1、1 Chapter 3 Asphalt Mixtures2Main topicsTechnical Properties of Asphalt Mixture3.2Principal of Composition Mix Design 3.3Other Asphalt Mixtures3.4Basic Concepts on Asphalt Mixture3.13ACSMAOGFCTypes and Composition Structure3.14Based on temperature of mix and temperature of paving processes: mixture
2、of hot mix and paving; mixture of cold mix and paving; mixture of hot mix and cold paving; worm mix and cold paving.Types and Composition Structure Classifications3.1According to different ways it has differentclassifications:5 Based on gradation types continuous gradation asphalt: ( Asphalt Concret
3、e: AC); open grading asphalt mixture：(Open Graded Friction Course: OGFC); gap grading asphalt mixture (Stone Matrix Asphalt: SMA);Based on volume of voids dense asphalt mixture, volume of voids 36% (AC, SMA); open grading asphalt mixture, volume of voids 182.5% (OGFC or Asphalt Treated Permeable Bas
4、e: ATPB); half open grading asphalt mixture，volume of voids 612% (Asphalt Macadam: AM). Types and Composition Structure Classifications3.16Based on nominal maximum size (公称最公称最大粒径大粒径) of aggregate over coarser size: n.m.s37.5mm coarser size：n.m.s31.5mm, 26.5mm medium size: n.m.s19.5mm, 16mm fine siz
5、e: n.m.s13.2mm, 9.5mm sand size：n.m.s4.75mmAbout maximum particle: maximum size: the minimum sieving size that aggregate 100% passing; nominal maximum size: the sieving size which firstly retains some aggregates (not more 10%). Example of maximum sizeMaximum size:Nominal maximum size:16mm13.2mmTypes
6、 and Composition Structure Classifications3.17 The density for total aggregates under some composition proportion: Compound bulk relative density (sb):1212100.sbnnPPP1212100.sbnnPPPCompound apparent relative density (sa):Compound Density(合成相对密度合成相对密度) of Mineral MixtureTypes and Composition Structur
7、e Volume Parameters of Mixture3.18 Effective volume of aggregate: Vactual +VImpermeable voids +Vpart permeable pores Effective relative density （ se ）:(1)sesasbCC20.0330.29360.9339xxC11()xsbsaWhere: C mineral absorption coefficient for asphaltwxmineral water absorption for waterTypes and Composition
8、 Structure Volume Parameters of Mixture3.1Effective Volume and Effective Density9Definition: the total mass (including mass of asphalt and aggregates) per unit volume (including asphalt volume, effective volume of compound agg. and voids among aggregates particles ).Determination methods: According
9、to water absorption or percentage of voids, different methods are used: Absorption is less than 0.5%weighing the mass in water; Absorption is 0.52%weighing the mass in saturated condition; Absorption is greater than 2%sealing with wax method; when percentage of voids is over 18% volume method is use
10、d.Types and Composition Structure volume parameters of mixture3.1Bulk Density of Asphalt Mixture10Definition: the density without any voids.Determination method:Measurement method for ordinary asphalt mixture；Calculation method for modified asphalt mixture：Types and Composition Structure volume para
11、meters of mixture3.1The maximum theory relative density100100ataseaPPIf asphalt consumption is in theratio of asphalt and aggregate (%)Pa油石比（%） =(沥青/矿料)If asphalt consumption is in the content of mixture (%)100(100)tbbseaPPPb沥青含量（%） =沥青/(沥青+矿料)11Definition: volume of voids (VV) within the asphalt mi
12、xture over the total mixture volume in percent under compaction condition.Significance: if VV is too low, the mixture will be easily to cause plastic deformation especially rutting under hot weather condition. If VV is too high, it not only causes rutting but brings about water damage. Calculation:T
13、ypes and Composition Structure volume parameters of mixture3.1(%)(1) 100ftVVPercentage of voids for asphalt mixture (VV)(空隙率空隙率)12Definition: the voids among the mineral particles over total mixture volume in percent under compaction condition.Calculation:(%)(1) 100fssbVMAPTypes and Composition Stru
14、cture volume parameters of mixture3.1Voids in the mineral aggregate (VMA)(矿料间隙率矿料间隙率)where: relative density of asphalt mixture specimen; compound relative density of mineral; the total mass of aggregates per total mass of mixture in percent.sbsPf13Definition: the volume of asphalt over the volume o
15、f voids among the mineral particles in percent under compaction.Calculation:Types and Composition Structure volume parameters of mixture3.1Voids filled with asphalt (VFA)(沥青饱和度沥青饱和度)(%)100VMA VVVFAVMA14ACSMAOGFCTypes and Composition Structure3.115(Relative) density: including density for compound mi
16、neral； density for mixture; and maximum theory density;Volume of air voids (VV);Voids in the mineral aggregate (VMA);Voids filled with asphalt (VFA).Types and Composition Structure Volume Parameters of Mixture3.1161.白色加黄色白色加黄色矿料间隙率（矿料间隙率（VMA）3.黄色黄色沥青体积百分率（沥青体积百分率（VA）2.白色白色空隙率（空隙率（VV）体积参数示意图体积参数示意图4.
