Economic input-output life cycle assessment of concrete pavement containing recycled concrete aggregate

Journal of Cleaner Production 225 (2019) 414e425

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Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro

Economic input-output life cycle assessment of concrete pavement containing recycled concrete aggregate Xijun Shi a, *, Anol Mukhopadhyay b, Dan Zollinger c, Zachary Grasley d a

Center for Infrastructure Renewal, Texas A&M University, Dwight Look Engineering Building, Suite 601A, College Station, TX, 77843, United States Texas A&M Transportation Institute, 402 Harvey Mitchell Parkway South, Suite 173, College Station, TX, 77845, United States c Zachry Department of Civil Engineering, Texas A&M University, Dwight Look Engineering Building, Suite 501D, College Station, TX, 77843, United States d Center for Infrastructure Renewal, Texas A&M University, Dwight Look Engineering Building, Suite 503B, College Station, TX, 77843, United States b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 22 November 2018 Received in revised form 21 February 2019 Accepted 27 March 2019 Available online 1 April 2019

Concrete pavement recycling has become a common practice for many states in the U.S. While material properties and structural performance of pavements with virgin concrete aggregates replaced by recycled concrete aggregate (RCA) have been extensively characterized, very little effort has been made to assess potential sustainability benefits of this application. A life cycle assessment to compare an RCA based portland cement concrete (RCA-PCC) pavement and a plain PCC pavement (i.e., without RCA) from all three aspects of sustainability (i.e., economic impact, social impact, and environmental impact) was carried out using an economic input-output life cycle assessment (EIO-LCA) approach. An inventory of stressors during materials production and construction, use, and end-of-life phases of pavement life cycle was obtained, followed by a life cycle impact analysis using the Tool for Reduction and Assessment of Chemicals and other Environmental Impacts (TRACI). Based on the results, the benefits of using RCA during the materials production and construction phase are invariably achieved for all the sustainability categories, but the RCA-PCC pavement would pose higher negative impacts during the use phase of pavement life. Still, the pavement made with RCA-PCC was found to be generally more environmentally and socially friendly compared to the pavement made with virgin aggregates, especially for the TRACI categories of ecotoxicity, human health cancer, and human health non-cancer. The sustainability benefits of using RCA for concrete pavement application will only be magnified with a growing level of environmental awareness, further diminishment of local virgin aggregate sources, and a rapid increase of landfill tipping costs for construction demolition debris in the future. © 2019 Elsevier Ltd. All rights reserved.

Keywords: Recycled concrete aggregate Concrete pavement Economic input-output life cycle assessment Life cycle impact assessment Sustainability

1. Introduction Pavement recycling has become a common practice for many states in the U.S. Recycled aggregates produced from old pavements (e.g., reclaimed asphalt pavement (RAP) and recycled concrete aggregate (RCA)) have been continuously promoted to be reused in new pavement construction (FHWA, 2004; Gu et al., 2018; Mukhopadhyay and Shi, 2019; Shi et al., 2018b; Shi et al., 2019a; Singh et al., 2017; Snyder et al., 2018). An effective utilization of recycled aggregates as virgin aggregate replacements in asphalt concrete or cement concrete or as aggregate materials in base layer

* Corresponding author. E-mail addresses: [email protected] (X. Shi), [email protected] (A. Mukhopadhyay), [email protected] (D. Zollinger), [email protected] (Z. Grasley). https://doi.org/10.1016/j.jclepro.2019.03.288 0959-6526/© 2019 Elsevier Ltd. All rights reserved.

not only helps reduce virgin aggregate consumption, but also facilities a sustainable disposal of pavement demolition debris (Mukhopadhyay and Shi, 2017; Shi et al., 2017). Concrete pavement demolition debris, which is generally free of potentially harmful contaminates that may be present in building demolition debris, is an excellent source for producing RCA for the use in concrete (Snyder, Mark; et al., 2018). During the past several decades, state highway agencies in Connecticut, Kansas, Minnesota, Wisconsin, Wyoming, Michigan, Texas, and Illinois all had successful experience constructing rigid pavements made with RCA based portland cement concrete (RCA-PCC) (Cuttell et al., 1997; Gress et al., 2009; Roesler and Huntley, 2009; Won, 2001). These existing field sections have demonstrated that it is practically viable to replace virgin aggregates with RCA in PCC to produce concrete pavements with acceptable performance, given some precautionary measures are taken (e.g., providing strong support, using

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shorter joint spacing, using better load transfer device). While a considerable amount of lab and field studies were conducted to investigate the feasibility of using RCA in PCC pavement from material characterization and pavement evaluation perspectives, very little effort has been made to assess the potential benefits of using RCA in PCC pavement (either for base layer application or for PCC layer application) through life cycle cost analysis (LCCA) or life cycle assessment (LCA). Mroueh et al. (2001) conducted a life cycle assessment of pavements focusing on the use of industrial by-products, which included the use of RCA as a base material. The study created an index to represent the weighted loadings on the environment. The investigators found that the pavements built with a RCA base could have less detrimental effect on the environment compared to the pavement built with natural materials. In all the compared cases, one of the constructions using RCA base achieved the greatest environmental benefits as it consumed lowest energy and emitted lowest amounts of NOx, SO2, CO2, and volatile organic compounds. Donalson et al. (2011) provided a sustainability assessment of RCA used in highway base construction. From their study, the use of RCA not only generates social and environmental benefits, but also offers economic benefits, provided the hauling distance of RCA is negligible compared to that for virgin aggregate. They further mentioned that it is possible that use of RCA could become the only viable option for pavement construction in the future due to the rapid reduction of natural aggregate resources. Ram et al. (2011) conducted a detailed life cycle assessment for a selected number of Michigan Department of Transportation (DOT) concrete pavement sections to evaluate the sustainability benefits of using recycled and industrial byproduct materials in concrete pavements. They found that use of RCA could lead to significant positive effects on the environment. These positive effects can be further maximized by using on-site recycling instead of regional recycling due to the reduction of pollution during transporting materials. Verian et al. (2013) conducted a costbenefit analysis of using RCA in new concrete pavements. In their study, a hypothetical 4.8-lane km-long pavement built with 50% of coarse RCA in concrete layer and 100% coarse RCA in base layer was evaluated. Considering the cost savings from replacing natural aggregate and landfilling less old concrete pavement demolition debris, around 3 million US dollars could be saved. Reza and Wilde (2017) conducted a life cycle cost analysis on use of RCA in PCC pavement covering eight different hypothetical pavement construction scenarios. The different scenarios considered varying RCA replacement level and water to cementitious material ratio (w/cm) in PCC layer, different pavement structure and thickness, and different pavement service life. The life cycle cost analyses indicate that incorporating RCA in new concrete pavement construction can be very economical because it avoids the high cost of purchasing and hauling natural aggregates. The saving in cost can be maximized when RCA is used in concrete slabs compared to the base application. The investigators also concluded that although RCA incorporation could yield detrimental effects on concrete properties, either changing the pavement structural design (e.g., increase concrete slab thickness) or strengthening the mix (e.g., increase the cementitious material, decrease the w/cm) can make RCA-PCC pavement have similar performance with plain concrete pavement (i.e., concrete pavement made with virgin aggregate materials) and counteract any detrimental effects. Their LCCA results showed that strengthening the mix is more cost-effective than increasing pavement thickness. Reza and Wilde (2017) also conducted a life cycle assessment in the same study and concluded that in many cases the RCA-PCC pavement poses lower burdens on the environment compared to the plain PCC pavement. Recently, a paper focusing on a sustainability assessment for PCC containing RAP aggregates has been published (Shi et al., 2018a). The

