Results and discussion

Chapter 10 Results and Discussion Paula Porras-Pereira and Pilar Mercader-Moyano Abstract This chapter presents a practical application of LCA within the context of nanotechnology in construction. Specifically, it focuses on an environmental evaluation aimed at determining the more sustainable alternative between a nano-silicamodified asphalt mixture and an unmodified asphalt mixture used in road paving. The practical exercise, titled Comparative Life Cycle Assessment (LCA) of Unmodified and Nano-Silica-Modified Asphalt Mixtures for Road Paving: A Practical Exercise, provides a detailed comparison of the two materials, emphasizing their environmental implications across key life cycle stages. By integrating nanotechnology into conventional construction materials, this study contributes to the understanding of its potential environmental benefits and challenges, offering valuable insights for sustainable infrastructure development. Keywords Life Cycle Assessment ·Nanomaterials ·Construction · Sustainability ·Nanosilica ·Asphalt After the investigation, it is concluded that one of the fundamental methodologies for assessing the environmental ramifications of a product or service is through the application of Life-Cycle Assessment (LCA). In this section, we delve into a practical demonstration of conducting a Life Cycle Assessment within a nanotechnology construction context, which main objective is to conduct an environmental evaluation to discern the most ecologically sound option between the utilization of a nano-silicamodified asphalt mixture and an unmodified asphalt mixture on the process of paving a road. The practical exercise is titled: Present Address: P. Porras-Pereira (B)·P. Mercader-Moyano Department of Building Construction I, Higher Technical School of Architecture, University of Seville, Seville, Spain e-mail: [email protected] P. Mercader-Moyano e-mail: [email protected] © The Author(s) 2025 P. Mercader-Moyano and P. Porras-Pereira (eds.), Life Cycle Analysis Based on Nanoparticles Applied to the Construction Industry, https://doi.org/10.1007/978-3-031-79115-4_10 163 164 P. Porras-Pereira and P. Mercader-Moyano Comparative Life Cycle Assessment (LCA) of Unmodified and Nano-SilicaModified Asphalt Mixtures for Road Paving: A Practical Exercise Asphalt stands as the predominant choice for pavement across the globe, boasting unparalleled popularity. It is comprised of bitumen, serving as the binding agent, intertwined with either crushed or natural aggregates. This amalgamation of components culminates in the creation of asphalt mixtures, the cornerstone of modern road construction. Consequently, asphalt mixtures are endowed with the capacity to offer unparalleled driving comfort while also facilitating adaptable maintenance procedures. The design of asphalt pavements is meticulously crafted to ensure peak performance over their intended lifespan. Nevertheless, these pavements undergo deformations within relatively short timeframes. This, exacerbated by escalating traffic volumes and harsh weather phenomena, has prompted authorities overseeing asphalt pavements to explore alternative remedies aimed at bolstering their resilience against mechanical wear and environmental stressors [1]. In this context, although few additives exist, nanotechnology and nanomaterials have recently garnered considerable attention from the pavement industry. Particularly, the utilization of nanomaterials as modifiers for asphalt is experiencing a surge in popularity, owing to their distinctive properties that significantly enhance asphalt binder performance [1]. Incorporating nano-silica into asphalt mixtures has been demonstrated to yield numerous advantages. It enhances resistance to oxidative aging, mitigates rutting effects, improves rheological properties, reduces asphalt molecule interaction, thereby lowering mixing and compaction temperatures. Furthermore, it bolsters adhesion, resilience against cracking and rutting, albeit at the expense of decreased ductility and temperature sensitivity [1]. Despite the manifold benefits of integrating nanomaterials into asphalt, uncertainties loom over their environmental repercussions. Hence, as aforementioned, this study endeavours to evaluate nano-silica-modified and unmodified asphalt mixtures using the LCA methodology. To accomplish the main objective of the practical demonstration of the investigation, initially, an LCA for an unmodified asphalt mixture will be conducted. Subsequently, the results will be thoroughly analysed and contrasted, based on their environmental impact categories, with the provided LCA results for a nano-silicamodified asphalt mixture. Ultimately, the most environmentally preferable asphalt variant will be identified. The application of LCA to NMAM offers a valuable tool for informing stakeholders and decision-makers in the judicious selection of pavement modification additives, empowering them to harness the complete advantages of integrating nanomaterials into pavements, while concurrently mitigating any possible adverse environmental impacts. 