Chapter 8 Slurry Seals - California Department Of Transportation

Chapter 8Slurry SealsFrom Maintenance TechnicalAdvisory Guide (MTAG)

Managers’ OverviewFrom Maintenance TechnicalAdvisory Guide (MTAG)

Slurry Seals What are slurry seals?Why use slurry seals?Where to use slurry seals?When to use slurry seals?Chapter 8 – Slurry Seals

What is Slurry Seal? A thin maintenance treatmentA mixture of: asphalt emulsiongraded aggregatesmineral fillerwaterAdditivesCURED FRESHWhen placed on the pavement surface themixture breaks and cures creating a newwearing surface.Chapter 8 – Slurry Seals

Why Use Slurry Seals? Cost EffectiveBenefits: Average performance life: 3 to 5 years minimize oxidation/ageing reduce water infiltration provide skid resistance improve aesthetics correct raveling and weatheringChapter 8 – Slurry Seals

Where to Use? Hot Mix AsphaltPavements: Roadways (All traffic levels)Parking LotsTaxiways and RunwaysBridges and Over-CrossingsGeographicRegions/Climate Zones: All throughout CaliforniaCape Seal (Slurry over Chip Seal)Chapter 8 – Slurry Seals

When to Use? To correct/improve: To prevent/reduce: raveling and weathering loss of frictional properties aesthetics ageing/oxidation of asphalt concrete surface water infiltration pavement degradation due to the elementsChapter 8 – Slurry Seals

When NOT to Use? On pavements withstructural defects: Alligator Cracking Rutting Bumps and Depressions Potholes Nighttime constructionChapter 8 – Slurry Seals

Slurry Seal Vs. MicrosurfacingDifferences in:MICROSURFACING SLURRY SEALAsphalt Emulsionalways polymermodified, quick setcould be polymermodifiedAggregateQuality/Gradationstricter spec. forsand equivalent;use only Type IIand Type IIICan use Type I, IIor IIIAdditives/Breakchemical breaklargelyindependent ofweather conditionsbreaking andcuring dependenton weatherconditionsChapter 8 – Slurry Seals

Slurry Seal Vs. MicrosurfacingDifferences in:MICROSURFACINGSLURRY SEALMix Stiffness/Equipmentstiffer mix, useaugers in thespreader box andsecondary strike-offsofter mix, use dragboxApplicationssame as slurry seal rut filling, nightwork, correction ofminor surface profileirregularitiescorrect raveling, sealoxidized pavements,restore skidresistanceChapter 8 – Slurry Seals

Module 8-1Design, Materials &SpecificationsFrom Maintenance TechnicalAdvisory Guide (MTAG)

Slurry Seal Design Design ProcessSpecificationMaterialsLaboratory TestsChapter 8 – Slurry Seals

Mix Design Process Select/TestMaterialsDesign/TestTrial Mixes RecommendMix Design Pre-screen materialsCheck materials compatibilityTry different mixingproportionsPrepare mixes at a range ofemulsion contentsCheck for cohesion build-upCheck for abrasion resistanceCheck for sand adhesionSelect optimum emulsioncontentTest proposed mix to meetspecification requirementsChapter 8 – Slurry Seals

Specification Caltrans 2006 Standard Specifications, Section 37-2 SlurrySealhttp://www.dot.ca.gov/hq/esc/oe/specs html/2006 specs.htmlInternational Slurry Surfacing Association(ISSA): A105 (2005) Recommended Performance Guidelinesfor Emulsified Asphalt Slurry Sealhttp://www.slurry.org/downloads/A105.pdf ASTM: ASTM D 3910-98(2004) Standard Practices forDesign, Testing, and Construction of Slurry Sealhttp://www.astm.orgChapter 8 – Slurry Seals

Materials Asphalt EmulsionAggregateMineral FillerWaterAdditivesChapter 8 – Slurry Seals

Asphalt Emulsion Type/Grade Anionic/Quick Set (QS-1h)Cationic/Quick Set (CQS-1h)Specification CALTRANS 2006 Standard Specifications Section 94Notes Could be polymer-modified, CALTRANS standardspecification for PMCQS not available at this timeChapter 8 – Slurry Seals