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economic, social, and environmental impacts of concrete pavement made with RAP aggregates were extensively studied via an economic input-output life cycle assessment (EIO-LCA) approach in this paper. It is concluded from the results that single-lift RAP-PCC pavement could yield the highest economic benefits, while two-lift construction using RAP-PCC in the bottom lift could have lowest detrimental impacts from social and environmental perspectives. Since RCA-PCC and RAP-PCC both contain recycled aggregates, they behave similarly in terms of having reduced strengths and modulus of elasticity (MOE) and having higher coefficient of thermal expansion (CoTE) (Shi, 2018). It is expected that RCA-PCC pavements could yield similar sustainability benefits as RAP-PCC pavements. 2. Objective Most of the existing RCA-PCC pavement studies (reviewed in Introduction) are life cycle cost analysis. There lacks an extensive investigation to compare RCA-PCC pavements with plain PCC pavements from all three aspects of sustainability (i.e., economic impact, social impact, and environmental impact). The objective of this study was to perform such a sustainability assessment using an EIO-LCA approach. The theory of the EIO-LCA was proposed by the Nobel Prize winner Wassily Leontief, and the method was operationalized by the Green Design Institute at Carnegie Mellon University (CMU). The EIO-LCA approach has been widely used in a variety of research areas, including the field of pavement sustainability assessment (Mukhopadhyay and Shi, 2017; Rew et al., 2018; Shi et al., 2018a). This research involves an LCA case study for an existing RCA-PCC pavement in Oklahoma. During the 1980s, the Oklahoma DOT constructed some sections of portland cement concrete pavement that contained recycled concrete aggregate as a virgin coarse aggregate replacement. Based on the information obtained from Hankins and Borg (1984), a field investigation by the authors (Mukhopadhyay et al., 2019; Shi et al., 2019b), and the database from the Oklahoma DOT, a hypothetical RCA-PCC pavement and a hypothetical plain PCC pavement were created to mimic the existing sections of RCA and control pavements on the Interstate 40 Highway (I-40) in Oklahoma in this study. Three critical phases of pavement life cycle were included in the EIO-LCA: materials production and construction, use, and end-of-life. Although the maintenance phase was not considered because the end-of-life of pavement is defined as the time point when the first major concrete pavement rehabilitation is needed, the life cycle assessment presented in this study is still regarded one of the most comprehensive studies in the field of pavement LCA. The findings from this case study could offer valuable insights on sustainability benefits of use of RCA in PCC pavement, which would greatly facilitate the decision-making process. 3. Pavement performance To make a valid comparison between two pavement cases for a life cycle assessment, one needs to ensure the compared pavements have equivalent performance. If creating two pavements with identical performance is difficult, then any remaining service life of the pavement beyond the analysis period needs to be counted towards the end-of-life salvage value. Accordingly, a good understanding of the effect of RCA on PCC pavement performance is needed in this study. A brief review of the existing literature analyzing changes of pavement performance caused by RCA incorporation was performed before the LCA. Based on the literature review findings, the hypothetical RCA-PCC pavement and the hypothetical plain PCC pavement which can be directly compared

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with each other were created for this LCA case study. 3.1. Effect of RCA on PCC pavement performance It is widely known that aggregate properties have profound impacts on concrete properties. Due to the existence of reclaimed mortar in RCA, properties of RCA-PCC can deviate significantly from those for concrete containing virgin aggregates. The changes of concrete properties by RCA incorporation and their effect on concrete pavement performance are summarized in Table 1. 3.2. Hypothetical pavement cases According to Table 1, the changes in PCC material properties caused by RCA incorporation could lead to significant detrimental impacts on pavement performance, which in return reduces pavement service life. To compensate the negative effects of RCA on concrete pavement, remedial measures (e.g., building stronger base support, using shorter joint spacing, increasing slab thickness) shall be considered in design and construction of RCA-PCC pavement. However, the existing concrete pavement design tools, such as AASHTO 1993 (AASHTO, 1993) and Pavement ME Design (AASHTO, 2003), are not capable of taking account of all the above-mentioned RCA altered PCC properties in predicting pavement performance. Accordingly, it is difficult to set up a scenario for which an RCA-PCC pavement has exactly equivalent performance with its control pavement due to the limitations of the current pavement simulation approaches. On the other hand, there are a considerable amount of existing RCA-PCC field sections in the U.S, but most of these existing RCA-PCC pavements were constructed using the same pavement structure parameters (such as same slab thickness) as the control pavement. This is because these RCA-PCC pavements were built a few decades ago when pavement engineers did not gain sufficient understanding of RCA-PCC regarding material characterization and pavement design. Due to the challenges of using the existing pavement design tools to set up two pavement cases (with and without RCA) that have equivalent performance and service life, along with the fact that most of the RCA-PCC pavement field sections in the U.S used the same design parameters with the control pavement sections, this life cycle assessment was focused on an RCA-PCC pavement and a plain PCC pavement that have the same structure design (i.e., same PCC slab thickness and support conditions). The hypothetical RCA-PCC pavement and the plain PCC pavements were set up to

