3. Application of life cycle assessment in China

production stage of materials, the energy consumption of asphalt concrete pavement is about 40% more than that of CRCP, but most of the environmental indica-

Roudebush compared and analyzed the cement concrete pavement and asphalt concrete pavement in the United States. The author concluded that the value of the asphalt pavement is approximately one time more than that of the cement pavement, about 90.8%. In the stage of material production and pavement maintenance, the energy value of asphalt concrete is approximately two times that of cement concrete [9]. Berthiaume and Bouchard applied exergy, an energy derivative, to study the energy consumption and environmental impact of asphalt and cement concrete pavement structure in Canada. Exergy describes the energy differences of thermodynamic equilibrium between products, which is a tool for measuring prod-

Mroueh et al. got rid of the traditional comparison between asphalt and concrete

and focused on the evaluation and analysis of the application of industrial byproducts in pavement structure. The report analyzed the environmental impact of seven pavement structures with fly ash, crushed concrete waste, and blast furnace

Stripple made a comparatively comprehensive study and comparison between cement concrete pavement and cold mix and hot mix asphalt concrete pavement, including accessory facilities of highway such as vegetation, fence, sign, and so on. According to the report, the energy consumption of cement

concrete pavement is higher than that of asphalt concrete pavement. For the asphalt mixtures, they both produce the same amount of energy in the stage of production, but the cold mix one increases the energy consumption due to the addition of

Nisbet et al. listed life cycle inventory (LCI) of urban roads and highways in the United States and analyzed the energy consumption of cement concrete pavement and asphalt concrete pavement, respectively. For asphalt concrete pavement, the impact of transportation factors is not obvious. When the feedstock energy of asphalt is included, cement concrete pavement requires less materials, has lower energy resources, and has less exhaust emissions, no matter for urban roads or

Park et al. based on the method of composite life cycle assessment, combined with the Korean economy and national energy balance sheet, applied the input– output model to assess energy consumption and gas emissions from roads in mate-

Zapata and Gambatese [15] found that the results of Horvath and Hendrickson [8] were contrary to those of Stripple [12]. Therefore, by using the same preset conditions as Horvath and Hendrickson, the energy consumption of asphalt concrete pavement and continuous reinforced concrete pavement (CRCP) during the material production and construction stage is analyzed to make a relatively fair comparison. The results show that CRCP consumes more energy in the material production and construction stage, of which the energy consumption of cement production is the main factor, while the drying energy consumption of mixed aggregates is the significant factor affecting the energy consumption of asphalt

The framework of life cycle environmental assessment is relatively complete after years of research, but there are still a lot of deficiencies in the detailed model, and the data collection is also in the initial stage. The framework and theory of LCA have been accurately described in ISO 14040/ISO 14044 series standards, but there

are still many different opinions and methods in its application on road.

tors of asphalt concrete pavement are better than that of CRCP [8].

uct energy and explaining energy quality differences [10].

slag as the substitutes of original materials [11].

Transportation Systems Analysis and Assessment

rial selection and production stages [14].

emulsifier [12].

highways [13].

pavement [15].

92

In China, research on road energy consumption is mainly carried out from a single aspect, such as production of raw materials or construction technics, but few research focus on the energy consumption during the lifetime of pavement.

From the perspective of economy and energy consumption, Fusen Fang studied and analyzed the cement pavement and asphalt pavement with a life span of 30 years in 1984. The author believes that when the discount rate is no more than 12%, the present value cost of cement concrete pavement is always less than asphalt concrete pavement. However, when the energy contained in asphalt itself is ignored, the energy consumption of cement concrete pavement is 8–17% more than that of the asphalt one [16].

Gu found that the less smooth the pavement, the higher the fuel consumption of the car. By studying the relationship between road surface smoothness and automobile fuel consumption, the author mainly discussed how to improve the pavement smoothness as a way to save energy and gain economic benefits [17].

Ye studied the fatigue and energy consumption optimization design of cementstabilized base. The multilayer elastic system theory is used to directly calculate the stress and strain of pavement structure to obtain its mechanical and fatigue characteristics. Based on this, the paper performs thickness optimization and simple energy consumption analysis and calculation and discusses the technical, economic, and social benefits of cement-stabilized base [18].

Zhang started with the application effect of the old asphalt regenerator researched and produced in Guizhou province and collected relevant work efficiency quota data in the regenerated asphalt pavement project in Anshun, Duyun, and Zunyi. After comprehensive analysis and comparison, it is found that the energy consumption is different due to different seasons [19].

Han made an economic comparison between cement pavement and asphalt pavement in terms of construction cost and fuel consumption, mainly comparing the price of raw materials and the cost of maintenance, and thought that cement pavement has great advantages over asphalt pavement in economy. Moreover, from the perspective of pavement operation, the author analyzed that the fuel consumption of asphalt pavement is about 10% more than cement pavement due to the phenomenon of "deflection basin" of flexible structure of asphalt pavement [20].

Yi et al. compiled the energy consumption calculation and environmental assessment methods for the warm mix asphalt (WMA) and half-warm mix asphalt mixture. The analysis shows that the heating of coarse aggregate and the evaporation of water consume nearly 70% energy in the process of mixing. The production temperature has a great influence on the energy loss in the process of asphalt mixture mixing. The higher the production temperature, the more the energy loss. The energy loss during the mixing process of half-warm mixed asphalt mixture is nearly 50% less than that of hot mix asphalt mixture [21].

