AAPA training Sprayed Seal Selection
AAPA training
Sprayed Seal Selection
Importance of Sprayed Seals • Extensive Network • Majority is relatively thin unbound granular
pavements in rural area • Need to maintain sealed network to ensure
sustainability of network • Covers a large range of climatic conditions
and traffic (AADT <100 to 40,000)
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Australian Asphalt Pavement Associa4on 3
4. Distribution of surface types (TMR)
7.0%
0.3%
92.7%
AsphaltConcreteSprayed seal
~33,000 km of State controlled roads
Rural freeway – AADT 20,000 (2005)
Granular pavement with prime & seal
Rural road - AADT < 100 10mm seal 14 yr. old
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Approved document for Seal
Selection & Design
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Sec. 2006 Update (AP-T68/06) 1 Introduction (11 pages)
2 SS seals ≥ 10mm
3 SS seals ≤ 7mm
4 SS seals with PMB
5 SS seals with Emulsion
6 DD seals
7 DD seals with PMB
8 DD seals with Emulsion
9 Geotextile Reinforced Seals (GRS)
10 Fibre Reinforced Seals (FRS)
11 Selection of Treatment Types
12 Priming & Primersealing
Refs 44 articles
Apps A. Worked examples B. Austroads Vehicle Classification C. Tables & Design Factors
• Prime • Primerseal • Seal
– single/single (1 coat) – double/double (2 coat)
• HSS, SAM and SAMI • GRS
Selection of Treatments
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• AIM – achieve and maintain a strong bond with the
surface – deal with surface dust – reduce risk of early failure – provide time between construction & sealing
• Prime all new pavements • Best in warm, dry conditions
Prime
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Prime
Types of Primer:
• cutback bitumen (AMC00 – AMC1)
• special bitumen emulsion primer
No aggregate: must close road to traffic until primer has dried
Design: based on experience with some guidelines available
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Prime 11
APPLICATION • Any time of the year
– greater application during winter months – conditions not suitable for priming
• Design Traffic > 250 - 300 v/l/d • Temporary seal (diversion) • Hold sections on large jobs • Time to rectify pavement weaknesses • Very porous pavements
Primerseal
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Primerseal
Aggregate – 5/7/10mm
Primerbinder
Typical life: 1 to 2 years Aggregate: 5/7mm for light traffic and/or soft pavement base
10mm for higher traffic and/or strong pavement base
Design: based on traffic & aggregate size
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Selec4on of primerbinder
Primer binder Grade Use
Bitumen emulsion
CRS 60 & 70%
Special
formulations with SBR
v All year v Care on cement stabilised pavements v When p/seal is to be sealed within 3
months, OR overlaid with asphalt within a few weeks
Cutback bitumen
Medium AMC4
Cooler conditions (autumn – winter)
Heavy AMC5
Warm – hot conditions (spring – summer)
NOTE: cutback bitumen p/seal MUST be left for minimum of 3 months of HOT weather before applying final seal/asphalt
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Prime & seal v Primerseal Type Advantages Disadvantages
Prime & seal
• More economic • Reduces absorption • More waterproof • Strong bond • Protects Pavement • Cope with non-uniform
surface
• Pavement dry • Warm/dry weather • Two stage process • Primer must dry/cure • Road closed • More easily damaged by rain
Primerseal • Applied to damp pavement • Single process • Less traffic delay • Immediate use • Repair pavement prior to
final seal
• Requires final seal • Cutback must be allowed to cure – 3 to 12 months • Soft pavement surface will result in embedment • Rain can cause: - binder emulsification - loss of aggregate
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• Seals can be applied over: – a prime – a primerseal – an existing seal, asphalt, slurry
• Initial Treatment – a prime and seal – a primerseal followed by a final seal – a light seal followed by a final seal
• Retreatment – reseal
Sprayed Seals
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USES • waterproof the pavement surface • provide required surface properties
( texture, skid resistance) • delineate for traffic guidance • provide an aesthetic treatment • improve night visibility
Sprayed Seals
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Typical Sprayed Seals Single/single
(1 coat)
Double/double (2 coat)
Most common type of seal Binder: C170 bitumen Aggregate: 7/10/14mm
More robust seal than S/S 1st seal = larger aggregate 2nd seal = smaller aggregate Typical: 10/5, 14/7, 20/7 and 20/10mm
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Weak or cracked base
Strain alleviating membrane binder
Seal aggregate
