# Draft Further Study

Warm Mix Asphalt

December 1, 2015

Project Team

Jessica Schlosser, Air Quality Specialist Chelsea Gonzales, Senior Air Quality Specialist Chay Thao, Program Manager Sheraz Gill, Director of Strategies and IncentivesWarm Mix Asphalt Further Study

i Table of Contents | SJVAPCD Table of Contents

EXECUTIVE SUMMARY

................................ ................................ .......................... 1 I.

COMMITMENT FROM THE 2012 AND 2015 PM2.5 PLANS

................................ ... 3 II.

WARM MIX ASPHALT

................................ ................................ ............................. 3 III.

WMA BENEFITS

................................ ................................ ................................ ...... 5 IV.

POTENTIAL EMISSION REDUCTIONS CAN BE NEGATED

................................ . 8 V.

CHALLENGES FOR IMPLEMENTING WMA IN THE VALLEY

............................... 9 VI.

FURTHER STUDY FINDINGS

................................ ................................ ............... 12 VII.Warm Mix Asphalt Further Study

1 EXECUTIVE SUMMARY | SJVAPCD EXECUTIVE SUMMARY I.

The San Joaquin Valley A ir B asin (Valley) faces unique and unprecedented air quality challenges in attaining National Ambient Air Quality Standards (NAAQS). The San Joaquin Valley Air Pollution Control District ( District ) must explore all available emission

reduction opportunities in ord er to demonstrate attainment for multiple federal ozone and PM2.5 standards in the coming years. In an effort to leave no stone unturned, t he District conducted a study to identify how to best promote low er emission asphalt production practices. Using warm mix asphalt (WMA) instead of hot mix asphalt (HMA) results in lower temperatures required for production, storage, and transport. This can lead to less fuel consumption, resulting in potential cost savings and emissions

reductions

. The District coll aborated with asphalt industry stakeholders and policy

makers in developing this further study in order to gain an understanding of the use of warm mix technologies in the Valley and identify potential opportunities and barriers for adoption of this techno logy

. As a result of this effort, the District found the following:

1. WMA is a Potential Alternative to HMA

WMA has been used in Europe since 1997 and the United States (U.S.) since 2002.

Several iterations of the technology have been developed for a variety of road applications. Case study results suggest that WMA performance can be equal to or

better than that of HMA in certain instances , although more evidence will be required to demonstrate its reliability in climates like the Valley

.

2. WMA Offers B enefits Compared to HMA

Although switching from HMA to WMA may require plant modifications

, more precise moisture control in some cases, and an overall higher cost, WMA offers benefits over HMA including:

 Potential reduced fuel c onsumption

 Improved p erformance d uring p aving in cooler c limates

 Extended transportation and compaction window

 Safer working conditions

3. Potential Emission s R eductions C an be Negated

Using WMA instead of HMA shows promise for reducing emissions associated with the production o f asphalt. Lower temperatures required for production, storage, transport, and application translates to potentially lower fuel consumption, which could lower the emissions associated with the fuel consumed. Additionally, lower temperatures could result in lower direct emissions of volatile organic compounds (VOCs) at the work site. However, the emission s reductions from fuel savings could potentially be negated in certain long haul transport cases. In order to extend the hauling benefit, WMA could be heated to HMA temperatures in order to keep the

material workable for even longer periods of time, thus reducing the fuel savings and eliminating po tential emission s reductions.Warm Mix Asphalt Further Study

2 EXECUTIVE SUMMARY | SJVAPCD 4. WMA has Several Challen ges in the Valley

While the WMA markets are developed and growing in other states, there are still several uncertainties that may limit the adoption of WMA technologies in the Valley.