10 Results and Discussion 165 1 Life Cycle Assessment of an Unmodified Asphalt Mixture In order to carry the LCA for an unmodified asphalt mixture, it is essential to define the construction process of paving a street, which encompasses a series of intricate procedures aimed at guaranteeing the longevity, safety, and visual appeal of the roadway. To execute the paving of a new road correctly, multiple layers must be laid, each serving. In this instance, the following layers will be implemented on the existing compacted natural ground: a sub-base layer, a base layer, an intermediate layer, and a surfacing layer. Below, the various components comprising the construction detail are elaborated upon (Fig. 1). Considering the preceding statements, an analysis is conducted to determine the LCA of an unmodified asphalt mixture with the aim of identifying and quantifying the materials utilized. As aforementioned, the Functional Unit (FU) serves as the foundation of all LCA investigations. It represents a quantified measure of a product system’s performance, utilized as a standard reference unit in LCA analyses. Establishing a fixed value for the FU is essential, as the resulting environmental impact outcomes across various impact categories are contingent upon this chosen unit. For this study, a Functional Unit of 1000 kg (1t) of asphalt mixtures production was adopted. This assessment focuses initially on segmenting the mixture into its constituent layers, as depicted in Fig. 1. In the initial phase, the construction unit of the layer is determined, delineated by the material constituting the layer itself, which, in this instance, pertains to granitic artificial aggregate. The Life Cycle Inventory (LCI) phase entails the collection of actual data and the modelling of the product system. In order to gather data on material extraction, processing and production, the evaluation version (2024.f) of the ‘Generador de precios de la construcción’, a downloadable software tool developed by the Spanish company CYPE Ingenieros, S.A., has been utilized. This software is available for download at https://generadorprecios.cype.es/descarga_generador.htm?0. Fig. 1 Road pavement construction section of an unmodified asphalt mixture 166 P. Porras-Pereira and P. Mercader-Moyano Following this, the Life Cycle Impact Assessment (LCIA) phase ensues. During this stage, the collected data undergoes analysis to assess its contribution to each impact category. LCIA encompasses characterization, normalization, evaluation, and weighting, depending on the specific LCIA methodology utilized. The initiation of the LCA process of an unmodified asphalt mixture, the ’Construction Price Generator’ software will be accessed, which should have been previously downloaded. Upon program initiation, the tab for project type and geographical location selection will be opened. For this street paving exercise, ’urban spaces’ will be chosen as the project type, with Spain designated as the location. Subsequently, within the left-hand side brown menu of the interface, the precise work location will be defined by selecting the province followed by the municipal area. •Sub-base layer To initiate the LCA process, the first step involves evaluating the impact of the sub-base layer. Subsequently, in the broken-down prices tab of the menu, the material constituting the sub-base layer to be analysed, artificial granitic gravel, will be searched for. In this case, it can be found under the categories of urban pavements and pavements—bases and subbases—granular—granular subbase. Once the material is located, its properties will be configured, including the filling material (artificial granite gravel) and the compaction level relative to the maximum dry density achieved in the Modified Proctor test, set at 95%. With the material parameters defined, its information, including breakdown price, specifications, generated waste, environmental impact indicators, and health and safety data, can be extracted. For this instance, data concerning the breakdown price, waste generated, and environmental impact indicators will solely be retrieved using the export option in PDF format situated on the right-hand side of the interface. Following that, the downloaded information will be analysed. In the following table (Table 1), which identifies and quantifies the materials utilized for the layer construction, a detailed description of the material of the respective layer is provided first, along with its identification code and unit of measurement. Additionally, in the second part of the table, divided into six columns, the different materials comprising the layer are categorized, along with the equipment, machinery, and labour required for its execution, as well as the complementary direct costs stemming from it. The “code” column represents the identification code of the corresponding material used by the software tool employed; the “unit” column denotes the unit of measurement for the material; the “description” column offers a brief description of the material; the “performance” column indicates the execution time in hours, based on the equipment, machinery, and labour utilized; the “unit price” column defines the hourly rate of execution; and finally, the “cost” column represents the actual cost of execution, taking into account the performance and unit price. 