Fog Seals, Sand Seals, Scrub Seals, and Rejuvenators

Learning Outcomes

1. List benefits of fog seals, scrub seals, sand seals, and rejuvenators

2. Describe recommended materials

3. Describe recommended construction procedures

4. List key quality control activities

Learning Outcomes (cont.)

5. Describe potential construction and performance problems

6. Identify troubleshooting solutions

Description

Spray application of asphalt emulsionTreatment differences

– Emulsion type– Use of aggregate – Method of embedment

Application rate, timing, and construction quality are critical

Benefits

Slowed aging processWaterproofed surfacePrevention of stone lossIncreased surface frictionBetter surface appearance

[Nitrogen Bases]

[Paraffins]

Asphalt Components

What is an emulsion?

Mixture of asphalt binder, water, and emulsifying agent

50 to 75% of mix is asphalt“Breaking”—separation of water

and asphalt“Curing”—development of asphalt

mechanical properties

EmulsionIngredients

Asphalt– Slow setting: up to 43% water– Rapid setting: up to 35% water

Water: Impurities can be harmfulEmulsifying agent (surfactant)

EmulsionClassification

Electrical chargeSpeed of break: slow (SS), medium

(MS), and rapid set (RS)Asphalt relative viscosity: hard (h) or

soft (s)Polymer-modified asphalt (P or L)

CRS - 2

cationic

CSS - 1h hard asphalt

HFMS - 2s

65% asphalt

with solvent

EmulsionClassification Names

cationic

high-float

medium-setting(anionic)

slow-setting

rapid-setting

high viscosity(65% asphalt)

57% asphalt

EmulsionType

SlowSetting

MediumSetting

RapidSetting

Anionic SS-1SS-1h

MS-1MS-2MS-2h

HFMS-1HFMS-2

HFMS-2hHFMS-2s

RS-1RS-2

HFRS-2

Cationic CSS-1CSS-1h

CMS-2CMS-2h

CRS-1CRS-2

EmulsionClassification

EmulsionDistribution of Asphalt Particles

0.0037 mm (0.000145 in)

EmulsionTerminology

Original emulsion—asphalt, water, and emulsifying agent

Diluted emulsion—original emulsion diluted by additional water

Residual asphalt content—amount of asphalt left after water has evaporated

Aggregate

Applied to sand and scrub sealsClean material, smaller than 2 mm

(0.08 in)

Fog Seals

Fog SealsDescription

Light application of diluted slow-setting asphalt emulsion

Common uses– Seal aged surface– Improve lane delineation

Cost: 0.15 to 0.20 $/m2 (0.12 to 0.17 $/yd2)

Typical treatment life: 1 to 2 years

Fog SealsApplication Considerations

Seal must penetrate surface voidsEnvironment affects both break

and future performanceAllowing traffic before break is

hazardous!

Fog SealsSuitable Surfaces

Heavily aged, dense-graded HMA

Open-graded HMA

Dense-graded HMAwith closed surfaceDense-graded HMAwith closed surface

Fog SealsUnsuitable Surface

Fog SealsBefore and After

Fog seal over existing chip seal

Fog Seal Construction

1. Surface preparation

2. Material preparation

3. Emulsion application

4. Sand blotter and sweeping (if necessary)

Fog Seal ConstructionConfirmation of Site Conditions

Consideration of site conditions is essential to proper curing

Little or no chance of rainTemperature conditions

– Air: 5 °C (40 °F)– Pavement: 15 °C (60 °F)

Fog Seal ConstructionPavement Surface Preparation

Fog Seal ConstructionMaterials Preparation

Slow setting emulsion recommended

Check compatibility of water used to dilute the emulsion

Dilute emulsion no more than 24 hours before application

Fog Seal ConstructionEmulsion Application

Fog Seal ConstructionEmulsion Application—Distributor Calibration

Pre-constructionPump rateApplication rateCoverage test

Fog Seal ConstructionEmulsion Application

Application rate: 0.45 to 0.70 l/m2 (0.10 to 0.15 gal/yd2)

Spray temperature range: 20 to 70 °C (70 to 160 °F)

Spray Bar and Nozzles

Single Overlap

Fog Seal ConstructionAsphalt Distributor—Spray Bar Height

hh

Roadway SurfaceDouble Overlap

Roadway SurfaceTriple Overlap

Roadway Surface

h

15o 45o 90o

TravelDirection

Lateral Coverage

Fog Seal ConstructionAsphalt Distributor—Spray Nozzles

Fog Seal ConstructionPost Treatment Procedures

Sand blotter and sweeping (if necessary)

Pavement should NOT be opened to traffic until adequate friction is restored

Sand SealsDescription

Spray emulsion followed by a light covering of sand

Improves friction“Locks” a chip sealCost: 0.40 to 0.80 $/m2

(0.33 to 0.66 $/yd2)Typical treatment life: 3 to 6 years

Sand SealsApplication Considerations

Low-speed, lower volume roadsTypically 2 to 5 mm (0.1 to 0.2 in)

thickNot as good a delineator as fog

seal

Sand Seal Construction

1. Surface preparation

2. Material preparation

3. Emulsion application

4. Sand application

5. Rolling

Sand Seal ConstructionEmulsion Application

Rapid setting typical, no dilutionApplication rate: 0.70 to 1.25 l/m2

(0.15 to 0.28 gal/yd2)Spray temperature range:

RS-1 20 to 60 °C (70 to 140 °F)

MS-1, HFMS-1 20 to 70 °C (70 to 160 °F)

RS-2, HFRS-2,

CRS-1, CRS-2

50 to 85 °C (125 to 185 °F)

Sand Seal ConstructionApplication of Sand

Clean, typically < 2 mm (0.08 in)Application rate: 5.5 to 12 kg/m2

(10 to 22 lb/yd2)Surface temperature: >15 °C (60 °F)Sand applied with a spreader

immediately after spray emulsion

Sand Seal ConstructionPost Treatment Procedures

Embedment with pneumatic-tired rollers

Open to traffic: ~ 2 hours

Scrub Seals

Scrub SealsDescription

Spray applied emulsion, drag-broomed, lightly sanded, drag-broomed again, and rolled

Fills surface voids and cracksCost: 0.60 to 1.00 $/m2

(0.50 to 0.83 $/yd2)Typical treatment life: 3 to 6 years

Scrub SealsApplication Considerations

Low to moderate volume roadwaysBrushing works emulsion into

pavement surfaceCan be applied in multiple layersThickness from 10 to 40 mm

(0.4 to 1.5 in)

Scrub Seal Construction

1. Surface and material preparation

2. Emulsion application

3. Initial drag-brooming of surface

4. Sand application

5. Second drag-brooming of surface

6. Rolling

Scrub Seal ConstructionEmulsion Application

Polymer-modified emulsionApplication rate: 0.63 to 0.82 l/m2

(0.14 to 0.18 gal/yd2)Emulsion temperature: 44 to 71°C

(110 to 160 °F)Pavement temperature: 21 to 32 °C

(70 to 90 °F)

Scrub Seal ConstructionInitial Drag-Brooming of Surface

Scrub Seal ConstructionSand Application

Application rate: 6.5 to 8.1 kg/m2 (12 to 15 lb/yd2)

Minimum of two roller passes

Scrub Seal ConstructionSecond Drag-Brooming and Rolling

Rejuvenators

Emulsions that include asphalt, polymer latex, and other additives

Softens existing binderTrade names:

– Reclamite– PASS– Topien C

Rejuvenator Application

Rejuvenator ApplicationApplication of Sand

Fog Seals, Sand Seals, Scrub Seals, and Rejuvenators

QUESTIONS?