CivilEng

| October 19, 2015

Attached is the journal and below is the details required from the chosen journal

I require Relevance, Applicability and Critical Evaluation.?How is the work relevant to the field of cost engineering? Can the results be applied? Give example of the paper’s potential usefulness and identify what would make it more useful.

Submission: –
Your report shall contain at least 2,400 words but no more than 2500. Double spacing is required. Attach a copy of your selected article to your report.

*Journal articles can be searched via Library’s homepage. Examples are: –
1. ‘Cost Engineering’?
2. ‘Transactions of the American Association of Cost Engineers’;?
3. ‘International Journal of Project Management’?
4. ‘Journal of Construction Engineering and Management’, or?
5. …etc.?
Relevance, Applicability and Critical Evaluation
How is the work relevant to the field of cost engineering? Can the results be applied? Give example of the paper’s potential usefulness and identify what would make it more useful.

INTRODUCTION:
The report will reflect on the journal article ‘A methodology for cost-benefit analysis of recycled asphalt pavement (RAP) in various highway applications’ by Rebecca Franke & Khaled Ksaibati. It will assess the relevance; applicability and critically evaluate it by answering the following questions of howthe work is relevant to the field of cost engineering and if the results be applied. It will give examples from thepaper and by assessing the potential usefulness and identifying what would make it more useful.

RELEVANCE AND APPLICABILITY:
Relevance:

Applicability:

However the disadvantages are

COST ENGINEERING:
It is relevant to the field of cost engineering because????

RESEARCH USEFULNESS:
The research has identified which utilisation of RAP in various roadway applications is the most cost efficient. It has compared and evaluated the cost effectiveness of utilising RHPM, gravel roads and RAP in road base. For example ………….

What would make the research more useful is ……………

CONCLUSION:

REFERENCES:

