26

From Roofing to Roads:

A shingle shredding plant developed by the Telsmith and Astec subsidiaries ofAstec Industries, Inc. processes shinglesfor use in HMA.

July I797 C&D Debris Recycling

..... Just as using quality aggregate results in better construction material, using quality replacement ..*.*.. 116

parts keeps your Telsmith equipment producing efficiently and economically. From replacement liners to

integral components, Telsmith parts are right in both fit and function. They’re the right design, the right

material and the right tolerance to assure you of a quality repair today. ..and in the long run. So don’t gamble on

“maybe right,” get the parts that are guaranteed to be “Right as Rock.” Contact

your Telsmith dealer, or call our Parts Hot Line at: 1-800-688-6601.

Telsmith, Inc., P.O. Box 539, Mequon, Wisconsin 53092-0539, -- - ~- - Tel: (414) 242-6600, Fax: (414) 242-5812, An Astec Company.

C l P r l F 1136 nhl D F A n F D r h D n -

t one point, it may have been difficult to imagine that the road your car drives on was constructed, in part, from

the same material used to build your roof But the results of a study indicate that incorporating as much as 5% fac- tory-waste shingles into hot-mix asphalt (HMA) mixtures results in a paving product that meets quality control standards, and even increases the performance of the mix. In fact, the researchers concluded that roofing waste can be handled using techniques already established for reclaimed asphalt pavement (RAP).

The study consisted of a compilation of various research initiatives and labo- ratory tests conducted on the use of shin-

nical Information Service, 5285 Port Royal Road, Springfield, Va. 22 16 1.

The practicality of using recycled roofing waste Each year, roofing manufacturers in the United States produce approxi- mately 1 million tons of manufac- turing waste shingles and shingle trimmings, and about 8 to 10 mil- lion tons of consumer waste roofing. Historically, about 95% of this valu- able, nonbiodegradable solid waste has been placed in landfills. These by-products and waste materials are composed of such products as hard, crushed aggregate, high-viscosity asphalt, and fibers.

Recovering and reprocessing of

rough-textured, fibrous manufactur- ing roofing aggregate in place of the natural round, smooth aggregate particles (certain sands) may actual- ly provide improved resistance to plastic deformation in asphalt mix- tures and make a tenacious and cohesive paving mixture resistant to rutting and cracking. The hard asphalts in roofing that may con-

ing can be offset by using softer vir- gin asphalts or adding rejuvenating agents to the roofing waste.

tribute to thermal or fatigue crack- .______

Roofing waste material There are two types of roofing waste: manufacturing waste, or factory scrap materials, and consumer waste, or tear-

This article i s adapted from a Texas Transportation Institute report entitled “Roofing

Shingles and Toner i n Asphalt Pavements. ” The report was sponsored by the Texas

Department o f Transportation and written, in cooperation with the Federal Highway Ad-

ministration, by Joe W. Button, Research Engineer, Texas Transportation Institute; Devon

Williams, Research Associate,

Co nsu lting Engineer. des in HMA. Interviews with personnel associated with various state highway agencies, contractors, materials suppli- ers, scrap shingle shredders, and equip- ment and roofing manufacturers demonstrated positive results using fiber- glass or organic shingles in HMA. How- ever, consumer waste, or tear-offs, is a highly inconsistent material, and not nearly as widely used or recommended for use as manufaauring waste in HMA.

The researchers determined that standard Texas Department of Trans- portation HMA design and quality control procedures are satisfactory for designing and evaluating mixtures containing manufacturing waste. The main accommodation that may need to be made for the addition of the rel- atively stiffer shingle material into the mix is that HMA mixing and com- paction temperatures be increased in the laboratory and the field.

The entire research report can be obtained by writing: National Tech-

Texas Transportation Institute; andlames A. Scherocman,

this material began in the early 1980s, in response to federal legisla- tion and regulations prohibiting opening of new landfills and legis- lating high tipping fees. Those states that have had the earliest success with recycling shingles are those that have stringent landfill regulations. About 50% of all states have now adopted legislation aimed at recy- cling selected components of the waste stream.

