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PERFORMANCE AND COST EFFECTIVENESS OF SUSTAINABLE
TECHNOLOGIES IN FLEXIBLE PAVEMENTS USING THE
MECHANISTIC-EMPIRICAL PAVEMENT DESIGN GUIDE
Samuel B. Cooper, III1 E.I.
Yoonseok Chung2, MSCE
Bhanu Vijay Vallabhu3
Mostafa Elseifi4, Ph.D
Louay N. Mohammad5, Ph.D
Marwa Hassan6, PhD
Submitted to:
90th Transportation Research Board Annual Meeting
January 23-27, 2011
Washington, D.C.
Submission Date: July 31, 2010
Word Count
Abstract 172
Text 4029
Figures (8 x 250) 2250
Tables (4 x 250) 750
Total 7029
1 Ph.D. Graduate Student, Louisiana State University, Baton Rouge, LA 70808, Email: scoop15@lsu.edu
2 Ph.D. Graduate Student, Louisiana State University, Baton Rouge, LA 70808, Email: ychung3@lsu.edu
3 MSCE Graduate Student, Louisiana State University, Baton Rouge, LA 70808, Email: bvalla1@lsu.edu
4 Assistant Professor, Department of Civil and Environmental Engineering, Louisiana State University,
Baton Rouge, LA 70803, Email: elseifi@lsu.edu
5 Professor, Department of Civil and Environmental Engineering and Louisiana Transportation Research
Center, Louisiana State University, 4101 Gourrier Ave., Baton Rouge, LA 70808, Email: louaym@lsu.edu
6 Assistant Professor, Department of Construction Management and Industrial Engineering, Louisiana State
University, Baton Rouge, LA 70803, Email: louaym@lsu.edu
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
2
ABSTRACT
In recent years, an increase in construction prices coupled with a global change for
improved ecological stewardship led to the development of several sustainable
technologies for asphalt pavements. Past research evaluated the mechanistic properties,
economic benefits, and ecological impacts of these mixtures. However, questions remain
concerning the effects of these technologies on structural pavement design and
performance. The objective of this study was to evaluate the effects of selected
sustainable technologies on the predicted performance from the Mechanistic-Empirical
Pavement Design Guide (MEPDG) and to assess the life cycle costs of pavement
structures constructed with these sustainable alternatives. In addition, this study
evaluated if the MEPDG software is sensitive to variation in the mechanistic properties of
asphalt mixtures containing selected sustainable technologies. To achieve this objective,
three typical pavement structures were analyzed at three traffic levels (low, medium, and
high). The effects of warm-mix asphalt (WMA), reclaimed asphalt pavement (RAP),
crumb rubber (CRM), and Shell Thiopave® were evaluated. Based on the results of the
analysis, it was determined that the MEPDG was able to distinguish between different
sustainable technologies in terms of performance. In addition, results indicated that
sustainable technologies have the potential to improve pavement performance, reduce
production and life cycle costs when compared to conventional asphalt mixtures.
Keywords: MEPDG, WMA, RAP, Thiopave, Sustainable
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
3
INTRODUCTION
In recent years, an increase in construction prices coupled with a global change for
improved ecological stewardship has led to the development of several sustainable
technologies for asphalt pavements. A commonly accepted definition of sustainable
pavement is a pavement that is safe, efficient, and environmentally friendly while
meeting the needs of the present generation without affecting the ability of future
generations to meet their needs (1). The main objectives for sustainable pavements are to
minimize the use of natural resources, reduce energy consumption, reduce greenhouse
gas emissions, limit pollution, improve health and safety, and ensure a high level of user
comfort (1). The economic impact of a pavement should also be considered when
discussing sustainability. Examples of sustainable pavement technologies include warm-
mix asphalt (WMA) mixtures, mixtures containing recycled products, and mixtures
containing waste products from industrial processes. Engineers must consider new
technologies and design methodologies to comply with current and future stringent
environmental and economic constraints.
