19.+Transportation

Authors: Zac Jones, Clark Beach, Laura Medina, and Cristina Rodriguez

=19.1 Chapter Goal=

Describe how using sustainable transportation materials can save money and allow for more funding to be available for improving transportation systems. Better systems lead to less degradation, which in turn leads to lower and less frequent maintenance costs. For this chapter focus will be directed to asphalt pavements and roadway systems.

=19.2 Transportation=

Transportation is the movement of people and goods from one place to another. Goods can be thought of as any useful resource that is in demand, food, materials, natural resources, or even electricity. There are many ways in which goods are made accessible to consumers. Today's transportation systems include air, pipelines, waterways, roads, railways, cable/transmission lines, and even more recently space travel. It is important to remember that transportation systems also include pedestrian and bicycle travel ways.

Transportation is an important and integral part of infrastructure. It includes roads, railways, waterways, airports, and many other. Transportation systems, roadways specifically, allow for the average person to access goods and services more easily. This directly decreases costs and resource usage. The scope of this chapter will be limited to roadway transportation systems and constructions materials, production processes, and their impact on the sustainability of the system as a whole. The reason for this is because roadways are more common than other types of travel and it is more applicable to this study abroad course. The most logical way to improve the sustainability of roadways is to use more sustainable paving materials. The use of more sustainable materials reduces environmental impact and improves the lifespan of the roadway. Increased lifespan of a roadway will lead to a reduction in life cycle costs associated with maintenance and reconstruction. Savings incurred by the reduction in maintenance can be reinvested into the infrastructure in other areas such as public transit. Improvement to public transit will make its use more inviting and as a result even less damage and environmental impacts associated with both road construction and personal transportation. =19.3 Traditional Asphalt Pavement and the Environment= Asphalt concrete is the most predominately used material throughout the construction of roads and highways. It is a material that is composed of asphalt, coarse aggregates, and fine aggregates. Asphalt, a petroleum product, acts as the binder and gives the material elastic properties. The aggregates give the concrete strength and structure. Hot-mix asphalt (HMA) is the most common form of asphalt concrete. After the asphalt and aggregates are heated and mixed they are compacted in layers to complete the pavement. Asphalt concrete is generally used for local roads, highways, and landing strips, but has even been used in the core of some dams. The environmental impacts of HMA include effects from material extraction, production, and implementation [2]. Urban Heat Island Effect, energy use, and emissions will be expanded upon below. Keep in mind that these are just three of the numerous environmental impacts that are associated with HMA.

19.3.1 Urban Heat Island Effect (UHI)
The Urban Heat Island Effect (UHI) is the phenomenon where larger urban areas are consistently warmer than surrounding, less developed areas. This is especially true in the evenings. Throughout the day urban areas soak in the heat and then release it back into the air later in the day. Many areas have experienced 10°F differences from surrounding, undeveloped areas. Traditional asphalt contributes greatly to Urban Heat Islands because it is black. The effects of these UHIs are increased energy demand, emissions, and pollution. Figure 2 depicts an UHI profile [3]. It shows distinct increases in temperature within the boundaries of the city, especially at night.



19.3.2 Energy Use
Asphalt concrete requires large amounts of energy at all stages of production and use. These stages include obtaining the needed materials, production, transport, and construction. During production HMA components are heated to 250-350 ͦ F. This is an area where energy use can feasibly be decreased. There are asphalt concrete alternatives, such as warm mix asphalt, which will be discussed later in this chapter.

19.3.3 Emissions
Emissions resulting from the production of HMA are another concern. The emissions are divided into two categories; Criteria Air Pollutants and Hazardous Air Pollutants (HAP). Criteria Air Pollutants consist of particulate matter less than 10 micrometers, volatile organic compounds, Carbon Monoxide (CO), Sulfur Dioxide (SO2), and Nitrogen Oxides (NOx). HAP consists of polycyclic aromatic hydrocarbons, phenol, Volatile HAPs, and Metal HAPs [4]. These emissions can impact human health as well as contribute to environmental impacts such as global warming. A visual example of emissions associated with HMA can be seen in this video. The video shows fumes coming from a truck being loaded with HMA in Santa Clara, California. =19.4 Sustainable Pavement Alternatives= There are paving alternatives to HMA that can provide more sustainable solutions and still meet our needs. Paving mile after mile of roads has led to evident adverse effects on our environment. That being said, paved roadways are required in order to have efficient transportation. As long as society exists, we will continue to pave our roadways and have to deal with the impacts. Even though paving roads will continue, there are more sustainable options that will reduce impacts on the environment and resource volumes. The following sections describe a few of the many sustainable pavement alternatives and their properties.