10 Results and Discussion 167 Table 1 Unit cost of the sub-base layer MBG010 m3Granular base Granular base with artificial granite gravel, and compaction at 95% of the Modified Proctor with mechanical means, in 30 cm thick layers, until reaching a dry density of no less than 95% of the Modified Proctor of the maximum obtained in the Modified Proctor test, carried out according to UNE 103.501, to improve the resistant properties of the soil. The price does not include the performance of the Modified Proctor test Code Unit Description Performance Unit price Cost 1Materials mt01zah010d tArtificial granite gravel 2.200 10.93 24.05 Materials subtotal 24.05 2Equipment and machinery mq02rot030b hSelf-propelled tandem compactor, 63 kW, 9.65, working width 168 cm 0.110 46.83 5.15 mq04dua020b hFront dump dumper with 2 t payload 0.110 10.58 1.16 mq02cia020j hTanker truck, 8 m3capacity 0.011 121.25 1.33 Equipment and machinery subtotal 7.64 3Labour mo113 hOrdinary construction labourer 0.199 21.19 4.22 Labour subtotal 4.22 4 Additional direct costs % Additional direct costs 2.000 35.91 0.72 Direct costs (1 +2+ 3+4) 36.63 Table 2 Waste generated by the sub-base layer LER code Type Weight (kg) Volume (l) 01 04 08 Gravel and crushed rock waste other than those mentioned in code 01 04 07 15.603 10.402 Waste generated 15.603 10.402 To assess waste generation, Table 2provides detailed information on the waste generated from the execution of the layer, quantified in both mass (kg) and volume (l) units. As expected, since the sub-base layer consists solely of artificial granite aggregate, it constitutes the sole type of waste. 168 P. Porras-Pereira and P. Mercader-Moyano Table 3 Environmental impact and resource use indicators of the sub-base layer Life cycle stage Environmental impact indicators Use of resources GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Total A1-A2-A3 15.400 2.20e−06 0.220 0.044 0.220 1.10e−05 264.000 15.400 264.000 0.660 A4 2.891 0.004 0.202 0.040 0.011 0.002 318.035 39.071 0.607 A5 2.664 1.76e−07 0.012 0.048 0.002 9.86e−05 37.299 35.878 5.328 Total A4-A5 5.555 0.004 0.214 0.088 0.013 0.002 355.334 74.949 5.936 Total energy and emissions 20,955 0.004 0.434 0.132 0.233 0.002 619.334 15.400 338.949 6.596 A1: Raw materials supply A2: Transportation of raw materials A3: Product manufacturing A4: Product transportation A5: Construction and installation process GWP: Global warming potential ODP: Stratospheric ozone depletion potential AP: Potential for acidification of soil and water resources EP: Eutrophication potential POCP: Tropospheric ozone formation potential ADPE: Abiotic resource depletion potential for non-fossil resources ADFP: Abiotic resource depletion potential for fossil resources PERT: Total use of renewable primary energy PERNRT: Total use of non-renewable primary energy FW: Net use of tap water resources 10 Results and Discussion 169 Table 4 Environmental impact and resource use indicators of the sub-base layer during the manufacturing process Consumption Life cycle stage Manufacturing A1. Raw materials supply A2. Transportation of raw materials A3. Product manufacturing GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Natural aggregate 2,200.000 15.400 2.20e−06 0.22 0.044 0.22 1.10e−05 264.00 15.40 264.00 0.660 Machinery Volume (l) Total energy and emissions 15.400 2.20e−06 0.22 0.044 0.22 1.10e−05 264.00 15.40 264.00 0.660 170 P. Porras-Pereira and P. Mercader-Moyano Table 5 Environmental impact and resource use indicators of the sub-base layer during the construction process (transport) Consumption Life cycle stage Construction A4. Product transportation GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Natural aggregate 2,200.000 2.891 0.004 0.202 0.040 0.011 0.002 318.035 39.071 0.607 Machinery Volume (l) Total energy and emissions 2.891 0.004 0.202 0.040 0.011 0.002 318.035 39.071 0.607 10 Results and Discussion 171 Table 6 Environmental impact and resource use indicators of the sub-base layer during the construction process (construction) Consumption Life cycle stage Construction A5. Construction and installation process GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Natural