International Journal of Pavement Engineering
ISSN: 1029-8436 (Print) 1477-268X (Online) Journal homepage: http://www.tandfonline.com/loi/gpav20
A methodology for cost-benefit analysis of
recycled asphalt pavement (RAP) in various
highway applications
Rebecca Franke & Khaled Ksaibati
To cite this article: Rebecca Franke & Khaled Ksaibati (2015) A methodology for cost-benefit
analysis of recycled asphalt pavement (RAP) in various highway applications, International
Journal of Pavement Engineering, 16:7, 660-666, DOI: 10.1080/10298436.2014.943217
To link to this article: http://dx.doi.org/10.1080/10298436.2014.943217
Published online: 01 Aug 2014.
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A methodology for cost-benefit analysis of recycled asphalt pavement (RAP) in various
highway applications
Rebecca Franke and Khaled Ksaibati*
Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY, USA
(Received 26 November 2013; accepted 5 July 2014)
The purpose of this study is to determine which utilisation of recycled asphalt pavement (RAP) in various roadway
applications is the most cost efficient. Using a method developed by the National Asphalt Pavement Association, a system
was devised to assess the costs and benefits of using RAP in hot plant mix. A similar process was developed to evaluate the
value of using RAP in gravel roads and bases. The system normalises all of the costs and benefits into savings per tonne of
RAP as a means of equal comparison. Factors such as savings from dust loss, layer coefficients, haul and decreased need of
virgin aggregates were taken into account. Finally, a case study was conducted using these three different applications. Such
analysis can be used by other agencies interested in identifying the most cost-effective methods for using RAP in roadway
construction.
Keywords: RAP; recycled asphalt pavement; cost-benefit; hot plant mix; base layer; gravel roads
1. Introduction
When the volume of traffic on an unpaved road grows,
it causes increasing dust loss and surface losses to the
roadway. Roads tend to be paved when they carry a
volume that exceeds ,150 –400 vehicles per day (vpd).
Many unpaved roads that experience an upsurge in traffic
end up carrying over the suggested 400 vpd. It would make
sense to pave some of these roads, but many local agencies
cannot afford these expensive operations, especially when
the future traffic volume of these roads is uncertain. Those
activities that caused the upsurge might decrease, which
could result in a significant reduction in traffic volumes.
Therefore, other means of surface preservation must be
taken into consideration. An alternative option is needed to
reduce the dust loss and associated surface distresses,
while still being cost effective.
In a recent study investigating the usage of recycled
asphalt pavement (RAP) in gravel roads, it was found that
the use of RAP reduces dust without affecting the
serviceability of roadways (Koch 2010). As a result of this
study, RAP is now considered a viable alternative to the
maintenance of highly trafficked gravel roads, in addition
to the plethora of other uses it already has. This study is
being conducted to weigh the costs and benefits of utilising
RAP in various highway construction operations.
The primary objective of this study is to evaluate the
cost effectiveness of incorporating RAP in various
highway applications. The different applications include:
utilising RAP in hot plant mix (RHPM), gravel roads and
RAP in road base.
This paper will identify and quantify the various
factors that should be included in doing a cost-benefit
analysis of the different applications of RAP. In addition,
this paper will show how to utilise these factors when
carrying out the analysis. Finally, a case study will be
performed of various applications of RAP, which will
provide examples and descriptions of how to perform the
cost-benefit analysis. In this way, it is possible to make
specific recommendations on the most cost-effective
technique of utilising RAP in highway construction.
2. Background
Many past studies of RAP discuss its use in highway
surfacing, much of which include its usage in HPM and
base. Many of the benefits of RAP are defined in an
article published by the National Asphalt Pavement
Association.
The use of RAP in new asphalt mixtures has many
advantages to the environment, pavement owners and
contractors. Environmental benefits include a reduction of
the carbon footprint of the product and any of its end uses,
conservation of landfill space, making asphalt paving an
excellent sustainability practice.
From an economic standpoint, the use of RAP usually
reduces the cost of the mix. In addition, the reuse of
materials provides an opportunity to stabilise construction
