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1、Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,#,Lesson 4:Hot Mix Asphalt Mix Design,CEE 595 Construction Materials,Winter 2008,Reading,Virtual Superpave Laboratory,WSDOT Pavement Guide Interactive,Section,Subsection,Aggregate Test

2、s,Gradation&Size,Mix Design,All,Module,Section,Mix Design,Hveem Method,Mix Design,Marshall Method,Lesson Outline,Hot mix asphalt(HMA)description,Superpave mixture design procedure,Hot Mix Asphalt(HMA),Bituminous concrete,Distinguished by:,Materials(asphalt binder and aggregate),Mix design methods,El

3、evated mixing temperature,Other names:,Asphalt concrete(AC),Blacktop,Bitumen,Section 1,HMA by the Numbers,Item,U.S.,Europe,Japan,Annual Production in millions of tons,500 600,300 330,75 82,Percentage recycled,80%,0 80%,50%,Production Companies,1100,2500,1000,Production Plants,3600,4700,1500,Europe a

4、nd Japan numbers from the European Asphalt Pavement Association(,http:/www.eapa.org,),Section 1,HMA Constituents,Section 1,Types of HMA,Section 1,Hot Mix Asphalt,Described by:,Maximum aggregate size,Aggregate gradation,Asphalt binder,Asphalt binder content,Section 1,Maximum Aggregate Size,Largest ag

5、gregate“diameter”as defined by:,Maximum Size,The smallest sieve through which 100 percent of the aggregate sample particles pass,Nominal Maximum Size,The largest sieve that retains some of the aggregate particles but generally not more than 10 percent by weight,Section 1,Section 1,Gradation,Dense gr

6、aded,Most common,Gap graded,Stone matrix asphalt(SMA),Open graded,Used as a surface course in many areas,Uniformly graded,Not used as a construction material,Section 1,Section 1,Asphalt Binder,Choose asphalt binder grade,Select a grade based on:,Design pavement high temperature,Design pavement low t

7、emperature,Adjust based on reliability,Adjust based on traffic speed&loading,Add modifiers to achieve certain properties,Section 1,Asphalt Binder Content,Ratio of asphalt binder to aggregate,Determining this is a key component of mix design,Typical binder contents,Usually expressed as a percentage b

8、y weight of total mixture,Dense graded HMA=4.5 to 6.0 percent,SMA=6.0 8.0 percent,Section 1,Superpave Mix DesignProcedure,Section 2,Concepts,Mix design is a volumetric process,V,a,=volume of air,V,be,=volume of effective binder,V,agg,=volume of aggregate,V,T,=total volume,VMA=voids in the,mineral ag

9、gregate,V,be,=volume of absorbed binder,V,b,=Volume of binder=V,be,+V,ba,Section 2,Concepts,We design volume but measure mass,Specific gravity is very important,Converts mass to volume,Constituent,Typical Values,By Total Volume,By Total Mix Weight,Air,4%,0%,Asphalt,10%,5%,Aggregate,86%,95%,Section 2

10、,Variables,Aggregate,Asphalt binder,Ratio of aggregate to asphalt binder,Section 2,Goals,Stability(deformation resistance),Durability,Fatigue resistance,Ductility(low temp.cracking resistance),Moisture damage resistance,Skid resistance,Workability,Section 2,Basic Procedure,Select aggregate,Select as

11、phalt binder,Design aggregate structure,Select asphalt binder content,Conduct performance tests,Develop job mix formula(JMF),Section 2,Select Aggregate,Must meet:,Consensus requirements,Source properties,Section 2,Select Asphalt Binder,Almost always done to local standard,Eliminates the calculations

12、 associated with LTPP Bind software,Easier to follow in specifications,Easier for suppliers,Design Aggregate Structure,Not many formal procedures to do this,Typical Superpave aggregate structures create quarry waste,Select Asphalt Binder Content,Level of sample compaction is critical,Bleeding,Raveli

13、ng,Conduct Performance Tests,There are none for Superpave right now,Agencies typically use,Moisture susceptibility test,Laboratory wheel tracking devices,Hveem stabilometer,Important Volumetric Properties,Tests run on compacted samples,Mixture specific gravity(G,mb,),Aggregate specific gravity(gives

14、 G,sb,G,sa,G,se,),Test run on loose mix(uncompacted),Theoretical maximum specific gravity(G,mm,),Often called“Theoretical maximum density”,Often called“Rice density”,Calculated volumes(based on above tests),Air voids(V,a,),Voids in the mineral aggregate(VMA),Voids filled with asphalt(VFA),Equations,

15、Air voids,VMA,VFA,P,b,=%asphalt binder by weight of mix,P,s,=%aggregate by weight of mix G,sb,=aggregate specific gravity,Mix Design,Develop Job Mix Formula(JMF),End result of mixture design,A specification(along with tolerances)used for plant production of HMA,Cannot be significantly altered withou

16、t another mix design,Job Mix Formula(JMF),Mix Design,Other Mix Design Methods,Marshall Method,Hveem Method,All use the same basic procedure,Section 2,Marshall Hammer,Compacts samples in Marshall method,Analogous to Superpave gyratory compactor,California Kneading Compactor,Compacts samples in Hveem method,Analogous to Superpave gyratory compactor,Marshall Stability Test,Squeezes sample diametrically,Mix Design,Compacted Samples,Height2.5 inches,Diameter4 inches,Marshall&Hveem,Superpave,Height4.5