SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT

TECHNICAL ASSESSMENT FOR RULE 1108 – CUTBACK ASPHALT

June 2008

Deputy Executive Officer 

Planning, Rule Development, and Area Sources

Elaine Chang, DrPH

Assistant Deputy Executive Officer 

Planning, Rule Development, and Area Sources

Laki Tisopulos, Ph.D., P.E. 

Planning and Rules Manager

VOC Rule Development

Larry Bowen, P.E.

Author: Bill Milner - Air Quality Specialist

Reviewed By: Andrew Lee, P.E. - Program Supervisor
i

TABLE OF CONTENTS

EXECUTIVE SUMMARY .......................................................................................................... 1

BACKGROUND ........................................................................................................................... 1

TECHNOLOGY ASSESSMENT................................................................................................ 2

Hot Mix Asphalt......................................................................................................................................2

Warm Mix Asphalt.................................................................................................................................3

Cutback Asphalt.....................................................................................................................................3

Emulsified Asphalt .................................................................................................................................4

GENERAL PAVING USES OF LIQUID ASPHALTS............................................................. 5

UNIVERSE OF SOURCES ......................................................................................................... 5

EMISSIONS INVENTORY......................................................................................................... 5

COMPARATIVE ANALYSIS..................................................................................................... 8

CONCLUSIONS AND RECOMMENDATIONS...................................................................... 9

REFERENCES.......................................................................................................................... R-1

KEY CONTACTS..................................................................................................................... R-1

APPENDIX A – EXAMPLE RULE CONTAINING SEASONAL EXEMPTION ............ A-1
Technology Assessment for Rule 1108 – Cutback Asphalt

1

EXECUTIVE SUMMARY

As recommended by the United States Environmental Protection Agency (U.S. EPA), the 2007 

Air Quality Management Plan (AQMP) included Control Measure FUG-03 - Further Emissions 

Reductions from Cutback Asphalts, which commits the District to explore the feasibility of

further limiting the use of cutback asphalt to the fall and winter months where ozone formation is 

at its least, or replacing it altogether with surrogate water-based emulsion technology.

The only type of cutback asphalt being used today for paving, road construction and maintenance 

is slow cure cutback asphalt. Slow cure cutback is a blend of asphalt binder, a byproduct of the 

distillation of crude oil, and twenty to thirty percent by volume heavy nonvolatile oil such as 

diesel fuel or gas oil. The main use of slow cure cutback asphalt is stockpiled temporary coldmix maintenance patching material consisting of graded aggregate and small quantities of 

cutback asphalt, enough to coat the aggregate and bind it in place under compaction, and as a 

dust palliative on the road construction jobsite.

Previous District rulemaking has eliminated the use of faster curing cutback asphalt known as 

“rapid” cure and “medium” cure cutbacks. These materials contained lighter fractions of oil 

such as naphtha and kerosene and were problematic to air quality because they contained more 

evaporative oil by volume that flashed off more readily. Ninety-nine point five percent by

volume of the cutter stock used to make cutback asphalt, as required by Rule 1108, cannot 

evaporate when tested under ASTM distillation Method D402 at 500oF or less. Therefore, it 

cannot evaporate at application or atmospheric temperatures. The potential to emit volatile 

organic compounds (VOCs) from slow cure asphalts is de minimus.

Emulsified asphalts that are suitable replacements for stockpiled slow cure cutback asphalt will 

contain a small fraction of evaporative VOCs. Under Rule 1108.1 – Emulsified Asphalts, they

are prohibited to have more than three percent by volume VOCs that evaporate at 500oF or less. 

Substitution to an emulsion at this point will not benefit the environment, because replacement 

emulsions for slow cure asphalt will contain up to three percent VOCs. It is important to note 

that replacement emulsions have already taken the place of the more volatile medium and rapid 

setting cutbacks, and therefore have substantially reduced emissions to date. City streets, county

roadways, and state highways can be repaired with slow cure cutback asphalts and with very 

limited VOC emissions. They are needed year round in our sprawling metropolis, not just in 

seasons where smog formation is at its least.