aggregate 2,200.000 0.016 1.04e−09 6.91e−05 2.83e−04 1.34e−05 5.81e−07 0.220 0.108 0.031 Machinery Volume (l) Gasoil 0.968 2645 1.75e−07 0.012 0.048 0.002 9.79e−05 37.035 35.748 5.291 Auxiliary means 0.003 2.06e−10 1.37e-05 5.61e-05 2.65e−06 1.15e−07 0.044 0.021 0.006 Total energy and emissions 2.664 1.76e−07 0.012 0.048 0.002 9.86e−05 37.299 35.878 5.328 178 P. Porras-Pereira and P. Mercader-Moyano Table 10 Environmental impact and resource use indicators of the base layer during the manufacturing process Consumption Life cycle stage Manufacturing A1. Raw materials supply A2. Transportation of raw materials A3. Product manufacturing GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Asphalt bitumen 63.000 17.010 1.26e−06 0.126 0.013 0.004 6.30e−06 2,853.900 1.890 3,099.600 0.032 Natural aggregate 987.000 3.948 6.91e−07 0.079 0.010 0.079 2.96e−06 69.090 4.935 69.090 0.197 Total 1,050.000 20.958 1.95e−06 0.205 0.022 0.083 9.26e−06 2,922.990 6.825 3,168.690 0.229 Machinery Volume (l) Total energy and emissions 20.958 1.95e−06 0.205 0.022 0.083 9.26e–06 2,922.990 6.825 3,168.690 0.229 10 Results and Discussion 179 Table 11 Environmental impact and resource use indicators of the base layer during the construction process (transport) Consumption lePara> Life cycle stage Construction A4. Product transportation GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Asphalt bitumen 63.000 0.207 2.69e−04 0.014 0.003 7.66e−04 1.24e−04 22.768 2.797 0.043 Natural aggregate 987.000 3.243 0.004 0.227 0.045 0.012 0.002 356.706 43.821 0.681 Total 1,050.000 3.450 0.004 0.241 0.048 0.013 0.002 379.474 46.618 0.724 Machinery Volume (l) Total energy and emissions 3.450 0.004 0.241 0.048 0.013 0.002 379.474 46.618 0.724 180 P. Porras-Pereira and P. Mercader-Moyano Table 12 Environmental impact and resource use indicators of the base layer during the construction process (construction) Consumption Life cycle stage Construction A5. Construction and installation process GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Asphalt bitumen 63.000 4.50e−04 2.97e−11 1.98e−06 8.10e−06 3.82e−07 1.66e−08 0.006 0.003 9.00e−04 Natural aggregate 987.000 0.007 4.65e−10 3.10e−05 1.27e−04 5.99e−06 2.61e−07 0.099 0.049 0.014 Total 1,050.000 0.007 4.95e−10 3.30e−05 1.35e−04 6.37e−06 2.77e−07 0.105 0.052 0.015 Machinery Volume (l) Gasoil 0.178 0.486 3.21e−08 0.002 0.009 4.13e−04 1.80e−05 6.810 6.574 0.973 Auxiliary means 0.002 1.14e−10 7.58e−06 3.10e−05 1.46e−06 6.37e−08 0.024 0.012 0.003 Total energy and emissions 0.496 3.27e−08 0.002 0.009 4.21e−04 1.83e−05 6.939 6.637 0.991 10 Results and Discussion 181 •Intermediate layer To continue the LCA process, the next step involves evaluating the impact of the intermediate layer. Subsequently, in the broken-down prices tab of the menu, the material constituting the intermediate layer to be analysed, hot mix bituminous AC, will be searched for. In this case, it can be found at the same place as the base layer, under the categories of urban pavements and pavements—urban pavements— bituminous mixtures and irrigation—hot mix bituminous AC. Once the material is identified, its properties will be configured, including the type and maximum size of aggregate (32 mm limestone), the type of layer (intermediate layer) and the type of binder to use in the mixture (B35/50), as well as the type of mixture (semi-dense), the application tonnage (more than 1000 t/day) and the bitumen (0.05 t of bitumen per t of mixture). With the material parameters defined, its information, including breakdown price, specifications, generated waste, environmental impact indicators, and health and safety data, can be extracted. For this instance, as in the previous layers, data concerning the breakdown price, waste generated, and environmental impact indicators will solely be retrieved using the export option in PDF format situated on the right-hand side of the interface. Following that, the downloaded information will be analysed. As in the previous layers, in the following table (Table 13), which identifies and quantifies the materials utilized for the intermediate layer construction, a detailed description of the material of the respective layer is provided first, along with its identification code and unit of measurement. Additionally, in the second part of the table, the different materials comprising the layer are categorised, along with the equipment, machinery, and labour required for its execution, as well as the complementary direct costs stemming from it. To assess waste generation, Table 14 provides detailed information on the waste generated from the execution of the layer, quantified in both mass (kg) and volume (l) units. As expected, since the base layer consists solely of bituminous mixtures, it constitutes the sole type of waste. Regarding the environmental impact and resource utilization of the intermediate layer, detailed