Some of these barriers include:

 Uncertainties in performance with WMA i n the Valley

o Insufficient number of pilot projects to demonstrate viability in the Valley

o Durability demonstration

o Longevity demonstration

 Poor cooling in the Valley’s hot summer climate

o More time required to cool to necessary temperature

o Longer periods of road closures due to increased cooling time

o Increased costs due to longer periods of road closures

 Lack of accepted WMA specifications and guidelines in California

o Lack of awareness of WMA

 Lack of confidence in WMA

 Higher cost associated with WMA

o Retrofit or new equipment required

o Additional cost of chemical additives

 Low demand

Based on the above findings and i n order to continue evaluating and promoting the use of WMA in the Valley, the District recommends the following :

1. Encourage additional pilo t projects to assess viability and life cycle of WMA in the Valley.

2. Encourage Caltrans to further develop WMA specification s

.

3. If found to be feasible in the V alley

, work with stakeholders to educate and encourage WMA usage as a means of implementing additional pilot projects

.

4. Meet with stakeholders as necessary

.

5. If found to actually reduce emissions and be feasible, consider including WMA as an ISR mitigation measure.Warm Mix Asphalt Further Study

3 COMMITMENT FROM THE 2012 AND 2015 PM2.5 PLANS | SJVAPCD COMMITMENT FROM THE 2012 AND 2015 PM2.5 PLANS II.

L iquid asphalt production and paving in the Valley contribute s 0.16 0 tons per day ( tpd )

of oxides of nitrogen ( NOx ) emissions across the entire Valley

. While these emissions

are low and do not significantly contribute to elevated PM2.5 levels in the Valley , the District has adopted a “no stone left unturned” policy when identifying potential emission reduction opportunities. As such, the District made a co mmitment in the 2012 PM2.5

Plan and 2015 Plan for the 1997 PM2.5 Standard (2015 PM2.5 Plan) to evaluate the feasibility of WMA as an alternative to HMA to reduce NOx emissions from this source
category

. This further study includes the following elements :

1. Evaluate opportunities to further encourage transportation and county agencies to continue transitioning from HMA to WMA as feasible. As part of this evaluation, the District will explore the potential feasibility of additional control measures and granti ng mitigation credits for WMA usage through the District’s Indirect Source Review (ISR) program.

2. Evaluate potential outreach and education opportunities for encouraging project developers/construction managers to increase their adoption and implementation

of WMA.

This study was conducted with significant interaction and input from stakeholders, including asphalt pavement plant operators, road construction companies and contractors, county and city planning departments, pavement plant consultants

, and

state and federal policy makers.

On October 8, 2015, District staff held a kick

- off meeting with several members of the

local California Department of Transport ( Caltrans ) district, a representative from a local pavement production facility, an d an experienced local p ublic w orks engineer. This initial meeting gave insight into the regional issues that affect the adoption of WMA technologies here in the Valley and shed light on WMA barriers that were not addressed

in the District’s extensive literature review. Meeting attendees were also helpful in providing the District with additional contacts for further investigation. On October 28, 2015, the District conducted a larger and more comprehensive meeting with members from public works departments, local pavemen t plants, California Asphalt Pavement Association (Cal APA), Caltrans, Federal Highway Administration (FHWA), California Air Resources Board (CARB), and the Environmental Protection Agency (EPA). Following a presentation by District staff, attendees were asked a number of questions regarding their experiences with WMA. Through extensive stakeholder input during and following these meetings, the District was able to assess the challenges that still must be overcome before promoting WMA in the Valley. This report discusses the technological, economical, and practical efficacy of WMA use throughout the Valley.

WARM MIX ASPHALT III.

Asphaltic concrete is used worldwide for road construction. An asphaltic concrete mix consists of aggregate and liquid asphalt. The aggregate is comprised of rocks of varying size, angularity, and hardness. Liquid asphalt is a natural hydrocarbonWarm Mix Asphalt Further Study

4 WARM MIX AS PHALT | SJVAPCD substance primarily derived from the heaviest part of petro leum crude oil and is used to bind the aggregate to create a strong, durable material for an assortment of road

conditions. The final mixture is brought to the construction site, poured, and compacted to become highways, roads, and parking lots.