Cracks
Weak or cracked base
Binder
Aggregate
Asphalt
Typical Sprayed Seals
SAM (Strain Alleviating Membrane)
Performance of sprayed seals may be improved by using PMB binders in HSS, SAM and SAMI applica4ons
Treat cracked pavements Binder: medium modified PMB Aggregate: mainly 10 & 14mm
SAMI (Strain Alleviating Membrane Interlayer)
Treat cracked pavements & concrete bridge decks prior to AC overlay Binder: highly modified PMB Aggregate: mainly 10 & 14mm
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SAM after 1.5 years Before treatment
Typical Sprayed Seals
GRS (Geotextile Reinforced Seal)
Inverted Seal
Initial seal on very poor pavement materials Alternative to SAM and SAMI applications, generally using C170 binder & 14/7 D/D seal
To treat exis4ng non-‐uniform surfaces and as ini4al treatment on soO pavements Binder: C170 Aggregates – 7mm for 1st and 10 or 14mm for 2nd seal
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Typical Sprayed Seals
Dry ma0ng
A repair treatment for a stripped seal, or sealing over “faSy” areas Binder: C170 or PMB Aggregate: as required 7/10/14mm
Cape Seal
Treatment developed in South Africa as ini4al treatment/retreatment – can deal with high stress Generally 20mm seal overlaid with a slurry
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Extensively cracked and fatigued granular pavement
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Applying a GRS 1 tack coat 2 geotextile 3 binder 4 aggregate (1st layer of D/D seal)
1 2
3 4
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• Size of aggregate chosen should – relate to the conditions – be the best compromise for the various conditions – don’t automatically choose the largest aggregate
• Other factors to consider: • life expected from the treatment / pavement • nature of the pavement material • pavement surface condition (hard/soft) • aggregate type/availability • existing surface texture • uniformity of existing surface • nature of the terrain (straight/winding) • urban or rural • specific surfacing properties (noise/texture/skid resistance)
Selecting Aggregate Size
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Guide to aggregate size selec9on Ini9al treatments
Very light to light traffic<300 v/l/d
Maximum size 10
Light to medium traffic300 – 1200 v/l/d
Prefer size 10Maximum size 14
Medium to heavy trafficover 1200 v/l/d
Minimum size 10Normally size 14
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Treating Porous Pavements For expected high binder absorption, alternative initial
treatments are:
1. Apply a primerseal, size 5/7 aggregate, followed by a final seal (10/14mm) next season
2. Apply 5 or 7mm initial treatment prime and seal, using a high binder rate of application + reseal with a larger aggregate 2–3 years later
3. Use a polymer modified binder
Sprayed Seals
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Performance environment
Traffic volume (v/l/d)
> 2000 ≤ 2000
Heavy Vehicles Heavy Vehicles
> 15% ≤ 15% > 15% ≤ 15%
High stress areas
No suitable sprayed seal (asphalt)
S/S + scatter coat D/D + mod2
Cape seal or D/D + mod2
D/D or S/S + mod3
Grades > 5% D/D + mod3 D/D or S/S + mod3 D/D or S/S + mod3 S/S or D/D
Pavt. Strength
Stiff HSS S/S HSS S/S
Weak SAM (D/D only) HSS SAM (S/S) + mod3 HSS
Climate
Hot D/D + mod2 S/S + mod2 D/D or S/S + multi S/S + multi
Temp D/D S/S D/D or S/S S/S
Cold D/D + mod1 D/D or S/S + mod1 D/D S/S
Guide to seal selection (Table 11.1)
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S/S Single/single, C170/320 or multigrade binder Climate: Weighted mean annual pavement temp. (WMAPT)
Hot: > 35˚C e.g. Ayr, Cairns, Townsville, Mt Isa
Temperate: 29˚C < WMAPT ≤ 35˚C e.g. Rockhampton, Roma, Mackay, Gympie, Brisbane
Cold: ≤ 29˚C e.g. Warwick, Kingaroy, Toowoomba
D/D Double/double, C170 or 320 or multigrade binder
Cape Seal Single/single seal filled in with a slurry
HSS High Stress Seal is a S/S or D/D, with 7, 10 or 14 mm aggregate, medium/high concentration PMB, multigrade binder C600/170
Scatter coat Light application of small aggregate, 7 or 5 mm, to temporarily 'lock in' a larger aggregate. Suitable for intersections, driveways, turning slots
Pavement strength Stiff:
Rebound deflections < 0.9 mm Deflection ratio > 0.8 - rigid or bound
0.6 to 0.7 - stiff unbound Residual deflections < 0.15 mm
Weak:
Rebound deflections > 0.9 mm Deflection ratio < 0.6 (potentially weak
pavement) Residual deflections > 0.15 mm
Mod 1 Lightly modified PMB, S10E, S35E, 10% crumb rubber
Mod 2 Multigrade or lightly modified PMB, S10E, S35E, 10% crumb rubber
Mod 3 Higher grade PMB, S20E, S45R Applications also include small radii roundabouts, intersections, cul-de-sacs, turning lanes, etc.
Multi Multigrade binder Class 600/170