- Executive Summary
- Introduction to Urban Infrastructure Redevelopment
- Overview of a life cycle assessment for urban infrastructure redevelopment
- The roles of different types of engineering in urban redevelopment
- Project Management
1.0 Executive Summary
The aim of this report is to have learnt about urban infrastructure development, to understand a life cycle assessment of any project and to understand that different types of engineers are involved in each project and even each stage of the life cycle.
This report focuses specifically on asphalt pavements. It includes the life cycle stages of the pavement and its impacts to the socio, economic and environmental aspects of the society. It also explores the 4 different types of civil engineers involved in this process from the extraction of raw materials to its end of life.
2.0 Introduction to Urban Infrastructure Development
Urban; a lifestyle where people live-in built-up cities
Infrastructure; the essential framework required to support the needs of a population in an area
Development; a process that works to improve any aspect
The development of Urban Infrastructure has become a pivotal concern over the past few decades considering the exponential growth of populations in urban areas around the world. To put it in numbers, in 1950’s, around 30% of the population lived in cities. Now, there are over 55% and UN predicts that by 2030, the number will reach up to 68%. These numbers can be explained by the large increase of rural to urban migration and also the high birth rates in developing areas exceeding the pace where in which the urban areas can keep up with.
Therefore, the importance for cities to continue to improve their infrastructure has become a pressing issue. Research shows that more than 1 billion people worldwide now live in urban slums. People who migrate to urban areas hoping for better living standards are shut down due to the city’s inadequate public works.
Not only does this rapid urbanisation affect the society but also adds more stress to our environment due to its heavy dependence of having to destroy scenic areas to concrete and condensed ones.
To ensure a city maintains and works to improve their populations living standards, these infrastructure elements are vital: transportation, power, water, and telecommunication. As these elements run on a network system, each and every one has to advance to sustain the area.
Transportation infrastructure is pivotal to any city. As urban areas increase in its density of people and buildings, urban transportation needs to be able cope with this while providing an efficient method of movement.
One of the biggest problems faced would be traffic congestion. Roads in current society are packed due to the increased usage of cars and other vehicles for main mode of transportation. This would mean that roads play a massive role in infrastructure and designing and constructing them must be a priority in all cities.
Researchers at the Texas Transportation Institute estimate that costs of urban congestion annually can add up to $70 billion in US, representing 26 hours of delay and 42 gallons of fuel. This wastage of products and it repercussions to the environment needs to be addressed and solved.
One of the most used products for the design of roads, is asphalt. They make up 94% of pavements in the US and although they are a very important component to the transport system, in terms of its environmental effect, it is widely discouraged. Asphalt is said to release large amounts of toxic elements into atmosphere, largely contributing to global warming.
3.0 Overview of a life cycle assessment for urban infrastructure redevelopment
Sustainability plays a large role in urban infrastructure as our Earth continues to deteriorate due to excess levels of pressure humans place on its atmosphere. To reduce these levels of non-exhaust emissions, cities must be able to detect these emissions and assess them. A method used is called life cycle assessment (LCA).
LCA evaluates the total environmental burden of a product, in this case, asphalt pavements, by considering all the inputs and outputs of its life cycle from raw material production to its end of life. It is also used to increase the life cycle of its pavement because of mankind’s increase in vehicle use, service life span of it has become a lot shorter than it used to be.
Life cycle assessment involves 4 phases: Goal and Scope, Inventory Analysis, Impact Assessment and Interpretation. However, to establish the life cycle assessment, we first need to break down the life cycle to its stages and further analyse each in terms of the 4 phases.
3.1 Stage 1: Construction
This stage involves 2 processes; extraction of raw materials and processing them at the construction site.
The raw materials used include crude oil, aggregates and additives. Crude oil is then transported to a refinery where bitumen is extracted through fractional distillation which then makes up 4.5% of the asphalt mixture while the rest being aggregates. Aggregates deplete minerals and fossil fuels therefore contributing up to 30% of greenhouse gases of this entire process. They also contribute highly to the toxicity of air but less than that of bitumen.
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Construction involves processing of raw materials in the mixing plant, paving the asphalt layer, compacting it and transporting the materials to the construction site. Studies show that the most energy consumption process in a pavement’s life cycle involves the manufacturing of materials, where 1525.8 tonnes of oil only produces 1 km of pavement. This regards both electricity and fuel consumption as the mixing process requires heating of materials. Very high temperatures dry the aggregates while melting the bitumen and additives for storage in the future. All this adds up, causing it to be the highest energy intensive process. This is proved by a research in Europe which concluded that the construction of an asphalt pavement consumes 92.4 to 92.9 % of energy used in all the different types of road construction. The second highest would be transportation to and from sites. This involves diesel having to be burnt to transport the asphalt contributing to global warming.
An example of the emissions and energy use is shown below. This data is of experimental values in Arlanda, Sweden.
Figure 1: Transportation emission: https://www.researchgate.net/figure/Global-Warming-Potential-GWP-for-the-GHGs-Solomon-et-al-2007_tbl10_254255417
Figure 2: Raw material emission : https://www.researchgate.net/figure/Global-Warming-Potential-GWP-for-the-GHGs-Solomon-et-al-2007_tbl10_254255417
Due to this, new techniques are being developed to reduce the production process with less consumption of energy and less emission of greenhouse gasses, like using warm mix asphalt instead of hot mix as it requires much less energy.
