Performance Issues of RAS Mixtures in Missouri

transcript

Steve Jackson, PETechnical ManagerNB West Contracting

As seen on shinglerecycling.org

6th Asphalt Shingle Recycling ForumDenver, CO

With Solutions

Missouri’s Use of Reclaimed Materials in Asphalt Pavements2012 - MO AGC/MoDOT Conference

Joe Schroer, PEField Materials EngineerMissouri Department of Transportation

Steve Jackson, PEExcellence EngineerNB West Contracting

Steve Jackson

B.S. of Civil Engineering B.S. of Economics

University of Missouri- Rolla Professional Engineer 23 years in construction 15 years in asphalt

History

First shingle research in 2003 2.5%, 5%, 7.5%, 10%, 15%

First shingle project 2004

First MoDOT shingle project 2005

First MoDOT shingle – WMA project 2009

MoDOT RAS Mix Designs

Most contractors were using RAP & RAS concurrently (2006-2010) 18% RAP and 2% RAS 17% RAP and 3% RAS

Due to the Smooth Road Initiative most work was being done on interstates Superpave mixes Percent Within Limits (Pay Factors)

Tonnage

2005 2006 2007 2008 2009 2010 2011 YTD 2012

20 610

24,000

53,000 54,800

80,700

58,800

RAS in Asphalt Mixtures in Missouri (MoDOT)

RAS Percent Recycle

Industry Questions

Can we eliminate the fibers in SMA (Stone Matrix Asphalt) and replace them with shingles?

Can we use shingles and PG 64-22 asphalt cement in lieu of polymer modified asphalt?

Dynamic Modulus (E*)SMA

1E-06 1E-05 1E-04 1E-03 1E-02 1E-01 1E+00 1E+01 1E+02 1E+03 1E+04 1E+05 1E+0610

PG76-22

PG 64-22 RAS

Reduced Frequency, Hz

SMA with RAS

PG 64-22

PG 76-22

RAS Pooled Fund Study Iowa State, Dr. Chris Williams, P.I. Missouri Lead State

FHWA, MN, IA, IN, CA, CO, IL, WI (IL Tollway)

Binder & Mixture Properties QC/QA Grind Size RAP & FRAP Preconsumer vs. Postconsumer

Demonstration Projects

Ground Shingles

COARSE FINE

Thank You

Ground Shingles - RoadwayCOARSE FINE

1E+02 1E+03 1E+04 1E+05 1E+06 1E+07300

0% RAS 15% RAPPower (0% RAS 15% RAP)5% Fine RAS 10% RAP

Cycles to Failure (Nf)

450525

Fatigue Life(139)

0% RAS 15% RAP

5% Fine RAS 10%

5% Coarse RAS

10% RAP

0100200300400500600700800

Low Temperature Testing

0% RAS15% RAP

5% Fine RAS10% RAP

5% Course RAS10% RAP

0 5 10 15 20 25 30 35 40 45 50

Transverse Cracking, ft/500ft

Pavement Evaluation

Pavement Cracking

At the same time we introduced shingles we also made other changes: Warm Mix Asphalt to eliminate joint

bumps Added an elastic recovery specification

for asphalt binder AASHTO Mechanistic – Empirical Design

▪ AMPT/SPT – Mixture evaluation led to thinner pavements

9.5 mm Superpave mixture laid 1 ¼” thick

Lessons Learned Shingle size is key to success

Overheating shingle mixes to “melt” the shingles (370° - 390° F)

Variability in RAS asphalt content Real and perceived

Inflated specific gravities impact mixes*

SRI – Phase Two

Emphasis shifted from Primary Routes to Secondary Routes

Bituminous Pavements (MoDOT Section 401) in lieu of Superpave (MoDOT Section 403)

Less advanced quality control testing▪ Gradation, deleterious, asphalt content and

density▪ No Percent Within Limits

Work Availability and Recycle Contractor Perspective

Asphalt Cement prices are high Supply of shingles is high Less “Mill & Fill” projects

▪ Less RAP from projects▪ Large amounts of RAP stockpiled

Fiercely competitive market Longer haul distances

Longer Hauls – low volume roads

2011 MoDOT Specifications 401.4.4.1 Base, BP-1 and BP-2 mixtures shall

have the following properties, when tested in accordance with AASHTO T 245. The number of blows with the compaction hammer shall be 35 or the number of gyrations shall be 50 with the gyratory compactor.

Air Voids Stability lb (N) VMA 3.5-4.5 750 (3350) 13.0

MoDOT Bituminous Pavements

Sieve Percent Passing by Weight (Mass)

Base BP-1 BP-21 inch (25.0 mm)

100 100 100¾ inch (19.0 mm)

85-100 100 100½ inch (12.5 mm)

60-90 85-100 95-100No. 4 (4.75 mm)

35-65 50-70 60-90No.8 (2.36 mm)

25-50 30-55 40-70No. 30 (1.18 mm)

10-35 10-30 15-35No. 200 (75 µm)

6-12 5-12 5-12

MoDOT Bituminous Pavements

Sieve Percent Passing by Weight (Mass)

BP-1 BP-21 inch (25.0 mm) 100 100¾ inch (19.0 mm) 100 100½ inch (12.5 mm) 85-100 95-100No. 4 (4.75 mm) 50-70 60-90No.8 (2.36 mm) 30-55 40-70No. 30 (1.18 mm) 10-30 15-35No. 200 (75 µm) 5-12 5-12

MoDOT RAS Specification 2011 403.2.6.2 Reclaimed Asphalt Shingles. Reclaimed

Asphalt Shingles (RAS) may be used in any mixture specified to use PG 64-22 in accordance with AASHTO PP 53 except as follows: When the ratio of virgin effective binder to total binder in the mixture is between 60 and 70 percent, the grade of the virgin binder shall be PG 52-28 or PG 58-28.