BACKGROUND

Asphalt is found in nature and mined, but it is mostly manufactured as the remnants of crude oil 

distillation. Approximately 90 percent of the world’s asphalt is used in road construction. In 

general, asphalt is too firm at standard temperature and has to be liquefied either by heating it, 

mixing low-volatility cutting oils (cutback asphalt), or combining it with water, surfactant, and 

an emulsifying agent (emulsified asphalt). Once fluid, it is used as a binder for aggregate, a 

primer for new road construction, a tack coat between layers of asphalt concrete, a road surface 

sealer, and a road maintenance material. The amount of extremely low volatile cutter oils (gas 

oil, diesel fuel, and trace amounts of lighter distillates) used today range from 20 to 30 percent 

by volume.
Technology Assessment for Rule 1108 – Cutback Asphalt

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Rule 1108 – Cutback Asphalt was adopted in May of 1979, and amended three times, to address

the high air emissions from rapid curing, and to a lesser extent medium curing asphalts which 

contain lighter cutter oils that evaporate much more readily. Prior to September of 1983, the 

U.S. EPA opposed exemptions in Rule 1108 allowing the use of higher volatility cutback 

asphalts in areas where the elevation is higher that 2,000 feet above sea level, for penetrating 

prime coats, or when the temperature was forecast to be less than 50o F in the vicinity of the 

asphalt application. The 1983 amendment to Rule 1108 eliminated these exemptions. The rule 

now simply limits the use of cutback asphalts to one-half percent by volume of volatile organic 

compounds (VOCs) that evaporate at 500oF or less, as determined by ASTM distillation method 

D402.

During the 2007 AQMP development, the AQMD submitted to U.S. EPA a report to 

demonstrate that current AQMD rules and regulations fulfill the 8-hour ozone RACT 

(Reasonably Available Control Technology). During this review, EPA Region IX noted that 

District Rule 1108 does not meet RACT for cutback asphalt, because other local air districts 

within the United States with similar rules to Rule 1108 have seasonal restrictions on the use of 

cutback asphalt during spring and summer months; the ozone season. Due to this concern by

EPA, the AQMD developed Control Measure FUG-03 (Further Emissions Reductions from 

Cutback Asphalts) in its 2007 AQMP, with the purpose of limiting the use of cutback asphalt to 

the fall and winter months (November through February) where ozone formation is at its least or 

replacing it altogether with surrogate emulsion technology.

Asphalt emulsions are regulated under Rule 1108.1 - Emulsified Asphalt, which limits the 

quantity of organic compounds that evaporate at 500oF or less, as determined by ASTM Method 

D402, to three percent by volume for all types of emulsions be it rapid, medium, or slow setting 

types. This value was arrived at through incremental VOC limitation reductions through the 

beginning of 1987, previously based on the U.S. EPA’s Control Technique Guidelines (CTG) for 

asphalt emulsions.

TECHNOLOGY ASSESSMENT

There are four groupings of asphalt products used during road, parking lot, runway, driveway

and walkway construction and maintenance. They are hot mix asphalt (HMA), warm mix 

asphalt (WMA), cutback asphalt, and emulsified asphalt. Rule 1108 – Cutback Asphalt and its 

related Rule 1108.1 – Emulsified Asphalt represent both forms of solution asphalt binder, 

whereas HMA and WMA are mixes of asphalt binder and aggregate.

