Technical Report Final
Executive Summary
This proposal was prepared in response to the request for proposals on developing solutions for an engineering problem. The problem that has been identified is that of sustainable construction, which the BCA has stated is one of its key objectives.
One of the sustainability issues involved with construction is the use of steel reinforced concrete. Steel production is having a relatively large carbon footprint, and it involves a material that Singapore must import from overseas. This makes it relatively unfriendly to the environment and makes Singapore reliant on overseas supplies.
One alternative to steel-reinforced concrete is polymer-reinforced concrete. Polymer-reinforced concrete that makes use of recycled plastics is cheaper, easier to construct, and much more environmentally friendly. Plastics are also readily available in Singapore.
In order to encourage the use of polymer-reinforced concrete, new criteria can be included in the BCA Green Mark scheme, which will incentivize the use of polymer-reinforced concrete and make construction companies more likely to adopt it.
1. Introduction
1.1 Background Information
This document was written in response to the request for proposals on developing sustainable solutions for engineering problems.
It was mentioned in an interview with Dr. Fei Jin (2019) that steel reinforcement is the main form of concrete reinforcement used today in the construction industry. He claimed that on a technical level, steel is an excellent reinforcing material. However, there are a number of problems involved with the use of steel reinforcements.
One issue is that steel production generates plenty of carbon dioxide. According to the World Steel Association (2019), every tonne of steel being produced emits 1.8 tonnes of carbon dioxide. The steel production industry as a whole is also responsible for between 7 - 9% of “direct emissions from the global use of fossil fuel” (World Steel Association, 2019). Put simply, its carbon footprint is very high.
Another problem is specific to its use in Singapore. Singapore is practically void of any ore deposits or other natural resources (CIA World Factbook, 2019). The Building and Construction Authority (BCA) has acknowledged this lack of resources and has expressed concern regarding potential resource scarcity. They urged stakeholders in the construction industry to make as much use of recycled materials as possible to combat this (BCA, 2008).
One alternative to steel-reinforced concrete is polymer-reinforced concrete. One of the key benefits of using polymer-reinforced concrete is that it can make use of recycled material. In a paper by Rebeiz, et al. (1993), it was stated that polymer-reinforced concrete can be made by using recycled polyethylene terephthalate (PET) material found in plastic bottles.
From the technical side of things, the use of PET fibers makes quite a bit of sense as well. According to Sung, et al. (2010), the use of polymer material in concrete proved technical superiority in terms of improving crack resistance in concrete. Furthermore, PET fiber reinforcement effects a significant improvement in flexural strength over unreinforced concrete making it a viable alternative to steel reinforcements that is both cheap and environmentally friendly (Nibudey, R., Nagarnaik, P., Parbat, D., & Pande, A.
If construction companies make use of recycled PET fibers in the place of steel reinforcements where appropriate, the effects of plastic on the environment can be lowered and the reliance on steel may be reduced, effecting greater environmental and economic sustainability in the construction industry.
Despite these benefits, it’s a material that has seen little, if any, use in Singapore. In the same interview with Dr Jin (2019) he mentioned that the construction industry is very ‘stubborn’ and conservative by nature, relying much on the track record of any particular technology to determine whether or not it should be adopted. He said that this is good for safety as it means that the construction companies are not taking unnecessary risks, but at the same time, this culture stifles creativity and innovation. (See Appendix A for a summary of the interview.) Common knowledge suggests that plastic is much weaker than steel, and a lot of companies are quite dubious of its ability to reinforce concrete.
The key hurdle behind the lack of use of this material is simply the industry’s unwillingness to try something new. Ideally there would be some way to encourage the companies to make an effort to use technology like polymer-reinforced concrete. This report aims to tackle this issue.
1.2 Problem Statement
Construction companies in Singapore are unwilling to innovate and still predominantly utilize reinforced steel concrete in most building projects (Jin, 2019). Reinforced steel concrete uses a lot of raw materials and also causes harm to the environment. As such, new incentives should be implemented by BCA to encourage construction companies on the use of polymer reinforced concrete.
1.3 Purpose Statement
The purpose of this report is to propose to BCA the implementation of new incentives to encourage the use of polymer reinforced concrete by focusing on the technical benefits on how polymer reinforced concrete is a viable alternative to reinforced steel concrete.