The durability and longevity of the final pavement product depends on the asphalt

mixt ure components and the quality of compaction during the final paving stages. In the end, all asphaltic concrete must meet a host of construction specifications (specs)

, which can vary depending on the type of road. These specs can include a certain
tempe ratu re, density , and smoothness of the road required by state or local regulations

. To achieve these specs , contractors must ensure a high level of control when pouring and compacting the asphaltic concrete. This control is reliant on the quality and

wor kability of the asphalt mixture.

Conventional road asphalt ic concrete is unworkable at ambient temperatures. Heating the asphalt mixture to temperatures greater than 300°F (>150°C) temporarily reduces the viscosity (the “ thickness ” of the liquid) and all ows for mixing, pouring, and compacting of the material. This mixture is appropriately deemed hot mix asphalt (HMA) due to the hot temperatures needed during production and paving. The primary emissions source from asphaltic concrete production comes from the combustion of the diesel or natural gas fuel used to heat the dryers, hot bins, and mixers to these extreme
temperatures.

In order to reduce fuel costs, European and American companies developed several techniques, collectively known as warm mix asphalt (WMA), to increase the workability of asphalt by lowering the viscosity at temperatures as much as 100°F below that of

HMA. The lower temperatures require less fuel and therefo re have the potential to decrease emissions from asphalt production. The use of WMA in the U.S. has been growing steadily since the first test section was completed in 2004 at Auburn University's National Center for Asphalt Technology (NCAT) 1 . In 2012, W MA represented an estimated 30 % of the total asphalt market in the U.S

. FHWA has chosen WMA for rapid deployment under its Every Day Counts (EDC) initiative. The

EDC initiative is

, “designed to identify and deploy innovation aimed at reducing the time

it takes to deliver highway projects, enhance safety, and protect the environment

. ”

WMA Techniques

WMA is defined as an asphalt mixture that is produced at a temperature of 270 ̊F or

less. In order for WMA to be workable at these lower temperatures, it is formed using

one of t wo different techniques. The first technique is mechanical alteration of the asphalt properties. Mechanical methods include, but are not limited to, adding water

containing products or water

- based foaming processes to the mixing step during asphalt production

. Water foaming is the most common of the mechanical techniques and has been used in various WMA applications throughout the nation. All m echanical methods

r equire some plant modifications , including adding new equipment and cha nging

1 “Public Roads” FHWA. Retrieved from: https://www.fhwa.dot.gov/publications/publicroads/10julaug/05.cfmWarm Mix Asphalt Further Study

5 WMA BENEFITS | SJVAPCD production practices

. Mechanical methods for WMA have been shown to reduce the production temperature by 0

- 35 °F

. 2

The other technique for WMA production is the addition of chemicals in order to alter the asphalt properties. Chemical additives include, but are not limited to, organic wax, cationic surfactants, surface

- active agents, processing aids, and polymers. Additive dosages range from 0.2% to 3% by mass or weight. Chemical additives for WMA have been shown to reduce the produc tion temperature by 10

- 10 0 ° F. 2 While the transition to

the mechanical WMA methods require cha nge to the production facility, requiring additional investments, the use of additives can be accommodated with minimal

alteration to existing asphalt pl ant and production technology. However, with this technique, additives would be used in every batch and would still result in increased production cost s

.

In addition, b oth WMA technologies generally require more finesse in controlling moisture in the aggregate and in the overall system operation, such as tu ning of the burner to run efficiently at lower temperatures

. This requires training and education of operators and engineers before transition to WMA production at any HMA facility.

WMA BENEFITS IV.

WMA has been used in the U.S. for over a decade primarily for fuel cost savings and

other reasons beyond air pollution control. Ongoing lab studies, accelerated pavement testing, and field testing have guided the impleme ntation of WMA in California. Since
2010, Caltrans and the University of California Pavement Research Center have been evaluating WMA technology and its performance by testing the rutting and cracking performance, moisture sensitivity, durability, aging, and stability of multiple WMA products

. 3 I n the controlled testing environment, WMA has been shown to have equal

or better overa ll performance, increased workability , potential energy savings, and safer working conditions compared to HMA

.