19.4.1 Recycled Asphalt Pavement (RAP)
Roto-milling is the process of removing existing asphalt from the roadway surface and can be seen in Figure 3 below. Typically a roto-mill can remove about 2 inches of pavement per pass. The material taken from the roadway is hauled away by truck and is able to be recycled. This process not only helps save construction materials, it also helps mitigate the problem of asphalt layers piling up too high. Figure 4 shows a road in San Jose, Costa Rica that has multiple layers of asphalt laid on top of one another with the base layer being the original cobblestone roadway. After going through the crushing and screening process RAP is basically coated aggregates that are ready to be placed in another pavement mixture. In most cases roughly 10%-30% of the asphalt mix consists of RAP. The recycled asphalt and aggregates have already had the opportunity to age, so when they are incorporated into a mix they add more rigid properties require less virgin binder than a complete new mix. Physical properties of mixes containing RAP are less certain than new mixes. Although RAP can actually increase the performance of the pavement that it is integrated with it is impossible to know exactly how the mix will perform in the field. RAP may produce more emissions because of the need for a higher temperature during mixing, but this impact is countered by the fact that less new resources are required because older material is being recycled [2].





19.4.2 Rubberized Asphalt
Rubberized asphalt usually uses rubber as a percentage of the binder, but can also use rubber particles as a percentage of aggregates in the mix. The rubber generally comes from used tires. Rubberized asphalt produces quieter roads and reduces the UHI effect because rubber does not gain heat as quickly as asphalt, cement, and rock [6]. Other benefits of implementing the use of rubberized pavements have been found through research by Clemson University. These benefits include an increased resistance to cracking and rutting which directly translate to increased lifespan and a reduction in maintenance costs. It was also determined that between 500 and 2000 scrap tires are used in each lane mile of pavement [7]. It should be noted that the use of rubberized asphalt is not viable in all environments. Although the initial cost of rubberized asphalt is greater than that of traditional HMA it is still considered more sustainable because its lifecycle cost is less based upon reduced maintenance needs and longer lifespan of roadways.

19.4.3 Warm-mix Asphalt (WMA)
Warm-mix asphalt is produced at temperatures anywhere from 50-100 ͦ F lower than HMA. A foam process, emulsions, or other additives are used to make the asphalt more workable at the lower temperatures [2]. Advantages of using WMA include reductions of energy use and emissions. WMA is still in experimental stages for much of the world, but fuel costs and emissions during production are both less than HMA. As technologies improve WMA will likely become more popular in the pavement industry.

19.4.4 Portland Cement Concrete (PCC)
The Global Warming Potential (GWP) of PCC is greater the GWP of traditional asphalt if you only consider the production of a certain volume. However, PCC has double the lifespan of HMA (30-40) years, has an equivalent GWP to HMA after a 50 year lifecycle comparison, and has significantly less embodied energy [2]. The durability of PCC pavement is higher than any other paving material. Furthermore, UHI effect is also reduced because PCC's surface is light and reflective rather than absorbent as HMA is. =19.5 Costa Rica and Sustainable Transportation=

The University of Costa Rica (UCR) is in charge of the Transportation Infrastructure Program (PITRA). Costa Rica has over 9,000 km of paved roads. As of 2002, most of them were in ill repair. Law 8114 was put in place by Costa Rica in 2002 in order to evaluate and improve the nation's highway system as well as develop new standards for the transportation infrustructure system. PITRA is in control of the management and production of everything related to Law 8114 including the development of Green Pavements. The development of Green Pavements is just a small part of PITRA and UCR's goal to improve the quality of life for the citizens and improve their competitiveness as a nation [8].

19.5.1 Green Pavements
The University of Costa Rica’s research regarding Green Pavements is currently focused on recycled plastics. They can be used in asphalt either as aggregates, much like rubberized asphalt, or as an asphalt cement additive [2]. Asphalt cement additives, or asphalt cement polymer modifiers, are used to manipulate the ideal temperature range for the use of the asphalt cement by changing its viscoelastic behavior [9]. As temperatures increase the stiffness of the asphalt binder decreases, often causing rutting. As the temperature decreases binder becomes stiffer, often causing cracking. The ideal temperature range is between the two temperature extremes that lead to cracking and rutting. Recycled plastic asphalt cement polymer modifier is created from trash bags and sandwich bags. It is then added to asphalt cement. Percentages usually are in the ranges of 4%-7% of the binder weight [2].

Costa Rica has a warm, wet climate which is suitable for growing tropical foods such as bananas, but it is not comparable to most other climates in North America where asphalt concrete mixes have been designed for. Their roadways do not experience extreme temperature variations. This makes their asphalt binder suitable for the use of plastomers. Plastomers increase the strength of the binder, but they do not influence the elasticity. Companies, such as Dole, have large plantations in Costa Rica. As Figure 5 shows, bananas are covered with blue plastic bags to protect them and to control ripening. After the harvest these bags become part of the waste stream.