Pavement engineers are transitioning from a semi-empirical to a mechanistic
empirical pavement design methodology. Historically, pavements have been designed
using the American Association of State Highway and Transportation Officials
(AASHTO) Guide for Design of Pavement Structures. This design methodology is based
on empirical performance correlations developed from the American Association of State
Highway Officials (AASHO) road test conducted in the late 1950s and early 1960s in
Ottawa, Illinois. The major limitation of this methodology is that the correlations are
derived considering single climatic and subgrade conditions. In addition, traffic loads
have dramatically changed since the 1950s and 1960s; hence, there is a higher structural
demand for today’s pavement structures (2). These limitations prompted the need to
develop a design methodology that is based on the mechanistic properties of the
pavement structure. The Mechanistic-Empirical Pavement Design Guide (MEPDG) was
developed in response to the notable shortcomings of the 1993 AASHTO design
methodology.
Since the development of the aforementioned sustainable technologies, there has
been extensive research to evaluate the mechanistic properties, economic benefits, and
ecological impacts of these mixtures (4-13). However, questions remain concerning the
effect of these technologies on structural pavement design and performance. To this end,
this study evaluated if the MEPDG software is sensitive to variation in the mechanistic
properties of asphalt mixtures containing selected sustainable technologies and if the
MEPDG is an appropriate tool to use for designing sustainable pavements.
OBJECTIVES AND SCOPE
The objective of this study was to evaluate the effects of selected sustainable
technologies on the predicted performance from the MEPDG and to assess the life cycle
costs of pavement structures constructed with these sustainable alternatives. The effects
of warm-mix asphalt (WMA), reclaimed asphalt pavement (RAP), crumb rubber (CRM),
and Shell Thiopave® were evaluated. Three traffic levels (low, medium, and high) were
considered in the analysis. Level 1 analysis was used to describe the asphalt layers, while
Level 2 analysis was used for the granular base and subgrade layers. Several sustainable
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
4
pavement technologies were evaluated as components of the pavement structure to
determine whether the predicted performance would distinguish sustainable mixtures
from conventional mixtures. In addition, a cost comparison between conventional and
sustainable pavements was conducted to evaluate the cost effectiveness of sustainable
technologies.
BACKGROUND
The development of the MEPDG provided a tool to evaluate asphalt mixtures with
respect to pavement performance against major distresses. The purpose of the MEPDG is
“to provide the highway community with a state-of-the-practice for the design of new and
rehabilitated pavement structures, based on mechanistic-empirical principles” (3). The
MEPDG addresses the shortcomings of the semi-empirical 1993 AASHTO pavement
design guide that was developed based on the results of the AASHO road test conducted
in the late 1950s (4). The design guide software uses site-specific traffic, climate, and
subgrade data combined with mechanistic properties of the pavement structure to
evaluate the distress susceptibility of the design. The MEPDG can evaluate the pavement
structure on three levels of analysis. Level 1 considers measured mechanistic properties
for the structural layers. Level 2 evaluates the pavement performance using predicted
mechanistic values. In contrast, Level 3 uses national default values to analyze the
pavement structure (3).
Sustainable Technologies
Despite of the lack of a clear protocol for designing and constructing an environmentally
friendly highway, the asphalt industry had experimented with sustainable alternatives
since the 1970s. This had led to experimentation with various construction and recycling
techniques that are thought to reduce the environmental impacts of highway construction
and positively assist in the reduction of waste disposed in landfills. A brief description of
the sustainable technologies evaluated in this research is provided in this section.