Asphalt Emulsion - TestsTypicalSpecification(CQS1h)MethodViscosity, SSF @ 50 C, sec15 – 90AASHTO T 59Sieve Test, % 0.30AASHTO T 59Settlement, 5 days, % 5ASTM D 244Storage Stability, 1 day, % 1AASHTO T 59Residue by Distillation, % 57California Test 331Tests on EmulsionParticle ChargePositiveTests on Residue from DistillationTestPenetration, 25 CDuctility, 25 C, mmSolubility in trichloroethylene, %TypicalSpecificationMethod40 – 90AASHTO T 49 400AASHTO T 51 97AASHTO T 44Chapter 8 – Slurry Seals

Aggregate - GradationsSieveType IType IIType III3/8 in (9.5mm)-100100No. 4 (4.75 mm)10094-10070-90No. 8 (2.36 mm)90-10065-9045-70No. 16 (1.18 mm)60-9040-7028-50No. 30 (600-µm)40-6525-5019-34No. 200 (75-µm)10-205-155-15Chapter 8 – Slurry Seals

Slurry Surfacing Systems Aggregate GradationsPercent Passing10090Type I MinType I Max80Type II MinType II MaxType III MinType III Max7060504030201001010.1Sieve Size (mm)Chapter 8 – Slurry Seals0.01

Aggregate - QualityTestType IType IIType IIISand Equivalent (min)455560CT 217Durability Index (min)555555CT 229 Other aspects of interest: GeologyShapeTextureAge and ReactivityCleanlinessChapter 8 – Slurry SealsTest Method

Mineral Filler Portland cement, hydrated lime,limestone dust, fly ash or other approvedfiller meeting the requirements of ASTMD242Considered part of the dry aggregateMixing aid, improves cohesion, absorbswater from the emulsion causing it tobreak faster after placementChapter 8 – Slurry Seals

Water Water should be of such quality that theasphalt will not separate from theemulsion before the slurry seal is placedChapter 8 – Slurry Seals

Additives Emulsifier solutions, aluminum sulfate,aluminum chloride, boraxGenerally act as retardants, useful whentemperatures rise during the dayChapter 8 – Slurry Seals

Mixing Properties ISSA TB 102 (Mixing Test) Determine approximate proportions of componentmaterials by trying different “recipes”The amount of time the slurry can be mixed and retain itshomogenous consistency is recorded (mixing time)Foaming and coating are visually assessedThe test can be performed at expected field humidity andtemperature conditionsSelect the proportions that results in mixing times over180 seconds and good coating over the range ofhumidity and temperature condition expected atplacementChapter 8 – Slurry Seals

Cohesion Build-Up ISSA TB 139 (Modified Cohesion Test)Fabricate 3 test specimens:1.2.3.At selected emulsion content-2% emulsion content 2% emulsion contentDetermine the build-up of cohesion with timeDifferentiate between “Quick Set” and “SlowSet”; “Quick Traffic” and “Slow Traffic” mixesChapter 8 – Slurry Seals

Cohesion Build-UpChapter 8 – Slurry Seals

Abrasion Loss ISSA TB 100 (Wet Track Abrasion Test) Fabricate 3 test specimens: 1.2.3.At selected emulsion content-2% emulsion content 2% emulsion contentCure specimens for 16 hrs, than soak for 1 hrDetermine abrasion loss under waterPlot abrasion loss versus emulsion contentChapter 8 – Slurry Seals

Sand Adhesion Fabricate 3 test specimens:1.2.3. At selected emulsion content-2% emulsion content 2% emulsion contentISSA TB 109 (Loaded Wheel Test)Measure increase in weight of the specimen due tosand adhesionPlot sand adhesion versus emulsion contentChapter 8 – Slurry Seals

Sand Adhesion (g/ft2)Abrasion Loss (g/ft2)Emulsion Content SelectionMaxLoss/Adhesion (75g/ft2)Allowable EmulsionContent RangeEmulsion Content (%)Chapter 8 – Slurry Seals

CALTRANS nsistencyISSA TB 106 1.2 in.Wet StrippingISSA TB 114PassCompatibilityISSA TB 115PassCohesion, 1 hr.ISSA TB 139 200 kg-mmWet TrackAbrasion LossISSA TB 100 800 g/m2Chapter 8 – Slurry Seals

Final Notes Design is generally performed by outsidelaboratory, Caltrans will only review andacceptDesigner needs to have extensiveexperience with slurry systemsChapter 8 – Slurry Seals

Module 8-2Construction and InspectionFrom Maintenance TechnicalAdvisory Guide (MTAG)

