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Chapter2 Asphalt materials

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1 Chapter2 Asphalt materials
《Road Engineering Materials》 Chapter2 Asphalt materials

2 Coarse (A) retained in C.R.(%)
Aggregates mixture and design 1.3 ——the method of grading design: trial and error method 6.0 4~8 13.2 10.8 0.075 5.0 8~16 11.6 0.15 7.0 12~22 12.4 0.3 805 18~30 16.0 0.6 12.0 24~41 22.5 1.18 13.5 36~53 24.0 2.6 2.36 18.5 70~88 41.7 9.5 2.5 95~100 5.2 100 16 mid-value of Envelope in C.R. (%) grading Envelope in P. Fine (C) retained in C.R.(%) Medium (B) retained Coarse (A) retained in C.R.(%) Mesh size (mm) 21.0 48~68 1.6 50.5 4.75 1.2 pan 86.8

3 Example of Aggregate Mixture Design
6 4~8 70.5 0.075 15 10~20 94 11.0 0.3 16 15~27 97 23.0 0.6 27 20~34 100 36.0 1.18 37 28~46 58.7 2.36 48 38~58 77.9 4.6 4.75 62 52~72 93.8 19.8 9.5 82. 5 75~90 61.5 97. 5 95~100 19. 26.5 midenvlope envelope filler chip Crushed agg. Objective envelope(%) Passing for each kind aggregate (%) Sieve size (mm) 71 62~80 100 34.5 13.2 (65.5) (29) 10 6~14 92 0.15

4 Objective envelope(%)
Synthesis gradation Sieve size (mm) 不同规格集料各筛上通过量(%) Objective envelope(%) Crushed agg.×42.3 Chip ×46.8 Filler ×10.9 envelope 7.7 10.0 17.3 21.4 27.7 38.4 49 63.2 72.3 83.7 98.7 100 results 26.5 100 1.9 8.4 14.6 26.0 41.0 42.3 100 5.1 10.8 16.8 27.5 36.5 43.9 46.8 100 7.7 10.0 10.2 10.6 10.9 100 19. 97 100 100 95~100 16 61.5 100 100 75~90 13.2 34.5 100 100 62~80 9.5 19.8 93.8 100 52~72 4.75 4.6 77.9 100 38~58 2.36 58.7 100 28~46 1.18 36.0 100 20~34 0.6 23.0 97 15~27 0.3 11.0 94 10~20 0.15 92 6~14 0.075 70.5 4~8

5 Main topics Introduction Petroleum Asphalt
2.1 Technical Property of Petroleum Asphalt 2.2 Polymer Modified Asphalt 2.3 Other Asphalt 2.4

6 Petroleum asphalt 2.1

7 Organic cementing materials
Petroleum asphalt 2.1 ——Introduction Petroleum Asphalt Organic cementing materials Asphalts (Bitumen) Tars Pitches Natural deposits Petroleum asphalts Lake asphalts Rock asphalts See asphalts Asphalt cement (solid or semi-solid) Cutback asphalts (liquid) Emulsified asphalts (liquid) Blown asphalt (semi-solid) Slow curing Medium curing Rapid curing

8 Gasoline, kerosene, Diesel oil, etc
——Asphalt processing Petroleum asphalt 2.1 Petroleum refinery Residual matter Distillates Gasoline, kerosene, Diesel oil, etc Air Still Processing Gasoline Air-blown asphalt Asphalt cement Asphalt cement Rapid-curing Cutback asphalt Kerosene Asphalt cement Medium-curing Cutback asphalt Diesel oil Asphalt cement Slow-curing Cutback asphalt Water Asphalt cement Emulsified asphalt Emulsifying agent

9 ——Components of Petroleum Asphalt(沥青组分)
2.1 ——Components of Petroleum Asphalt(沥青组分) Asphalt 正庚烷沉淀 Asphaltene (沥青质) 不可溶解部分 Soft Asphaltene (软沥青质) 可溶解部分 正庚烷冲洗 甲苯冲洗 甲苯/乙醇冲洗 Saturated (饱和分) Aromatics (芳香分) Resin (胶质)