prices, which may fluctuate as the economy and demand
for raw materials change.
Both the environmental and the economic benefits of
recycling have been enhanced by new methods that allow
q 2014 Taylor & Francis
*Corresponding author. Email: khaled@uwyo.edu
International Journal of Pavement Engineering, 2015
Vol. 16, No. 7, 660–666, http://dx.doi.org/10.1080/10298436.2014.943217
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using increased amounts of RAP in asphalt mixtures.
Appropriately done, RAP mixtures can provide the same
or better level of service than virgin asphalt mixtures.
(NAPA 2009)
Due to its many benefits, RAP is an easily justifiable
option for those transportation departments that have
access to it through either new construction or stockpile.
The National Asphalt Pavement Association describes
RAP as ‘a very valuable resource for the HMA producer’.
It already contains aggregate and liquid asphalt, so when
RAP is used in HPM, it saves money and materials by
replacing both of these components. Research has shown
that recycled pavements offer the same durability as
pavements made with 100% virgin materials, but when
those new materials are substituted with recycled
materials, there are significant cost savings to the
consumer (NAPA 2007).
Financial considerations are a significant part of
decision-making regarding the use of RAP. Several states
have conducted studies to determine whether the use of
RHPM is cost effective. The Florida Department of
Transportation estimates that the use of RAP has saved the
agency $224 million since 1979, which is equal to twothirds
of their annual resurfacing budget (Horvath 2003).
Other agencies estimate average savings of up to 30%
when using 10– 25% RAP (Brown 1999). It is evident that
the use of RAP is cost effective.
The benefits of RAP extend further than just cost
savings. RAP reduces the need for natural resources, saves
room in landfills and decreases the distances for material
hauling, therefore reducing greenhouse gas emissions.
Recycled materials in roadways have also shown to be at
least equal to the quality of new materials (Kandhal and
Mallick 1997).
A research study on blending RAP into road base was
carried out by Sultan Qaboos University in the Sultanate of
Oman. Previous studies carried out at the University had
indicated that if RAP were mixed with virgin aggregate,
it could be used as a base material. Results from their
laboratory study proved this to be true, indicating that RAP
‘seems to be a viable alternative to dense-graded aggregate
used in road base and subbase construction’. The results
also suggested that a 100% RAP aggregate could be used
as a base material, if it were stabilised with cement (Taha
et al. 2002).
Rutgers University also conducted a study on the use
of RAP in the road base and subbase. Results showed that
RAP has a marginally higher resilient modulus and field
elastic modulus than the dense-graded aggregate that was
used in the study (Maher and Popp 1997). RAP’s base
potential was also evaluated in the construction of Lincoln
Avenue in Urbana, IL, USA. Laboratory and field
experiences indicated that RAP could be successfully
used as a conventional base material. Field performance
was comparable to that of a crushed stone base (Garg and
Thompson 1996).
Gravel roads are considered to provide lower service to
the user than paved roads. For the most part, gravel roads
exist to provide access or service. In many cases, gravel
roads will not be paved due to the very low traffic volumes
and/or not having the funds to adequately improve the
subbase and base and then pave the road (Henning et al.
2007).
The main problem associated with unpaved roads is
fugitive dust created by traffic and the loss of fines. Dust
control methods range from spraying the road with
chemicals to using geotextiles in the reconstruction of a
road. Other efforts may include reduction in vehicular speed
and the application of water. The use of dust suppressants is
justifiable when traffic is low and paving is not a feasible
option financially; the cost of the suppressants and
application are low when stage construction is planned.
Performance characteristics as well as the type and volume
of traffic, climate, roadway conditions and product cost
all play a significant role in selecting a dust suppressant
(Sanders and Addo 1993, Addo et al. 2004). A study
conducted in Wyoming maintains that dust reduction
through the use of RAP is very significant, up to 41%,
with no change in serviceability to the gravel surface (Koch
2010).
The structural stability of using RAP in gravel roads has
been limitedly explored. The appropriate ratio of RAP and
virgin material to be used is an important consideration.
When ambient temperatures are high enough to liquefy the