Slurry Seal Construction Project SelectionApplicationsSafety and Traffic ControlEquipmentConstructionQuality ControlTroubleshootingField ConsiderationsChapter 8 – Slurry Seals

Project Selection A pavement preservation treatment: protect thepavement before distresses appearCan correct: raveling, oxidized pavement,friction lossCannot correct: rutting, cracking, base failures,any structural deficienciesWhen applied correctly, it may increasepavement life by 3 – 5 yearsChapter 8 – Slurry Seals

Distress ConditionsPavement DistressSurface crackingEarly longitudinalHairlineSlurry*Micro*XXXXFull depth crackingThermal or TransverseFatigue or AlligatorBlockReflectiveLate longitudinalSlippage (tack failure)--Corrugation or Shoving (wash boarding)-XChapter 8 – Slurry Seals

Distress Conditions (cont.)Pavement DistressRuttingSound baseUnsound baseSlurry*Micro*-X-RavelingXXBleeding-XPolishing (loss of skid resistance)XXPatched potholePavement patch onlyBase repaired patchXXLoss of profile (crown, edge, etc.)-XChapter 8 – Slurry Seals

ApplicationsApplicationAggregateType IAggregateType IIVoid Filling Wearing CourseAADT 100 Wearing CourseAADT 1,000 AggregateType III Wearing CourseAADT 20,000 Minor Shape Correction0.4 – 0.8 inch (10 – 20 mm) Application Rates in lbs of dryaggregate per square yard8 - 12Chapter 8 – Slurry Seals10 - 1520 - 25

Safety and Traffic Control Ensure that the slurry surfacing has had adequate time tocure prior to reopening to traffic - very often driversassume that the slurry surfacing is drivable despite of thewarning signs and cause damage to the fresh placedtreatmentNotify the residents and provide information on how toaccommodate the construction activitiesProtect both employees and publicHave signs/barricades in place before commencing workChapter 8 – Slurry Seals

Equipment Requirements covered in CaltransStandard Specification Section 37Types: Continuous, self propelled unit Truck-mounted unitAll equipment should be properlycalibrated as per CT 109Chapter 8 – Slurry Seals

Typical SetupChapter 8 – Slurry Seals

Surface Preparation Restore pavement structural integrity andfunctional performance characteristics: PatchingCrack sealingClean pavement surface Sweeping or High Power Pressure WashingRemove rubber crack sealant and thermo-plasticmarkingsCover utility inlets with heavy paper or roofing feltChapter 8 – Slurry Seals

Utility InletsAFTERBEFOREChapter 8 – Slurry Seals

Application Conditions Humidity: 60% or lessTemperature: 50 F (10 C) and risingWind: slight breeze beneficialSunlight: necessary, DO NOT apply atnightDO NOT start work if: Rain is imminent Freezing anticipated within 24 hoursChapter 8 – Slurry Seals

Starts/Stops All starts, stops, and handwork onturnouts should be done on roofing felt toensure sharp, uniform joints and edgesChapter 8 – Slurry Seals

Longitudinal Joints May be overlapped or butt jointedShould be straight or curve with thetraffic laneOverlaps should not be in the wheelpaths and should not exceed 3 in (75mm) in widthTypically 3 passes required on a 2-laneroadwayChapter 8 – Slurry Seals

Transverse Joints Transitions at these joints must be smooth toavoid creating a bump in the surfaceThe joints must be butted to avoid thesebumps and handwork should be kept to aminimumDo not over wet - this leads to poor texture andscarring at the joints.Start transverse joints on roofing felt toeliminate these problemsChapter 8 – Slurry Seals

Transverse Joints ExamplesPOOR QUALITYGOOD QUALITYChapter 8 – Slurry Seals

Edges and Shoulders The edge of the spreader box should beoutside the line of the pavementEdge boxes should be used whenshoulders are coveredChapter 8 – Slurry Seals

Edges and Shoulders ExamplesPOOR QUALITYGOOD QUALITYChapter 8 – Slurry Seals

Uneven Mix and Segregation Non-uniform mixes that appear to besetting very slowlyBlack and flush looking surface withpoor texture“False Slurry” - where the emulsionbreaks onto the fine materialCauses: too much water or not enoughcementResult: segregation and delaminationChapter 8 – Slurry Seals

Smoothness Washboarding – mix too stiff or spreaderbox incorrectly set upDrag marks – dirty strike-offOriginal surface too roughChapter 8 – Slurry Seals