Improved Performance i n Cooler Climates

WMA provides improve d workability and eas ier pavement compaction

, which is critical to long

- term performance of the road

. 4 In cooler climates, this longer compaction window and slow cooling time provides superior in

- place density, which is one of the most important me trics of a successful pavement project. Asphalt becomes more workable as the viscosity decreases. Figure 1 is a plot of viscosity as related to temperature for two different asphalt mixtures. The compatibility range of an asphalt

mixtu re is a measure of the range of temperatures during which the material is able to be rolled to the final density and smoothness specs prior to cooling and opening for

2 Asphalt Pavement Association of Michigan Presentation. Retrieved from: http://www.apa

- mi.org/docs/2013LRW

WarmMixAsphalt.pdf

3 Jones et al. Research Findings on the Use of Warm

- Mix. Retrieved from: http://ra

- foundation.org/wp

- content/uploads/2013/02/040

- PAP_060.pdf

4 MyAsphaltPavingProject.Com. (2011). “What are the Specifications?” Retrieved from http://www.myasphaltpavingproject.com/whatisasphalt/what

- are

- the

- specificationsWarm Mix Asphalt Further Study

6 WMA BENEFITS | SJVAPCD traffic operations

. Conventional HMA, labeled in the figure as “Liquid AC,” is compactib le only at higher temperatures. The WMA, labeled as “Foamed AC”

, has a larger compactability range.

Figure 1 V

iscosity of T

wo A sphaltic C oncrete (AC) M ixtures P lotted O ver a R ange of P roduction T

emperatures 5

Safer Working Conditions

The lower mixing and paving temperatures of WMA has the potential to minimize visible smoke and odor emissions. These emissions consist of particulate matter, CO 2 , and VOCs. One study indicates that fumes released at the paving site are reduce d at a rate
of 50% for each 10 ̊C. 6 The lower temperatures also create cooler working conditions for the asphalt workers. Less fume s and odor reduces the public nuisance of placing asphalt and improves worksite safety for the construction team.

Extended Transport Time

WMA allows for longer (slower) cooling periods than HMA

. Slower cooling means the material can be hauled longer distances or compacted during a longer window of opportunity before the material begins to become too viscous and unwor kable. Improved hauling time allows the material to be transported to more remote locations and introduces more flexibility in transportation schedules. Additionally, a longer cooling window allows the material to be compacted at safer, lower temperature s for a longer period of time.

5 Astec Products Brochure (2015). Retrieved from: http://www.astecinc.com/products/liquid

- additives/warm

- mix

- systems.html

6 EAPA (2010). Retrieved from: http://www.eapa.org/usr_img/position_paper/the_use_of_warm_mix_asphalt_january_2010.pdfWarm Mix Asphalt Further Study

7 WMA BENEFITS | SJVAPCD Potential Energy a nd Cost Savings

By lowering the production, storage, transport, and placement temperatures, manufacturers require less fuel to heat aggregate and liquid asphalt. These e nergy savings can potentially offset the cost of additives or needed modifications to plants, especially where energy costs are high. Reduced plant temperatures may also cause less wear on plant equipment, thus reducing plant maintenance costs. 7

A ssessments outside of the Valley hav e shown potential for reduced costs. Although production facilities must modify some aspect s of their plant by installing additional equipment in order to accommodate WMA technologies, the hauling, laydown, and compaction equipment do not need to change. The initial incremental cost of WMA over HMA is primarily due to the foaming equipment or additive chemical s used at the time of production. Over time, as WMA demand increases, t he cost and fuel savings

associated with WMA has the potential to outweigh the cost to purchase the WMA technology

.