10 Petroleum asphalt 2.1 ——Components of Petroleum Asphalt(沥青组分) 四组分:饱和分(Saturated)芳香分(Aromatics )胶质( Resin ) 沥青质( Asphaltene ) ( S, Ar, R, As )

11 Petroleum asphalt 2.1 ——Colloid structure of Petroleum Asphalt(沥青的胶体结构) 2 4 1 2 4 1 4 sol-gel type Gel type 3 3 sol type Diagram of Colloid structure of Petroleum Asphalt 1- Saturated; 2-Aromatics; Resin; 4-Asphaltene

12 Petroleum asphalt 2.1 Colloid structure sol type sol-gel type gel type
——Colloid structure of Petroleum Asphalt(沥青的胶体结构) Colloid structure sol type sol-gel type gel type P.I <-2 -2~+2 >+2

13 main properties of asphalt
Technical Property of Petroleum Asphalt ——introduction 2.2 main properties of asphalt physical properties Viscosity (黏滞性) low temperature property temperature susceptibility Adhesiveness 黏附性 密度 体积 膨胀 系数 介电 常数 黏 度 稠 度 延性 脆性 针入 度指 (PI) Durability 耐久性 visco-elastic 粘弹性

14 Technical Property of Petroleum Asphalt ——Density
2.2 Relative density (25℃/25 ℃)= Asphalt density (15 ℃) ×0.996 密度瓶 Weigh the following mass successively: 1. m瓶 2. m瓶+满水 3. m瓶+沥青 4. m瓶+沥青+水 14

15 Technical Properties of Petroleum Asphalt
2.2 Technical Properties of Petroleum Asphalt

16 银烛秋光冷画屏, 轻罗小扇扑流萤。 天阶夜色凉如水,坐看牵牛织女星。 ——杜牧
Across the screen the autumn moon stares coldly from the sky; With silken fan I sit and flick the fireflies sailing by, The night grows colder every hour,—— it chills me to the heart To watch the Spinning Damsel from the herd boy far apart. By Du Mu

17 Technical Property of Petroleum Asphalt ——Viscosity (黏滞性)
2.2 Viscosity means a capability that the particles of asphalt material resist shearing deformation under external force. 得到表征动力粘度的公式: 表示沥青层间的速度变化梯度(剪变率)为一个单位 时,单位面积沥青可承受的的内磨阻力。 动力黏度与密度之比为运动黏度:

18 Measurement on viscosity
Technical Property of Petroleum Asphalt ——Viscosity (黏滞性) 2.2 Viscosity can be measured by different methods. Measurement on viscosity 动力黏度 (Pa.S) 运动黏度 (mm2/S) 表观黏度 (Pa.S) 相对黏度 真空减压 毛细管法 毛细管法 布洛克菲尔德 粘度计法 稠 度 高温稳定性 针入度 (0.1mm) 软化点 (℃)

19 Technical Property of Petroleum Asphalt
——Relative viscosity: Penetration(针入度) 2.2 Relative viscosity such as penetration is consistency rather than viscosity actually, which means a standard needle penetrates depth (0.1mm) into the asphalt sample under specified conditions (test temperature 25℃, mass of standard needle 100g, time of penetration 5s). So penetration can be expressed as P25℃,100g,5s. Penetrometer Schematic of penetration test The lower of penetration value, the higher consistency is. Penetration not only expresses the consistency of asphalt sample, but it is the basis of asphalt grading. The greater of the value of penetration, the higher asphalt grade is.