Hot Mix Asphalt

HMA is a mixture of asphalt binder and aggregate conducted at a mixing plant (stationary or 

portable). Asphalt binder is heated to melting then combined in a pug mill with clean, dried 

aggregate of a graded size and density. The mix contains approximately 95 percent aggregate 

and 5 percent asphalt binder to coat the aggregate in the temperature range of 260oF - 325oF. It is 

supplied to trucks that deliver the HMA to the job site, where it is loaded into a paver that lays 

the mix down and is subsequently compacted with a roller to a prescribed density and thickness 

usually between 2 and 6 inches and at a delivery temperature of approximately 200oF. Because 

the asphalt binder is the residue from the distillation from crude oil, it contains virtually no 
Technology Assessment for Rule 1108 – Cutback Asphalt

3

remaining VOCs. The asphalt binder is chosen on the basis of its minimum flash point, viscosity

at 135oC, ductility at 25oC, and its rolling thin film oven test results; that tests for dynamic shear, 

ductility, and creep stiffness of aged binder, and they are further graded by penetration. The 

most common asphalt binder classifications are: penetration grade, viscosity grade and 

performance grade. These asphalt grades are specified in HMA mix design. It is HMA that 

replaces temporary patches of cold-mix slow cure cutback asphalt (aggregate and cutback mixed 

together), that so many departments of transportation use in stockpiles.

Warm Mix Asphalt

This technology uses emulsion (water-based) technology together with additives that foam when 

added to less hot aggregate/asphalt mix. The result is a thin-film, high volume asphalt binder 

with greater aggregate coating potential than HMA. The process reduces the viscosity of the 

asphalt binder through foaming. Lower viscosities mean lower heat input required when mixing, 

transporting, and applying, resulting in an energy savings and lower emissions from the 

combustion of fuels used to heat the mix. The foaming additives are based on zeolite and 

combinations of soft binder and foaming hard binder cement. Both result in lowering the 

viscosity of the asphalt, and lowering the energy requirements. Other warm technologies are 

based on synthetic paraffin wax and low molecular weight ester compounds that reduce the 

viscosity of the asphalt binder during mixing. Still others inject water into the mix to create a 

controlled sudden vaporization or explosion to coat the aggregate in a thin-film in the mill.

Cutback Asphalt

Cutback asphalts made from various grades of asphalt binder and are blended with kerosene or 

naphtha that more rapidly evaporates to leave hard viscous asphalt behind (rapid cure), to a 

slowly evaporative asphalt/gas-oil blend that leaves a softer, less viscous base to combine with 

aggregate (slow cure). Medium curing products are also available such that the hardness and 

viscosity of the binder is between the rapid and slow curing types (medium cure). There are 

several uses for cutback asphalts: prime coats, tack coats, dust control, and cold mix applications 

for temporary road repairs (potholes and cuts for public utility services, etc.).

Prime coats are used to provide a temporary waterproofing layer and for stabilizing the first 

course of new construction and promoting a bond to the HMA layer. Tack coats are used in 

between layers of asphalt concrete to provide good bonding. Dust control refers to bonding of 

loose dust. Cold-mix is a combination of aggregate and slow cure asphalt; depending on type, it 

can be made for immediate use or stockpiled for later application.

The only use of cutback asphalt within the Departments of Transportation within the South Coast 

Air Basin today is slow cure (SC) cutback asphalt of the softest variety, used principally for 

temporary road repair. The grades in use are SC-800 (immediate use) and SC-3000 (stockpiled).

Some use of SC-70 and SC-250 may occur for prime coats in new parking lot and driveway

construction; the higher the viscosity, the higher the specification number. Tack coating with 

cutback asphalt has been replaced with emulsified asphalt.

Slow cure asphalt by definition and regulation may only contain up to one-half percent by

volume of VOCs that evaporate at less than or equal to 500oF. This means that 99.5 percent by

volume of the cutter oil will not evaporate at ambient air conditions. The associated air 
Technology Assessment for Rule 1108 – Cutback Asphalt

4

emissions are a maximum of 0.01125 pounds of VOC per applied gallon at 30 percent cutter oil, 

or 1.35 grams of VOC emissions per applied liter.

Emulsified Asphalt

Emulsified asphalt are made with various grades of asphalt (hard, medium, and soft) that has 

been sheared in a colloidal mill to form globules, combined with surfactant, water, and soap as 

an emulsifying agent that leaves asphaltic particles suspended in solution. They are ionic in 

nature are will either have a negative charge (anionic), or a positive charge (cationic) for use in 

road and pavement applications. They contain less asphalt solids than slow cure cutback; 

approximately 65 percent by volume compared to 75 percent by volume for cutback, so it takes a 

greater amount of emulsified asphalt compared to cutback asphalt to complete the same job.