recycled asphalt binder, the roadway may take of the
characteristics of a weak paved road, therefore causing
potholes and maintenance issues. A gravel road manual
recommends a blend of 50/50 virgin gravel and recycled
asphalt mix in order to allow for better maintenance of the
road (Selim and Skorseth 2000). A blended material will
prevent the road from performing poorly.
3. Methodology
3.1 Study area
In order to fulfil the objective of this study, the research
team utilised cost information from an interstate highway
project where WYDOT utilised RAP in the base and
asphalt surface layer. In addition, a local agency was
provided with RAP so that it could be incorporated in a
gravel road with very heavy truck traffic. The gravel test
sections were constructed on a county road in Southern
Wyoming (Sweetwater County). The entire gravel section
spanned 12.87 km (8 miles). There were two 0.8 km
(0.5 mile) paved interstate sections constructed using
RAP. The cost and benefits obtained at these locations
were used to develop the methodology to determine which
application is more cost effective. The interstate data will
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be used for the cost analysis of RHPM and RAP in base,
and the county road data will be used for RAP in gravel
roads.
For the interstate highway sections, the RAP was
distributed using bottom discharge dump trucks and then
spread with a motor grader. The RAP and base were then
mixed by a CAT RM-500 Rotary Mixer as shown in
Figure 1. This machine mixed the RAP with 25 cm (6 in.)
of base and released the mixture back onto the road
surface. See Figure 1 for further description on the
application of the mixing chamber. The RAP mixture was
then sprayed with water and compacted to achieve
maximum density.
The cost-benefit analysis method that was utilised is
described in the appendix of Informational Series 123:
Recycling Hot-Mix Asphalt Pavements (NAPA 2007).
While this method was followed precisely for the RHPM
application, there were adjustments made for the analysis
of RAP in base and RAP in gravel roads. The procedure
for this analysis is described in Section 3.2, and the
modifications are shown in the individual applications
within the case study.
The economic comparison was developed by analysing
the price per tonne (also known as a metric ton, or
1000 kg) of applied RAP for three different application
types. First, the difference between RHPM and virgin hot
plant mix (HPM) was evaluated. The individual prices for
materials and the amount of each material in the mixture
were taken into consideration. Second, the economic
difference between RAP in road base and virgin road base
was studied. Finally, the economic benefit was calculated
for RAP in gravel roads. These analyses include savings
factors such as dust reduction, layer coefficients, haul cost
and savings from virgin aggregate.
3.2 Cost-benefit
The cost analysis was completed by calculating the savings
of implementing RAP in each highway application. It must
be noted that this method of cost analysis is only intended
to show savings in material costs. It only takes into account
the reduction in materials such as aggregate, hydrated
lime and asphalt binder when implementing RAP into the
mix. The savings is achieved through a decrease of high
quantities of these costly materials. The loading, milling,
placing and compacting costs are not included in this cost
analysis because these processes are similar for both
recycled and virgin materials. Social and environmental
benefits are also not included because their values are
difficult to assign a monetary amount and vary between
projects. However, savings from dust reduction, layer
coefficients (LCs), haul cost and costs of additional virgin
aggregate are all applied in the benefit analysis.
The following steps, A through E, are used to
determine the pertinent benefits for each of the
applications. This model follows the process described in
the appendix of Informational Series 123: Recycling Hot
Mix-Asphalt Pavements. Each step shows the benefit of the
use of RAP in that application in price per tonne of RAP,
which shows how much each tonne of RAP saves when it
is used in that particular application.
3.2.1 Step A: Dust reduction
The dust reduction benefit was analysed using several
factors. The application rate and price of the dust
suppressant was taken into account. These values may
differ for different companies and dust suppressants. The
surface area of an average segment was calculated along
Figure 1. Rotary mixing chamber CAT RM-500.
662 R. Franke and K. Ksaibati
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with the aggregate tonnage per segment. The last piece in
this calculation was the dust reduction percentage of 20%
