Technical Report Draft #1B : Converting Waste Plastic Into Aggregate

1.1 Introduction (Background information)

This report aims to request for funds to aid on the research on recycling Polyethylene Terephthalate (PET) bottles for construction materials. According to National Environment Agency (NEA, 2017) it was estimated that 1.76 billion of plastic items were used a year in Singapore,and only 6% of the waste plastics were being recycled. The reason why plastic was used at an abundance is due to its ability to form into different forms and for its durability, but the disadvantage of plastic items would take centuries to be decomposed naturally and landfills. Those plastic that were not recycled would be incinerated and be shipped to Pulau Semakau Landfill (NEA, n.d.). It was originally estimated that Pulau Semakau Landfill would be able to sustain until 2045, but due to the increasing reliance on disposable plastic products, the current estimation is that the landfill would run out of space by 2035 (MEWR, n.d.).

Currently, the two main ways Singapore dispose waste plastic is by burning them and disposed it to the landfills or sell the waste to other countries that are willing to buy them (Aqil, 2018). The practice of burning waste plastic would cut down the amount of space needed in the landfills, but it is very harmful to our environment.

According to Aqil, 2018, It was reported that the fumes produce from burning plastic posed harmful health risk such as, increase the risk of heart disease, aggravate asthma and cause damage to the human nervous system. Aqil also mentioned that Singapore sells approximately 42,000 tons of the waste plastic to China, Malaysia, Vietnam and Indonesia in 2016. However, China announced a ban on importing “foreign garbage”, this ban would post a major problem as singapore’s biggest plastic waste buyer is china.

With the plastic waste management challenges singapore is facing, creative ideas for plastic recycling should be implemented to reduce the harmful impacts. According to BCA, singapore is expecting to have a higher volume of construction activities per annum, as singapore is still developing.

The main stakeholders for the application of recycled would be Building and Construction Authority (BCA), as BCA governing the quality control of all construction materials and methods. Singapore have been using natural resources of fine and coarse aggregates in the mixture of concrete. In a BCA handout, it was stated that ECO-Concrete which are concrete that consisted of 50% or more recycled content.

Therefore, BCA had set rules and standards for the quality of building materials to be used in singapore for contractors to strictly adhere to. With the given BCA standards, lab test and research can be done to the recycled polyethylene to be introduced into the concrete as a replacement of natural aggregates.

WIth the gradual increase in plastic usage in singapore, the landfill at Pulau Semakau would be filled up in no time, and singapore have to find alternative solution for disposing plastic waste.Singapore authorities should start adopting the use of recycling plastics into green aggregates and find alternative ways to incorporate the waste plastic to other forms of construction materials to ultimately reduce the contribution of plastic waste to our landfill.

1.2 Problem Statement

Currently, the percentage of plastic waste not being recycled is at 94%. With the aim of being a “zero waste” nation, the ideal goal is for Singapore to no longer rely on landfill as a means to dispose our plastic waste, but through alternative methods. One solution is to utilise the waste plastic by converting them into green construction material. With this, not only are we working towards a “zero-waste” nation, but also extending the life spend of landfills for other waste disposal.

1.3 Purpose Statement

The purpose of this report is to propose the adoption of green aggregates by recycling waste plastic. The aim is to increase the percentage of waste plastic being recycled instead of being sent for incineration and end up in Pulau Semakau Landfill. Adopting this solution would bring Singapore a step closer to being a “zero waste” nation.

1.4 Problem Solution

BCA had made an initiative by encouraging the use of recycled concrete materials by incorporating Recycled Concrete Aggregate (RCA) into the production of concrete. RCA are aggregates that are recovered from demolition of building, where demolition debris are then crushed and sieved into different category of aggregates.

Sands and granites are deemed as aggregates in the concrete mixture, and the roles of aggregates in a concrete mixture is to give the basic property which determine the concrete behaviour such as durability, strength and workability. Therefore, concrete properties depend heavily on the properties of the aggregates which determine the quality of the concrete produced. As natural resources are of a scarcity in singapore, singapore have to rely on other countries as these natural resources are imported into singapore.

