Statement

Samwoh Corporation should be incorporating 30-40% of plastic waste into concrete as it is environmentally friendly and provides a new purpose for plastic waste. Plastic waste is one of the largest waste contributors and they are not being investigated extensively as a material in green concrete. According to National Environmental Agency (NEA), there were 822,200 tonnes of plastic waste being generated in 2016 and only 7% of them were being recycled resulting in depletion of space in the landfill as our landfill would be filled up by 2035. Looking at the problem, this research team decided that there is a need to incorporate 30-40% of plastic waste into concrete.  This will reduce the amount of plastic waste being sent to landfills and reducing the need for raw materials of conventional concrete.

1.3 Purpose Statement

This report aims to promote the idea of incorporating plastic waste into concrete to Samwoh Corporation which then can be adopted by Singapore’s construction industry. This will reduce the amount of plastic waste needed to be sent to the landfill. The intention is to enhance the understanding of the advantages of plastic waste in concrete.

2. Proposed Solution

Green concrete refers to concrete that has partial or complete replacement of either cement, fine or coarse aggregates with waste or residual products. When the substitution materials are less dense than the conventional materials, lightweight concrete is produced. There are various ways plastic waste can be incorporated into concrete.

Plastic waste can be processed, typically through shredding and low temperature melting. The processed plastic can be used as coarse aggregate replacement in concrete.

Another way of using plastic waste into concrete is to convert plastic waste into carbon nanotubes. Carbon nanotubes are tiny cylinders of carbon atoms. They can be group into two different types of carbon nanotubes which are the single-walled carbon nanotube (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). MWCN is most commonly used as they are cheaper to make and have a better reinforcement in cement concrete. An innovation by technology company called BlueRen believes that more plastic waste can be recycled and the use of cement to make concrete reduced, as carbon can be used as an additive in concrete idea.

The project team is focusing on the process of converting plastic waste into shredded plastic which can be used as a replacement material for coarse aggregates in concrete.

2.1 Benefits

Kumar. P. and Kumar. G (2016) mentioned that in the last 20 years, research on the usage of urban waste in building materials has been increasingly published. Aside from the environmental benefits, the wastes yield positive effects on the properties of the final product. Amidst the municipal solid waste, plastics have received a lot of attention because they are not biodegradable.  Plastic waste has been increasingly used as a partial substitute of aggregates. The usage of plastic waste as aggregates can greatly reduce the weight of the concrete, this is called lightweight concrete.

It is identified that the usage of plastic aggregates can improve the ductility in concrete. Ductility helps the material to stretch under tensile stress, this property very important in the safety of the building. In an event where the building starts to collapse, people in the building still have time to escape as the concrete would deform significantly before reaching failure. Using plastic aggregate is also cost effective and energy efficient. Plastic aggregates can effectively help to maintain the building interior temperature in hot weathers.

According to Sofi. and Jaivignesh. (2016), the incorporation of shredded plastic, properties such as abrasion resistance, impact resistance, ductility, shock absorption, and thermal conductivity can be improved. Apart from the benefits mentioned, Kumar. P. and Kumar. G (2016) also explained that plastics are versatile and it can be customised to meet specific technical requirements. They have a lighter weight than other materials, therefore, reducing the fuel consumption during transportation. Plastics are very durable and can last a very long time. Moreover, they also have great resistance against chemical, water, and impact. Most importantly, they cost less to produce than traditional concrete. This serves as a way to improve the properties of concrete and act as a solution to the disposal of plastic to some extent.

Samwoh can become one of the leading construction companies in Singapore to use lightweight concrete effectively. Lightweight concrete can be used as non-loadbearing concrete such as concrete panels that are used in facades. By using shredded plastics as an aggregate, Samwoh can bring down the cost of producing concrete as aggregates are relatively pricier than plastic wastes. Samwoh can have a centralised plastic waste collection centre to collect plastic waste disposed by their employees and use it in their concrete batch. This provides self-reliance, hence, reducing the cost to purchase and transport plastic waste from contractors. Furthermore, this shows that plastic aggregates can also be used as a plastic disposal method in the company.