Shingles shall be ground to 3/8-inch minus.

Mix Designs and the Market Higher percentages of recycled materials Less virgin binder in the mixes

Dryer looking mixes Rut resistant roadways Fatigue cracks earlier?

Is there a limit on recycled materials? Contractors attempted to run up to 12% RAS Not the mix Ron Sines spoke about yesterday

2012 MoDOT 401 Specifications Changed design air voids to 3.5% Increased VMA requirements:

Bit Base 13.0% BP-1 13.5% BP-2 14.0% (Surface Leveling)

50 gyration mix design was eliminated and replaced with a 35 gyration mix design Requires a higher asphalt content

What happened?

Corelok specific gravities were used in lieu of traditional AASHTO T 84/T 85

Gse values were variable 2.450 to 2.800 Could be impacted by reported asphalt content

No significant change in virgin binder content in some areas, but some higher quality aggregates were used

Gse Calculation

Pb = Percent binder in the shingles Gmm = Rice value of the shingles Gb = Specific gravity of the shingle binder Gse is used as the Gsb during mix design

Gse Calculation

Higher RAS asphalt content the higher the specific gravity Higher specific gravity makes it easier to meet the VMA requirements however it allows for lower asphalt content

Volumetric Properties of High RAP Mixtures Based on Calculated Bulk Specific Gravities of RAP and Constituent Aggregates

Nassim SabahferMustaque Hossain, Ph.D.,P.E.

Department of Civil EngineeringKansas State University

VMA Obtained Using Gsb from Different Methods (Shilling RAP)

20% RAP 30% RAP 40% RAP 30% FRAP 40% FRAP0

1614.1 14 14.2 14.1 14.3

12.611.8

11.311.9 11.412.5

11.511

11.711.112.4

11.4 10.811.5 10.9

GseGsb (Ignition)Gsb (Extract)RAP Gmm

VMA (%)

KDOT Require-ment

Effective Binder

403.2.6.2 Reclaimed Asphalt Shingles. Reclaimed Asphalt Shingles (RAS) may be used in any mixture specified to use PG 64-22 in accordance with AASHTO PP 53 except as follows: When the ratio of virgin effective binder to total binder in the mixture is between 60 and 70 percent, the grade of the virgin binder shall be PG 52-28 or PG 58-28.

Gse Calculation

Lower RAS asphalt content the lower the effective binder replacement Allows more shingles to be used in the mix

Effective Binder calculation

Contribution of Binder from Recycled Materials

Effective Binder ComputationPb 5.70 Gmm 2.434 Gse 2.653Pbmv 4.50 Gb 1.030 Pba 1.52

Gsb 2.547 Pbe 4.18

Stockpile Type Ps Pbr Psr x Pbr Psmv Psmr Pbmr

1 virgin 80 76.412 RAS 2 25 0.50 1.43 0.473 RAP 18 4.3 0.77 16.45 0.7345678

100 94.29

Pbe 4.18

Pbev 2.98

Psmv 76.41

Psr x Pbr 1.27

Psmr 17.88

Pbmr 1.20R 71

Effective Binder calculation

Contribution of Binder from Recycled Materials

Effective Binder ComputationPb 6.37 Gmm 2.434 Gse 2.683Pbmv 4.50 Gb 1.030 Pba 1.92

Gsb 2.547 Pbe 4.45

Stockpile Type Ps Pbr Psr x Pbr Psmv Psmr Pbmr

1 virgin 92 87.902 RAS 8 25 2.00 5.73 1.873 RAP 0 4.3 0.00 0.00 0.0045678

100 93.63

Pbe 4.45

Pbev 2.58

Psmv 87.9

Psr x Pbr 2.00

Psmr 5.73

Pbmr 1.87R 58

Problems with RAS Mixtures Sporadic Mixing Problems

Confined to Plants not Mixture Harder to Place in Cool Weather Low Voids on Long Haul Tenderness Asphalt Foamers Run at HMA Temps. Shingle Pancakes – Clumps, Wads,

Clinkers

Not Acceptable

MoDOT Response

No shingles were permitted to be used in the surface leveling mixtures for the May and June contracts.

Not very many contracts - 2

Did not impact Superpave or other low volume route mix designs

Industry Action

Contractors got together in a morning session, worked together to provide recommended specification changes.

Met with MoDOT representatives after lunch and discussed the recommendations.

Adopted as a job special provision for the next bid letting.

2013 Job Special Provision - SL Set Gsb of RAS at 2.600

Changed the gradation of the Surface Leveling mix design: 90-100% passing the 3/8” sieve.

Set Gsb of RAP at the Gsb of the virgin aggregates*

VMA minimum: 14.5%

Effective Binder Mixtures containing a combination of RAS

and RAP may have a 30 to 40 percent effective virgin replacement under the following conditions: (1) with a virgin binder grade change from a PG64-22 to a PG 58-28 or (2) with a combination of a PG64-22 binder and a rejuvenator provided testing demonstrates that a PG58-28 , meeting the requirements of AASHTO M320, is achieved.

How NB West is Successful

Coffee Grounds not Corn Flakes

Education

Warm Mix Asphalt

Compaction Aid

Surfactant

Anti-Strip

Metallica

56th ANNUAL ASPHALT CONFERENCE

December 3-4, 2013

Havener Center, Campus of Missouri S&TRolla, MO

asphalt.mst.edu

Questions?

sjackson@nbwest.com

www.nbwest.com

@sjackson_nbwest

Steve Jackson

Performance Issues of RAS Mixtures in Missouri

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