The University of Costa Rica is researching the use of the plastic banana bags as an asphalt cement modifier. The application of the banana bags improves the pavement in two ways: PG grade increases by 6 ͦ C, permanent deformation is reduced by up to 50% under normal traffic conditions. The use of the banana bags in the pavement accounts for about 4 kg of material per cubic meter of asphalt. It also traps toxic gases, that would produce acid rain, from being expelled into the atmosphere during incineration of the material [11]. This is a solid example of a sustainable pavement alternative because not only does it increase the lifespan of the pavement, but it also reduces the waste stream for plantations. Figure 6, below, shows an example of rutting. Rutting is a type of permanent deformation on roads that the banana bags will help to reduce.



=19.6 Effects of Implementing Sustainable Pavement Alternatives=

In order to analyze the effects of more sustainable material usage it is beneficial to use a framework. The Triple Bottom Line, as seen in Chapter 7, can help us understand how each effect is connected to the others.

19.6.1 Economic
The implementation of sustainable materials in pavement construction can start a chain reaction. Some sustainable pavements options may have a lower life cycle cost because they require less maintenance. In turn, the government can use this savings to improve transportation systems as a whole. When the efficiency of transportation systems increases consumers are more likely to take advantage of their mobility, thus leading to more spending, better money flow, and an improved economy.

19.6.2 Social
Improvements to the transportation infrastructure can impact the social spectrum both positively and negatively. The up front expense of using sustainable pavement alternatives is higher than using traditional HMA. The money to fund this has to come from somewhere, and the somewhere, unfortunately for citizens, is likely to be in the form of taxes. However, the counter to that is that air quality will improve due to lower emission and the fact that the transportation system used by the citizens on a day to day basis will be improved. This can translate to safer, faster, and smoother commutes for everyone.

19.6.3 Environmental
The environmental effects of using sustainable pavement alternatives have been addressed throughout this chapter. Emissions, UHI, energy use, and waste volume along with other negative impacts impacts of asphalt can be reduced. This is the biggest and most clear upside for the use of sustainable pavements within the transportation system.

=19.7 Conclusion=

Transportation is an important and integral part of infrastructure. Sustainable pavement alternatives appear to be competitive in life cycle costs to traditional HMA and also appear to have better longevity. Although the upfront cost is higher, the application of these materials in the transportation system can lead to savings that can be used to improve the transportation system as a whole. It is clear that sustainable pavement alternatives can reduce environmental impact in many ways. Emissions and energy consumption are decreased by requiring less heat and reusing resources. UHI can be reduced by implementing lighter, more reflective pavements. Embodied energy of roadways can be significantly reduced by using pavement materials with greater lifespans. Use of waste materials like tires and banana bags can improve the performance of pavements while simultaneously relieving waste issues we already face. Together, the use of multiple sustainable pavement options can lead to less environmental impact, more savings, and an improved transportation system. =19.8 List of References=

[1] Transportation for Illinois Coalition, "TFIC," 2011. [Online]. Available: http://tficillinois.org/Pavdeinfull.html. [Accessed 28 May 2011].

[2] M. Calkins, Materials for Sustainable Sites, Hoboken: John Wiley and Sons, Inc., 2009.

[3] EPA, "State and Local Climate and Energy Program," EPA, 23 May 2012. [Online]. Available: http://www.epa.gov/statelocalclimate/local/topics/heat- islands.html. [Accessed 4 June 2012].

[4] U.S. Environmental Protection Agency, "Hot Mix Asphalt Plants Emission Assessment Report," Research Triangle Park, 2000.

[5] Norwest Blacktop, "Roto Milling/Grinding," Norwest Blacktop, 2012. [Online]. Available: http://norwestblacktop.com/1562/roto_millinggrinding. [Accessed 5 June 2012].

[6] S. B. Sarte, Sustainable Infrastructure, Hoboken: John Wiley and Sons, Inc., 2010.

[7] Clemson University Department of Civil Engineering, "Benefits of Rubberized Asphalt," Clemson University, [Online].  Available: http://www.clemson.edu/ces/arts/benefitsofRA.html. [Accessed 5 June 2012].

[8] A.-M. C.-A. Loria, "Advances in Asphalt Research Specifications in Central America," San Jose, 2012.

[9] Illinois Department of Transportation, "Pavement Technology Advisory - Polymer-Modified Hot Mix Asphalt," Springfield, 2005.

[10] M. Southern, "Are organic foods really about better nutrition?," 1 September 2009. [Online].  Available: http://www.mnn.com/food/healthy-eating/stories/are-organic-foods-really-about-better-nutrition. [Accessed 6 June 2012].

[11] G. S. L. Villegas, "Paper Eurobitumen Banana Bags," San Jose, 2011.

[12] Pioneer Valley Planning Commision, "Pavement Management System Program," Pioneer Valley Planning Commission, [Online]. Available: http://www.pvpc.org/activities/transportation-pms.shtml. [Accessed 10 June 2012].