Anionic emulsions are based on reacting fatty acids with chemical base to form a salt. It is the 

salt that will attach itself to an asphalt particle with a non polar tail and a polar head (-). The 

polar head is balanced by free charges in the water phase. Cationic emulsions are based on acid 

salts of amines prepared from fatty acids. They work the opposite way of anionic emulsions 

with positive head and a non polar tail attached to an asphalt particle.

Once the asphalt globules begin to come together, or “break”, the asphalt will eventually return 

to its original solid or semi-solid phase. In the anionic emulsion formula the asphalt particles 

and the aggregate particles will repel each other until the attractive forces between all things 

overcomes the repulsion and begins to flocculate the particles into larger particles upon 

evaporation, and further coalesce into a uniform asphalt residue. It is the point of flocculation 

that the solution begins to break. This can be forced along by pumping the material at high 

shear, or heating or freezing. Cationic formulas break in a similar manner but deposit more 

rapidly on aggregate due to the electrostatic attraction of the positively charged emulsion and the 

negatively charged mineral matter, and stronger bonds between the asphalt and aggregate are 

obtained. Cationic emulsions are easier to apply and obviate many of the disadvantages of 

anionic emulsions, such as unpredictable break and a weaker bond to the aggregate surface. The 

rate of set is determined by the type and the amount of emulsifier and the pH of the cationic soap 

solution. Some emulsions have a relatively short shelf life and can break while still in their 

unopened drums, rendering it useless. The break point can be extended by the choice of 

emulsifier, by shearing the binder into smaller globules, or by adding stabilizer.

All of the above asphalt system types can contain modifiers. Modifiers improve the asphalt 

binder’s stiffness, which improve the resistance to form ruts and reduce cracking while in 

service. Some of the modifiers used are latex, polymers, and ground tire rubber. Additions of 

modifiers increase the cost of the asphalt binder but the increased cost is usually offset by less 

maintenance and increased lifetime of the asphalt pavement.

According to the literature, emulsions are developed for every aspect of critical maintenance and 

construction including all plant and mix-in-place pavement bases and surface treatments 

including chip seals, tack coats, dust suppressants, crack fillers, and maintenance mixes for 

immediate and stockpiling use. Stockpile mixes (cold-mix temporary patch material) use about 

10 percent of the total emulsion volume added as diesel or kerosene.
Technology Assessment for Rule 1108 – Cutback Asphalt

5

As per Rule 1108.1, the maximum allowable air emissions of emulsified asphalts are three

percent by volume. This would equate to approximately 0.20 pounds of VOC emitted per gallon 

of equivalently applied asphalt, and about 18 times more emissive than slow cure asphalts on a 

concentration basis.

GENERAL PAVING USES OF LIQUID ASPHALTS

The American Society for Testing and Materials (ASTM) specification D 2399-83 – Standard 

Practice for Selection of Cutback Asphalt and D 3628-08 – Standard Practice for Selection and 

Use of Emulsified Asphalts outlines the general uses for both types of solution asphalts, 

emulsified and cutback, according to their respective grades (slow, medium, and rapid setting 

cutback, anionic and cationic emulsions). The use of cutback asphalt is for prime coating with 

SC-70 or SC-250 grades, whereas SC-800 and SC-3000 are cold-laid plant mixes with densegraded aggregate, for immediate and stockpiled applications.

In the case of rapid setting emulsions, mainly used for repair work of old wearing courses, the 

emulsion is applied on the existing surface and aggregate is spread on top, and after compaction, 

the road can be opened to traffic shortly after the application of the new coat. These are 

generally road surface treatments involving graded aggregate, sand, or aggregate chips imbedded 

into the roadway. Medium setting emulsions are used for hot and cold plant mixes and for 

mixing with aggregate on the job-site with portable equipment (mix-in-place). Slow setting

emulsions are the most versatile with applications for cold plant mixes, mix-in-place, for low 

viscosity, penetrative bond coats or tack coats between new layers of asphalt concrete, and for 

crack filling. Only one emulsion is recommended for stockpiled maintenance mixes as a high–

float medium setting soft variety. Safety data sheets indicate the inclusion of cutter stock into 

the emulsion for this type, presumably to retard the break and potentially increasing air 

emissions.