The production of WMA using foaming and Rediset additives was evaluated in
this research (4). Harmful emission and energy costs are reduced by lowering asphalt
concrete production temperature. Foaming the binder is accomplished by introducing
small amounts of water to reduce asphalt cement viscosity and aid in mixing and
compaction at lower production temperature (4). Rediset is a surfactant added to asphalt
cement at a rate between 1.25 and 2% and is used to aid in the mixing and compaction of
the mixture at lower production temperature. This study also evaluated the use of
Reclaimed Asphalt Pavement (RAP) in HMA. The use of RAP can reduce the amount of
virgin aggregates and asphalt cement used in HMA production (5). In this study, the
performance of a PG 64-22 HMA mixture containing 40% RAP was compared to a
conventional mix prepared with PG 64-22 and no RAP.
The use of crumb-rubber modifier (CRM) additives, which can reduce virgin
asphalt content in the mixture, was evaluated in this study (5). The use of waste tires also
reduces the need for unsanitary tire disposal yards. In this study, the performance of a
PG 64-22 HMA mixture containing 10% Mesh 30 CRM blended in a wet process (which
yielded a PG 76-22 binder) was compared to a conventional 76-22 HMA mixture
containing no CRM.
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
5
With the recent increase in the price of liquid asphalt, the use of sulfur as a binder
extender appears economically attractive. Shell Thiopave® modifier consists of small
sulfur pellets, which are added to the aggregate during the mixing process. Mixture
preparation consists of heating the sulfur pellets and the aggregate blends. The binder is
then mixed with the hot aggregates, followed by adding the heated sulfur pellets and
mixing thoroughly to ensure that all the pellets melted. To address concerns with sulfur
emissions, it is required that the mixing temperature be lower than 140 ± 5°C (6). The use
of Thiopave® may reduce the use of virgin asphalt cement and reduce energy costs during
production (7). In this study, the performance of a PG 64-22 WMA mixture containing
40% Thiopave additives was compared to a conventional PG 64-22 HMA. Table 1
provides a description of the mixtures evaluated in this study.
Table 1 Mixture Descriptions
Technology Mixture
Name
Binder
Grade Description
WMA
HMARAP15
PG 70-22
HMA containing 15% RAP (Control)
WMAFoam15 Foamed WMA containing 15% RAP
WMARedi15 WMA with Rediset additives containing 15%RAP
WMAFoam30 Foamed WMA containing 30% RAP
Crumb
Rubber
76Conv PG 76-22 Conventional HMA with PG 76-22 binder
76CRM HMA containing 10% CRM additives (wet blend)
RAP 64RAP40 PG 64-22 HMA containing 40% RAP and CRM (dry blend)
64Conv Conventional HMA with PG 64-22 binder
Thiopave 64Thio PG 64-22 WMA containing 40% Thiopave modifiers
64Conv Conventional HMA with PG 64-22 binder
A number of studies evaluated the effects of WMA mixtures and mixtures containing
various quantities of RAP on the predicted performance from the MEPDG. Buss et al.
conducted a series of experiments comparing the effects of multiple WMA technologies
on pavement performance using the MEPDG (4). Results of this study showed that
WMA performance was equal to or slightly better than conventional HMA. Similarly,
Goh et al. evaluated the performance of several WMA mixtures in comparison with
conventional HMA (8). The results from this study showed that, based on a Level 1
analysis, WMA had a lower predicted rut depth than conventional HMA. Diefenderfer et
al. evaluated the long-term performance effects of WMA in Virginia using the MEPDG
and found that the predicted performance did not differ significantly from conventional
HMA (9). Daniel et al. evaluated the sensitivity of the MEPDG to RAP binder grade.
Results showed that Level 1 analyses were not significantly affected by fluctuations in
the predicted RAP binder content. Contrarily, Levels 2 and 3 were greatly affected by
variation in the RAP binder content. Based on these results, the authors suggested using
Level 2 and 3 analyses for more conservative results. They also stated that further
research was necessary to evaluate the effects of RAP mixtures used in additional
pavement structures, traffic levels, and climates (10).
