Highway Design C E 427
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This 59 page Class Notes was uploaded by Charley Wintheiser DVM on Monday October 5, 2015. The Class Notes belongs to C E 427 at California State University - Long Beach taught by Shadi Saadeh in Fall. Since its upload, it has received 14 views. For similar materials see /class/218763/c-e-427-california-state-university-long-beach in Civil Engineering at California State University - Long Beach.
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Date Created: 10/05/15
Asphalt Concrete Mix Design History Hot Mix Asphalt Concrete HMA Mix Designs Objective Develop an economical blend of aggregates and asphalt that meet design requirements Historical mix design methods Marshall Hveem New Superpave gyratory Requirements in Common Sufficient asphalt to ensure a durable pavement Sufficient stability under traffic loads Sufficient air voids Upper limit to prevent excessive environmental damage Lower limit to allow room for initial densification clue to traffic Sufficient workability MARSHALL MIX DESIGN Marshall Mix Design Developed by Bruce Marshall for the Mississippi Highway Department in the late 30 s WES began to study it in 1943 for WWII Evaluated compaction effort No of blows foot design etc Decided on 10 lb Hammer 50 blowsside 4 voids after traffic Initial criteria were established and upgraded for increased tire pressures and loads V m 0 w w Ald w E w U m m w w 9 J Marshall Mix Design Select and test aggregate Select and test asphalt cement Establish mixing and compaction temperatures Develop trial blends Heat and mix asphalt cement and aggregates Compact specimen 100 mm diameter WWWGEM Tema iscosity Pa 5 10 5 Compaction Range Mixing Range l 100 110 120 130 140 150 160 170 180 190 200 Temperature C Marshall Design Criteria Light Traffic Medium Traffic Heavy Traffic ESALlt104 104ltESALlt 10 ESALgt106 Compaction 35 50 75 Stability N b 3336 750 5338 1200 8006 1800 Flow 025 mm 01 in 8 to 18 8 to 16 8 to 14 Air Voids 3to5 3to5 3to5 Voids in Mineral Agg VMA Varies with aggregate size m m warm m w r a Na ma u 7h Iailvlirrliilllu 53 m 1 mm mm jlllxlljjmjjp p uns r l s VW39A mad M B dm1aannuar Marshall Mix Design Tests Heights Used to correct stability measurements Bulk specific gravity of compacted sample Maximum specific gravity of loose mix Stability and flow 60 C water bath 30 to 40 minutes 50 mmlmin loading rate Max load uncorrected stability Corresponding vertical deformation flow Marshall Stability and Flow m m I Mm Air Voids 0 Emmi gpha Agglh l Target optimum asphalt content average OK OK Wham EEIngllm i E Use target optimum asphalt content to check if these criteria are met Marshall Design Use of Data NAPA Procedure Air Voids Asphalt Content Marshall Design Use of Data NAPA Procedure Stability Asphalt Content OK OK Wham EEIngllm i E Use target optimum asphalt content to check if these criteria are met Marshall Design Method Attention on voids strength durability Inexpensive equipment Easy to use in process controlacceptance Impact method of compaction Does not consider shear strength Load perpendicular to compaction axis Asphalt Concrete Mix Design Superpave Superpave Volumetric Mix Design Goals Compaction method which simulates field Accommodates large size aggregates Measure of compactibility Able to use in field labs Address durability issues Film thickness Environmental Specimen Preparation Mechanical mixer 0170 Pas binder viscosity Short term oven aging 4 hours at 135 C 2 hours at 135 C optional MiximQm Teams Viscosity Pa 5 1 O 5 Compaction Range Mixing Range l 100 110 120 130 140 150 160 170 180 190 200 Temperature C Specimen Preparation Specimen Height Mix Design 115 mm 4700 9 Moisture Sens 95 mm 3500 9 Loose Specimen for Max Theor Rice varies with nominal max size 19 mm 2000 g 125 mm 1500 g MRMg Place preheated aggregate in bowl and add hot asphalt Mixing Place bowl on mixer and mix until aggregate is wellcoated Short Term Aging Empty mix into pan and place in oven to simulate short term aging 2 hours for low absorption aggregates 4 hours for high absorption aggregates Short Term Aging Important Allows time for aggregate to absorb asphalt Helps minimize