best mimic the I-40 RCA and control sections investigated in Oklahoma by the authors (Mukhopadhyay et al., 2019; Shi et al., 2019b): Both the RCA-PCC pavement and the plain PCC pavement were assumed to be 12.8-km long and 14.4-m wide (two lanes in each direction; each lane is 3.6 m wide) with the same PCC layer thickness (25 cm). The mix designs of the two pavement cases, which were originally used for the I-40 pavement sections, are presented in Table 2. By analyzing the performance data of the existing RCA-PCC pavements, the relatively poorer pavement performance of RCAPCC pavement can be reflected by its shorter service life. In the LCA, the analysis period can be then set as same as the service life of the RCA-PCC pavement case, while the longer pavement service life of the plain PCC pavement can be counted for in the end-of-life savage value. To reasonably determine the pavement service life of the two pavement cases, the long-term performance data for the RCA-PCC pavements and plain PCC (non-RCA) pavements from Reza et al. (2018a) were used. In Reza et al. (2018a)'s study, data concerning long-term performance of approximately 341 km of RCA-PCC pavement sections along with 341 km of plain PCC pavement sections covering a variety of case studies in Minnesota was extensively analyzed through a statistical analysis. Based on their findings, the mean time to reach the condition of the first major concrete pavement rehabilitation was found to be 27 years for RCA-PCC pavement and 32 years for plain PCC pavement. Accordingly, the pavement service life for the RCA-PCC pavement and the plain PCC pavement in this life cycle assessment study was set as 27 years and 32 years, respectively. The analysis period was chosen as 27 years, and the 5-year remaining service life of the plain PCC pavement was included in the calculation of the end-oflife salvage value. It is worth noting that although the determination of pavement service life was based on a fairly large amount of data using robust statistical approaches and the results could

Table 2 Mix design for the plain PCC and RCA-PCC (Hankins and Borg, 1984). Materials 3

Portland cement (kg/m ) Fly ash (kg/m3) Natural sand (kg/m3) Coarse aggregatea (kg/m3) Water (l/m3)

Plain PCC

RCA-PCC

284 68 715 1106 148

284 68 670 1006 148

a For plain PCC, the coarse aggregate was 100% virgin limestone; for RCA-PCC, the coarse aggregate was 100% coarse RCA.

Table 1 Effect of RCA on PCC properties and concrete pavement performance. PCC properties

Changes due to RCA incorporation

Effect of the changed properties on concrete performance

Recommendation to compensate the negative effects

CoTE

Higher

Use short joint spacing

MOE

Lower

Shrinkage

Higher

Aggregate interlock

Worse

Chloride content

Higher

Higher CoTE induces higher curling stresses and causes more distress in pavement slabs (Shi, 2018) PCC slab with reduced MOE would induce higher differential energy to the base support, causing higher slab faulting and base erosion (Shi, 2018) Cause pavement to crack prematurely (Reza and Wilde, 2017) Lower aggregate interlock yields reduced load transfer efficiency and consequently leads to more pavement distress (FHWA, 2004) Steel corrodes faster than normal due to existence of deicing salt in RCA (Reza and Wilde, 2017)

Note: CoTE: coefficient of thermal expansion; MOE: modulus of elasticity.

Build a strong base and subgrade support

RCA concrete pavement may not be placed in hot summer Use better load transfer device

Use epoxy-coated steel or other corrosion resistant steels or restrict the use of RCA concrete in reinforced concrete pavement

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represent the Minnesota's situation very well, whether or not they are applicable to the pavements in Oklahoma remains questionable. Nonetheless, the findings from the Minnesota study was still used in this study because Oklahoma does not have so many existing RCA-PCC pavement sections to generate statistically meaningful results. 4. EIO-LCA An EIO-LCA model developed by CMU was used in this study (CMU, 2018). Based on the large-scale matrix computations, the EIO-LCA model uses economic inputs to output the material and energy resources required for, and the environmental emissions resulting from, activities in the economy (CMU, 2018). The resulting economic, social, and environmental burdens form an inventory of stressors, which will be the inputs of a life cycle impact analysis to quantify the potential impacts of the stressors on environment and society. In this study, the Tool for Reduction and Assessment of Chemicals and other Environmental Impacts (TRACI) was used to assess these impacts. 4.1. EIO-LCA economic inputs The key to an EIO-LCA study is to accurately prepare economic inputs for different phases of pavement life cycle. A pavement life cycle includes raw materials production, construction, use, maintenance, and end-of-life (Santero et al., 2010). A summary of each phase is shown in Table 3. Each phase of the life cycle poses a unique burden on economy, environment, and society. A complete LCA shall incorporate all these phases. However, according to Santero et al. (2010), LCA of pavement is an area which is still maturing. The materials production phase is the primary focus of nearly all the existing studies, while the use phase and maintenance phase are often excluded due a lack of reliable data inputs. This study intends to present a complete pavement life cycle assessment by including different phases in the analysis. In this EIO-LCA, three critical phases including material production and construction (the material production and construction phases are categorized into one phase in this study), use, and end-of-life phases were included. The pavement service life is defined as the time point when first major concrete pavement rehabilitation is needed; the remaining service life of the plain PCC pavement counts towards the end-of-life salvage value. It is noted that pavement can have salvage values even though it reaches to a condition when a major concrete pavement rehabilitation is required. These salvage values are considered identical between the plain PCC pavement and RCA-PCC pavement, so they were excluded in this LCA. The maintenance phase was excluded in this life cycle assessment as well because there is a lack of reliable maintenance data for the plain PCC pavement and the RCA-PCC pavement. As a