Additionally, the low temperatures used in WMA production allows for higher percentages of recycled highway materials to be used in the mixture with no effect on ultimate pavement performance. This type of mixture is called reclaimed asphaltic pavement (RAP)

. 8 The low temperatures of WMA result in less aging of the old recycled material, so a larger ratio of reclaimed aggregate can be used to meet the same aging properties as HMA with recycled aggregate

. T he use of RAP is less expensive than producing an asphalt mixture completely from raw materials, and additional savings can be generated from avoiding landfill disposal or recycling fees. The cost savings gained from using RAP could potentially further offset costs for additives or required plant modifications needed for WMA production

. Fuel savings, an increase in reclaimed asphalt pavement content, and reductions in fuel and labor during the process of installing WMA could translate to reduced costs f or WMA projects over time

.

Potential Emissions Reductions

T able 1 shows an estimate of the maximum potential NOx emissions reductions as a result of the complete transition from HMA to WMA at all asphalt production sites in the Valley. This estimate is not intended to reflect an estimate of realistic potential emissions reductions given the lack of information and potential implementation issues associated with converting from HMA to WMA. The District’s 2017 emissions inventory

from th e 2015 PM2.5 Plan estimates 0.160 tpd of NOx emissions from asphalt production at all 19 asphalt production facilities in the Valley. While fuel savings for WMA at production facilities have been reported to be from 20% to over 50% for some WMA technologi es, U.S. studies h ave reported actual burner fuel savings of zero to

7 Caltrans. (2013, April). Caltrans Activities to Address Climate Change: Reducing Greenhouse Gas Emissions and Adapting to Impacts. Retrieved from: http://www.dot.ca.gov/hq/tpp/offices/orip/climate_change/documents/Caltrans_ClimateChangeRprt

Final_April_2013.pdf

8 Canadian Asphalt Institute Presentation (2009). Retrieved from: http://www.captg.ca/docs/pdf/09presentations/Wednesday%20PM/Warm%20Mix%20Asphalt_Sandy %20Brown.pdfWarm Mix Asphalt Further Study

8 POTENTIAL EMISSIONS REDUCTIONS CAN BE NEGATED | SJVAPCD 40%, with the average typically around 30%. 9 If every plant changed completely from HMA to WMA, there would be an estimated 0.048 tpd in NOx emissions reductions Valley

- wide. This is a small potential emission reduction opportunity, especially considering the investments asphalt plants would have to incur to allow for the production of WMA at their plants.

Table 1 Potential Emissions Reductions if all Valley Plants Changed all HMA to

WMA



### Estimated Reductions

Hot Mix Asphalt (Production only)

projected 2017 0.160 tpd NOx

Possible Average Fuel Savings 30%

Maximum Reductions 0.048 tpd NOx

Potential GHG Reductions

In response to climate change objectives, Caltrans included WMA in an April 2013 report as an activity to reduce GHG emissions and adapt the state’s transportation system to prepare for t he impacts of climate change. As stated in this report, Caltrans

identif ied that WMA can reduc e production temperatures by 35

- 100°F compared to conventional HMA, potentially yielding 30% fuel savings and an 18% reduction in the

overall GHG emissions associated with manufacturing, mixing, and laying the asphalt.

POTENTIAL EMISSION S REDUCTIONS CAN BE NEGATED V.

While emission s reductions are possible due to the fuel savings benefits of WMA, these reductions could be negated if standard WMA production temperatures are exceeded. During the District’s research, asphalt production and paving experts stated that contractors around the state have requested WMA be heated to high temperatures for the purpose of extending transport time. WMA is already ideal for long transport due to

the longer cooling period, so contractors ordering asphalt for remote location s take advantage of this property and attempt to further extend the hauling benefit

. In this case, the WMA would be produced at HMA temperatures in order to keep the material workable for longer periods of time

. This p ractice eliminates the fuel savings and leads

to no di fference in emissions from HMA. A ny fuel or emissions savings will not be realized if there is no consistency in practice in keeping the temperatures lowered.

While transportation emissions should be the same regardless of material properties, the use of WMA for longer hauling distances may actually produce more emissions

overall compared to HMA from the additional truck miles generated

. W ith the initial

9 http://www.warmmixasphalt.com/submissions/may2009/08_Marks_wmatwgprovidence.pdfWarm Mix Asphalt Further Study

9 CHALLENGES FOR IMPLEMENTING WMA IN THE VALLEY | SJVAPCD limited number of Valley asphalt facilities producing WMA, contractors intending to use

the material may need to travel further for WMA than HMA. The probability of longer hauling distances combined with the possibility of heating WMA to hotter temperatures may negate and actually increase emission s associated with the use of WMA compared

to HMA

.