variability in volumetric calculations Most terms dependent upon volumes which change with changes in the amount volume of absorbed asphalt Compaction Place funnel on top of mold and place mix in mold Take care not to allow the mix to segregate Compaction Place another paper on top of mix and place mold in compactor misting amllhl iil a i 3 X by w W 9 O I 1 A m 3 pl I m Compac tion size compactors Compaction Key Components of Gyratory Compactor height control and data measurement acquisition panel reaction frame oading V ram tilt bar 2 mo Compaction Gyratory compactor Axia and shearing action 150 mm diameter molds Aggregate size up to 375 mm Height measurement during compaction Aows densification during compaction to be evaluated Compaction After aging take mix and preheated mold from oven Place paper in bottom of mold Compaction Once compaction is finished extrude sample from mold Compaction Remove the paper and label samples SGC Results 100 1000 7 Log Gyrations Three Points on SGC Curve A 4 10 100 Design Compaction N based on des verage design high air temp N traffic level Log Nmax 110 Log Ndes l 0 Log Nini 045 L09 Ndes 10 100 1000 Log Gyrations Data Presentation 100 Ndes E 96 94 92 90 Specimen 1 88 A Average 86 84 1 N 100 Superpave Mix Design Analysis Superpave Testing Specimen heights Mixture volumetrics Air voids Voids in mineral aggregate VMA Voids filled with asphalt VFA Mixture density characteristics Dust proportion Moisture sensitivity Superpave Mix Design Gmb estimated W m 9W me Where Wm mass of specimen 9 me volume of compaction mold cma gw density of water gcm3 Assumption specimen is smoothsided cylinder Superpave Mix Design However surface irregularities cause the volume of the specimen to be slightly less than volume of cyHnder Actual bqu specific gravity measurement of compacted sample used to determine correction factor C Gmb measured Gmb estimated Gmm Gmb estimated C l Gmm measured Superpave Mix Design Determine mix properties at N criteria and compare to Design Air voids 4 or 96 Gmm VMA See table VFA See table Gmm at Nini lt 89 Gmmat Nmax lt 98 Dust proportion 06 to 12 96 4 Voids SGC Results N 1ni Ndes Increasing asphalt cement content N max 10 100 L V 1000 Log Gyrations Each line avg of two samples Superpave Mix Design 39 VMA requirements Nomina max agg size Min VMA 95 mm 15 125 mm 14 19 mm 13 35 mm 12 375 mm 11 Superpave Mix Design VFA requirements Traffic millions of ESALs Range of VFA lt 03 70 to 80 1 to 3 65 to 78 gt 30 65 to 75 Superpave Mix Design weight of 0075 material 06 5 5 12 weight of effective asphalt Effective asphalt content is asphalt on surface of aggregate asphalt not absorbed by aggregate Superpave Mix Design Moisture Sensitivity Prepare set of 6 specimens 6 to 8 voids Represents anticipated inservice voids Determine tensile strength of 3 of specimens Condition remaining 3 in water bath 60 C 24 hr Option for freeze cycle Bring to test temperature 25 C and determine wet conditioned tensile strength Moisture Sensitivity AASHTO T 283 Measured on proposed aggregate blend and asphalt content Reduced compactive effort to increase voids 3 Conditioned Specimens 3 Dry Specimens y g L Aquot Vacuum saturate specimens Soak at 60 C for 24 hours Soak at 25 C for 2 hours Moisture Sensitivity AASHTO T 283 Determine the tensile strengths of both sets of 3 specimens Calculate the Tensile Strength Ratio TS R Avg wet tensile strength TSR Avg dry tensile strength Minimum of 80 needed Moisture Sensitivity AASHTO T 283 gth apparatus 4 td r 100 mm specimens 1 Example of Superpave Mix Design Trial Blend 3 39il i i em 1mm i ilg t i LiixiM W 54 Aggregate Consensus Properties Blended Aggregate properties are determined Property Criteria Blend 1 Blend 2 Blend 3 Coarse Ang 95l90 min 96l92 95l92 97l93 Fine Ang 45 min 46 46 48 FLatlElong 10 max 0 0 0 Sand Equiv 45 min 59 58 54 Combined Gsb nla 2699 2697 2701 Combined Gsa nla 2768 2769 2767 Compaction Characteristics Blend Nini Ndes 1 43 869 960 2 45 859 960 3 47 871 960 Volumetric Properties Blend AC Air VMA VFA 1 43 40 127 685 2 45 40 130 692 3 40 40 135 701 Selection of Design Asphalt Binder Content I binder blnder Questions
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