2. Proposed Solution
The solution being proposed is to create new criteria in the BCA Green Mark scheme that specifically target the use of polymer reinforced concrete.
BCA Green Mark is a green building rating system to evaluate a building for its environmental impact and performance. It provides a comprehensive framework for assessing the overall environmental performance of new and existing buildings to promote sustainable design, construction and operations practices in buildings. (BCA, 2018)
This system can be leveraged to create the incentive needed to encourage companies to begin using polymer-reinforced concrete. The use of polymer-reinforced concrete can be inserted into the Green Mark system’s criteria to encourage its use.
Use of polymer-reinforced concrete can be one of the criteria to attaining higher green mark rating. It directly targets the use of polymer-reinforced concrete and it helps to encourage construction companies to consider the use of polymer reinforced concrete.
The criteria specified in BCA Green Mark fail to include the use renewable or recyclable materials. This is in contrast to the Leadership in Energy and Environmental Design (LEED), a global certification of sustainability achievement, has policies to encourage building owners to use renewable and recycled materials. A comparison of the two is shown in the table below.
Table 1. Comparison of LEED and BCA green building assessment (Ahankoob, et al., 2013)
While the Green Mark scheme is more comprehensive in some areas, it does not include reusable and renewable materials. In addition, neither system specifies the use of polymer-reinforced concrete. By specifying the use of polymer-reinforced concrete as part of the Green Mark design criteria, the BCA can more strongly encourage its use by construction companies in Singapore.
3. Benefits of Proposed Solution
There are a multitude of technical, economic and environmental benefits to adopting polymer-reinforced concrete.
3.1 Cost
The Alibaba online store (n.d.) shows that recycled PET fibres and steel rebar both cost roughly $500/tonne depending on the supplier. However, PET fibres only make up about 1 - 3% of a reinforced concrete member’s overall volume whereas steel reinforcements can make up to 10 - 20% of a concrete member’s overall mass (Zhao, 2019). This means that more steel is needed to reinforce any particular concrete member, making the PET fibre far more cost-effective.
3.2 Weight
The use of polymer-reinforced concrete makes the structure very load-efficient compared to steel-reinforced concrete. According to the Engineering Toolbox (n.d.), steel has a density of 7830kg/m3 whereas concrete has a density of around 2000kg/m3. Because of this, steel can make up about 10 - 20% of a concrete member’s overall mass, steel-reinforced concrete can be significantly heavier than unreinforced concrete of an equivalent size. Polymer-reinforced concrete on the other hand can weigh very similarly to unreinforced concrete due to how little reinforcing material is being used. This makes the structure very lightweight which further reduces the need for steel reinforcements elsewhere.
3.3 Ease of construction
Steel-reinforced concrete has a bit of preparation time involved in its construction. The rebars must be shaped, placed into the mold at the correct height, and secured in place before the concrete can be added. It is a relatively time-consuming process. With fibre-reinforced concrete, all that needs to be done is for the fibres to be added slowly as the concrete is being poured to ensure an even distribution. This is a very simple and quick process that saves a lot of time relative to fibre reinforced concrete and requires very little skill and training to carry out effectively. According to Steel Reinforcement Institute of Australia (2001), a typical construction process of steel reinforced concrete requires several procedures to be carried out. First, a concrete underlay must be laid out. This serves as a sheet of impermeable material which is resistant to ultraviolet deformation and impact during construction. Then the steel reinforcements are affixed to the bottom of the mold. The steel reinforcement has to be chaired in a proper position to act effectively. If necessary, reinforcements are fixed to the top of the structure, according to the design specifications. Finally, concrete is poured over and around the steel. This concrete is the compacted with the use of a vibrator. This is far more time consuming than the creation of polymer-reinforced concrete.
3.4 Sustainability
For every 1 tonne of PET material produced for use in drinking bottles, 3 tonnes of CO2 is emitted (Blue, 2018). Because the polymers being used can come from recycled PET, this method of reinforcing concrete is very beneficial to the environment, as it makes full use of plastic that is already being produced. It also means that there is very little chance of shortage because these plastics come from a product that would otherwise be considered waste.
4. Proposal Evaluations
In this section, the feasibility and challenges of the proposed solution will be evaluated and discussed.
4.1 Case Study: Polyester Fibre Waste in Concrete
While the use of polymer reinforced concrete is very rare and even unheard of in Singapore, its use has been experimented with in India. A study in 2014 was conducted by S. Panda and N.H.S. Ray regarding the use of polymer reinforced concrete.