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matter of fact, it is extremely hard to precisely quantify the impact of maintenance on concrete pavement performance (e.g., international roughness index (IRI)), therefore maintenance over the life of pavement is either entirely eliminated or is dealt with simplistically for the most existing LCA studies (Santero et al., 2010). Additionally, a recent study indicates that the average discounted maintenance cost during a 40-year service life is only around 15% of the initial construction cost (Moretti, 2014), despite the study did not consider any construction-related traffic congestion that could contribute to more energy consumption and greenhouse gas emissions during the pavement maintenance stage (Lu et al., 2018; Lu and Xin, 2018). While this study still has some limitations, it is regarded as one of the most comprehensive studies in the field of pavement LCA thus far. 4.1.1. Materials production and construction phase Based on the pavement structure and mix design information, the amount of raw materials needed to construct the plain PCC pavement and the RCA-PCC pavement was calculated. The costs of the raw materials including cement, fly ash, virgin coarse aggregate, and virgin fine aggregate were obtained from the RSMeans Database (Gordian, 2018). The cost data (total cost including overhead and profit) are modified values by considering the city cost index for Oklahoma City, so they represent the local mean raw material costs at Oklahoma City in year 2018. The cost of water is obtained from the Utilities Department of OKC's website (OKC, 2018). An important assumption of this study is that both the plain PCC pavement and the RCA-PCC pavement are reconstructions of two old plain PCC pavements which are 23 cm thick, 12.8 km long, and 14.4 m wide. The RCA is produced from the demolition waste of the old PCC pavement, so a zero material cost is assumed for the RCA. If not recycled and reused, the remaining concrete pavement debris would be landfilled for both the plain PCC pavement and the RCA-PCC pavement cases. While processing RCA from pavement debris could yield additional cost, such cost is considered negligible compared with much larger costs associated with demolishing and removing old pavements. The costs related to old pavement demolition are not included in the life cycle assessment because these costs are identical for the two cases. The costs associated with transporting pavement debris to the landfill site as well as the landfill tipping fees will be discussed later in this section. Table 4 summarizes the unit price of the raw materials, the amount of raw materials needed, and the total cost for each raw material. The total weight of pavement slab debris was calculated to be 100,508 ton. For the plain PCC pavement case, all the debris would be transported to a landfill site which is assumed to be 80 km away with a hauling cost of $0.24/ton/km. For the RCA-PCC pavement case, the remaining concrete debris that needs to be hauled away is 52,776 ton, and the hauling cost is also $0.24/ton/km. The hauling

Table 3 Different phases of pavement life cycle (Santero et al., 2010). Phase of pavement life Description cycle Material production Construction Use Maintenance End-of-life

Includes each step in the materials manufacturing process, from extraction of raw materials (e.g., limestone) to their transformation into a pavement input material (e.g., cement). Also includes any necessary transportation that occurs between facilities. Processes used in the placement of pavement material at the project location. Includes onsite construction equipment and traffic delay caused by construction activities. Activities that occur while the pavement is in place. Pavements interact with the environment through multiple pathways, including albedo, vehicle rolling resistance, carbonation, and lighting. The maintenance, rehabilitation, and reconstruction activities that occur during the life of a pavement. The maintenance phase usually involves its own materials, construction, and use phases. Depending on boundary conditions, the end-of-life phase can include demolition, disposal in a landfill, recycling processes, and/or other activities that occur when the pavement it taken out of service.

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Table 4 Summary of raw material costs. Material

Cement Fly ash Virgin coarse aggregate Virgin fine aggregate Water RCA

Unit price

$288.1/ton $67.5/ton $27.7/ton $24.4/ton $0.79/ton 0

Amount needed (ton)

Material cost

Plain PCC pavement

RCA-PCC pavement

Plain PCC pavement

RCA-PCC pavement

13,488 3238 52,491 33,961 7062 0

13,488 3238 0 31,820 7062 47,732

$3,886,519 $218,484 $1,452,933 $830,158 $5589 $0

$3,886,519 $218,484 $0 $777,843 $5589 $0

Note: the metric ton is used in this study.

cost is reasonably assumed by referring to several previous publications for pavement LCA (Shi et al., 2018a; Verian et al., 2013). A landfill fee of $42/ton is used for both the plain PCC pavement and the RCA-PCC pavement cases based on a review of construction and demolition landfill tipping fees in Oklahoma. According to Kuennen (2007), the landfill costs have been continuously increasing during the past several decades; the nationwide mean value could be significantly higher than the value used in this study. The National Solid Wastes Management Association has reported that the tipping fees increased from an average of $8.89/ton in 1985 to $38.1/ton in 2004, with an average as high as $78.37/ton in the Northeast region in 2004. In addition to hauling RCA to the landfill site, virgin coarse aggregate is assumed to be transported from an aggregate supply which is 48 km away from the ready-mix concrete plant. The cost for hauling virgin aggregates to the plant is assumed to be $0.24/ton/km as well. Table 5 summarizes the costs associated with hauling materials and landfilling concrete debris. According to the RSMeans Database, the average PCC pavement paving cost at Oklahoma City in year 2018 is $4.27/m2. This yields a total cost of $803,047 for paving a PCC pavement 12.8 km long and 14.4 m wide (which was used in this study). It has been reported that construction of RCA-PCC pavement can be successfully done with conventional concrete pavement construction equipment (FHWA, 2004), so it is reasonably assumed that the total paving cost of the RCA-PCC pavement is also $803,047. 4.1.2. Use phase The use phase for a pavement LCA usually includes potentially influential components such as fuel consumption, vehicle repair and maintenance, tire wear, the urban head island effect, radiative forcing, concrete carbonation, and leachate (Santero et al., 2010). Unfortunately, most of the existing pavement LCA studies did not consider the use phase due to a lack of effective models and tools to quantify the relevant impacts. Therefore, the use phase is considered the largest research gap in pavement LCA (Santero et al., 2010). Impacts of the use phase (especially those contributed by fuel consumption) can be huge factors for determination of pavement sustainability. According to Hakkinen and Makela (1996), a 0.1e0.5% decrease in fuel consumption due to beneficial pavement characteristics would produce sustainability benefits comparable to the total benefits achieved from all the other phases of the pavement life cycle. With the EIO-LCA approach, impacts from the pavement use phase can be easily characterized. The major components evaluated