UNIVERSE OF SOURCES

There are at least five refineries that manufacture asphalt for paving operations within the South 

Coast Air Basin. They are Edgington Oil, Lunday-Thaggard, Paramount, Owens Corning, and 

Valero. Hot mix asphalt plants are numerous and include Vulcan Materials Company, All 

American Asphalt, Industrial Asphalt, and Sully-Miller Contracting Company and they also 

formulate cutback and emulsified asphalt products. There are literally hundreds of contractors 

and applicators. Some cities and counties have their own crews to address maintenance 

operations and surface treatments. All other work is usually performed by pavement contracting 

companies.

EMISSIONS INVENTORY

As background information, staff contacted CAL Trans which is responsible for highway

construction and maintenance, the Los Angeles County Public Works Department, the San 

Bernardino Transportation Department, the Orange County Public Works Department, as well as 

the Riverside County Transportation to inquire on the use of cutback asphalt. Most county

representatives related the use of slow cure asphalts for temporary road maintenance (SC-800 

and SC-3000). Temporary can mean backfilled with HMA after a few days to several months or 

even longer. Slow cure cutback asphalt as a dust palliative was also mentioned in use by

industry representatives. Pertinent associations such as the Asphalt Emulsion Manufacturers 
Technology Assessment for Rule 1108 – Cutback Asphalt

6

Association, the Asphalt Pavement Association of California and membership representatives, as 

well as the asphalt manufacturers were contacted.

The presented inventory is based on a report by Sonoma Technology Inc., under contract by the 

California Air Resources Board circa 2001. The data generated is based on the number of road 

miles in the four county areas that encompass the South Coast AQMD, and approximations were 

used as to the amount of asphalt contained in one road mile (10 tons/mile), and an allocation 

factor is derived from the product of statewide emissions to the ratio of county road miles to state 

road miles. This is then used as a factor against the reported statewide asphalt consumption to 

obtain approximations of the amount of asphalt consumed by each AQMD County. The total 

quantity of asphalt sold in California is from state energy data as reported by the Energy

Information Administration (EIA) as of 2005. The fraction of asphalt binder used for pavement 

is stated to be 88 percent of the total California State consumption of asphalt binder as reported 

by the EIA. Usage factors are then applied using historical reported data from local air districts 

with regard to the percentage of road miles of asphalt using HMA (88 percent), cutbacks (1

percent), road oils (slow cure cutbacks) (2 percent), and emulsions (9 percent). Conversions are 

then made using the maximum allowable emission factor of Rule 1108 (0.5 percent by volume), 

as well as physical data available for cutback SC-800 and SC-3000 (diluent density, cutback 

density, volume asphalt binder, volume of cutter stock, etc.). An example calculation is given 

below and Table 1 shows all counties and totals the inventory.

Gallons of Asphalt Binder Used in Los Angeles County for Cutback Asphalt = (Total CA 

Asphalt Binder Usage in bbl) x (Fraction Used for Paving in CA) x (Fraction Asphalt Binder in 

Use for Slow Cure Cutbacks in CA) x (Los Angeles County Allocation Factor) x (42 gal/bbl)

Gallons of Cutback Asphalt Used in Los Angeles County = (Number of Gallons of Asphalt 

Binder Used in Los Angeles County in California) + (Number of Gallons of Cutter Stock in 

Cutback Asphalt), 

Where, the number of gallons of cutter stock is proportional to the total gallons of binder used to 

make specific cutback asphalts.