determined in previous research conducted by Koch
(2010). The savings from dust reduction is only applicable
to RAP in gravel roads because road base with RAP and
RHPM do not produce dust. Equation (1) can be used to
calculate the benefit from dust reduction.
ðsurface area ðm2ÞÞðapplication rate ðL=m2=kmÞÞðprice ð$=LÞÞ
ðtotal aggregate ðtonne=kmÞÞðpercent dust reductionÞ :
ð1Þ
3.2.2 Step B: Layer coefficients
The LC benefit became negligible because WYDOT
specifications dictate that blended and crushed base have
equal LCs of 0.12. Other agencies may use this same
calculation for determining a LC benefit when blended and
crushed base have different coefficients. When calculating
the savings, the crushed base would be divided by the
blended base coefficient. Equation (2) would be used to
determine the monetary benefit due to LCs.
ðblended base LCÞðprice virgin aggregateð$=tonneÞÞ
crushed base LC : ð2Þ
3.2.3 Step C: Haul costs
The haul costs were an important factor because additional
cost is incurred to haul aggregate to the site of application.
Considering the RAP in this case study was stockpiled on
site, the haul distance was negligible and therefore had no
effect on costs. Haul costs could still have an impact in
other projects, so a method for evaluating haul is shown
below. The haul cost would be affected depending on the
percent of RAP in the mix. A higher percentage of RAP in
the mix design would require more material and thus more
haul. Equation (3) was used to find the additional costs
from haul. The hauling costs should be subtracted from the
total benefit.
ðdistance ðkmÞÞðhaul rateð$=ðtonne £ kmÞÞÞ: ð3Þ
3.2.4 Step D: Savings from virgin aggregate
This savings comes from the difference in cost by using
RAP in the mix rather than additional virgin aggregate
from outside sources. The utilisation of RAP will lead to a
lower cost in the new road application. This value will
differ for the RHPM, RAP in gravel roads and RAP in road
base. The savings from the decreased use of virgin
aggregate can be determined using Equation (4).
ðvirgin aggregate ð$=tonneÞÞ
2 ðblended aggregate ð$=tonneÞÞ: ð4Þ
3.2.5 Step E: Total benefit
The total benefit of using RAP in an application is calculated
using the four steps listed (A–D). Table 1 outlines the
process for determining the net benefit from each of the
factors considered. Steps A through D are completed and
the final step E is used to sum the benefits and costs to
determine which application of RAP is the most ideal.
4. Case study
A case study was conducted to test this cost-benefit
approach and illustrate how it could be applied in many
situations. This case study utilised the three Wyoming
RAP applications: RHPM, RAP in base and RAP used on
gravel roads. The following section shows how each
highway application is evaluated and illustrates the benefit
analysis process.
In Wyoming, when paying for paving materials,
WYDOT pays for lime and binder separately from the
mix. In addition, when milling is required, WYDOT
retains ownership of the milled materials. Depending on
the type and location of the project, WYDOT may allow
contractors to use recycled materials in the specific
project. When excess RAP material is available and
WYDOT does not need RAP for other projects, then they
allow local governments to use the recycled materials on
local roads. Local governments are then responsible for
the loading and transportation of RAP to their local roads.
The data collection began by acquiring prices and
amounts of materials required in each of the three RAP
applications. The 2010 WYDOT Average Bid Prices, as
well as the Materials and Rates Summary from Project IM-
0803135, were obtained for both RHPM and RAP in road
base examples. More information on RAP in gravel roads
was contributed by Sweetwater County. RAP for the case
study was used from the WYDOT stockpile; therefore, its
cost in this case study is negligible. The value of the RAP,
however, would be more if it had to be purchased.
4.1 RAP in hot plant mix
This cost analysis involves two materials; an asphalt
pavement with RAP used in the mix (RHPM) and a HPM
Table 1. Benefit analysis template using all factors.
Step Factors Road application
A Savings from dust reduction
(Equation (1))
$/tonne RAP
B Savings from LCs (Equation (2)) $/tonne RAP
C Negative savings from haul
(Equation (3))
$/tonne RAP
D Savings from virgin aggregate
(Equation (4))
$/tonne RAP
E Total benefit (A þ B þ C þ D) $/tonne RAP
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pavement. The asphalt cement content was 4.5% in the
RHPM and 5.2% in the HPM. The 2010 WYDOT
Average Bid Prices showed that the price per tonne of
asphalt binder was $686.05 ($622.37/ton), $169.40 for
hydrated lime ($153.68/ton) and $33.74 for HPM