In recent years, India had been researching on the possible ways to recycled plastic into construction base material. Research had shown that PET bottles could be grinded and blended to achieve sand like textural which allows it to replace natural sand and act as a fine aggregate in the concrete mixture. Due to PET having a different chemical properties as natural sands, it bonds differently with cement matrix causing the concrete to have a weaker strength and durability. But by treating PET with chemicals mixture and reducing the size of the PET particles, the reaction bond between the PET and cement matrix is showing improvement (Thorneycroft et al. 2018).

Brick is a type of building material that used to make walls, pavements and other elements in masonry construction.During 1990s, towns in singapore were built out of bricks. But as technology advanced, Singapore had became “a city of glass and steel skyscrapers” (Justin Zhuang, 2014). Therefore,Singapore no longer have any brick factories, hence all brick used in Singapore were imported from overseas. Bricks are no longer visible is because contractors tend to paint over facing bricks or plastering it up so only the plaster work can be seen and not the bricks.

PET bottles are able to be transform into construction bricks, by compacting sand into the plastic bottles and giving it the ideal strength which is comparable to original bricks. By sorting the PET bottles into different size and shape, and a strict selection of suitable PET bottles. The bottles are then compacted and filled with sand, this sand filled bottles are then deem as ECO-bricks. This ECO-bricks would be stacked and cemented together, creating a partition walls that is made up of plastic bottles and cement mortar. (Himanshu, 2017)

1.5 Benefit

There are many potential benefits of the proposed solution such as: conserving natural resources, relieving stress on landfill, versatility and light weight.

Conserving natural resources

According to the Portland Cement Association, approximately 60%-75% of the concrete is made up of aggregates, in average 114 tonnes of aggregates are used per month in singapore. That contributes to a hefty amount of percentage in the mixture of cement.

In the 4th quarter of 2018, Singapore’s construction industry average usage of cement was estimated to be 377 000 tonnes. By adopting waste plastic aggregates, it would help conserve natural resources by reducing the need for virgin materials

Figure 1. Forecast and actual construction demand (BCA, 2019)

Relieving stress on Pulau Semakau landfill

The proposal of the creation and adopting of plastic waste aggregates would redirect substantial amount of plastic waste away from landfills, prolonging Pulau Semakau’s lifespan. It could potentially reduce energy consumption and emissions from burning the waste.

Versatility

The recycled plastic aggregates can be used for various different functions, suitable for use with different construction Incorporating plastic aggregates projects in Singapore.

Lightweight Concrete

Incorporating plastic aggregates improves properties of a concrete due to its toughness, low thermal conductivity, high heat capacity and good abrasion behaviour. Moreover, the incorporation lowers the densities of the resulting concrete thus developing a ‘lightweight concrete’. This development lowers the earthquake risk of a building and it could be beneficial in the design of an earthquake-resistant building in the future (Semiha, Cengiz, Kubiley, 2010, as cited in Saikia, Brito, 2013)

1.6 Proposal Evaluation

There are some challenges to overcome in order to achieve our proposed solution. One challenge faced by the team is the cost of sorting plastics. There are no exact cost stated in articles. According to Quah (2018), V1 Recycle’s managing director Richard Lim stated that the sorting process is the costly parts of the process as it requires expensive machines or very skilled workers. On top of that contamination and land constraints affects the cost of sorting plastics. Mr Dave Wong, a business development manager at A~Star Plastic Recycling, mentioned that the cost of recycling plastics will increase when plastic is contaminated as cleaning and sorting are required. (Mahmud, 2018)

1.7 Research and Methodology

1.7.1 Primary Research

An online survey questionnaire was conducted to Singaporeans as a form of a primary survey. Singaporeans are one of the main stakeholders as they play a part in producing plastic waste. Furthermore, there is a need to spread the awareness of the importance in plastic waste. The objective of this survey is to find out what Singaporeans know about plastic waste management and to showcase the importance of this proposal.

This is crucial as the team wants National Environment Agency (NEA) and Building and Construction Authority (BCA) to know that there is room for improvement for Singapore’s recycling efforts and that our proposed solution could be alternative way to recycle plastic.