within are the specific embodied energy values of the material, along with their corresponding conversion factors (see Table 15). Likewise, the table illustrates environmental impact and resource use indicators itemised for various stages of the life cycle. Subsequently, in Tables 16,17, and 18, the environmental impact and resource consumption metrics of the intermediate layer are organized by life cycle phase, characterized by the materials, machinery, and auxiliary resources utilized. During the production phase (Table 16) and the transportation of the product phase (Table 17), the 182 P. Porras-Pereira and P. Mercader-Moyano Table 13 Unit cost of the intermediate layer MPB001 t Hot mix bituminous AC Continuous hot bituminous mix AC 32 bin B35/50 S, for intermediate layer, semi-dense, with limestone aggregate of 32 mm maximum size, with 0.05 t of bitumen per t of mixture, for an application tonnage of more than 1000 t/day. The price does not include transportation of the mixture Code Unit Description Performance Unit price Cost 1Materials mt47aag001ngj tContinuous hot bituminous mix AC 32 bin B35/50 S, for intermediate layer, semi-dense, with limestone aggregate of 32 mm maximum size, with 0.05 t of bitumen per t of mixture, according to UNE-EN 13,108–1 1.050 83.42 87.59 Materials subtotal: 87.59 2Equipment and machinery mq11ext030 h81 kW chain asphalt paver 0.011 231.73 2.55 mq02ron010a h Self-propelled tandem vibrating roller, 24.8 kW, 2450 kg, working width 100 cm 0.011 56.81 0.62 mq11com010 h Self-propelled tire compactor, 12/22 t 0.011 66.47 0.73 Equipment and machinery subtotal: 3.90 3Labour mo041 h1st civil works construction officer 0.066 22.25 1.47 mo087 hCivil works construction assistant 0.044 21.56 0.95 Labour subtotal: 2.42 4 Additional direct costs (continued) 10 Results and Discussion 183 Table 13 (continued) MPB001 t Hot mix bituminous AC Continuous hot bituminous mix AC 32 bin B35/50 S, for intermediate layer, semi-dense, with limestone aggregate of 32 mm maximum size, with 0.05 t of bitumen per t of mixture, for an application tonnage of more than 1000 t/day. The price does not include transportation of the mixture Code Unit Description Performance Unit price Cost % Additional direct costs 2000 93.91 1.88 Ten-year maintenance cost: 13.41ein the first 10 years Direct costs (1 +2+3+4): 95.79 Reference and title of the standard ApplicabilityaObligationbSystemc EN 13,108–1:2006 1.3.2007 1.3.2008 Bituminous mixtures. Material specifications. Part 1: Bituminous concrete EN 13,108–1:2006/AC:2008 1.1.2009 1.1.2009 1/2+/3/4 aDate of applicability of the harmonized standard bDate on which the coexistence period ends cSystem for evaluating and verifying the constancy of benefits Table 14 Waste generated by the intermediate layer LER code Type Weight (kg) Volume (l) 17 03 02 Bituminous mix other than those mentioned in code 17 03 01 11.025 11.025 Waste generated 11.025 11.025 environmental impact and resource consumption metrics for the intermediate layer are delineated based on the two constituent materials: asphalt bitumen and natural aggregate. Unlike the sub-base and base layers, in the manufacturing phase of this intermediate layer, asphalt bitumen exhibits higher impact values than natural aggregates, whereas during the construction phase, natural aggregate demonstrates higher impact values across all environmental impact and resource consumption indicators.During the production phase (Table 16), asphalt bitumen generally shows significantly higher values across most environmental impact indicators compared to natural aggregate. However, there are exceptions where both materials exhibit more balanced values, particularly in indicators related to soil and water resource acidification depletion, eutrophication potential, tropospheric ozone formation potential, and abiotic resources for non-fossil resources depletion potential. Resource utilization indicators show greater variability: natural aggregate tends to have a more pronounced impact on the indicator concerning total renewable primary energy consumption, while asphalt bitumen typically demonstrates substantially higher values for the indicator of total non-renewable primary energy consumption. Nonetheless, for the 184 P. Porras-Pereira and P. Mercader-Moyano Table 15 Environmental impact and resource use indicators of the intermediate layer Life cycle stage Environmental impact indicators Use of resources GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Total A1-A2-A3 20.958 1.95e−06 0.205 0.022 0.083 9.26e-06 2,922.990 6.825 3,168.690 0.229 A4 3.450 0.004 0.241 0.048 0.013 0.002 379.474 46.618 0.724 A5 0.496 3.27e−08 0.002 0.009 4.21e−04 1.83e–05 6.939 6.637 0.991 (continued) 10 Results and Discussion 185 Table 15 (continued) Life cycle stage Environmental impact indicators Use of resources GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Total