in the use phase of this LCA are vehicle operation costs (VOC), which are the costs relevant to vehicle repair and maintenance, fuel consumption, and tire wear. The vehicle operation costs for the two PCC pavement cases were estimated using the VOC model developed under NCHRP 720 (Chatti and Zaabar, 2012). In the VOC model at the project level, the inputs which are different between the plain PCC pavement and the RCA-PCC pavement are IRI and texture depth. In this study, an initial IRI of 98 cm/km was assumed for both the plain PCC pavement and the RCA-PCC pavement cases. According to Reza and Wilde (2017)'s statistical analysis results, the mean IRI increase rate over time is 2.7427 cm/km/year for plain PCC pavement and 3.1911 cm/km/year for RCA-PCC pavement. These values were used in this study to compute pavement IRIs for each year. The texture depths of the pavements were directly obtained from the Oklahoma DOT's measurements for the I-40 control and RCA pavement sections in 2016. The measured texture depth was 0.73 mm for the control section and 0.84 mm for the RCA-PCC section; these two values were adopted and held constant with time in the VOC analysis because no historical data is available to establish pavement texture depth deterioration models for the plain PCC pavement and the RCA-PCC pavement. Furthermore, the effect of texture on fuel consumption is found statistically not significant at high speed, and pavement surface texture has an effect on fuel consumption only for heavier trucks (Chatti and Zaabar, 2012). The VOC model also requires having annual average daily traffic (AADT) and traffic distribution as inputs. According to the Oklahoma DOT AADT Traffic Counts database (ODOT, 2018), the AADT of the I-40 pavement sections was 49,200 for the year of 2017. A traffic growth rate of 1.5% (assuming an exponential growth) was used to estimate the AADT for each year during the entire analysis period for both the cases. The traffic distribution is listed in Table 6, which is also estimated based on the data provided by the Oklahoma DOT. The VOC of the plain PCC pavement and the RCA-PCC pavement cases for each year during the entire analysis period were calculated using the model. The costs at each year were then converted to present worth (i.e., year 1's value) based on the following equation:

P¼

F ð1 þ iÞn

(1)

Where P ¼ present worth; F ¼ future worth; i ¼ annual discount rate, i ¼ 1.5% is used in this study (Reza et al., 2018b), and

Table 5 Summary of costs associated with hauling materials and landfilling concrete debris. Cost category

Plain PCC pavement case

RCA-PCC pavement case

Haul virgin aggregates from the aggregate supply to the concrete plant Haul concrete debris away to the landfill site Landfill concrete debris

$1,008,599 $1,954,327 $4,243,680

$371,243 $1,026,219 $2,228,360

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Table 6 Traffic distribution of the I-40 pavement section (estimated based on the data from the Oklahoma DOT). Traffic category

Description (Ko, 2010)

Distribution

Small car Medium car Large car Light delivery car Light goods vehicle Four-wheel drive Light truck Medium truck Heavy truck Articulated truck Mini bus Light bus Medium bus Heavy bus Coach Total

Small passenger cars (approx.<1.0 ton) Medium passenger cars (1.0e1.2 ton) Large passenger cars (1.2e1.4 ton) Panel van, utility or pickup truck Very light truck for carrying goods (4 tires) Landover/jeep type vehicle Small two-axle rigid truck (approx.<3.5 ton) Medium two-axle rigid truck (approx.>3.5 ton) Multi-axle rigid truck Articulated truck or truck with drawbar trailer Small buss based on panel van chassis (usually 4 tires) Light buss (approx.<3.5 ton) Medium bus (3.5e8.0 ton) Multi-axle or large two-axle bus Large bus designed for long e

21.33% 21.33% 21.33% 22.86% 1.71% 1.71% 0.37% 2.23% 6.56% 0.27% 0.06% 0.06% 0.06% 0.06% 0.06% 100%

Table 7 Cumulative VOC for the case study.

Table 8 Summary of the salvage value for the plain PCC pavement case.

Cost

Plain PCC pavement

RCA-PCC pavement

Repair and maintenance Tire Consumption Fuel Consumption

$281,806,174 $60,968,158 $861,016,189

$281,806,174 $61,122,108 $863,418,887

4.1.3. End-of-life phase From Section 3.2, the pavement service life for the plain PCC pavement and the RCA-PCC pavement was set as 32 years and 27 years, respectively. For the sake of comparison, a 27-year analysis period was used for both the cases, and the remaining service life of the plain PCC pavement counted towards the end-of-life salvage value. The salvage value is given by (Reza et al., 2018b):

% change ¼

Remaining service life  Initial cost Expected service life

Salvage value Value for the 27th year Value converted to the 1st year

n ¼ number of years. The cumulative VOC for the 27-year analysis period are shown in Table 7. From Table 7, since the RCA-PCC pavement has higher IRIs compared to the plain PCC pavement, the rougher surface of the RCA-PCC pavement induces higher damage to vehicle tires and causes higher fuel consumption. Therefore, the VOC related to the tire and fuel consumption are greater for the RCA-PCC pavement than those for the plain PCC pavement. It is noted that both the two cases yield same vehicle repair and maintenance cost. This is likely attributed to that the difference in the pavement roughness between the plain PCC pavement and RCA-PCC pavement is not significant enough for the model to yield a different result.

Salvage value ¼

Sector

(2)

Cement Fly ash Virgin coarse aggregate Virgin fine aggregate Water Paving

$607,269 $34,138 $227,021 $129,712 $873 $125,476

$412,348 $23,180 $154,152 $88,077 $593 $85,201

4.2. EIO-LCA inventory of stressors After the economic inputs were prepared, a U.S. 2002 purchaser model in the EIO-LCA model was used to calculate the resources, energy requirement, and the environmental emissions for each phase of pavement life, respectively. The total LCA stressors were obtained by summing up the stressors from each phase. In the EIO-LCA, the economic activities for various sectors representing different categories in the life cycle inventory were input into the model. The LCA inventory of stressors including economic activity, energy, conventional air pollution, greenhouse gases, land use, toxic releases, transportation, and water withdrawal was then output. 4.2.1. Materials production and construction phase The economic inputs for different sectors for the material production and construction phase are tabulated in Table 9. The inventory of stressors is shown in Table 10. The % change in Table 10 is defined:

stressor or impact of RCA PCC pavement  stressor or impact of the plain PCC pavement  100% stressor or impact of the plain PCC pavement

The salvage value which is associated with the 27th year worth was then converted to present worth at the 1st year. The salvage values for different categories including raw materials and paving costs are tabulated in Table 8.