CHALLENGES FOR IMPLEMENTING WMA IN THE VALLEY VI.

There are several advantages of WMA over HMA

, as demonstrated by success ful WMA

installation in many parts of the U.S

. However, the District has identified a number of

barriers for the adoption of WMA technology in the Valley based on extensive input from asphalt producers and road paving experts.

Uncertainties i

n Performance w

ith WMA i

n t he Valley

Caltrans has been involved in a n umber of WMA performance studie s since 2012, leading to a steady increase in adoption of WMA technology in some parts of the state

. However, there are still a number of uncertainties in construction operations and pavement performance that limit WMA use here in the Valley. The ability of WMA to decrease fuel consumption and improve worksite conditions has been demonstrated in

controlled enviro nments and cooler climates , but there have been an insufficient

number of studies to demonstra te viability in the Valley.

There have only been two Caltrans pilot projects for WMA in the Valley. One such project was a 5 mile stretch of highway laid on a hot day in 2014 in Kings County. After rolling out the material, the asphalt took much long er to cool and resulted in difficult compaction and extended lane closures, which significantly increased project costs

. More pilot projects are critical to identifying these and other Valley

- specific problems.

These uncertainties in paving operations an d durability performance in the Valley

extend to long

- term concerns

. Because WMA is relatively new, a full life cycle analysis has not yet been assessed here in California

. While there are experiments that have simulated long

- term erosion of WMA, the lon gevity and durability of WMA in the Valley’s unique climate is unknown. If longevity of the WMA product is not known , the cost and emissions benefits cannot be assessed properly. For example, if a road paved with WMA has to be repaved earlier than it wou ld have with HMA due to accelerated aging or poor durability, the emissions associated with that additional round of paving would offset any reductions achieved with WMA production

. Depending on the difference in lifecycle, the WMA could actually have more lifetime emissions than HMA. While experiments indicate that this is not likely, Valley contractors and public works agencies will not transition to WMA until more is known about p erformance in the Valley.

Poor Cooling in the Valley’s Hot Summer Climate

Laying WMA in high heat can lead to poor compaction and delayed cooling. T he difference in temperature between the ambient air and the asphalt mixture affects the rate of cooling. Reducing that temperature difference allows for longer (slower) coolingWarm Mix Asphalt Further Study

10 CHALLENGES FOR IMPLEMENTING WMA IN THE VALLEY | SJVAPCD periods and is part of what makes WMA a superior material to HMA in most uses. In addition, slower cooling means the ma terial can be hauled longer distances and compacted at safer, co oler temperatures for a longer window of time. However, if that temperature difference is too small due to hot ambient temperatures, the material may not properly set or completely cool to the temperature approved for traffic use. Unfortunately, Valley s ummers are some of the hottest in the State

, often reaching temperatures well above 10 0 °F

. Waiting for the asphalt to cool during typical Valley summer days can also cause significant project delays resulting in increased costs and longer periods of road closures. Pavement plant operators who participated in the WMA study session indicated that almost all of the WMA orders their company receives are for Central Coast or Bay Area construction projects , places with cooler climate s

. Until clear WMA specs are written and the use of this material is mor e widely implemented by Caltrans in the Valley , public works and other local agencies will not readily adopt WMA technologies

.

Lack of Accepted WMA Specifications and Guidelines i n California

One necessary step to reducing uncertainties in WMA is to identify effective and safe WMA practices and ensure the materials are suitable for a variety of conditions. This research is commonly done through Caltrans conducting iterative pilot pr ojects throughout various climates and conditions. While it takes years to complete each of

these state

- funded Caltrans projects, these are necessary in order to write new specs and promote the safe, easy use of a new material.