A4-A5 3.945 0.004 0.244 0.057 0.013 0.002 386.413 53.256 1.716 Total energy and emissions 24.903 0.004 0.449 0.080 0.096 0.002 3,309.403 6.825 3,221.946 1.945 A1: Raw materials supply A2: Transportation of raw materials A3: Product manufacturing A4: Product transportation A5: Construction and installation process GWP: Global warming potential ODP: Stratospheric ozone depletion potential AP: Potential for acidification of soil and water resources EP: Eutrophication potential POCP: Tropospheric ozone formation potential ADPE: Abiotic resource depletion potential for non-fossil resources ADFP: Abiotic resource depletion potential for fossil resources PERT: Total use of renewable primary energy PERNRT: Total use of non-renewable primary energy FW: Net use of tap water resources 186 P. Porras-Pereira and P. Mercader-Moyano Table 16 Environmental impact and resource use indicators of the intermediate layer during the manufacturing process Consumption Life cycle stage Manufacturing A1. Raw materials supply A2. Transportation of raw materials A3. Product manufacturing GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Asphalt bitumen 63.000 17.010 1.26e−06 0.126 0.013 0.004 6.30e−06 2,853.900 1.890 3,099.600 0.032 Natural aggregate 987.000 3.948 6.91e−07 0.079 0.010 0.079 2.96e−06 69.090 4.935 69.090 0.197 Total 1,050.000 20.958 1.95e−06 0.205 0.022 0.083 9.26e−06 2,922.990 6.825 3,168.690 0.229 Machinery Volume (l) Total energy and emissions 20.958 1.95e−06 0.205 0.022 0.083 9.26e−06 2,922.990 6.825 3,168.690 0.229 10 Results and Discussion 187 Table 17 Environmental impact and resource use indicators of the intermediate layer during the construction process (transport) Consumption Life cycle stage Construction A4. Product transportation GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Asphalt bitumen 63.000 0.207 2.69e−04 0.014 0.003 7.66e−04 1.24e−04 22.768 2.797 0.043 Natural aggregate 987.000 3.243 0.004 0.227 0.045 0.012 0.002 356.706 43.821 0.681 Total 1,050.000 3.450 0.004 0.241 0.048 0.013 0.002 379.474 46.618 0.724 Machinery Volume (l) Total energy and emissions 3.450 0.004 0.241 0.048 0.013 0.002 379.474 46.618 0.724 194 P. Porras-Pereira and P. Mercader-Moyano Table 21 (continued) Life cycle stage Environmental impact indicators Use of resources GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Total A4-A5 3.945 0.004 0.244 0.057 0.013 0.002 386.413 53.256 1.716 Total energy and emissions 24.903 0.004 0.449 0.080 0.096 0.002 3,309.403 6.825 3,221.946 1.945 A1: Raw materials supply A2: Transportation of raw materials A3: Product manufacturing A4: Product transportation A5: Construction and installation process GWP: Global warming potential ODP: Stratospheric ozone depletion potential AP: Potential for acidification of soil and water resources EP: Eutrophication potential POCP: Tropospheric ozone formation potential ADPE: Abiotic resource depletion potential for non-fossil resources ADFP: Abiotic resource depletion potential for fossil resources PERT: Total use of renewable primary energy PERNRT: Total use of non-renewable primary energy FW: Net use of tap water resources 10 Results and Discussion 195 Table 22 Environmental impact and resource use indicators of the surfacing layer during the manufacturing process Consumption Life cycle stage Manufacturing A1. Raw materials supply A2. Transportation of raw materials A3. Product manufacturing GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Asphalt bitumen 63.000 17.01 1.26e−06 0.126 0.013 0.004 6.30e−06 2,853.900 1.89 3,099.600 0.032 Natural aggregate 987.000 3.948 6.91e−07 0.079 0.01 0.079 2.96e−06 69.09 4.935 69.09 0.197 Total 1,050.000 20.958 1.95e−06 0.205 0.022 0.083 9.26e−06 2,922.990 6.825 3,168.690 0.229 Machinery Volume (l) Total energy and emissions 20.958 1.95E−06 0.205 0.022 0.083 9.26E−06 2,922.990 6.825 3,168.690 0.229 196 P. Porras-Pereira and P. Mercader-Moyano Table 23 Environmental impact and resource use indicators of the surfacing layer during the construction process (transport) Consumption Life cycle stage Construction A4. Product transportation GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Asphalt bitumen 63.000 0.207 2.69e−04 0.014 0.003 7.66e−04 1.24e−04 22.768 2.797 0.043 Natural aggregate 987.000 3.243 0.004 0.227 0.045 0.012 0.002 356.706 43.821 0.681 Total 1,050.000 3.450 0.004 0.241 0.048 0.013 0.002 379.474 46.618 0.724 Machinery Volume (l) Total energy and emissions 3.450 0.004 0.241 0.048 0.013 0.002 379.474 46.618 0.724 10 Results and Discussion 197 Table 24 Environmental impact and resource use indicators of the surfacing layer during the construction process (construction) Consumption Life cycle stage Construction A5. Proceso de construcción e instalación GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Materials Weight (kg) Asphalt bitumen 63.000 4.50e−04 2.97e−11 1.98e−06 