3.2 Stage 2: Use
This stage has the most diverse effect on the environment impacting climate change, fossil fuel depletion, acidification and eutrophication. Due it to wide range of effects, it is very difficult to reduce the emissions and since populations continue to grow, traffic continues to increase. Therefore engineers have begun to research and implement substitutive and creative techniques.
In a highly populated urban area, where many of the population use vehicles for transportation, over time, if not maintained, deterioration of pavements due to friction will increase rolling resistance. This then increases fuel usage as more energy is required to break the vehicle. Ultimately fuel prices will be lowered as the value of fuel would decrease, affecting the cities economy. Fuel production would also have to increase, increasing greenhouse gases emitted due to the burning of fossils.
To prevent this from happening, pavement condition can be modelled and estimated. This is achieved by a model developed by PIARC, a World Road Association, which can simulate the deterioration of pavement conditions and calculate vehicle energy consumption from IRI(International Roughness Index).
Another aspect to consider is the Urban the Heat Island Effect. Compared to concrete which has an albedo of 15-25%, asphalt only has 5-10% meaning that more heat is being absorbed from the sun, causing cities to become warmer in average. This would increase energy consumption, especially in the summer time, to cool down buildings and houses causing electrical demand to spike. Research from Lawrence Berkeley show that electricity demand increased up to 2% for every 1-degree Fahrenheit increase in temperature. Moreover, this can cause an increase in the activity of chemical and biological reactions, bringing more pollutants, such as NOx, into the environment. This would eventually require actions to be placed to rid of these pollutants, leaving a burden on the economy. Therefore, some cities have begun to use cool pavements as they have high reflecting capabilities, reducing the chances of all these repercussions.
Furthermore, since asphalt pavements are impermeable, it cuts off the soil beneath, reducing evaporation of water. This can eventually lead to floods during heavy rainfall which can result in destruction of many buildings and surfaces. Also, due to leachate, the water will become contaminated and polluted requiring deeper cleansing processes increasing cost. To chose a more sustainable substitute, some urban areas use permeable pavements to prevent these complications.
3.3 Stage 3: Maintenance
Maintenance of asphalt pavements is crucial in the life cycle of roads due to the over use of it like mentioned above can have serious impacts on urban economic and social aspects.
The 2 main ways the roads are maintained is through milling and repaving, and rehabilitation.
Both these processes cause environmental exhaustion, but due to effects in the production stage, the maintenance is not too focused upon. However, new ways to improve, as mentioned in 3.2, are being implemented.
Figure 3 : Environmental effect due to maintenance
3.4 Stage 4: End of Life Cycle
When a pavement reaches the end of its life cycle, there are 2 ways to approach it; recycle it or send it to landfill.
If recycled, they are used in another pavement project as the base layer or used to fill in between layers. This however presents challenges as different types of pavements require different materials. And since significant amounts of bitumen is present in asphalt, it has to be replaced which causes more stress on the environment.
Moreover, if sent to landfill, the effects of transportation has to be taken under consideration. And also dumping waste to a site can result in leachate which can consequently pollute the water, bringing us back to having to filter it, increasing cost of the entire life cycle.
4.0 The roles of different types of engineering in Asphalt Pavements
Civil engineers are the ones that design and construct pavements, but since the life cycle of pavements involves a wide range of responsibilities, different types of civil engineers are employed to manage the entire process. These include material engineers, design engineers, maintenance engineers and construction engineers.
Material engineers are in charge of assuring the quality of the raw materials that are used in the construction process. They achieve this by testing and inspecting practice rounds of hot mix asphalt and provide suggestions to the design engineers. They are also responsible for reviewing and approving of project plans. This all takes place either before or at the very early stages of the life cycle.
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Design engineers are often misunderstood as architects; however, their role is very much so different. They are required to conduct surveys, investigations and testings of the construction site before they begin to design. They also need to consider all the geotechnical issues that are present at the site and take into consideration the buildings, bridges and other structures that surround the site. They also take part in working to improve the performance and decrease the environmental effects of asphalt pavements. So, they are both involved in the construction stage and the maintenance stage.
Maintenance engineers’ job is very much self-explanatory. They check, repair and service pavements and ensure that nothing is out of place or damaged. Their job is more hands-on than other engineers because they require going to the site and making sure that everything is running smoothly with no hindrance. They are however not involved in the actual maintenance stage of the pavement, but they do instruct workers to mill and repave.
Finally, construction engineers overlook the process of construction of the pavement. They are usually located in offices near the construction, allowing them to manage the entire process. They also manage cost, risks and the contracts involved.
5.0 Project Management
5.1 Budget vs Actual:
We were introduced to this project on the 1st of august, and I intended to begin it immediately. However, as shown on the actual plan, I had other commitments therefore delayed starting this. When I did start my research on the urban infrastructure, it took too long as I was very contemplative on the type of infrastructure I wanted to research on. I was originally going to do it on water pipes, but I did not find it that interesting after some more research, therefore changed it to pavements. But since pavements was such a wide topic with so many different types, I continued to research specific kinds. I decided to do permeable pavements due to its sustainable approach but there was barely any information on its life cycle assessment since it’s a newly introduced type of pavements. Eventually, I picked asphalt as it was the most common type and had many harmful effects on the environment, which would allow me to write more. I found heaps of information of the LCA during my research, but I barely looked into the types of engineering involved. Therefore, when I got up to that section of this report, I was a little stuck. I gave the report a break and opened it back up a few days later. After a day of researching, with additional information from job websites, I was able to finish this portion of the report. The rest of the report, including project management, conclusion and referencing was done all in one day, as they weren’t too time consuming. Finally, I read over the entire report and edited it until I found it satisfactory.
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