Most public and private age ncies follow the Caltrans spec s when cons tructing or maintaining roads. These agencies, including city and county public works departments, rely heavily on the Caltrans spec s for operational guidance. Since 2012, Caltrans has tested and approved a growin g list of WMA techniques and materials listed in the paving specs as available options for contractors. While the Caltrans specs identify WMA materials as an option, they do not contain the detailed procedures necessary for implementing WMA projects. 10 Th ere is no differentiation in the specs between certain HMA and WMA practices; the section in which one can find any WMA information is titled “HMA Specifications.” Unclear specs can be confusing and misleading. Without WMA

- specific procedures, contractor s ultimately decide to pave with HMA, a familiar product that has been tested and handled in a variety of situations. Since proper handling of WMA can make a significant difference in the fuel and emissions reductions realized during a project, it is crit ical to have unified WMA specs in

order to achieve the economic and environmental benefits.

Lack o f Confidence in WMA

The District found that one of the largest barrier s to adoption of WMA in the Valley is the lack of confidence in the technology and its potential benefits, especially when used with other technologies.

10 Caltrans Section 39 HMA Specifications. Retrieved from: http://calapa.net/section_39.htmlWarm Mix Asphalt Further Study

11 CHALLENGES FOR IMPLEMENTING WMA IN THE VALLEY | SJVAPCD As an example, the District learned from stakeholders involved in this study that WMA

use could clash with the state mandate that Caltrans use rubberized asphalt. This

mandate is derived from a provision in Assembly Bill 338 (Levine) which requires

Caltrans to use a minimum of 35% Crum Rubber Asphalt (CRA) 11 as paving material.

CRA is a HMA mixture in whi ch recycled rubber is added as an aggregate in order to reduce sound (when driving) and increase stability. This technique is cost effective and environmentally friendly due to rubberized asphalt’s better aging properties and greater durability

. 12 The rub ber used in the mixture typically equals 3 recycled tires per ton, which can mean approximately 2,000 recycled tires per lane mile for a road overlay project. 13 While CRA is a green technology, stakeholders attending the District’s WMA study meetings voic ed concerns over the use of rubber in the WMA mixture until rubberized asphalt is fully understood or exhaustively tested

.
These concerns were raised even though Caltrans conducted a large study in conjunction with the UC Pavement Research Center and tested the performance of WMA made with rubberized aggregate. T his study reported that there was not a significant difference in performance between rubberized WMA and HMA . However, none of the projects in the UC Pavement study took place in the Valley, which has contributed to the concerns and uncertainties by Caltrans and local contractors regarding the implementation of WMA in th is region. 14 Education and outreach regarding these studies about the performance and benefits of WMA may assist in increased use of WMA in the Valley, but ultimately additional pilot tests in Valley locations are necessary in developing WMA specs and instilling confidence in the pavement contractors and regional Caltrans staff.

Higher Cost Associated w ith WMA in the V

alley

The incremental cost of producing WMA is a barrier to production facilities and end

users. Mechanical methods for WMA production

, like water foaming

, require some plant modifications, including adding new equipment and changing production practices

, which can lead to high up

- front costs associated with WMA production

. Similarly, while

the use of chemical additives can be accommodated with minimal alteration to existing asphalt plant production technology , the chemicals or materials can be costly and are used in every batch, nonetheless increasing the overall cost of WMA. Additionally, each facility must incur the cost of t ransition training and education of operators and engineers in order to successfully expand their operation to incorporate WMA. Finally, pavement plants must pay to obtain n ew permits for any new tanks.