Annual Emissions for Los Angeles County = (Total Gallons of Cutback Asphalt Used in Los 

Angeles County) x (Emissions Factor in lb/gal)

Los Angeles County:

(13,843,000 bbl/yr) x (0.88) x (0.02) x (0.084) (42 gal/bbl) = 859,551 gallons of asphalt binder

859,551 gal binder x (0.3 gal cutter stock/0.7 gal binder) = 368,379 gallons of cutter stock

859,551 + 368,379 = 1,227,820 gallons of cutback asphalt

(1,227,820 gallons of cutback asphalt) x (0.01125 lb VOC emitted/gal) = 13,813 lb VOC/yr = 38

lb VOC/day
Technology Assessment for Rule 1108 – Cutback Asphalt

7

The use of slow cure cutback asphalt in Orange and Riverside Counties is assumed to occur with 

mid-point cutter stock (25 percent by volume gas oil or similar cutter stock), whereas Los 

Angeles and San Bernardino Counties use 30 percent and 20 percent by volume cutter 

absolutely.

Table 1: Emissions Inventory for Rule 1108 – Cutback Asphalts

Location VOC Emissions From Asphalt

California

Total State

Asphalt 

Binder 

Usage

Total 

Asphalt 

Binder 

Used for 

Paving

Asphalt 

Binder In

Use for 

HMA and 

WMA

Asphalt 

Binder in 

Use for 

Emulsions

Asphalt 

Binder in 

Use for 

Slow Cure 

Cutbacks

Asphalt 

Binder in 

Use for 

Slow Cure 

Cutbacks

Percentage of 

Use 100% 88% 88% 9% 2% -

Barrels/Year 13,843,000 12,181,840 10,720,019 1,096,366 243,637 -

Gallons/Year - - - - - 10,232,746

Percent by

Volume 

Gas Oil or 

Similar 

Material in 

Slow Cure 

Cutbacks

County

Allocation 

Factor

Approx. 

Volume 

(Gal) SC 

Cutback 

Used Per 

AQMD 

County Per 

Year

Pounds of 

VOC 

Emitted 

per Gallon 

of 

Cutback 

Asphalt

VOC 

Emissions 

(lb/yr)

VOC 

Emissions 

(lb/day)

Los Angeles 30.00% 0.0840 1,227,820 0.01125 13,814 38

Orange 25.00% 0.0225 306,982 0.00938 2,879 8

Riverside 25.00% 0.0414 564,848 0.00938 5,298 15

San 

Bernardino 20.00% 0.0817 1,045,019 0.00750 7,838 21

Total 82

Tons VOC/Day 0.04

The replacement of slow cure cutback asphalts with emulsions that perform the same function 

will result in potentially higher emissions, based on the upper evaporative VOC limit in Rule 

1108.1 (3 percent by volume). See Table 2.

An example calculation is given below:

Los Angeles County:

(Solids Adjustment Factor) x (Volume of SC Cutback Used) x (Density of Typical VOC in 

Replacement Emulsions) x (Volume Percent VOC Allowable in Rule 1108.1)
Technology Assessment for Rule 1108 – Cutback Asphalt

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(0.70/0.65) x (1,227,820 gal) x (6.6 lb VOC/gal of VOC) x (0.03 gal VOC/gal emulsion) = 

261,809 lb VOC/yr [if emulsion substitution occurs]

Table 2: Emission Inventory if Substitute Emulsions Replace Cutbacks

Location

Volume 

Fraction of 

Asphalt 

Binder in 

Specific SC 

Cutback 

Asphalt Used 

Per County

Volume 

Fraction 

Asphalt 

Binder in 

Emulsified 

Asphalt

Approx. 

Volume 

(Gal) SC 

Cutback 

Used Per 

AQMD 

County Per 

Year

Approx. 

Gallons of 

Substitute 

Emulsion

Emissions 

From 

Emulsion 

(lb/yr)

Los Angeles 0.70 0.65 1,227,820 1,322,386 261,809

Orange 0.75 0.65 306,982 354,210 70,134

Riverside 0.75 0.65 564,848 651,747 129,046

San 

Bernardino 0.80 0.65 1,045,019 1,286,177 254,663

Total 715,652

Tons/Day 0.98

Therefore, the use of emulsion technology cannot replace slow cure cutback because it will not 

result in a positive environmental impact.