As well as being beneficial from a recycling standpoint, the use of recy- cled shingles in HMA has been proven economical. The use of roof- ing waste in a HMA mixture can lower the virgin asphalt requirements and increase the total HMA tonnage at lower cost.

The use of recycled shingles in the mixture also has some potential to improve the performance and thus extend the life of HMA at no addi- tional cost. The incorporation of

offs (also known as field waste). Con- sumer waste may contain nails, wood, paper, asbestos felt, and other debris and therefore, may vary in quality and com- position; the asphalt content also varies in this type ofwaste. Therefore, it is not as suitable for use in HMA mixtures as manufacturing waste.

There are three types of manufac- turing waste: fiberglass, which contains 18% to 20% asphalt; organic, which contains 34% to 36% asphalt; and build-up roofing (BUR), which contains more than 50% asphalt and so is not consid- ered at all in this study.

A consistent HMA mixture can be produced by using either all fiber- glass or all organic roofing shingles. In order to control the amount of asphalt in the final mix, it is impor- tant that only one type of shingle is used, and that the type of shingle be either fiberglass or organic; using BUR or consumer waste is not rec-

C&D Debris Recycling July 1997 27

ommended. Also, less manufactur- ing waste should be used in a surface mix than in a base mix.

Manufacturing waste is preferred over consumer waste for use in HMA paving mixtures for several reasons:

the shingles are more uniform in content;

the asphalt is softer and more func- tional for use in a paving mixture;

the shingles are not contaminated with deleterious materials; and

the shingles contain no organic roof- ing felt or asbestos.

Test findings and utilization of shingles in HMA Roofing waste has been successfully ground, screened, stockpiled, and recycled in hot and cold applied asphalt paving mixtures by a number of state highway agencies and recy- cling companies. In addition, labo- ratory and/or field tests have been conducted on asphalt paving mix- tures containing waste roofing in 13 different states. Draft specifications for HMA containing roofing waste or mixture information were obtained from several of these states’ departments of transportation.

The findings indicate most high- way agencies agree that:

acceptable paving mixtures con- taining as much as 10% by weight roofing waste can be produced;

using a softer binder than normal- ly utilized will offset the hard binder in the roofing shingles;

virgin asphalt content can be reduced when manufacturing waste is added;

using factory waste is preferable because of its uniform quality;

gradation of the aggregates in the roofing waste should be considered during mixture design; and

aggregates in the virgin mix should be reduced by the amount of aggre- gates of the same sizes added in the recycled roofing material.

There are no known highway departments that allow consumer waste to be used in asphalt paving mixtures; however, some do use manufacturing waste. The Indiana, Maryland, and Minnesota Departments of Trans- portation (DOTS) have written speci- fications that allow for up to 5% man- ufacturing waste to be used in HMA. However, the manufacturing waste used must be consistent; i.e., either fiberglass or organic shingles must be used. These states do not allow for the use of consumer waste in the mixture. This is because the amount of asphalt in these shingles varies so widely and the amount of fiberglass cannot be determined; therefore, the mixture properties cannot be controlled.

The Florida DOT has used as much as IO% of manufacturing waste

!

shingles by mass of HMA. Because’of the harder asphalt in the shingles, the agency used AC-20 in place of the standard AC-30 when shingles are implemented in the mixture. The agency found increased Marshall sta- bility, tensile strength, and resistance to rutting when manufacturing waste was included in asphalt concrete. However, according to Gale Page of the Florida DOT, it has not been eco- nomical for the state to use this mate- rial in their HMA mixtures, due in part to a lack of availability of manu- facturing waste.

The Tennessee DOT conducted a study on the effects of recycled con- sumer roofing waste in HMA. It deleted 5% sand and 5% screenings from a dense-graded mixture in common use and replaced it with 10% recycled roofing. Since the roofing contained 28% asphalt, the virgin asphalt content was reduced. Because the asphalt in the roofing was quite hard, the asphalt plant mixing temperature was raised by 43” F. Laboratory data suggested the mix was “very satisfactory.”