(3)

A negative value of % change means that the pavement made with RCA-PCC reduces the economic, social or environmental burden. From Table 10, the benefits of using RCA in PCC pavement are obvious for all the stressor categories. The production of the RCA-PCC pavement saves 35% in total costs, consumes 18% less

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Table 9 Economic inputs for different sectors for the material production and construction phase. Sector

Sector group

Detailed sector

Economic inputs Plain PCC pavement RCA-PCC pavement

Cement Fly ash Virgin coarse aggregate Virgin fine aggregate Water Paving Haul (virgin aggregates) Haul (RCA aggregates away) Landfill pavement demolition

Plastic, rubber, and nonmetallic mineral products Plastic, rubber, and nonmetallic mineral products Mining and utilities Mining and utilities Mining and utilities Construction Trade, transportation, and communications media Trade, transportation, and communications media Management, administrative, and waste services

Cement manufacturing Cement manufacturing Stone mining and quarrying Sand, gravel, clay, and refractory mining Water, sewage and other systems Other nonresidential structure Truck transportation Truck transportation Waste management and remediation services

$3,886,519 $218,484 $1,452,933 $830,158 $5589 $803,047 $1,008,599 $1,954,327 $4,243,680

$3,886,519 $218,484 $0 $777,843 $5589 $803,047 $371,243 $1,026,219 $2,228,360

Table 10 Inventory of stressors for the material production and construction phase. LCA stressor category

Economic activity (million US dollars) Total Direct economic Energy (TJ) Total Coal Natural gas Petroleum-based fuel Biomass/waste fuel 31% non-fossil fuel electricity Conventional air pollution (ton) Total CO NH3 NOx PM10 PM2.5 SO2 Volatile organic compounds Greenhouse gases (ton CO2 eq) Total CO2 fossil CO2 process CH4 N2O HFC/PFCs Land use (kha) Total Toxic releases (kg) Total Fugitive air Stack Total air Surface water Underground water Land Off-site POTW metal POTW non-metal Transportation (  106 ton-km) Total Air Oil Pipe Gas pipe Rail Truck Water International air International water Water withdrawal (kGal) Total

Values

% Change

Plain PCC pavement

RCA-PCC pavement

27.3 21.4

17.8 13.9

35% 35%

375 156 43.1 126 20.7 29.3

308 149 33.7 80.2 19.9 25.1

18% 4% 22% 36% 4% 14%

500.9 134.0 1.4 166.0 68.9 19.6 93.6 17.4

387.7 104.0 0.9 134.0 37.1 12.8 87.1 11.8

23% 22% 30% 19% 46% 35% 7% 32%

56374.2 26000 19900 10200 187 87.2

47033.9 21600 19700 5550 118 65.9

17% 17% 1% 46% 37% 24%

0.42

0.32

25%

15318 118 2920 3040 158 698 6240 1880 3.63 260

11263 83.6 2750 2830 115 384 3870 1060 2.47 168

26% 29% 6% 7% 27% 45% 38% 44% 32% 35%

164.108 0.00782 2.29 1.47 12.6 19.6 5.12 0.0206 123

138.830 0.00577 1.29 1.26 9.34 12.2 1.72 0.0144 113

15% 26% 44% 14% 26% 38% 66% 30% 8%

207000

136000

34%

X. Shi et al. / Journal of Cleaner Production 225 (2019) 414e425

421

Table 11 Economic inputs for different sectors for the use phase. Categories

Repair and maintenance Tire Consumption Fuel Consumption

Sector group

Detailed sector

Vehicle and Other Transportation Equipment Plastic, rubber, and nonmetallic mineral products Petroleum and basic chemical

energy, emits 23% less conventional air pollution and 17% less greenhouse gases, uses 25% less land, releases 26% less toxic substances, occupies 15% less transportation, and saves 34% in water withdrawal. These achieved sustainability benefits are combined effects of less consumption of virgin aggregate, less virgin aggregate transported to the ready-mix plant, and less concrete debris transported to and disposed to the landfill site for the RCA-PCC pavement case.

Economic inputs

Motor Vehicle Parts Manufacturing Tire manufacturing Petroleum refineries

Plain PCC pavement

RCA-PCC pavement

$281,806,174 $60,968,158 $861,016,189

$281,806,174 $61,122,108 $863,418,887

4.2.2. Use phase The economic inputs for different sectors for the use phase are presented in Table 11, and the LCA inventory of stressors is shown in Table 12. Based on the results, the RCA-PCC pavement is slightly less sustainable compared to the plain PCC pavement for the use phase. The rougher pavement surface of the RCA-PCC pavement causes higher tire and fuel consumption for vehicles, which consequently poses higher negative impacts on economy, environment and

Table 12 Inventory of stressors for the use phase. LCA stressor category

Economic activity (million US dollars) Total Direct economic Energy (TJ) Total Coal Natural gas Petroleum-based fuel Biomass/waste fuel 31% non-fossil fuel electricity Conventional air pollution (ton) Total CO NH3 NOx PM10 PM2.5 SO2 Volatile organic compounds Greenhouse gases (ton CO2 eq) Total CO2 fossil CO2 process CH4 N2O HFC/PFCs Land use (kha) Total Toxic releases (kg) Total Fugitive air Stack Total air Surface water Underground water Land Off-site POTW metal POTW non-metal Transportation (  106 ton-km) Total Air Oil Pipe Gas pipe Rail Truck Water International air International water Water withdrawal (kGal) Total

Value

% Change

Plain PCC pavement

RCA-PCC pavement

2450 1860

2460 1860

0.41% 0.00%

15673 2230 5760 5580 583 1520

15693 2230 5770 5590 583 1520

0.13% 0.00% 0.17% 0.18% 0.00% 0.00%

11561.5 3810.0 53.5 2780.0 552.0 216.0 2010.0 2140.0

11582.5 3820.0 53.5 2780.0 553.0 216.0 2020.0 2140.0

0.18% 0.26% 0.00% 0.00% 0.18% 0.00% 0.50% 0.00%

1269780 866000 111000 277000 6350 9430

1271800 868000 111000 277000 6360 9440

0.16% 0.23% 0.00% 0.00% 0.16% 0.11%

33.7

33.7

0.00%

590164 37600 121000 159000 26900 17600 132000 67800 564 27700

590365 37700 121000 159000 26900 17600 132000 67800 565 27800

0.03% 0.27% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.18% 0.36%

15061.106 0.996 1690 69.9 439 383 276 2.21 12200

15061.207 0.997 1690 70 439 383 276 2.21 12200

0.00% 0.10% 0.00% 0.14% 0.00% 0.00% 0.00% 0.00% 0.00%

7920000

7930000

0.13%

422

X. Shi et al. / Journal of Cleaner Production 225 (2019) 414e425

Table 13 Economic inputs for different sectors for the end-of-use phase. Sector

Cement Fly ash

Sector group

Amount of activity Salvage value at the end of life cycle

Converted to the value at year 1

Cement manufacturing

$607,269

$412,348

Plastic, rubber, and nonmetallic mineral products Plastic, rubber, and nonmetallic mineral products Mining and utilities

Cement manufacturing

$34,138

$23,180

Stone mining and quarrying

$227,021

$154,152

$129,712

$88,077

Mining and utilities Construction

Sand, gravel, clay, and refractory mining Water, sewage and other systems Other nonresidential structure