Shang et al. used the LCA theory and method to divide the life cycle of highways into four stages: material production, construction, maintenance, and dismantling, so as to study the energy consumption and atmospheric emissions within the life cycle of highways. According to the research, the proportion of energy consumption in the production stage of building materials is about 55.7% of the total energy consumption, followed by the maintenance and repair stage 40.5%, the construction stage 5.6%, and the dismantling stage 4%. The results show that most of the highway life cycle energy consumption is the direct and indirect energy consumption in the material production process [22].

Tang and Song summarize the low-energy warm mix asphalt concrete construction technology in the application of G109 national highway rebuilding project and, through the experiment monitoring, found that after the application of the technology, mixing, transporting, and paving of the mixture temperature were significantly reduced, saving energy consumption, reducing the CO2 and smoke emissions, and effectively reducing the negative impact of the project which brings to the plateau fragile ecological environment [23]. Pan studied the life cycle energy consumption and carbon emission of highway. After modeling and quantitative analysis of energy consumption and greenhouse gas emissions in different stages of highway life cycle, the author thinks that the average annual energy consumption of cement concrete pavement is less than that of asphalt concrete pavement. Therefore, from the perspective of energy saving, cement concrete pavement is superior to asphalt concrete pavement [24]. Shi analyzed the energy consumption of asphalt pavement regeneration materials in road maintenance. After investigating the energy consumption of five different pavement materials in the four stages of raw material production, mixing plant, transportation, and construction machinery, it was found that the energy consumption of regenerative mixture is less. Therefore, from the perspective of energy saving, the regenerative technology is worth spreading [25].

4. Existing problems in current research

DOI: http://dx.doi.org/10.5772/intechopen.86854

mental impact.

5.1.1 Owner cost

calculated:

95

5.1 Life cycle cost analysis

There are relatively few studies on the integrated evaluation methods of life cycle economic cost and environmental impact. For the research in this field, the economic cost and environmental impact of multiple schemes are usually calculated separately, and then the advantages and disadvantages of the schemes are compared by multi-objective optimization. Shu et al. firstly analyzed the differences between the two life cycle methods and introduced the basic principles and disadvantages of PTLaser and TCAce, two software platforms that integrate the two in foreign countries, so as to provide references for domestic researchers [29]. Batouli et al. evaluated the life cycle costs and environmental impacts of different pavement design schemes, and the results showed that the initial cost of flexible pavement was lower, but it would bring higher long-term costs and environmental impacts [30]. Umer et al. proposed a road scheme evaluation system, integrating LCCA and LCA, and carried out a multi-objective analysis based on economic cost and environmental impact. It is proved that geosynthetics can be used to improve the service life of low-traffic road surface and to minimize the cost and environ-

Integrated Life Cycle Economic and Environmental Impact Assessment for Transportation…

In general, the research on the comprehensive evaluation of economic cost and environmental impact within the life cycle in China is still in the stage of indepen-

5. Life cycle economic and environmental impact assessment analysis

tion, has been recognized and used in a number of states in the United States, becoming a widely recognized LCCA evaluation software. RealCost's LCCA method

divides the life cycle cost into two parts, owner cost and user cost [31].

to reach its useful life, the size of the second type of remnant is.

RealCost, an LCCA software developed by the US federal highway administra-

The owner cost is the cost borne by the operator of the pavement. In the range of life cycle, it includes the initial construction cost, maintenance cost, and pavement management cost. The economic costs associated with these processes are attributed to the owner's costs, which can be calculated by the budget method. It must be noted that the calculation range is the life cycle of the road, so it is necessary not only to calculate the economic cost of the whole process of construction acceptance but also to estimate the economic cost of daily maintenance, rehabilitation, and recycling after the road is put into use as well as the economic value in the end of the road life cycle. Here is a simple example of how this economic value is

Suppose that the life cycle economic cost of two different road schemes needs to be evaluated and the time range of evaluation is 30 years. If one of the roads just reaches its service life in the 30th year, then the second kind of residual value is 0. If one of the highways is reconstructed in year 28 and will remain in use until year 35

ð Þ 35–30 =ð Þ� 35–28 the cost of the road rehabilitation (1)

dent research, lacking the integration and comprehensive use of the two.

Ma et al. evaluated the energy consumption of continuous reinforced concrete pavement and hot mix asphalt pavement in the construction process and made it clear that reducing the amount of early energy consumption in the production stage of raw materials in the pavement life cycle is conducive to promoting the sustainable development of the highway engineering field [26].

Li used LCA method to compare the environmental impact of continuous reinforced concrete pavement with asphalt pavement. The energy consumption and emission are quantitatively analyzed by selecting a reasonable calculation method for each stage. Among them, the calculation method of energy consumption includes quota method and IRI—speed—fuel consumption model. The results show that the green degree of continuous reinforced concrete pavement is higher than that of asphalt concrete pavement [27].

Zhang et al. analyzed the influence of different asphalt structural layer design parameters on the carbon emission characterization results. The results show that the greenhouse effect is the most serious in the construction period of asphalt pavement, accounting for more than 95%, and the carbon emissions in the production stage have the greatest impact on the greenhouse effect [28].

Due to the complexity of pavement system, problems still exist in the application of LCA in China:


Integrated Life Cycle Economic and Environmental Impact Assessment for Transportation… DOI: http://dx.doi.org/10.5772/intechopen.86854
