7/25/2019 Recycled Asphalt Shingles (RAS)

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With precise quality control & assurance, RAS that

meets specifications can be produced for use in HMA.

Due to the aging of asphalt and the reinforcing effects

of the fibres and fillers in RAS, adding it to HMA results

in a stiffer mix that has increased rutting resistance.

However, the stiffening effects may also lead to large

thermal stresses in cold climates, resulting in thermal

cracking (though asphalt rejuvenators can be used to

soften the blended binder).

A safe portion of RAS that can be used in HMA in cold

climates is 3% to avoid over-stiffening.

Incorporating RAS in HMA is economically and

environmentally beneficial.

CONCLUSIONS

PAVEMENT REHABILITATION:

Recycled Asphalt Shingles (RAS) in Hot Mix Asphalt OverlaysPresented by: John Catigay, Dustin Chase, Marc Tablan

Two waste sources for RAS:

1. Tear-off (a.k.a. post-consumer shingles)

2. Manufactured waste

Shingles are made with either:

Organic felt (wood product; usually paper)

or

Fibreglass mat

BACKGROUND

Due to the useful materials making up asphalt roofing

shingles, recycled asphalt shingles (RAS) can be used in place of

some portion of virgin materials in conventional hot mix asphalt

(HMA) design.

This project discusses the economic, environmental, and

performance outcomes of incorporating RASinto HMA

overlays.

OBJECTIVES

Source: Best Practice for using RAS in HMA (FHWA/TxDOT)

TYPICAL COMPONENTS OF ASPHALT SHINGLES

ORGANIC

SHINGLES

FIBREGLASS

SHINGLES

Component% content by

weight

% content

by weight

Adhesives

(modified asphalt-based)0.22 0.22

Reinforcing Mat 215 215

Mineral Filler/Stabilizer 840 840

Mineral

Granules/Aggregates2038 2038

Asphalt Cement (AC) 3036 1922

Source:

Best Practice

for using RAS in HMA

(FHWA/TxDOT)

Source: Performance of Recycled Asphalt Shingles

in Hot Mix Asphalt

(Iowa State University)

PERFORMANCE

Debris separation

at waste source

Haulingfrom source torecycling site

Separation

of nails, felt, etc

Asbestos

testing

Grindingto specified

size

Screeningtospecifications

and for uniformity

Storingunder cover to

minimize absorption

Loading anduse into

HMA

Tipping at recycling site Asbestos testing Grinding Screening Storing

An average cost of $300/tonne for traditional asphalt

mixes and a upper cost of $60/tonne for processed RAS is

used to conduct a cost analysis:

Life cycle costs are currently unavailable, however due

to the increased performance in RAS mixes, it can be

assumed that mixes containing RAS are more

economical than traditional mixes.

ECONOMIC EVALUATION

Manitoba generates approximately 45,000 tonnes of

waste asphalt shingles per year.

Asphalt shingles are a non-biodegradable construction

waste that are a constant greenhouse gas load at

landfill sites.

It is cheaper and 'greener' to unload asphalt shingles at

an asphalt shingle recycling depot than unloading at a

landfill ($30/tonne as opposed to $61/tonne).

Two barrels of virgin binder is saved for every tonne of

RAS used, reducing production costs associated with

asphalt pavements.

SUSTAINABILITY

Performance Grade (PG)

Performance grade increased for high temperature with

the addition of RAS while decreasing its grade in lower

temperature.

Material

Identification

High PG

Temperature,oC

Low PG

Temperature,oC

Performance

Grade

Virgin

PG 58-2861.1 -28.2 58-28

RAS 124.1 - -

0% RAS 73.0 -19.7 72-16

4% RAS 75.8 -16.8 72-16

5% RAS 81.1 -16.8 76-16

6% RAS 86.1 -14.7 86-10

Dynamic Modulus

Addition of RAS in higher

temperature increased the

overall stiffness of the mixture.

Mixtures with RAS resulted in a

higher dynamic modulus than the

mixture with 0% RAS.

Flow Number

Mixture with 0% RAS is more

vulnerable to permanent

deformation.

Flow Number increased with

each addition of percentage of

RAS which suggest higher

resistance to permanent

deformation than the mixture

with no RAS added.

Transverse Cracking

Mixture with the highest fracture

energy showed the least amount

of cracking in the field.

1-kilometre,

two-lane,

undivided highway

without shoulders

75mm HMA Overlay 0 % RAS $ 427,500 per km

75mm HMA Overlay 3 % RAS $ 417,240 per km

PROCESSING OF RECYCLED ASPHALT SHINGLES