$873 $125,476

$593 $85,201

Virgin coarse aggregate Virgin fine aggregate Mining and utilities Water Paving

Detailed sector

society. However, compared to the numerous amounts of economic, social and environmental burdens generated during the use phase, the % change of the stressors between the two cases is relatively small (i.e., % change is below 1% for all the categories). 4.2.3. End-of-use phase The salvage economic activities of the plain PCC pavement case for different sectors were input into the model (Table 13). The salvage resources, energy, and the environmental emissions are calculated in Table 14. Since the salvage values are deducted values, the LCA stressors in Table 14 are all negative. These salvage stressors will be deducted from the total stressors for the entire life cycle of the plain PCC pavement case. Because the service life of the RCA-PCC pavement equals to the analysis period of this study, 0 salvage value is defined and no stressors for the end-of-use were deducted for the RCA-PCC pavement case. It is understood that the pavements have some salvage value even when they need a major concrete pavement rehabilitation, but these salvage values are considered identical for the two cases in this study. Accordingly, salvage values for pavements reaching a condition that needs a major concrete pavement rehabilitation are not included in the LCA. 4.2.4. Entire pavement life cycle The total stressors for the entire pavement life cycle for the plain PCC pavement and the RCA-PCC pavement are shown in Table 15. From Table 15, recycling old concrete to make RCA-PCC pavement could reduce the unfavorable output flows in terms of all the stressor categories except for the economic activity. Although the % change between the RCA-PCC pavement and the plain PCC pavement cases is not significant, the differences in terms of absolute values are substantial. Considering this study only focused on 12.8km pavements, if all the concrete pavement reconstruction in the U.S used RCA, the reduction in the environmental and social burdens would be enormous. On the other hand, the RCA-PCC pavement yields a slightly higher economic burden, which is attributed to the higher tire and fuel consumptions caused by the rougher pavement surface. These negative impacts of using RCA in PCC pavement can be mitigated in the near future when new cars whose tire and fuel consumptions are less sensitive to pavement roughness are manufactured. 4.3. Tool for reduction and assessment of chemicals and other environmental impacts One important step of a life cycle assessment is to evaluate the potential impacts of stressors on environment and society.

Table 14 Inventory of stressors for the end-of-use phase. LCA stressor category

Salvage value for the plain PCC pavement

Economic activity (million US dollars) 2.2 Total Direct economic 1.7 Energy (TJ) Total 46.3 Coal 23.3 Natural gas 5.1 Petroleum-based fuel 10.9 Biomass/waste fuel 3.0 31% non-fossil fuel electricity 4.0 Conventional air pollution (ton) Total 61.3 CO 14.6 NH3 0.1 NOx 19.7 PM10 9.1 PM2.5 2.7 SO2 13.7 Volatile organic compounds 1.4 Greenhouse gases (ton CO2 eq) Total 6446.1 CO2 fossil 3250.0 CO2 process 3080.0 CH4 99.5 N2O 8.0 HFC/PFCs 8.7 Land use (kha) Total 0.041 Toxic releases (kg) Total 1172.8 Fugitive air 10.1 Stack 420.0 Total air 431.0 Surface water 14.5 Underground water 8.2 Land 234.0 Off-site 41.2 POTW metal 0.2 POTW non-metal 13.6 Transportation (  106 ton-km) Total 23.32 Air 0.001 Oil Pipe 0.147 Gas pipe 0.201 Rail 1.86 Truck 2.96 Water 0.75 International air 0.002 International water 17.4 Water withdrawal (kGal) Total 27300

X. Shi et al. / Journal of Cleaner Production 225 (2019) 414e425

423

Table 15 Inventory of stressors for the entire pavement life cycle. LCA stressor category

Economic activity (million US dollars) Total Direct economic Energy (TJ) Total Coal Natural gas Petroleum-based fuel Biomass/waste fuel 31% non-fossil fuel electricity Conventional air pollution (ton) Total CO NH3 NOx PM10 PM2.5 SO2 Volatile organic compounds Greenhouse gases (ton CO2 eq) Total CO2 fossil CO2 process CH4 N2O HFC/PFCs Land use (kha) Total Toxic releases (kg) Total Fugitive air Stack Total air Surface water Underground water Land Off-site POTW metal POTW non-metal Transportation (  106 ton-km) Total Air Oil Pipe Gas pipe Rail Truck Water International air International water Water withdrawal (kGal) Total

Values

% Change

Plain PCC pavement

RCA-PCC pavement

2475.1 1879.7

2477.8 1873.9

0.11% 0.31%

16048.0 2362.7 5798.0 5695.1 600.7 1545.3

16000.9 2379.0 5803.7 5670.2 602.9 1545.1

0.29% 0.69% 0.10% 0.44% 0.37% 0.01%

12001.0 3929.4 54.8 2926.3 611.8 233.0 2089.9 2156.0

11970.2 3924.0 54.4 2914.0 590.1 228.8 2107.1 2151.8

0.26% 0.14% 0.57% 0.42% 3.54% 1.78% 0.82% 0.19%

1319708.1 888750.0 127820.0 287100.5 6529.0 9517.2

1318833.9 889600.0 130700.0 282550.0 6478.0 9505.9

0.07% 0.10% 2.25% 1.58% 0.78% 0.12%

34.1

34.0

0.30%

604308.8 37707.9 123500.0 161609.0 27043.5 18289.8 138006.0 69638.8 567.4 27946.4

601628.1 37783.6 123750.0 161830.0 27015.0 17984.0 135870.0 68860.0 567.5 27968.0

0.44% 0.20% 0.20% 0.14% 0.11% 1.67% 1.55% 1.12% 0.01% 0.08%

15201.89 1.00 1692.14 71.17 449.74 399.64 280.37 2.23 12305.60

15200.04 1.00 1691.29 71.26 448.34 395.20 277.72 2.22 12313.00

0.01% 0.03% 0.05% 0.13% 0.31% 1.11% 0.95% 0.20% 0.06%

8099700.0

8066000.0

0.42%

According to Bare (2002), the TRACI is an impact analysis tool which provides category indicators for life cycle impact assessment, industrial ecology, and sustainability metrics. The category indicators in the TRACI quantify the potential impacts for the specific categories with common equivalence units. In this case study, the TRACI results were also obtained directly from the EIO-LCA model outputting results. The TRACI results for the plain PCC pavement and RCA-PCC pavement are compared in Table 16. The TRACI category indicators include global warming potential, acidification air, human health particulate air, eutrophication (air and water), ozone depletion air, smog air, ecotoxicity (low and high), human health cancer (low and high), and human health non-cancer (low and high). A brief explanation of these indicators is summarized in the second column of Table 16. Readers can obtain more detailed information from Bare (2002). Based on the results, compared to constructing concrete pavement using virgin aggregate, the use of