($30.61/ton). (A ton refers to the US ‘short ton’ equalling
2000 pounds.) These values were used in the cost
analysis, along with the materials and rates summary
shown in Table 2. RAP was used at a rate of 15% for the
RHPM mixture.
To calculate the cost difference by using RHPM, the
price for each component of the total material must be
calculated. This is done by taking the amount of that
individual material and multiplying it by its inverse unit
weight, to obtain an amount. Then, this amount is
multiplied by the price per tonne to finally reach a cost
figure for that respective component. This process is
shown in Table 3, and the savings calculations are shown
in Table 4.
Table 4 illustrates the savings incurred when using
RHPM over HPM. The calculations were converted to
price per tonne of RAP to provide for a comparison
mechanism of cost savings for all the three construction
techniques. This was accomplished by incorporating the
percent of RAP in the mixture with the savings. Therefore,
$ð6:76=tonneÞ HMA=0:15 ¼ $45:07 would yield the savings
per tonne of RAP.
It can be observed from the calculations in Table 5 that
a substantial savings is accomplished by using RAP in the
asphalt mixture. A savings of $45.07/tonne of RAP was
realised by implementing a 15% RAP mix, meaning the
value of RHPM is $45.07/tonne. This savings would
increase by using a greater amount of RHPM.
4.2 Road base with RAP
Two materials were compared for this RAP use: a road
base including RAP and a virgin base. The 2010 WYDOT
Average Bid Prices showed that the price per tonne of
crushed aggregate was $14.82 ($13.44/ton). This value
was used in the cost analysis, along with the Materials and
Rates Summary shown in Table 6. RAP was used at rate of
20% in the base mixture.
This analysis was completed using the same method as
the RHPM cost-benefit analysis. The amount of each
component was converted into a ratio by multiplying its
amount by the inverse unit weight. Then, the value was
multiplied by the price per tonne to reach a price figure.
For the case study, the only component being calculated
was the aggregate because RAP and water were supplied
by WYDOT. Tables 7 and 8 show the calculations and
steps to determine the savings associated with using RAP
in base.
From Table 8, the difference saved was $3.46 when
using base with RAP over a virgin base. The converted
price per tonne of RAP was accomplished by incorporating
the percent of RAP in the mixture with the savings.
Table 2. Materials and rates summary for HPM.
Material
RHPM, kg/m3
(LB/CF)
HPM, kg/m3
(LB/CF)
Virgin aggregate 1921.8 (119.9) 2203.9 (137.5)
RAP 339.8 (21.2) 0 (0)
Asphalt binder 101 (6.3) 121.8 (7.6)
Hydrated lime 19.2 (1.2) 22.4 (1.4)
Total HPM 2381.1 (148.6) 2348.1 (146.5)
Table 5. Benefit analysis of RHPM.
Step Factor RHPM
A Savings from dust reduction N/A
B Savings from LCs N/A
C Negative savings from Haul N/A
D Savings from virgin aggregate $45.07
E Total benefit (A þ B þ C þ D) $45.07
Table 4. Cost savings of RHPM versus HPM.
Material
RHPM, $/tonne
($/ton)
HPM, $/tonne
($/ton)
Savings, $/tonne
($/ton)
Asphalt binder 29.08 (26.39) 35.59 (32.29) 6.51 (5.90)
Hydrated lime 1.37 (1.24) 1.62 (1.47) 0.25 (0.23)
Total HPM 33.74 (30.61) 33.74 (30.61) 0.00 (0.00)
Total 64.19 (58.24) 70.95 (64.37) 6.76 (6.13)
Table 6. Materials and rates summary for base.
Material
Base with RAP,
kg/m3 (LB/CF)
Virgin base,
kg/m3 (LB/CF)
Aggregate 16,573 (103.4) 2208.7 (137.8)
Water 150.7 (9.4) 150.7 (9.4)
RAP 551.4 (34.4) 0 (0)
Total RAP base 2359.4 (147.2) 2359.4 (147.2)
Table 3. RHPM material calculations.
RHPM HPM
Unit weight, m3
/kg (CF/LB) 0.00042 (0.0067) 0.00043 (0.0068)
Asphalt binder
Needed, kg/m3 (LB/CF) 101 (6.3) 121.8 (7.6)
Price, $/tonne ($/ton) $686.05 ($622.37) $686.05 ($622.37)
Cost $29.08 ($26.39) $35.59 ($32.29)
Hvdrated lime
Needed, kg/m3 (LB/CF) 19.2 (1.2) 22.4 (1.4)
Price, $/tonne ($/ton) $169.40 ($153.68) $169.40 ($153.68)
Cost $1.37 ($1.24) $1.62 ($1.47)
HPM
Needed, kg/m3 (LB/CF) 2381.8 (148.6) 2348.1 (146.5)
Price, $/tonne ($/ton) $33.74 ($30.61) $33.74 ($30.61)
Cost $33.74 ($30.61) $33.74 ($30.61)
Total $64.19 ($58.24) $70.95 ($64.37)
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Therefore, $ð3:46=tonneÞ=0:2 ¼ $17:30=tonne of RAP
was saved by implementing a 20% RAP mix.
Table 9 shows that the price for the RAP mixture is
$17.30/tonne of RAP less than the price for base without
RAP. These savings are largely due to the fact that less
virgin aggregates were needed. The blended RAP base is
cheaper, proving that the addition of RAP to highway
applications is economically feasible.
4.3 RAP in gravel roads
The Sweetwater County project was used to determine the
costs for this roadway application of RAP. The cost for
aggregate and RAP in gravel roads was $10.98/tonne