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
6
To ensure that economic aspects are considered in performance evaluation, it is
necessary to evaluate the life-cycle cost (LCC) of sustainable technologies. A reduction
in the LCC is accomplished by either reducing the initial investment in the project or
extending the service life of the structure. The service life of a pavement is a function of
the pavement structure’s resistance to distresses caused by traffic and environmental
loading. Typically, the performance of flexible pavements is controlled by the thickness
of the structural layers. Pavements subjected to higher traffic loads need higher layer
thicknesses to achieve acceptable performance. When evaluating multiple traffic cases,
layer thicknesses are changed to reduce fluctuation in pavement performance due traffic
levels. Studies show that the use of sustainable technologies can significantly reduce the
life-cycle cost of pavement structures (9, 11).
METHODOLOGY
Pavement Performance Prediction
The MEPDG was used to predict the performance of three pavement structures designed
with nine asphalt mixtures. Three pavement designs representing typical pavement
structures used in the state of Louisiana were considered for three traffic levels (low,
medium, and high). Figure 1 depicts the pavement structures evaluated in this study.
The layer of interest is the “HMA” layer. The MEPDG analysis was conducted by
altering the material properties of the “HMA” layer for each of the mixture in the
factorial. All other layers’ properties were kept constant.
FIGURE 1 Pavement Structures
Design Inputs
The pavement structure was designed for a service life of 20 years as a new flexible
pavement. The national default value available in the MEPDG software for initial IRI
was used in the analysis. However, values consistent with Louisiana Pavement
Management System (PMS) failure limits were used for terminal IRI and permanent
deformation. The Louisiana PMS system uses index values to describe pavement distress
a. High Volume Traffic b. Medium Volume Traffic c. Low Volume Traffic
50mm SMA
152mm
HMA Layer
A-7-6 Clayey
Subgrade
A-7-6 Clayey
Subgrade
50mm HMA La
y
er
305mm
Crushed
Stone Base
102mm
HMA Layer
305mm
Crushed
Stone Base
305mm
Crushed
Stone Base
A-7-6 Clayey
Subgrade
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
7
limits. In order to use these limits in the MEPDG software, the index values were
converted to the appropriate units. LADOTD provides conversion equations for IRI and
rutting as well as trigger values for rehabilitation. The values used in this study are given
in Table 2. The MEPDG national default reliability level of 90% was used in the
analysis. However, during evaluation of the results, the actual predicted distress values
were used (i.e., reliability of 50%).
TABLE 2 Louisiana PMS Distress Triggers
Traffic Level
Distress High Medium Low
IRI (mm/km) 1973 3157 3946
Rut Depth (mm) 9.6 14.2 14.2
Traffic
Average Annual Daily Traffic (AADT) values for multiple traffic classifications, as well
as truck factors, and distribution for vehicle classes 1 to 13 were provided by LADOTD.
Since the MEPDG only supports truck classes 4 to 13, the vehicle classes 1 to 3 were not
considered, and the truck class distributions were adjusted to consider only classes 4 to
13. Monthly distribution data were obtained from previous research (14). The national
default values from LTPP data for hourly distribution and growth factor were used.
Climate
Climatic data were obtained from the MEPDG climate database for the City of Baton
Rouge, LA (15). There was 116 months of data available for the selected location and an
assumed average water table depth of 2.1 m. The water table depth was determined via
an equation developed to estimate the water table based on surface elevations in the Gulf
coast regions in the United States (16). The elevation was determined from the MEPDG
climatic database:
Water Table Altitude = Land-surface altitude * 0.8978 (1)
AC Layer Properties
Measured dynamic modulus (E*) and binder complex shear modulus (G*) data for each
of the mixtures were measured in the laboratory and were used in the MEPDG to
describe the mixture properties for Level 1 analysis. The gradations and volumetric
properties were also available for each mixture evaluated in this study. Figure 2 presents
a comparison of the master curve constructed for each of the mixtures evaluated in this
study. It is worth noting that the master curves of the four WMA mixtures were nearly
identical, see Figure 2a. Figures 2c and 2d indicate that the use of RAP and Thiopave®
resulted in increased mix stiffness when compared to conventional mixtures at high
temperatures; while Figure 2b illustrates that, the use of CRM additives increased the
stiffness at intermediate temperatures.