RCA to reconstruct concrete pavement could have fewer negative impacts on the indicators including global warming potential, acidification air, human health particulate air, smog air, ecotoxicity (both low and high), human health cancer (both low and high), and human health non-cancer (both low and high). The beneficial effects concerning reducing ecotoxicity (both low and high) and potentials for human health cancer (both low and high) and human health non-cancer (both low and high) are very significant. This infers that these negative impacts are largely posed during the processes of mining virgin aggregate, transporting materials, and landfilling concrete debris. On the other hand, the RCA-PCC pavement case yields slightly higher values for the other category indicators including eutrophication (both air and water) and ozone depletion, which is caused by the higher tire and fuel consumption during the use phase. According to Table 16, the pavement made with RCA-PCC is generally more environmentally and socially

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X. Shi et al. / Journal of Cleaner Production 225 (2019) 414e425

Table 16 Life cycle impact assessment results. TRACI category indicator

Explanation and interpretation

Values

Global warming potential (ton An average increase in the temperature of the atmosphere near the Earth's surface and in the CO2 eq) troposphere, which can contribute to changes in global climate patterns. Acidification air (ton SO2 eq) Lead to acid rain, fog, or snow or dry deposition; cause damage to building materials, paints, and other human-built structures, lakes, streams, rivers, and various plants and animals. Human health particulate air A collection of small particles in ambient air which have the ability to cause negative human health (ton PM10 eq) effects including respiratory illness and death. Eutrophication air (ton N eq) Enrichment of an aquatic ecosystem; accelerate biological productivity and an undesirable Eutrophication water (ton N accumulation of algal biomass. eq) Ozone depletion air (ton CFC- Lead to increased frequency of skin cancers and cataracts in the human population; also has effects on 11 eq) crops, other plants, marine life, and human-built materials. Lead to a variety of respiratory issues including increasing symptoms of bronchitis, asthma, and Smog air (ton O3 eq) emphysema; Permeant lung damage may result from prolonged exposure to ozone. Ecological impacts include damage to various ecosystems and crop damage. Ecotoxicity (low) (ton 2,4D) Characterize potential adverse effect that a chemical causes to an aquatic or terrestrial receptor Ecotoxicity (high) (ton 2,4D) Human health cancer (low) Characterize potential cancer human health hazards (ton benzene eq) Human health cancer (high) (ton benzene eq) Characterize potential non-cancer human health hazards Human health non-cancer (low) (ton toluene eq) Human health non-cancer (high) (ton benzene eq)

friendly compared to the pavement made with virgin aggregates. 5. Conclusions Concrete pavement recycling has become a common practice for many states in the U.S. While material properties and structural performance of pavements with virgin concrete aggregates replaced by RCA were extensively characterized, very little effort has been made to assess potential sustainability benefits of this application. A life cycle assessment to compare an RCA-PCC pavement and a plain PCC pavement from all three aspects of sustainability (economic impact, social impact, and environmental impact) was carried out through an EIO-LCA approach. The LCA inventory of stressors during the materials production and construction, use, and end-of-life phases of pavement life cycle was obtained. These stressors were further assessed with the TRACI subsequently. The following conclusions are made from this LCA case study:  The inventory of stressors for the materials production and construction phase indicates that the RCA-PCC pavement yields significantly less economic, environmental, and social burdens compared to the plain PCC pavement. The sustainability benefits of the RCA-PCC pavement in this phase of life cycle are attributed to less consumption of virgin aggregate, less virgin aggregate transported to the ready-mix plant, and less concrete debris transported and disposed of at the landfill site.  The RCA-PCC pavement is slightly less sustainable compared to the plain PCC pavement during the use phase. The rougher pavement surface of the RCA-PCC pavement causes higher tire and fuel consumption for vehicles, which poses higher negative impacts on economy, environment, and society.  The results of the total stressors and the category indicators in the TRACI for the entire pavement life cycle are slightly mixed. Although the benefits of using RCA in PCC pavement during the materials production and construction phase are invariably achieved for all the categories, the higher amount of negative impacts by using RCA in pavement during the use phase can be

% Change

Plain PCC pavement

RCA-PCC pavement

1319708

1318834

0.07%

4538

4536

0.05%

1198

1174

2.05%

136 0.470

136 0.471

0.33% 0.14%

0.401

0.402

0.14%

80385

80280

0.13%

67 68 99

52 53 90

22.30% 21.90% 9.93%

506

458

9.51%

63266

56300

11.01%

1345530

1061000

21.15%

more dominating throughout the entire life cycle for a few categories. As a result, the unfavorable impacts from the use phase cancel out the benefits achieved during the materials production and construction for the RCA-PCC pavement to some extent. Still, the pavement made with RCA-PCC is generally more environmentally and socially friendly compared to the pavement made with virgin aggregates; such sustainability benefits are especially significant for the categories of ecotoxicity (both low and high), human health cancer (both low and high) and human health non-cancer (both low and high). In conclusion, use of RCA in PCC pavement not only is a technically sound strategy, but also can lead to significant sustainability benefits. These benefits will only be magnified with a growing level of environmental awareness, further diminishment of local virgin aggregate sources, and a rapid increase of landfill tipping costs for construction demolition debris in the future. The limitations of this study lie in the fact that the sensitivity of the predictions of the economic inputs for the use phase from the VOC model and the stressors outputs from the EIO-LCA is still unclear. Future research on how much more sustainability can be achieved with the increase of costs of quarrying and transporting virgin aggregate and disposing of construction demolition debris is highly warranted. Declarations of interest None. Acknowledgement This work was supported by the Oklahoma Department of Transportation under research project 2278. The work was conducted by the authors in Texas A&M Transportation Institute and Center for Infrastructure Renewal of the Texas A&M University System. Any opinions, findings, conclusions, and recommendations expressed in this paper are those of the authors alone and do not necessarily reflect the views of the sponsoring agencies. The

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