A Canadian recycling company has developed a patented process whereby the asphalt mastic and fiber are separated from the aggregate component of roofing shingles. The separated asphalt mastidfiber flakes, called recycled roofing shingle mate-

28 July 1997 C&D Debris Recycling

Pial (RRSM), is designed to be uti- lized in HMA paving mixtures; the aggregate may also be used. Only about 2% of the incoming roofing waste (nails and other metals) ends up in a landfill site. The mixture generally requires an asphalt one grade softer than in a conventional mixture. RRSM is used at a rate of about 2% by weight of the total mix- ture, depending on the viscosity of the virgin asphalt and the specific application. A research program is under way to design paving mixtures containing RRSM.

Processing roofing waste Roofing waste must be shredded to a size that can be processed by the asphalt batch or drum mix plant. The degree of shredding depends on the type of roofing waste and the end use of the reclaimed product. Most engi- neers agree that the finer the roofing is shredded, the more suitable the material is for incorporation into asphalt mixes. Hammermills, shred- ders, and different types of cutting machines have been employed for shredding shingles. For efficient pro- cessing by an asphalt plant, the maxi- mum dimension of the shingle pieces generally should be smaller than X in., and preferably smaller than % in.

Because the aged binder is hard and sometimes even embrittled, con-

sumer waste is normally easier to shred than manufacturing waste. Heat generated during grinding makes the factory waste become sticky and thus interferes with the process. For this reason, most of the recycling companies that have devel- oped equipment for size reduction of waste roofing shingles grind con- sumer waste.

One of the recycling companies contacted grinds consumer waste roofing and screens it over a 4.75 mm and 1 mm sieve. This produces three grades of ground roofing mate- rial: coarse (25 mm to +4.75 mm), intermediate (-4.75 mm to + I mm), and fine (-1 mm). It appears that the intermediate and finer materials could easily be blended into asphalt paving mixtures much like reclaimed asphalt pavement (RAP).

Ideally, roofing waste should be used within no more than a few days after shredding the material. Because of the high asphalt content, stock- piles of roofing waste will consoli- date over time and form clumps that impede handling and effective incor- poration into an asphalt mixture, especially during hot weather. This material must be “delumped” for practical applications.

To alleviate stockpile conglomer- ation, it may be possible to blend the shredded roofing with crusher

e of two forms: (1)

irements stated above.

screenings, sand, or RAP. Ideally, a preplanned, controlled quantity of crusher fines would be added. This blend would need to be included during the mixture design process to determine the optimum quantity to meet grading specifications and pro- duce a quality mix.

Constructing HMA containing roofing waste Based on the data obtained, it appears that quantities of manufac- turing waste of 5% or less in HMA surface mixtures and 10% or less in typical HMA base mixtures are sat- isfactory. However, consumer waste should be limited to 3% in surface mixtures and 6% in base mixtures, and the shingle waste must be very carefully controlled.

During the mixture design process, waste roofing can be handled in a manner essentially the same as handling reclaimed asphalt pavement (RAP). The gradation of the aggregate in the shingles needs to be determined, and a blend of shingle aggregate and the other avail- able conventional aggregate needs to be calculated so that the measure- ments will fall within the mixture specification. Also, the amount and viscosity of asphalt cement in both the shingles and the RAP material, if this material is used in the mixture,

on the plans, stockp decantation of 5% or less when tested in acc 406-A, Part I, or test This requirement which the asphalt h Shredded shingles may tity fine aggregate and aggregate may be nec stockpile shredded manu glomeration of the sticky s

The polish value of the not be used in any determi ification compliance.

Any contractor-owned RA project shall remain the while stockpiled. Any u shall be removed from tion of the project.

C&D Debris Recycling july 1777 29

Roojngparticle recoueredfiom a laboratory test specimen. (Material size in photo is larger than actual size.)

need to be determined for the specifications.