17、沥青饱和度沥青饱和度(VMA)？沥青饱和度沥青饱和度(VMA) =VA/(VA+VV) =(VMA-VV)/VMA17Asphalt mixture is a multi-level decentralized system with network spatial structure; Each level plays different role for asphalt mixture;The function of each level can be explained by following schematic diagram. Types and Composition Struc
18、ture Composition Structure of mixture3.118粗分散系粗分散系沥青混合料沥青混合料分散相分散相细集料细集料分散介质分散介质沥青胶浆沥青胶浆分散相分散相粗集料粗集料分散介质分散介质沥青沥青分散相分散相填料填料Types and Composition Structure Composition Structure of mixture3.1Multi-level decentralized system分散介质分散介质沥青砂浆沥青砂浆19Good durability, good stability both athigh and low temperatu
19、re, but poor workability.Gap gradationDense framework structure(密实骨架结构)characteristicsgradationType of structureDense, low voids, good durability and good stability at low temperature but poor high temperature stability.Continuous gradationSuspended dense structure(悬浮密实结构)Good stability at high temp
20、erature; a lotvoids, poor durability and stability at low temperature.Open gradationVoid framework structure(骨架空隙结构)Types and Composition Structure Composition Structure of mixture3.120Strength formation for asphalt mixture: depending on the asphalt viscosity and internal friction among the aggregat
21、e particles;Mechanism theory: Coulomb theory. Types and Composition Structure Structure strength of mixture3.1tanc21Asphalt properties asphalt properties：the higher viscosity, the stronger of mixture strength; asphalt content：only under the optimum asphalt content, dose mixture show the highest stre
22、ngth.Types and Composition Structure Structure strength of mixture3.1Influence Factors on the Strength 22Mineral properties gradation(级配)：dense framework structure; particle shape(颗粒形状): closely to cubic or round shape, rather than elongated or flat; surface characteristics (表面特性): rough surface and
23、 plentiful edges; Interaction between aggregate and asphalt alkali mineral materials contribute to raising the strength, because chemical reaction takes place between aggregate and asphalt, forming more structural asphalt.Types and Composition Structure Structure strength of mixture3.1Influence fact
24、ors on the strength 23Types and Composition Structure Structure strength of mixture3.1Application conditions temperature: With the environmental temperature heat up, asphalt viscosity becomes low, so adhesion stress of mixture decreases continuously; deformation rate: because asphalt adhesive presen
25、ts reduce trend with increase of deformation rate under loading, so adhesion stress of mixture decreases too, but inner friction angle of the mixture dose not has much variation with the rate.Influence Factors on the Strength 24Discussion沥青混合料结构强度与荷载或变形速率关系描述存在的问题本书认为沥青混合料黏结力（当然来自于沥青的黏度）随变形速率的增加而减小（
26、P104,第二节标题之上一段），理由是沥青的黏度随变形速率的增加而减小，即沥青黏度公式表达的内容：而本书前四版以及我校编写的版本却认为沥青混合料黏结力随变形速率的增加而增加，理由是有相应试验结果的证明。见下图（黏度）（剪应力） （式2-4 P46）（剪变率）25It is the ability that asphalt mixture withstands repeated loading without forming permanent deformation (rutting) under high temperature condition.Evaluation method com
27、monly used rutting test: Technical Properties of Asphalt Mixture Stability of high temperature3.2211221()42ttDSccddwhere： DSDynamic stability (load timesmm)； d1，d2 deformation at period of t1 and t2 (t145min、t2=60min)(mm); 42 load number per one minute； c1，c2Correction Coefficient.ChannelizationDefi
28、nition26Technical Properties of Asphalt Mixture Stability of high temperature3.2Mineral features closely to cubic or round shape, rather than elongated or flat; rough surface and plentiful edges preferred; crushed sand much better; dense and skeleton structure of gradation benefit greatly to high-te
29、mperature stability.asphalt adhesiveness: the higher viscosity and lower temperature susceptibility, the better for high temperature stability; reducing asphalt content properly. Influencing Factors27Definition When the temperature drops, especially at winter time, asphalt mixture has the ability to
30、 resist shrinkage without cracking.Evaluation method estimated temperature of cracking; creep test at low temperature; bending test at low temperatureInfluencing factor Depending on the asphalt properties mostly, it has higher capability to show better low temperature performance when asphalt is hig
31、h penetration and low stiffness modulus. .Technical Properties of Asphalt MixtureCrack resistance at low temperature3.228Definition It is the ability that asphalt mixture resists environmental impact and repeat loading without damage. Durability includes anti-aging, water stability and fatigue resis
32、tance, which resistance to water damage is most common concern issue. Evaluation method on water stability adhesiveness test； water immersion test: Marshall test； freeze thawing split test .Technical Properties of Asphalt Mixture Durability3.229Influencing factors adhesiveness: alkali is much better
33、 than acid type aggregate; volume of voids: low vv benefits to water stability; thickness of asphalt film: more asphalt content and thicker film contribute to stability.Technical Properties of Asphalt Mixture Durability3.230Principal of Composition Mix DesignFor hot mix mixture 3.331The performances