Th e added cost s of WMA production are incorporated in the final cost of the material to

the end user. 15 With most Valley agencies operating on a tight budget in low

- income

11 AB 338 (Levine) (2005) Retrieved from: http://www.leginfo.ca.gov/pub/05

- 06/bill/asm/ab_0301

- 0350/ab_338_cfa_20050427_134930_asm_comm.html

12 Alameda County COG Presentation (2013). Retrieved From: http://www. acgov.org/sustain/documents/roundtable_rubberasphalt_gci.pdf

13 Alameda County COG Presentation (2013). Retrieved From: http://www.acgov.org/sustain/documents/roundtable _rubberasphalt_gci.pdf

14 http://www.dot.ca.gov/newtech/researchreports/reports/2013/final_report_task_2385c.pdf

15 Asphalt Pavement Association of Michiga n Presentation. Retrieved from: http://www.apa

- mi.org/docs/2013LRW

WarmMixAsphalt.pdfWarm Mix Asphalt Further Study

12 FURTHER STUDY FINDINGS | SJVAPCD communit ies, it could be difficult for these public entities to choose WMA over

conventional HMA when the cost difference is $0.50

- 5.00 more per ton

. While most Valley operators who participated in this study indicated that they may be able to

overcome these incremental costs, they could not do so without an increase in demand.

L ow D emand

Due to uncertainties about the performance, longevity, operational procedures, and

associated costs , WMA is not yet widely requested or ordered by asphalt plants . As such, v ery few Valley asphalt plants produce WMA. U ntil there is widespread request of the material, pavement plants have very little incentive to begin large

- scale WMA production. As long as the demand for WMA remains low, the cost to purchase will be $0.50

- 5. 00 more per ton than HMA (at an overall $60

- 80 per ton). Since contracts for road construction projects go to the lowest bidder, it is difficult for production facilities and contractors to promote WMA use when the competition is selling cheaper material,

no matter the other benefits WMA has to offer.

FURTHER STUDY FINDINGS VII.

This study has found that WMA has the potential to reduce emissions by using less fuel and the potential to provide safer condition s by producing less odor and fumes. However, this potential reduction in emissions must be further evaluated given that a number of other factors with respect to implementation may negate and actually

increase emissions associated with WMA.

I n other states and countries, WMA has shown to be a feasible alternative to HMA and continues to grow steadily due to performance and cost

- savings advantages. However, in the Valley, many barriers still remain

. P oor paving performance in the Valley’s high summer heat, lack of confidence in WMA techno logy, an insufficient number of pilot projects to support feasibility in the Valley , lack of Caltrans WMA specifications to support proper WMA usage, and not enough demand to provide the needed economies

of scale to achieve the identified cost benefits hav e all hindered wides pread adoption of WMA throughout the Valley.

In order to continue evaluating and promoting the use of WMA in the Valley , the District recommends the following:

1. Encourage additional pilot projects to assess viability and life cycle of

WMA in the V alley

. Promote and support additional WMA pilot projects in the valley to reduce uncertainty and improve confidence in the performance and

benefits (including emissions reductions) of WMA.

2. Encourage Caltrans to further develop WMA specificati on s

. Encourage Caltrans to develop WMA specs to provide the appropriate guidance to contractors and public work agencies

.Warm Mix Asphalt Further Study

13 FURTHER STUDY FINDINGS | SJVAPCD 3. If found to be feasible in the V alley

, work with stakeholders to educate and encourage WMA usage as a means of implementing additional pilot projects

. Continue to m eet with public works agencies , including Caltrans, to help educate and encourage WMA use. The District could also provide WMA literature and information during the permitting process at various pavement plants or through the ISR process for construction projects that require paving as a means of implementing additional pilot projects

.

4. Meet with stakeholders as necessary

. Continue to meet with Caltrans, Cal APA, plant operators, and other pavement industry leaders to assess feasibility

and emission reductions. If found to be feasible and to result in actual emission

reductions

, identify challenges and look for solutions for adoption of WMA technology.

5. If found to actually reduce emissions and be feasible, consider including

WMA as an ISR mitigation measure

. District Rule 9510, Indirect Source Review (ISR)

, requires developers of larger residential, commercial and industrial projects to mitigate smog

- forming and pa rticulate emissions generated by their projects. If WMA is found to actually reduce emissions and be feasible, t he District could consider allowing the use of the emission reduction s achieved by using WMA in place of HMA to mitigate project emissions.