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ECU CMGT 2210 - Lecture 12-Asphalt

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Slide 1In This Unit…ApplicationsSlide 4Asphalt Concrete ProductionProduction of AsphaltBituminous MaterialsSlide 8Asphalt Cement (Binder)Asphalt Cutback = asphalt cement + Petroleum solventSlide 11Asphalt in PavingAsphalt Binder PropertiesAsphalt Binder TestAsphalt Binder TestAsphalt Binder TestAsphalt Binder TestFlash PointAsphalt GradingSuperpave & Performance Grade BindersBinder SpecificationsSlide 22Slide 23Slide 24HMA Desirable PropertiesLecture 12: AsphaltKamalesh Panthi, Ph.D.Department of Construction ManagementEast Carolina UniversityCMGT 2210 - Construction & Civil MaterialsIn This Unit…DefinitionAsphalt productionAsphalt typesAsphalt testsPerformance GradingApplications•Roads-Asphalt Concrete (93%)•Bituminous waterproofing•roofing felt, roof shingles•sealing flat roofsHistoric Pennsylvania AveAsphalt PavementSubgradeSubbase4Asphalt Concrete Productionhttp://www.youtube.com/watch?v=WNYjcKGtX6A&feature=relatedProduction of Asphalt-Natural Asphalts-Limited supply-Use of asphalt in road exceeded supply in 18007Bituminous MaterialsAsphaltTarAsphaltCementEmulsionCutbackNaturalorRefined from petroleum oilByproduct of Coal ProductionSource of Asphalt & Types8•Adheres well to most rock•Waterproof•Fairly durable•Resistant to reaction with most acids, alkalis, and salts•Temperature sensitiveAsphalt Cement (Binder)9Hot Mix AsphaltAsphalt Cutback = asphalt cement + Petroleum solvent•Hazardous, volatile solvents and hydrocarbons are released•Cold mix maintenance, patching, chip seals, crack sealing, base and sub-base stabilization, and surfacing low volume roads10Chip SealAsphalt Emulsion = asphalt cement + water + emulsifying agent (e.g., soap)•Many of the same uses as cutback•Safer•Environmentally better11Freshly Placed Emulsion Tack Coat- The brown color indicates that it has not yet brokenThe Same Tack Coat After 23 Minutes- The brown color now appears in splotches indicating it is beginning to break.Tack Coat Using an Asphalt Emulsion- The black color indicates it has broken.Asphalt Cement = asphalt binder •asphalt binder alone is also used for sealing and waterproofingAsphalt in Paving12Asphalt concrete = asphalt binder + aggregate•used mainly for hot mix asphalt pavement surfacing (HMA)Asphalt Binder PropertiesIn selecting a suitable asphalt the engineer must consider the following•What is the consistency of the asphalt at different temperatures?•What is its tensile strength at low temperature?•How will the asphalt change due to aging?A number of different tests have been developed in the SHRP for evaluating these factorsAsphalt Binder TestHigh Temperatures•Liquid-like at high temperatures-the viscometers are used to measure asphalt viscosity - this information helps the engineer to decide•What is the best temperature for mixing the asphalt with the binder•What is the appropriate temperature for compaction during constructionhttp://pavementinteractive.org/index.php?title=Rotational_ViscometerAsphalt Binder TestIntermediate Temperatures•The dynamic shear rheometer is used to measure visco-elastic properties such as complex modulus and the phase angle at pavement surface temperature.• These tests tell the condition of the asphalt at intermediate service temperatures. •This information is needed to design against fatigue cracking and permanent deformation.http://pavementinteractive.org/index.php?title=Dynamic_Shear_RheometerAsphalt Binder TestLow Temperatures•At low temperatures the asphalt is glass-like. •The bending beam rheometer is used to measure the stiffness modulus. And the direct tensile test is used to measure the tensile strength. •Both of these parameters are used to assess whether or not the asphalt pavement will be able to resist low temperature crackinghttp://classes.engr.oregonstate.edu/cce/winter2012/ce492/Modules/03_materials/03-3_body.htmAsphalt Binder TestBinder Aging•Asphalt properties change over time on exposure to high temperature and the atmosphere- aging•oxidation and volatilization (this is same thing that happens to plastic which gets hard and starts to crack after some time).•rate and amount of aging affect how long the pavement will be able to perform adequately•Aging is considered to occur in two stages •during production and construction (short-term aging) – rolling thin film oven test•during the life of the pavement (long-term aging)- pressure aging vesselFlash Point•Safety test•Minimum temperature with sufficient vapors to “flash” when exposed to flame18Asphalt Binder TestAsphalt GradingHistory1. Penetration grading (pen)2. Viscosity grading (AC)3. Aged residue grading (AR)•CurrentPerformance grading (PG)19Superpave & Performance Grade Binders•After the Strategic Highway Research Program (SHRP)•Superpave (Superior Performing Asphalt Pavements)•mix design method for asphalt concrete•performance grading method for asphalt binder specification 20Binder Specifications•The specification sets the minimum standard for the important properties of the asphalt •Asphalts are selected for a given application based on their grade (which is determined by the specification)•The SHRP specification system is based on the extreme temperatures that the asphalt is expected to see during service in the pavementPerformance Grading (PG)22For example, an asphalt rated PG58-28 means that that asphalt should be used where-the maximum average pavement temperature is 58 C -the minimum pavement temperature is -28 CPG64-22 is used in KentuckyPG64-34 is used in NebraskaPG52-28 is used in MichiganPG52-34 is used in WisconsinToo brittle (Thermal cracking)Too soft (Rutting)•Asphalt is highly affected by temperature•Slope indicates degree of susceptibility•Some additives can reduce temp. susceptibilityTemperature Susceptibility of Asphalt23•Asphalt comes in different grades (soft and hard)•Soft (low viscosity) asphalt is used in cold climates to avoid thermal cracking•Hard (high viscosity) asphalt is used in hot climates to avoid rutting24•stable – resist permanent deformations under load•fatigue resistant – under repeated loading•resistant to thermal cracking – due to contraction at low temps•resistant to hardening or aging – during production and in service•resistant to moisture induced damage – stripping asphalt from aggregate•skid resistant – by texturing surface, small aggregate, gap-grading•workable – ease of mixing, placing,


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