(a)
(c)
(b)
(d)
FIGURE 2 Master Curve Comparisons
Base and Subgrade Properties
Measured resilient modulus (Mr) values for crushed limestone and clayey subgrade were
collected from previous projects (17) and were used in the analysis of the various
pavement structures. These values were kept constant for all three-pavement structures.
Cost Effectiveness
Contact with experts and producers from the industry provided accurate cost information
regarding sustainable technologies. In addition, a number of assumptions were based on
historical cost indices. Table 3 summarizes the cost data used to evaluate the production
cost of the mixtures evaluated in this study. A simplified Life Cycle Cost (LCC) for a
mixture was determined by dividing the total cost of producing one ton of each mixture
1.0E+03
1.0E+04
1.0E+05
1.0E+06
1.0E+07
‐6‐4‐20246
E*(psi)
Log(ReducedTime(sec))
WarmMix
HMARAP15 WMAFoam15
WMAFoam30 WMARedi15
1.0E+03
1.0E+04
1.0E+05
1.0E+06
1.0E+07
‐6‐4‐20246
E*(psi)
Log(ReducedTime(sec))
RAP
64Conv 64Rap40
1.0E+03
1.0E+04
1.0E+05
1.0E+06
1.0E+07
‐6‐4‐20246
E*(psi)
Log(ReducedTime(sec))
CRM
76Conv 76CRM
1.0E+03
1.0E+04
1.0E+05
1.0E+06
1.0E+07
‐6‐4‐20246
E*(psi)
Log(ReducedTime(sec))
Thiopave
64Conv 64Thio
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
9
by the number of years of service predicted by the MEPDG software for each traffic level
by the predicted service life. Service life was defined as the period that the pavement
structure performed adequately with distress indices lower than the Louisiana pavement
management system’s rehabilitation triggers’ values. Rehabilitation costs were assumed
constant for all mixture types.
TABLE 3 Cost Data
Item Cost
Asphalt Concrete $375 - $575/Liquid Ton
Virgin Aggregate $35 /Ton
RAP Aggregate $0/Ton
CRM Additives $500/Ton
Rediset Additives $4000/Ton
Thiopave® Additives $150/Ton
Energy and Emission Data for Warm-Mix Asphalt
Data were collected to quantify cost savings based on the reduction in energy
consumption for WMA. Energy consumption data for WMA were collected from three
plants around the state of LA. Results showed that energy consumption in the three
plants was reduced by 12, 14, and 13.2% due to the use of warm-mix asphalt. A review
of relevant studies found reported energy savings between 20 and 35% (18), indicating
that the data collected for LA is on the conservative side. This energy reduction was
associated with lowering the mixing temperature from 150oC for HMA production to
120oC for WMA. Table 4 summarizes the energy and cost saving associated with WMA
production. WMA energy consumption was calculated as 87% of the HMA needed
energy for plant operations and construction. This resulted in an energy saving of 43.7
MJ/ton for WMA.
TABLE 4 Energy Cost Saving
Production Source Energy Cost
($/Ton)
HMA (19,20,21) 5.80
WMA
LA Plant 1 4.83
LA Plant 2 3.20
LA Plant 3 4.54
Average Energy Cost Savings 1.37
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
10
RESULTS AND ANALYSIS
Pavement performance distresses were predicted using the MEPDG software for the three
flexible pavement designs at the three traffic levels (low, medium, and high). Sustainable
pavement technologies were evaluated as components of the pavement structures to
determine whether the design guide would distinguish sustainable mixtures from
conventional mixtures in terms of performance. In addition, a cost comparison between
conventional and sustainable pavements was conducted to evaluate the cost effectiveness
of the sustainable technologies. Summaries of the results for performance predictions
and cost analysis are provided.