20 Technical Property of Petroleum Asphalt
——Relative viscosity: Softening point (软化点) 2.2 Softening point expresses the specified softening level (℃: TR&B) of asphalt sample when heated under some specified conditions (e.g. rate of temperature: 5℃/min.). The higher softening point, the better of performance at high temperature asphalt is. Softening point can be considered as a temperature under same consistency, while penetration is a consistency under same temperature condition. Schematic of softening point test Softening point test apparatus

21 Technical Property of Petroleum Asphalt
——properties at low temperature: Ductility(延度) 2.2 Ductility is the total plastic deformation (mm) of asphalt sample when it is stretched under specified condition (e.g. temperature: 15℃ or10 ℃, drawing speed: 5cm/min.). The greater ductility at lower temperature, the better low temperature performance of asphalt is. Test specimen Demonstration of ductility test

22 Technical Property of Petroleum Asphalt
——Temperature susceptibility(感温性) 2.2 Asphaltic material may vary from solid to liquid, depending on the temperature. This characteristic is known as temperature susceptibility. Temperature susceptibility can be expressed as penetration index (PI: 针入度指数) and index of penetration and viscosity number (PVN:针入度黏度指数). The former indicates the temperature susceptibility of asphalt under softening point, while the latter indicates the property above the softening pointer.

23 Technical Property of Petroleum Asphalt
——Temperature susceptibility(感温性) 2.2 PI can be expressed as: Here: which(A) is coefficient of penetration and temperature. PI determining (1) When temperature of asphalt is at the softening point, penetration of the asphalt is nearly 800(0.1mm) at this temperature, So

24 Technical Property of Petroleum Asphalt
——Temperature susceptibility(感温性) 2.2 (2) Measuring several penetrations under different temperature condition (such as 15℃, 20 ℃, 25 ℃, 30 ℃, etc), through the mathematical regression, the coefficient of penetration and temperature (A) is find out. (Note the regression coefficient should not less than 0.997) (3) Through the monograph to find PI directly.

25 Technical Property of Petroleum Asphalt
——Temperature susceptibility(感温性) 2.2 Significance of PI Expressing the degree of temperature susceptibility under softening point; The greater PI, the lower temperature susceptibility of asphalt is; Division types of colloid structure of asphalt: PI<-2, sol type PI>+2, gel type PI= -2~ +2, sol-gel type

26 Technical Property of Petroleum Asphalt
——Temperature susceptibility(感温性) 2.2 Equivalent softening point: means the corresponding temperature when penetration is 800(0.1mm), which shows the high temperature performance of asphalt. Equivalent breaking point: the corresponding temperature when penetration is 1.2(0.1mm), which reflects the low temp. performance.

27 Technical Property of Petroleum Asphalt ——Adhesiveness (黏附性)
2.2 When asphalt mixes with aggregate particles, asphalt forms film on the particles. Adhesiveness represents connection degree of this thin film. The higher degree, the better adhesiveness is. Alkali aggregate has better adhesiveness with asphalt than acid agg, which means the better water stability of asphalt mixture is. Evaluation method: Boiling water method for coarse agg; Immersion method for fine agg.

28 Technical Properties of Petroleum Asphalt
2.2 Technical Properties of Petroleum Asphalt

29 Technical Property of Petroleum Asphalt ——Durability (耐久性)
2.2 Influence factors on durability of asphalt: temperature oxidation ultraviolet ray water hardening Evaluation methods thin film oven test(TFOT): for short-term aging rotation thin film oven test (RTFOT): for short-term aging, especially for modified asphalt pressure aging vessel (PAV): for long-term aging Evaluation indexes mass loss penetration ratio residual ductility 薄膜烘箱 (Thin film oven test) 压力老化箱 (Pressure aging vessel) 旋转薄膜烘箱 (Rotate thin film oven test)

30 Technical Property of Petroleum Asphalt ——Visco-elastic property (黏弹性)
2.2 Asphalt is a typical visco-elastic material, which means asphalt shows viscosity property under low temperature condition while shows elastic property under high temperature condition. This kind special property can be expressed by the stiffness modulus. This modulus is related not only with stress and strain, but with temperature and loading time. Stiffness of asphalt can be read from the nomograph.