34、 of asphalt mixture are closely related with to environmental conditions, such as temperature, rainfall etc., so the weather condition must be considered during the process of mix design or properties testing. Climate condition is considered from three aspects: high temperature in summer, low temper
35、ature in winter and rainfall in annual time. Principal of Composition Mix Design Climate areas 3.332Principal of Composition Mix Design Climate areas 3.3Climate AreaIndexes of Climate Area20203030Maximum average temperature on July ()Cool areaHot areaBurning hot areaName321Climate Area on high tempe
36、ratureIndex on high temperature-9.0-9.0-21.5 -9.5- -37.5-21.5-37.5-37.5Extreme lowest temperature ()warmcoldVery coldSevere cold areaName 4321Climate area on low temperatureIndex on low temperature250250500250100050010001000Annual rainfall (mm)Arid regionSemi-arid regionsHumid regionMoist regionName
37、4321Climate Area on rainfallIndex on rainfall33LowerMarkHeavy loadstrafficHightemperaturelast long timeHigh TemperatureIn summer Channelization Mountain hilly area Section with low speedPrincipal of Composition Mix Design Materials Requirements 3.3AsphaltHow to choice proper mark for asphalt34Qualif
38、ied the requirements on physical and mechanical specifications (Table 3-9);Satisfied adhesiveness to asphalt: not less than grade4; if it dos not meet the requirements, improving methods are apply antistripping agent; add appropriate amount cement or slaked lime powder to substitute for mineral fill
39、er.Favorable specifications. (Table 3-10). Coarse aggregatePrincipal of Composition Mix Design Materials Requirements 3.335Qualified the physical and mechanical specifications (table 3-11);Favorable specifications.Principal of Composition Mix Design Materials Requirements 3.3Fine aggregateEnough fin
40、eness to ensure contact surface area between filler and asphalt, forming much more structural asphalt;Obviously alkaline characteristic.filler36Principal of composition mix design : the Marshall design methodDesign process: the stage of target composition mix design ; the stage of production composi
41、tion mix design ; the stage of confirmation on composition mix design .The work of asphalt composition mix design includes two parts: design process of mineral composition; determining optimum asphalt content;Principal of Composition Mix Design Introduction of Mix Proportion Design 3.337 Marshall te
42、st specimen The Marshall test method was invented by a American in the 40 s last century. Size of test specimen: 101.663.5(mm);Test index：Marshall stability (kN); Flow value (mm). Principal of Composition Mix Design Introduction of Mix Proportion Design 3.3Marshall instrumentMarshall Test Method38Te
43、chnical requirements of mix proportion design: Technical standards of Marshall test; （Table 3-19, 3-20） Technical standards of dynamic stability; (Table 3-21) Technical standards of water stability; (Table 3-22) Technical standards of bending test at low temperature. (Table 3-23 )Principal of Compos
44、ition Mix Design Introduction of Mix Proportion Design 3.339Principal of Composition Mix Design Introduction of Mix Proportion Design 3.3Index of EvaluationMethod of ProcessMineral Grading DesignGradation envelop recommended bythe specificationsGrading type selectionOptimum Asphalt Content Determina
45、tion Marshall testIndexes ofvolumeResults VerificationLaboratoryexperimentRoad performances40Main purposes of mineral composition design: higher condense; excellent inner friction resistance;Choosing suitable type of asphalt mixture based on road class and the position of the pavement structure laye
46、r (Table 3-15);Keeping nominal maximum size of aggregate into correspondence with the structure layer thickness, that is layer thickness is 2.53.0 times of maximum aggregate size.Method of Composition Mix Design (1) Design on Mineral Composition 3.341Making the grading curve close to the middle of t
47、he envelope, especially at the size of 4.75mm, 2.36mm and 0.075mm;Or adjusting passing percent on the key sieve mesh to make gradation into coarser type or finer type (Table 3-18 );Choosing coarser one for heavy traffic road, while finer one for light duty traffic or side walk. Method of Composition
48、 Mix Design (1) Design on Mineral Composition 3.342Principal of Composition Mix Design Introduction of Mix Proportion Design 3.3Index of EvaluationMethod of ProcessMineral Grading DesignGradation envelop recommended bythe specificationsGrading type selectionOptimum Asphalt Content Determination Mars
49、hall testIndexes ofvolumeResults VerificationLaboratoryexperimentRoad performances43According to previous experience or suggestion by design document , a initial amount of asphalt is selected (in ratio of asphalt over mineral);Method of Composition Mix Design (2-1) Marshall Stability Test 3.3Marshal
50、l compaction device Marshall specimen Initial asphalt content is considered as median one, setting other four contents of asphalt at same interval to prepare Marshall samples, respectively. 44By the method of calculation or experiment, the maximum theory relative density of each asphalt content mixt