($9.96/ton), while the price for gravel roads excluding
RAP was $22.05/tonne ($20.00/ton). The savings from
applying dust suppressants to the road was also included as
a benefit.
This analysis compared gravel roads with and without
RAP. The typical savings from using RAP in the material
was found using the two prices provided by Sweetwater
County. This savings was $11.07/tonne ($10.04/ton) of
RAP. This was obtained by finding the difference between
$10.98/tonne ($9.96/ton) of RAP for gravel roads and
$22.05/tonne ($20.00/ton) for gravel roads without RAP.
This savings would be included under the factor ‘Savings
from Virgin Aggregate’.
The other factor applied to this analysis was the saving
from dust reduction. RAP in gravel roads was the only
highway application affected by this factor because it
is essentially the only one that releases dust to the
environment. The savings was found by using Equation (1)
under the Dust Reduction method explained earlier. This
savings was $7.75/tonne ($7.03/ton) of RAP. The costbenefit
analysis is summarised in Table 10.
This analysis shows that the use of RAP in this
highway application saves money. RAP in gravel roads
resulted in a savings of $18.82/tonne ($17.07/ton) of RAP.
This was due to the savings from virgin aggregate and the
savings through dust reduction, which will keep the road in
better condition by retaining the fine particles embedded in
the road. The air quality will also be improved as a result
of the reduction in dust.
Each of the three RAP applications resulted in savings,
especially on materials costs. Using RHPM resulted in a
savings of $45.07/tonne. Using RAP in the road base
caused a savings of $17.30/tonne. Gravel roads with RAP
had a savings of $18.82/tonne.
5. Conclusions
RAP can be a very effective material in highway
construction applications. It is very economically feasible
to use RAP because the recycled material greatly reduces
the need for virgin aggregates. Other studies have shown
that, while being cost effective, RAP has generally not
been found to decrease pavement performance. Surface
distresses have been shown to not occur because of the use
of RAP. The addition of RAP significantly reduces the
dust loss on gravel roads from travelling vehicles.
This study has shown that the application of RAP in
highway construction is cost effective. The amount of
savings can increase exponentially when large quantities
are used and when a greater percentage of RAP is
included. The use of RAP in asphalt mix is the most cost
effective in this case study. Depending on other factors,
such as haul or LCs, a different application method could
be more beneficial in other situations.
This approach to determining which application of
RAP is most cost effective and beneficial to the area and to
the sustainability of the roadway is very advantageous.
Table 8. Cost savings of base with RAP versus virgin base.
Material
Base with RAP,
$/tonne ($/ton)
Virgin base,
$/tonne ($/ton)
Savings,
$/tonne ($/ton)
Aggregate 10.41 (9.44) 13.87 (12.58) 3.46 (3.14)
Water 0 (0) 0 (0) 0 (0)
RAP 0 (0) 0 (0) 0 (0)
Total 10.41 (9.44) 13.87 (12.58) 3.46 (3.14)
Table 7. Base with RAP versus virgin base cost savings.
Base with RAP Virgin base
Unit weight, m3
/kg (CF/LB) 0.0004 (0.0067) 0.0004 (0.0067)
Crushed aggregate
Needed, kg/m3 (LB/CF) 16,573 (103.4) 2208.7 (137.8)
Price, $/tonne ($/ton) $14.82 ($13.44) $14.82 ($13.44)
Cost $1041 ($9.44) $13.87 ($12.58)
Total $1041 ($9.44) $13.87 ($12.58)
Table 9. Benefit analysis of RAP in road base.
Step Factors RAP in base
A Savings from dust reduction N/A
B Savings from LCs N/A
C Negative savings from Haul N/A
D Savings from virgin aggregate $17.30
E Total benefit (A þ B þ C þ D) $17.30
Table 10. Cost-benefit analysis of RAP in gravel roads.
Step Factors RAP in gravel roads
A Savings from dust reduction S7.75 ($7.03)
B Savings from LCs N/A
C Negative savings from Haul N/A
D Savings from virgin aggregate $11.07 ($10.04)
E Total benefit (A þ B þ C þ D) $18.82 ($17.07)
International Journal of Pavement Engineering 665
Downloaded by [University of Auckland Library] at 18:02 20 September 2015
It allows several factors to be assessed and provides for a
common comparison among the different uses of RAP.
Normalising the benefit to the savings per tonne of RAP
allows quick and useful comparisons to be made by not
only highway officials, but local agencies and the public.
Acknowledgements
The authors would like to thank Burt Andreen and Harry
Rocheville for their initial contributions to this paper, as well as
Jon Zumwalt for his involvement during early stages of this
project.
Funding
The authors would like to thank the Wyoming Department of
Transportation and the Mountain Plains Consortium for funding
this study.
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