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