This involves a feasibility study on use of polyester fiber waste as reinforcing admixture in concrete for use in road works. In this, concrete pavement slabs of size 3.5m x 3.5m, with thickness of 10cm and 15cm were cast with plain cement concrete (PCC) and polyester fiber reinforced concrete (PFRC). The slabs were subjected to load deflection test using Falling Weight Deflectometer (FWD). Concrete cube specimens were also subjected to abrasion resistance test. Further, cube specimens were tested under compression and for their Ultrasonic Pulse Velocity after a period of 2 years. The polyester fibers used in this study is primarily a waste product from textile industry and, are non-biodegradable. (Panda & Ray, 2014)
The study went on to show that the concrete’s strength was of an acceptable level and that the concrete was still in very good condition after 24 months.
4.2 Feasibility
The proposed solution of creating new criteria in the BCA Green Mark scheme to encourage the use of polymer reinforced concrete is a viable solution. The purpose of the BCA Green Mark scheme is to promote sustainability in the built environment and improve environmental awareness among building owners and builders as they embark on their construction project. Polymer reinforced concrete is an optimal sustainable construction material based on its technical superiority in certain circumstance (e.g. lightweight), and its origin where it is formed by incorporating recycled plastic and concrete. Thus, the benefits of polymer reinforced concrete should be considered to serve as an alternative to steel reinforced steel concrete, in order to also address the issue of resource scarcity in the built environment.
4.3 Challenges
One of the potential challenges posed to the proposed solution would be the local construction firms’ unwillingness to innovate. Due to steel’s ability to withstand high tensile strength, most building projects still preferred the use of the traditional steel reinforced concrete. However, based on the Government’s Land Sales Programme (GLS), selected strategic locations in Singapore are subjected to mandatory higher green mark standards (BCA, 2009). It requires interested companies to incorporate sustainable methods in their building designs as well as construction processes. With the use of polymer reinforced concrete in certain applications, it would meet the criteria of the use of sustainable material. Therefore, utilizing polymer reinforced concrete will help the companies in acquiring the Green Mark standard.
The primary issue with the proposed solution is that in a very fundamental way, it does not directly address the main hurdle regarding the construction companies’ lack of willingness to make use of polymer reinforced concrete, which is the fact that it has seen very little use in other projects. What the solution being proposed intends to do is to tip the scales just enough for some more enterprising corporations to give it a shot. If these companies are successfully convinced to make use of polymer reinforced concrete, then there would be a much stronger track record for other companies to cite in order to justify the use of polymer-reinforced concrete themselves.
5. Methodology
5.1 Primary Research
In order to obtain more information about the feasibility and challenges involved with the use of polymer-reinforced concrete, Dr. Fei Jin, an assistant professor with the School of Engineering, University of Glasgow Singapore was interviewed. Dr Jin holds a PhD in Civil Engineering and his primary field of research is cementitious materials. His experience makes him an authority in the research that is being performed for this report. A ten-minute-long interview was conducted with Dr Jin. The transcript of this interview can be found in Appendix A.
Dr Zhao Ming Shan, a professional officer at Singapore Institute of Technology was also interviewed. He provided information on the weight of steel-reinforced concrete which was used to make comparisons between it and polymer-reinforced concrete.
5.2 Secondary Research
A range of secondary research was used such as LEED vs BCA Green Mark (Ahankoob, et al., 2013). A paper by a group of civil engineers, which served as a credible source for the proposal, documented comprehensive information which tells us what can be improved in the Green Mark as compared to LEED. Several Other websites are used such as news article 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 BCA.
6. Conclusion
Polymer-reinforced concrete is very well-researched and is an absolutely viable alternative to steel reinforced concrete under the right circumstances. It is lighter, cheaper, more sustainable and more environmentally friendly than steel reinforced concrete, and it should be used whenever possible. The proposed solution aims to encourage this use.
There is a significant amount of resistance to change of any sort in the civil engineering industry. The solution outlined above will be met with much skepticism and stakeholders will not be so easily convinced into adopting it. However, such resistance is found whenever any sort of innovation is introduced. By specifying polymer reinforced concrete as a criterion for the Green Mark Scheme, the BCA can hopefully reduce this resistance that’s so prevalent in the industry and bring about some change to it as a whole.
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