8.10e−06 3.82e−07 1.66e−08 0.006 0.003 9.00e−04 Natural aggregate 987.000 0.007 4.65e−10 3.10e−05 1.27e−04 5.99e−06 2.61e−07 0.099 0.049 0.014 Total 1,050,000 0.007 4.95e−10 3.30e−05 1.35e−04 6.37e−06 2.77e−07 0.105 0.052 0.015 Machinery Volume (l) Gasoil 0.178 0.486 3.21e−08 0.002 0.009 4.13e−04 1.80e−05 6.810 6574 0.973 Auxiliary means 0.002 1.14e−10 7.58e−06 3.10e−05 1.46e−06 6.37e−08 0.024 0.012 0.003 Total energy and emissions 0.496 3.27e−08 0.002 0.009 4.21e−04 1.83e−05 6.939 6.637 0.991 198 P. Porras-Pereira and P. Mercader-Moyano 2 Life Cycle Assessment of a Nano-Silica-Modified Asphalt Mixture Upon completion of the LCA for an unmodified asphalt mixture, confirming the substantial environmental and resource utilization impact of asphalt bitumen throughout different stages of its life cycle, especially in the initial phases, the subsequent course of action entails conducting a comparable evaluation for a nano-silicamodified asphalt mixture. Due to the absence of materials with nanoparticles in the ‘Construction Price Generator’ software, data concerning the LCA of a nanosilica-modified asphalt mixture will be sourced from published scientific literature. However, it’s worth noting that this data could have been sourced from any database containing such information. By adopting this approach, it becomes possible to ascertain the asphalt variant that is most environmentally preferable. This methodology proves to be applicable across diverse geographical regions and databases, provided that requisite data is accessible. The impact values for each of the various categories employed in the LCA of a nano-silica-modified asphalt mixture will be sourced from the scientific article entitled “Life Cycle Assessment for the Production Phase of Nano-Silica-Modified Asphalt Mixtures,” authored by Sackey Solomon, Lee Dong-Eun, and Kim ByungSoo, who are associated with Kyungpook National University of Korea. This article was published in the MDPI “Applied Sciences” Journal on March 29th, 2019. For this study, as well as for the previous LCA, a Functional Unit of 1000 kg (1 t) of asphalt mixtures production was adopted. Table 25 Environmental Impact Categories [1] Impact Category Reference Unit Impact Result Environmental impact|global warming kg CO2-eq 7.44563 ×103 Human health|respiratory effects, average kg PM2.5-Eq 8.86935 ×102 Environmental impact|ozone depletion kg CFC-11-Eq 3.71600 ×10–2 Environmental impact|eutrophication kg N-Eq 1.49156 ×101 Human health|carcinogenic kg benzene-Eq 2.18467 ×103 Environmental impact|photochemical oxidation kg NOx-Eq 3.03420 ×101 Human health|non-carcinogenics kg toluene-Eq 6.07040 ×106 Environmental impact|ecotoxicity kg 2.4-D-Eq 1.08917 ×104 Environmental impact|acidification moles of H +-Eq 1.87879 ×105 10 Results and Discussion 199 The forthcoming table (Table 25) displays the different environmental impact indicators published in the referenced scientific article, along with their respective impact values. These values will serve as the basis for comparison with the outcomes derived from the LCA of an unmodified asphalt mixture. In the ensuing table (Table 26), adopting a similar format to that employed in the LCA of an unmodified asphalt mixture, a condensed summary of Table 25 is provided, exclusively presenting the values of environmental impact indicators shared by both LCAs. These indicators will be pivotal in facilitating a comparative analysis, aiding in the determination of the asphalt variant with the highest environmental preference. As depicted in the preceding table (Table 26), this scientific publication does not provide data categorized by each of the life cycle stage, but instead presents overall values for the product’s entire lifespan. Therefore, the comparison between both case studies will be conducted using the total values for each asphalt mixture. Table 26 Environmental impact and resource use indicators of the nano-silica-modified asphalt mixture Life cycle stage Environmental impact indicators GWP ODP AP EP CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) Total A1-A2-A3 – – – – A4 – – – – A5 – – – – Total A4-A5 – – – – Total energy and emissions 744.563 ×103371.600 ×102187.879 ×105149.156 ×101 A1: Raw materials supply A2: Transportation of raw materials A3: Product manufacturing A4: Product transportation A5: Construction and installation process GWP: Global warming potential ODP: Stratospheric ozone depletion potential AP: Potential for acidification of soil and water resources EP: Eutrophication potentia 200 P. Porras-Pereira and P. Mercader-Moyano 3 Quantitative Assessment of the Attained Outcomes Subsequent to the completion of the LCA of an unmodified asphalt mixture and the acquisition of results from a LCA of a nano-silica-modified asphalt mixture, a graphical representation is employed to compare the results obtained for each case study across