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SMA
I-83 MD 1999
Completion Date: 1994
Traffic: AADT: 119,000, Trucks: 11%
SMA Premium Surface for High Volume Roadways
SMA
Stone Matrix Asphalt is a coarse/gap gradedrut resistant hot mix asphalt surface layer.
It is composed of a strong aggregate skelton,and a binder mastic composed of a highasphalt cement content, a cellulose or mineralfiber and high percentage of mineral filler.
SMA
SMA
Comparison
SMA - AC
SMA
Aggregate Requirements
Test Property
Specification
Limits
L.A. Abrasion loss % max
30
Flat and Elongated Particles,
% retained on the No. 4 sieve, max
3:1
5:1
20
5
Sodium Sulfate Soundness Loss
5 cycles, T104
15% max
Crushed Aggregate
One fractured face
Two fractured face
100% min.
90% min.
(Same now in AASHTO MP8)
SMA
100
0.075 .3 2.36 4.75 9.5 12.5 19.0
Sieve Size (mm) Raised to 0.45 Power
Initial Aggregate Gradation
SMA19 mm
50
25
75
Sieve Size Percent Passing
19 mm 100
12.5 mm 85 - 95
9.5 mm 75 % maximum
4.75 mm 20 - 28
2.36 mm 16 - 24
600 um 12 - 16
300 um 12 - 15
75 um 8 - 10
Draindown
• 1200 + 200 gms
• 60 + 5 minutes
• Temperatures
– Plant
– and 15 C above
• Criteria - maximum
of 0.30%
AASHTO T 305-97
SMA
SMA Aggregate Gradation
12.5 mm nominal size
Superpave Design Data
N design 100
VTM % 4
VMA % 18.0 min
AC % 6.5 min
Sieve Size mm
Master Band %
19.012.59.54.752.361.180.600.300.075
100.095.070.030.020.0
8.0
(MD DOT 1996)
SMA
US 50 1999
PG 76-22 airblown w/
cellulose fibers
Production Data
Plant Type: Drum
Tonnage: 70,000
AC %: 6.4
VTM %: 3.5
VMA %: 17.1
% passing
4.75 mm: 22
75 um: 9.9
Density %: 95.6
Condition Survey:
General Appearance: Good to excellentRut measurement: 0 mmMinimal tightness in wheelpaths Very smooth ride
Completion Date: 1996
Traffic: AADT: 53,000Trucks: 13%
SMA
AGGREGATE GRADATIONNominal Size: 12.5 mm SMA
& 12.5 mm Superpave
SMA
Superpave
100
0
.075 .3 2.36 4.75 9.5 12.5 19.0
Sieve Size (mm) Raised to 0.45 Power
SMA 12.5 mm
50
25
75
SMA
AASHTO Specifications MP 8-04Standard Specification for Designing SMA
Sieve 12.5 mm
Lower Lower Upper
19.0 mm 100
12.5 mm 90 100
9.5 mm 50 80
4.75 mm 20 35
2.36 mm 16 24
1.18 mm — —
0.60 mm — —
0.30 mm — —
0.075 mm 8.0 11.0
SMA Gradation Specification BandNominal-Maximum Aggregate Size
SMA
AASHTO Specifications MP 8-04Standard Specification for Designing SMA
SMA Mixture Specifications w/SGC
Property Requirement
Voids air % 4.0
VMA % 17.0 min.
Binder Content %
TSR % 70 min.
Drain down at Production Temperature
%
0.30 max.
6.0 min.
SMA
14
What is RAP?• Reclaimed Asphalt Pavement
• Removed and/or reprocessed pavement materials containing: ~ binder (5%)~ aggregates (95%)
SMA
RAP in SMA
• Aggregate Properties– RAP aggregated from high quality pavements
that originally met SMA specifications can be used.
– Gradation control critical to good SMA performance. NCAT studies show RAP variability typically as good or better than virgin aggregate.
SMA
Fractionated vs. Unfractionated
16Source Randy West
SMA
Keep millings from different projects in separate stockpiles.
Milled RAP can typically be used “as is” in HMA without further crushing.
Milled RAP
Source Randy West
SMA
Multiple Source RAP
Small Jobs
also known as GOK piles
God Only Knows what’s in there
Source Randy West
SMA
19
Fractionated RAP
-3/16” RAP+3/4” RAP
3/4 x 3/16” RAPIn back
• Screening RAP into two or more sizes• A huge advantage for mix design. Allows
RAP to be used in practically any mix typeSource Randy West
SMA
Fractionated RAP from GOK stockpile have to be checked very carefully for aggregate properties to assure SMA requirements are met. If region generally has good aggregate this is not a problem
SMA
100
0.075 .3 2.36 4.75 9.5 12.5 19.0
Sieve Size (mm) Raised to 0.45 Power
50
25
75
RAP in SMA
• Use of one stockpile RAP will limit use.– Typically less than 10%
• Fractionated fine RAP can replace fines in SMA mix with higher percentages.– Higher percentages 15% to 20%
• With SMA you must control the gradation.
SMA
22Source Randy West
SMA
SMA and RAP mix design
• Follow standard mix design process for SMA design using RAP mix design procedures.
• RAP should be preheated before adding to mixing bowl.
• Coarse RAP has lower binder content and Fine RAP will have higher binder content.
• Know your fines content.
SMA
Look at best practices to optimize the use of RAP.
SMA
Screening to Remove Oversized RAP Particles
26Source Randy West
SMA
Illinois Tollway
• Reconstruction of the I 90, I 39 section.– 1.4 million vehicles a day– Existing PCC pavement with AC overlay– Reconsrtuction designed to use 100% recycling
of all materials
SMA
Tollway Mainline FRAP Allowances
50%
25%
15%
15%
12-in. “Aggregate Subgrade”
Rich Bottom Base (N50, 2% Air Voids)
Strong Binder (N90, 4% Air Voids)
SMA Binder
SMA Surface
40%Intermediate Binder (N70, 4% Air Voids)
SMA
GTR modified SMA – Warm Mix
SMA
GTR modified SMA – Warm Mix
• GTR SMA -– 310ºF typical mixing temperature – Compactable to 240ºF
• Evotherm modifier• Warm Mix
– Started mixing at 310ºF– Mixed down to 250ºF– Compactable to 190ºF
SMA
Other RAP in SMA Projects
• I 95 Delaware 10% RAP used in SMA surface mix.
• I 270 Maryland 10% RA used in SMA surface mix.
• Georgia and Alabama running experimental mix designs with up to 25% RAP in SMA.
SMA
RAP in SMA
• SMA mixes can be successfully designed with RAP.
• Good plant management practices are needed to achieve high quality product
• SMA with RAP has shown good performance in the field.
SMA
Thanks for you Attention
Questions