Goy (2016) mention that carbon nanotubes have many uses as they are light, strong and can conduct electricity well. While Goy (2016) may have mentioned the physical properties of carbon nanotubes, Suhendro (2004) provides even more physical properties of carbon nanotubes to prove that carbon nanotubes are better to add to concrete. Suhendro (2004) states ‘multi-walled carbon nanotubes (MWCNTs) are usually high strength, ductile, crack-free and durable’.

2.2 Evaluation

There are two main disadvantages when it comes to incorporating plastic into concrete. Firstly, plastics have a low bonding property. Hence, it causes the compressive, tensile and flexural strength of the concrete to reduce. The concrete might not be strong enough to be used as a load-bearing beam, even at the higher part of the building. Even with reinforced steel added, normal concrete would be more suitable to support a higher amount of load.

Secondly, plastic wastes have to be cleaned condition before being added to the concrete mixture as aggregates. Therefore, it is a hassle and an additional cost to ensure that plastics are unsullied. The overall cost would also increase when equipment might be required to monitor the gas emission and the presence of toxic and polluting elements. However, this only applies when there heating is required in the process.

Despite the mentioned disadvantages, incorporating plastic waste as aggregates into concrete are extremely effective has numerous advantages, such as the improvement of properties of concrete at a cost-efficient approach. These concretes need not be loadbearing concrete as its decreased strength might make it suitable for places with heavy loads. They can be placed in the higher part of the building where the higher floor would mean that it would be carrying lesser loads. They can be used concurrently as a lightweight concrete for aesthetic purposes in the building, without drastically increasing the total load. High ductility is one of the most useful properties in this concrete, it is useful in harsh conditions as it will expand and contract well, as well as having freeze-thaw resistance.

Aggregates can be partially replaced by plastic waste as it can effectively improve the properties of the concrete and lessen the total weight of the building. The reduction in compressive, tensile and flexural strength can be overcome by placing the concrete at higher levels. So that it does not have to withstand addition load from other floors. The use of waste plastic aggregate can be effectively used because of its properties enhancing and lightweight benefits

There is one major weakness about carbon nanotubes which is barriers to green concrete  Barriers to green concrete, Due to building industry’s profitability, it depends on how quick the construction schedules. The faster the building is being built, the faster they get their profit.  Thus, they prefer not to use green concrete as green concrete requires a life-cycle cost saving from the conversion of material and energy.

3. Methodology

This project team performed primary and secondary research that includes a site visit and online materials from various sources and government organizations.

3.1 Primary Research

The project team had the opportunity to visit Samwoh Research and Development Centre as one of our module site visit. The project team talked to the lab manager, Mr. Teo Yong Boon regarding incorporation of plastic into concrete and there is researches on lightweight aggregates and adding of carbon fibres into concrete. However, there was no information regarding the recycling of plastic waste for concrete.

3.2 Secondary Research

A range of secondary data was obtained from official websites, news articles and research journals. This project team gathered statistics regarding Singapore’s waste generation and recycling rate from National Environment Agency (NEA)’s website. A news article has been published quoting NEA promoting Singapore’s construction industries to incorporate more recycled and waste materials as building materials were used as a motivation to promote our idea to Samwoh Corporation.

4. Conclusion

Research has shown that our only landfill will be fully filled by the year 2035. This project team seeks to reduce one of the main culprit, plastic waste, through promoting the recycling of plastic waste and using them as a material in concrete to our local construction industry. While processing the plastic waste can be costly, we believe that it would reduce the amount of plastic waste and benefit the country in the long run.

In conclusion, it is crucial that Singapore explores new ways of waste management. We believe that our proposed solution will be one of the stepping stones towards reducing the amount of plastic waste sent to landfill.