31 2.2 Technical Property of Petroleum Asphalt
——Visco-elastic property (黏弹性) 2.2 Nomograph of asphalt stiffness modulus

32 Technical Specifications of Petroleum Asphalt
2.2 Based on current specifications of our country, asphalt marks are divided by penetration, which means the greater penetration, the higher marks asphalt is. To heavy traffic asphalt (GB/T15180—2000), the are 5 marks: AH-50, AH-70, AH-90, AH-110 and AH-130. To road petroleum asphalt (JTG F ), there are 7 marks, commonly used asphalt marks are: mark50, mark70, mark90, mark110 and mark130, etc.

33 Technical Specifications of Petroleum Asphalt
2.2 The smaller of penetration, the lower mark asphalt is, and the more consistency to asphalt, which this mark of asphalt is more suitable to the hot weather condition.

34 Chinese specification
Technical Specifications of Petroleum Asphalt 2.2 Chinese specification 粘稠道路石油沥青(针入度分级penetration grade) Index Level Asphalt 160# 130# 110# 90# 70# 50# 30# Penetration degree @25 oC, , 5s (0.1mm) 80-100 60-80 40-60 20-40 Suitable climate subarea 2-1 2-2 3-2 1-1 1-2 1-3 2-3 1-4 2-4 Penetration Index A -1.5~+1.0 B -1.8~+1.0 Softening point (R&B) ≥ 38 40 43 45 44 46 49 55 36 39 42 53 C 35 37 41 50 Viscosity @ 60 oC (Pa.s)≥ - 60 120 160 140 180 200 260 10 oC (cm) ≥ 30 20 15 25 10 8 15 oC (cm) ≥ A、B 100 80 Wax content (%) ≥ 2.2 3.0 4.5 Flashing point (COC)(oC) ≥ 230 245 solubility ≥ 99.5 After TFOT (or RTFOT) Quality loss % ≤ 0.8 Penetration ratio after evaporation ≥ 48 54 57 61 63 65 52 58 62 Ductility ratio after evaporation (10 oC) ≥ 12 6 4 2 Ductility ratio after evaporation (15 oC) ≥ 34

35 Asphalt quality grades
Technical Specifications of Petroleum Asphalt 2.2 Asphalt quality grades (沥青质量等级) All layers of third and under third grade highway C Lower layer of expressway and first grade highway All layers of second and under second grade highway Used for basis asphalt B All layers of all grade highway A Suitable for Grades

36 Technical Specifications of Petroleum Asphalt
2.2 ——The brief Introduction of Stratagem Highway Researching Plan (SHRP) in America 美国战略公路研究计划(SHRP)是1987年由美国国会通过的一项为期5年( )的研究计划,其投资总额为1.5亿美元,目的是改善其国家道路的使用性能和耐久性,使得这些道路对使用者及其维护者都更加安全。该计划的资金来自联邦资助公路基金的0.25%的预留费。开发及评价道路施工、养护、管理创新技术的工作都以合同的形式委托给了大学、咨询机构和研究人员。研究成果分为四大部分:沥青、混凝土及结构、路面性能、公路管理等。 1991年ISTEA(水路运输功效联合法案 )提供了1.08亿美元,由联邦公路管理局(FHWA)管理,主要是用6年的时间帮助各州及公路行业把SHRP的成果推广应用并继续路面长期性能(LTPP)的研究。 如今,已开发的SHRP技术每年可以为美国节约大量的资金。联邦公路管理局已开发出一个有效的、创新的、灵活的实施计划,并承诺和公路行业的合作伙伴一起尽快地、有效地发挥这些效益. 

37 Technical Specifications of Petroleum Asphalt
2.2 ——characteristics of SHRP Asphalt properties are evaluated according to different three stages: ——during the transportation and storage stage; ——blending and spreading process; ——service stage of asphalt pavement. All specifications are provided under same requirement rather than same temperature. Put forward some new evaluate indexes and corresponding instruments.