their entire life cycle, in order to discern the most ecologically sound option. As indicated in the preceding section, due to the absence of categorized data for each life cycle stage in the consulted scientific publication, the comparison between both case studies will rely on the total values for each of the asphalt mixtures compared. Consequently, the results obtained from the LCA of an unmodified asphalt mixture for each layer of the road asphalt process (unit of work) are consolidated into a single table (Table 27). Due to the absence of asphalt mixture and the exclusive use of artificial granitic gravel in the sub-base layer, the results obtained for this layer will not undergo evaluation. Finally, a graphical comparison is generated to illustrate the results obtained for each case study throughout their entire life cycle, focusing on the impact categories shared by both LCAs: global warming potential, stratospheric ozone depletion potential, potential for acidification of soil and water resources, and eutrophication potential (Table 28). After evaluating a conventional asphalt mixture in terms of materials production emissions through the LCA methodology and comparing these findings with those of a nano-silica-modified asphalt mixture, the research underscores significant disparities in their impact contributions. Notably, the nano-silica-modified variant exhibits notably worse performance across all four analysed impact categories, particularly in the categories of global warming potential and stratospheric ozone depletion potential. The category demonstrating the most pronounced disparity lies in the potential for acidification of soil and water resources, where the nano-silica-modified asphalt mixture registers an impact magnitude exceeding conventional asphalt by a factor of 100.000. Similarly, the analysis reveals substantial variability in the impact category of stratospheric ozone depletion potential, on account of the near-negligible impact of unmodified asphalt, which is almost zero. Furthermore, notable disparities are also observed in the category of global warming potential, where the impact of the nanosilica-modified asphalt mixture is 10 times greater. Conversely, the eutrophication potential category showcases more balanced values in both asphalt mixtures. However, the conclusions derived from this research concerning nano-silica should not be extrapolated to all other types of nanomaterials. The environmental effects and overall outcomes associated with the integration of nanomaterials into asphalt depend on the manufacturing methods specific to each nanomaterial type. 10 Results and Discussion 201 Table 27 Environmental impact and resource use indicators of the base, intermediate and surfacing layers Life cycle stage Environmental impact indicators Use of resources GWP ODP AP EP POCP ADPE ADFP PERT PERNRT FW CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) etileno eq. (kg) Sb eq. (kg) (MJ) (MJ) (MJ) (m3) Total A1-A2-A3 62.874 5.85e−06 0.615 0.066 0.249 2.78e−05 8,768.97 20.475 9,506.07 0.687 A4 1.035 0.012 0.723 0.144 0.039 0.006 1,138.422 139.854 2.172 A5 1.488 9.81e−08 0.006 0.027 1.26e–03 5.49e−05 20.817 19.911 2.973 Total A4-A5 11.835 0.012 0.732 0.171 0.039 0.006 1,159.239 159.768 5.148 Total energy and emissions 74.709 0.012 1.347 0.24 0.288 0.006 9,928.209 20.475 9,665.838 5.835 A1: Raw materials supply A2: Transportation of raw materials A3: Product manufacturing A4: Product transportation A5: Construction and installation process GWP: Global warming potential ODP: Stratospheric ozone depletion potential AP: Potential for acidification of soil and water resources EP: Eutrophication potential POCP: Tropospheric ozone formation potential ADPE: Abiotic resource depletion potential for non-fossil resources ADFP: Abiotic resource depletion potential for fossil resources PERT: Total use of renewable primary energy PERNRT: Total use of non-renewable primary energy FW: Net use of tap water resources 202 P. Porras-Pereira and P. Mercader-Moyano Table 28 Comparison of the environmental impact and resource use indicators of the upper layers Environmental impact indicators GWP (Global warming potential) ODP (Stratospheric ozone depletion potential) AP (Potential for acidification of soil and water resources) EP (Eutrophication potential) CO2eq. (kg) CFC 11 eq. (kg) SO2eq. (kg) (PO4)3−eq. (kg) Unmodified asphalt mixture 74.709 0.012 1.347 0.24 Nano-silica-modified asphalt mixture 7,445.63 371.60 187,879.00 14.92 Reference 1. S. Solomon, L. Dong-Eun, K. Byung-Soo, Life Cycle Assessment for the Production Phase of Nano-Silica-Modified Asphalt Mixtures. Appl. Sci. 9(7), 1315 (2019) Open Access This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The images or other third party material in this chapter are included in the chapter’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.