Figure 3 presents the effects of sustainable pavement technologies on IRI
predictions after 10 years in service. As shown in this figure, the use of sustainable
technologies improved the IRI performance predictions as compared to conventional
mixtures at all traffic levels.
(a)
(c)
(b)
(d)
FIGURE 3 Ten-Year IRI Comparison
1350.0
1400.0
1450.0
1500.0
1550.0
Low Med High
IRI(mm/km)
TrafficLevel
WarmMix
HMARap15 WMAFoam15
WMAFoam30 WMARedi15
1350.0
1400.0
1450.0
1500.0
1550.0
Low Med High
IRI(mm/km)
TrafficLevel
RAP
64Conv
64RAP40
1350.0
1400.0
1450.0
1500.0
1550.0
Low Med High
IRI(mm/km)
TrafficLevel
CRM
76Conv
76CRM
1350.0
1400.0
1450.0
1500.0
1550.0
Low Med High
IRI(mm/km)
TrafficLevel
Thiopave
64Conv
64Thio
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
11
Figure 4 presents the effects of using sustainable technologies on the predicted
performance against rutting after ten years in service. Similar to the IRI predictions, the
use of WMA, CRM, RAP, and Thiopave® resulted in lower total rut depth for the
pavement structures as compared to conventional asphalt mixtures. Laboratory
measurements conducted using the Hamburg Loaded-Wheel Tester (LWT) showed
improved rutting performance for the 76 CRM, 64RAP40, and 64Thio mixtures, see
Figure 5. As shown in this figure, the mixture containing 40% RAP (64RAP40)
significantly improved the rutting performance of the conventional HMA prepared with
PG 64-22.
(a)
(c)
(b)
(d)
FIGURE 4 10-Year Total Rut Depth Comparison
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
Low Med High
TotalRutDepth(mm)
TrafficLevel
WarmMix
HMARap15 WMAFoam15
WMAFoam30 WMARedi15
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
Low Med High
TotalRutDepth(mm)
TrafficLevel
RAP
64Conv
64RAP40
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
Low Med High
TotalRutDepth(mm)
TrafficLevel
CRM
76Conv
76CRM
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
Low Med High
TotalRutDepth(mm)
TrafficLevel
Thiopave
64Conv
64Thio
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
12
FIGURE 5 Rutting Performance from the LWT Test Results
Figure 6 presents the predicted service lives for the various sustainable technologies. The
design life of a pavement was defined as the moment in time when the first pavement
distress exceeded the terminal threshold. In all cases, the critical distress was the total
pavement rut depth. All sustainable technologies resulted in greater pavement service
lives when compared to conventional mixtures at all traffic levels. The 64RAP40
mixture resulted in the greatest increase in the predicted service life. The service life of
the pavements subjected to high traffic levels was much shorter than that of the low and
medium designs. This indicates that the design selected for high traffic level needs to be
increased to withstand heavy traffic conditions.
0
2
4
6
8
10
12
RAP CRM Thiopave
RutDepth(mm)
MixtureAnalysis
LWTAnalysis
64Conv
64RAP40
76Conv
76CRM
64Thio
(a)
(c)
(b)
(d)
FIGURE 6 Design Life Comparison
Figure 7 presents the results of the production costs analysis of the various mixtures.
Figure 7a shows that, with the energy savings, the cost of the Rediset additives increased
the production costs of the WMA. In addition, the cost of the WMAFoam30 was much
lower than for the other mixtures due to the higher percentage of RAP used in the mixture
design. Figures 7b through 7d show that a cost saving is possible for all other sustainable
technologies evaluated in this study. The 64RAP40 mixture provided the greatest cost
saving due to the high percentage of RAP in this mix.
In order to gain a better understanding of true pavement costs versus predicted
performance, the production cost of each mix was divided by the predicted service life of
the pavement at each traffic level. Figure 8 shows the results of the simplified life cycle
economic analysis. The results show that sustainable mixtures provided lower life cycle
cost when compared to conventional mixtures at all traffic levels. In addition, the
64RAP40 mixture yielded the greatest improvement in LCC. The high traffic level case
yielded high LCC because the predicted service life of the pavement was relatively short.