COMPARATIVE ANALYSIS

Rule 1108 – Cutback Asphalt currently prohibits the use of medium and slow curing cutback 

asphalt that contains more than 0.5 percent by volume organic compounds which evaporate at 

500oF or lower as determined by ASTM Method D402, and is specific to pavement applications.

The EPA CTG calls for substitution of emulsified asphalt for cutback asphalt. Its “Blue Book”

suggests seasonal exemptions (i.e., outside of the ozone season) as opposed to temperature 

forecasting (e.g., applied when <50oF), and specifies (1) no higher than 7 percent oil distillate as

maximum allowable solvent content in emulsified asphalt, as determined by ASTM distillation 

test D244 or (2) allow use of certain grades or applications of emulsified asphalt with the 

following maximum solvent contents as determined by ASTM D244: 

(a) 3 percent limit for seal coats used in early spring or late fall; 

(b) 3 percent limit when chip seals used with aggregate that is dusty or dirty;

(c) 8 percent limit when mixing with open graded aggregate that is not well washed; and

(d) 12 percent limit when mixing with dense graded aggregate.

Other exemptions are listed for use solely for penetrating prime coats and when stockpiled for 

extended periods.
Technology Assessment for Rule 1108 – Cutback Asphalt

9

According to the 2007 AQMP, Control Measure FUG03, many states, such as Maine, Missouri, 

New York, Pennsylvania, and Rhode Island have adopted rules on cutback asphalt that prohibit 

their use during the ozone season. (See Appendix A for an example from the State of Missouri). 

However, they provide exemption for every application they are actually used for including, 

prime coats, stockpiled material for pothole and road patching, as well as dust palliatives on the 

jobsite. Allowing for these exemptions completely negates the seasonal restriction.

CONCLUSIONS AND RECOMMENDATIONS

AQMD Staff has reviewed the potential for limiting cutback asphalt or replacing it altogether 

with emulsion technology and concludes that slow cure cutback asphalts do not emit as much 

VOC as suitable replacement emulsions do. Furthermore, staff’s review of the rules adopted by

other states that call for seasonal restrictions on cutback asphalt have exemptions where cutback 

asphalt is needed within the ozone season, negating the benefits of their rule. Therefore, staff is 

recommending no changes to Rule 1108. Rule 1108 is a highly effective rule, as is Rule 1108.1,

because both rules in tandem act to disallow the much more evaporative “rapid” and “medium”

cutback asphalts and to replace them with lower emitting rapid and medium curing emulsified 

asphalts, and non-volatile slow cure cutback asphalts.
Technology Assessment for Rule 1108 – Cutback Asphalt

R-1

REFERENCES

1. ASTM D-2399, Standard Practice for Selection of Cutback Asphalts, Reapproved 

2005.

2. ASTM D3628, Standard Practice for Selection and Use of Emulsified Asphalts, 2008

3. U.S. EPA AP-42, Volume 1, Chapter 4.5, July 1979.

4. Energy Information Administration, State Energy Data System, Table F8, 2005.

5. Sonoma Technology Inc, Report on Asphalt Paving and Roofing, Attachment C, 

2001.

6. U.S. EPA, Control of Volatile Organic Compounds from use of Cutback Asphalt, 

EPA-450/2-77-037.

7. Emultec.com

8. Western Emulsions, Inc., Presentation Materials, An Introduction to Warm Mix 

Asphalt, 2007

KEY CONTACTS

Los Angeles County Public Works

San Bernardino Transportation Department

Paramount Petroleum Corp

Asphalt Emulsion Manufacturers Association

Sully-Miller Contracting Company

Justice & Associates

Asphalt Pavement Association of California
Technology Assessment for Rule 1108 – Cutback Asphalt

A-1

APPENDIX A – EXAMPLE RULE CONTAINING SEASONAL EXEMPTION