1.7.2 Secondary Research

The main source of secondary research is NEA and BCA. An online journal published by Zainab Z. Ismail benefits the proposal as a reliable source. This journal provides credible studies that proves that “reusing waste plastic as a sand-substitution aggregate in concrete gives a good approach to reduce the cost of the materials are problems posed by plastics” (Zainab, 2008)

1.7.3 Findings

Among the 72 survey respondents, 88.9% of the respondents use more than 3 disposal plastic products a day and 91.7% of them do not take the initiative to recycle their plastic waste. 97.2% of the respondents are not aware of Singapore’s low recycling rate for plastic, however, 95.8% agreed that more needs to be done by the Singapore government to improve recycling efforts. The survey results support the team’s idea of the call for the improvement of Singapore’s recycling efforts and also highlight Singaporeans consumption of disposable plastic products.

1.8 Concluding Statement

In conclusion, with plastic being one of the top contributor being sent to our landfills and having the lowest recycling percentage, the adoption of converting waste plastic to aggregate would help reduce Singapore’s plastic waste problem. With the application of recycling plastic into construction base materials will greatly reduce the usage of semakau landfill by a huge amount.

By incorporating plastic into construction materials, we are able to discover better materials for the construction. New and improved construction materials with plastic incorporated could deliver a better result as compared to the original materials, as plastic have a different physical properties as compared to traditional materials. This could help Singapore to explore more possible new construction methods with the new products produced.

With the cost of sorting plastics are very high, Singaporeans can play a huge part by sorting their recyclables and disposing it into seperate bins instead of the ‘blue recycling bins’ as a single-stream recycling. This will contribute in reducing its total cost.

We hope that BCA is able to provide adequate aid in terms of research and development fundings, which allows us to test and identify any flaws to be rectified.

1.9 Reference:

(n.d.). Retrieved March 12, 2019, from https://www.cement.org/cement-concrete-applications/concrete-materials/aggregates

Akçaözog˘lu, S., Atis, C. D., & Akçaözog˘lu, K. (2010). An investigation on the use of shredded waste PET bottles as aggregate in lightweight concrete. Waste Management,30(2), 285-290. doi:https://doi.org/10.1016/j.wasman.2009.09.033

Hassani, A., Ganjidoust, H., & Maghanaki, A. A. (2005). Use of plastic waste (poly-ethylene terephthalate) in asphalt concrete mixture as aggregate replacement. Waste Management and Research,23(4), 322-327. doi:https://doi.org/10.1177/0734242X05056739

Ismail, Z. Z., & AL-Hashmi, E. A. (2008). Use of waste plastic in concrete mixture as aggregate replacement. Waste Management,28(11), 2041-2047. doi:https://doi.org/10.1016/j.wasman.2007.08.023

Mahmud, A. H. (2018, June 3). ‘Cannot sell ... so they burn’: What’s next in the uncertain future for plastic waste in Singapore? Channel News Asia. Retrieved March 12, 2019, from https://www.channelnewsasia.com/news/singapore/china-bans-plastic-waste-whats-next-for-recycling-in-singapore-10281026

PUBLIC SECTOR CONSTRUCTION DEMAND IS EXPECTED TO STRENGTHEN THIS YEAR. (2018, January 11). Retrieved March 12, 2019, from https://www.bca.gov.sg/newsroom/others/pr_prospectsseminar2018.pdf

Quah, J. (2018, September 25). How Singapore's plastic waste is recycled. Today. Retrieved March 12, 2019, from https://www.todayonline.com/singapore/how-singapores-plastic-recycled-3

Saikia, N., & Brito, J. D. (2013). Waste polyethylene terephthalate as an aggregate in concrete. Materials Research,16(2), 341-350. http://dx.doi.org/10.1590/S1516-14392013005000017

Waste Statistics and Overall Recycling. (n.d.). Retrieved March 12, 2019, from https://www.nea.gov.sg/our-services/waste-management/waste-statistics-and-overall-recycling

Zhuang, J. (2014, August 16). Building Singapore Brick by Brick. Retrieved March 12, 2019, from http://justinzhuang.com/posts/building-singapore-brick-by-brick/