0.0
5.0
10.0
15.0
20.0
25.0
Low Med High
DesignLife(years)
TrafficLevel
WarmMix
HMARap15 WMAFoam15
WMAFoam30 WMARedi15
0.0
5.0
10.0
15.0
20.0
25.0
30.0
Low Med High
DesignLife(years)
TrafficLevel
RAP
64Conv
64RAP40
0.0
5.0
10.0
15.0
20.0
25.0
Low Med High
DesignLife(years)
TrafficLevel
CRM
76Conv
76CRM
0.0
5.0
10.0
15.0
20.0
25.0
Low Med High
DesignLife(years)
TrafficLevel
Thiopave
64Conv
64Thio
(a)
(c)
(b)
(d)
FIGURE 7 Production Cost Comparison
48.21 47.32
40.81
50.17
35.00
40.00
45.00
50.00
55.00
60.00
ProductionCost($/Ton)
MixtureID
WarmMix
HMARap15 WMAFoam15
WMAFoam30 WMARedi15
48.60
30.79
20.00
25.00
30.00
35.00
40.00
45.00
50.00
55.00
60.00
ProductionCost($/Ton)
MixtureID
RAP
64Conv
64RAP40
56.60
50.60
35.00
40.00
45.00
50.00
55.00
60.00
ProductionCost($/Ton)
MixtureID
CRM
76Conv
76CRM
48.60
46.02
35.00
40.00
45.00
50.00
55.00
60.00
ProductionCost($/Ton)
MixtureID
Thiopave
64Conv
64Thio
(a)
(c)
(b)
(d)
FIGURE 8 Life Cycle Cost Comparison
SUMMARY AND CONCLUSIONS
The objective of this study was to evaluate the effects of selected sustainable
technologies on the predicted performance from the MEPDG and to assess the life cycle
costs of pavement structures constructed with these sustainable alternatives. To achieve
this objective, pavement performance against major distresses were determined using the
MEPDG for three designs at three traffic levels. In addition, a life-cycle cost assessment
was conducted for the evaluated mixtures. Comparisons were drawn between sustainable
and control mixtures. The following conclusions are drawn based on the results of this
study:
The MEPDG was able to distinguish between different sustainable technologies in
terms of performance.
0.0
5.0
10.0
15.0
20.0
25.0
30.0
Low Med High
LifeCycleProductionCost
($/ton/year)
TrafficLevel
WarmMix
HMARap15 WMAFoam15
WMAFoam30 WMARedi15
0.0
5.0
10.0
15.0
20.0
25.0
30.0
Low Med High
LifeCycleProductionCosts
($/ton/year)
TrafficLevel
RAP
64Conv
64RAP40
0.0
5.0
10.0
15.0
20.0
25.0
30.0
Low Med High
LifeCycleProducitonCost
($/ton/year)
TrafficLevel
CRM
76Conv
76CRM
0.0
5.0
10.0
15.0
20.0
25.0
30.0
Low Med High
LifeCycleProductionCost
($/ton/year)
TrafficLevel
Thiopave
64Conv
64Thio
Cooper, Chung, Vallabhu, Elseifi, Mohammad, & Hassan
16
Sustainable mixtures evaluated in this study provided enhanced performance with
respect to rutting and IRI. The HMA mixture containing 40% RAP resulted in the
most favourable predicted performance.
The use of RAP resulted in the greatest reduction in production costs. The
mixture containing 40% RAP had the lowest life cycle cost; followed by the
Thiopave® mixture, the WMAFoamed30 mixture, then the crumb rubber modified
mixture.
ACKNOWLEDGEMENT
The authors would like to acknowledge the valuable assistance of Yoonseok Chung and
Bhanu Vijay Vallabhu.
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