The conventional aggregate used in an HMA material is a combina- tion of coarse and fine particles with a small amount of mineral filler added on occasion. In roofing shin- gles, the aggregate is normally a very fine gradation, generally with 100% of the material passing the 2.36 mm sieve and up to 40% of the aggregate passing the 75 pm sieve. To accom- modate the fine gradation in the shingles, it may be necessary to reduce the amount of fine aggregate normally used in the mixture.

Manufacturing waste shingles generally have a significantly higher viscosity than paving grade asphalt. When blended with regular paving grade asphalt such as AC-20, the resulting binder viscosity will typi- cally be above the specification lim- its. If only 2% or 3% shingles is being incorporated into the mix, it may not be necessary to make any

adjustment to the grade of asphalt cement. However, if 4% to 6% shin- gle scrap is used, it might be neces- sary to use a virgin binder one grade softer than usual (e.g., an AC-10 grade). If 7% to 10% shingles are used, the virgin asphalt might have to be two grades softer than normal (e.g., an AC-5 grade).

Tables 1 and 2 show a typical mixture design using 5% fiberglass roofing shingles, and 5% organic base roofing shingles. As shown in the charts, the mixtures vary slight- ly depending on the type of base material (organic or fiberglass) con- tained in the shingles.

Although the necessary heat is usually available in a batch or drum mix plant to soften and melt the shredded shingles during plant mix- ture production, it normally will be necessary to increase the temperature and mixing time of the new aggre- gate in the mixture during the labo- ratory process to assure that all of the

shingle pieces are melted and prop- erly dispersed in the mix.

The shredded shingle material is typically delivered into the asphalt plant through the RAP cold feed sys- tem. In order to prevent consolidation of the shingles in the bin and bridging of the material over the discharge con- veyor at the bottom of the bin, the shingles should not be packed into the RAP cold feed bin. The front-end loader operator should slowly deposit the shingles into the bin over a long period of time. Manufacturing waste should not be left in the bin for very long, especially not overnight, or the shingles may conglomerate. Con- ~

sumer waste, however, may not pre- sent this problem, due to the harder asphalt in these shingles.

In the plant production process, it is important that when the HMA mixture is discharged from the drum mix or batch plant, no significant quantity of whole shingle particles are present.

30 July 1777 C&D Debris Recycling

Material Sieve Size No. 8 Stone 314” Sand 112” Glass Shingle 318”

No. 4 No. 8

MARSHALL PROPERTIES AT OPTIMUM ASPHALT CONTENT No. 16

1,950.0 No. 30 13.8 No. 50

No. 100 No. 200

149.3

Percent Passing 100.0 99.0 96.0 57.0 39.0 24.0 14.0 9.0 6.0 4.2

Asphalt content, YO

Stability, Ibs Flow, 0.01’’ Unite Weight, Ib/ft3 Voids Analysis, %:

Air Voids Voids Mineral Aggregate Voids Filled

Added Total 5.1 6.0 4.5

‘1 8.9

Sieve Size 314” 112” 318” No. 4 No. 8 No. 16 No. 30 No. 50 No. 100 No. 200 Asphalt content, YO

‘81 .O

Percent Passing 100.0 99.0 96.0 58.0 39.0 23.0 13.0 8.0 5.0 3.5

Added Total 4.5 6.0

ted assuming no asphalt absorption into aggregate

al MIX Utillzlng In

AGGREGATE PROPORTIONS (COLD FEED)

Material No. 8 Stone Sand Organic Shingle

MARSHALL PROPERTIES AT OPTIMUM ASPHAIT CONTENT

Stability, Ibs 11,550.0 13.8 45.5

Flow, 0.01’’ Unite Weight, Ib/ft3 Voids Analysis, %:

Air Voids Voids Mineral Aggregate Voids Filled

1

4.5 19.5 78.0

assuming no asphalt absorption into aggregate \ C&D Debris Recycling July 1997