38 ——The brief Introduction of SHRP
Technical Specifications of Petroleum Asphalt 2.2 ——The brief Introduction of SHRP RV试验(P48) Rotary viscosimeter(旋转式粘度计):measure viscosity of asphalt (用于测量沥青的 粘度). 38

39 ——The brief Introduction of SHRP
Technical Specifications of Petroleum Asphalt 2.2 ——The brief Introduction of SHRP DSR试验 Dynamic Shear Rheometer(动态剪切流变仪)(P58):Determination of viscoelastic properties of asphalt within temperature at 5-85℃ before and after aging, and also presentation the ability for anti-rutting at high temperature condition (测定未老化和老化之后的沥青在5-85℃温度范围内线粘弹性性质,并可用于反映沥青的高温抗车辙能力).

40 ——The brief Introduction of SHRP
Technical Specifications of Petroleum Asphalt 2.2 ——The brief Introduction of SHRP DTT试验(P51) Direct Tension Test(直接拉伸仪):Evaluation of asphalt material performances at low temperature, such as stress and strain when destruction, especially to evaluate the performances for polymer modified asphalt. (评价低温下沥青胶结料性质,如破坏时的应力和应变,特别适用于聚合物改性沥青,也用于评价沥青的低温性能) 40

41 ——The brief Introduction of SHRP
Technical Specifications of Petroleum Asphalt 2.2 ——The brief Introduction of SHRP BBR试验(P50) Bending Beam Rheometer (弯曲梁流变仪):Measurement accurately of stiffness at low temperature and creep rate for asphalt (精 确测量沥青的低温劲度模量和蠕变速率,用于评价沥青的低温性能). 41

42 Technical Specifications of SHRP
2.2 Performance Grade PG46 PG52 -34 -40 -46 -10 -16 -22 Average 7-day Maximum Pavement Design Temp(℃) <46 <52 Minimum Pavement Design Temp(℃) >-34 >-40 >-46 >-10 >-16 >-22 Original Binder Flash Point (℃) >230 Viscosity,max,3Pa.s,Test Temp(℃) 135 Dynamic Shear,G*/sinδ,min,1.0kPa, Test (℃) 46 52 RTFOT or TFOT Mass loss, max, (%) 1 Dynamic Shear,G*/sinδ,min,2.2kPa, Test (℃) PAV PAV Aging Temp, (℃) 90 100 Dynamic Shear,G*/sinδ,min,5000kPa, Test (℃) 10 7 4 25 22 19 Creep stiffness,S,max,300MPa,m-value,min,0.35 Test (℃) -24 -30 -36 -6 -12 Direct Tension Failure Strain,min,1.0% Test (℃)

43 Other Asphalt 2.3

44 这张图是从网络上得到的截图(网址如上),表达了young式方程。注意由于考虑的三相体与书中的不同,所以这里:
这张图是从网络上得到的截图(网址如上),表达了young式方程。注意由于考虑的三相体与书中的不同,所以这里: 说明书中的式2-26符号也有误。所以将上式带入式2-25正确表达式, ,得到与书中相同的结果:

45 Polymer Modified Asphalt

46 Purposes of modification
Polymer Modified Asphalt ——Introduction 2.3.1 Purposes of modification Improve high temperature stability Resist cracking under low temperature Enhance anti-aging capability Improve adhesiveness between asphalt and aggregate

47 Polymer Modified Asphalt
——classifications 2.3.1 SBS Rubber Main types of modifications: Resin—聚乙烯(PE)、乙烯-乙酸共聚物(EVA); Rubber—丁苯橡胶(SBR)、废弃轮胎橡胶粉; Thermoplastic elastomeric—苯乙烯丁二烯嵌段聚合物(SBS). Anti-rutting agent fiber

48 Polymer Modified Asphalt ——Index Evaluation Methods
2.3.1 Segregation test(离析试验)——to judge the consolute stability between modified agent and asphalt; Elastic recovery test(弹性恢复试验)——to evaluate automatic recovery capacity on deformation for asphalt modified with SBS after stretching; Dynamometric ductility test(测力延度试验)——to detect the ability of modified asphalt resisting external tension. Toughness and tenacity test(黏韧性试验)——to be appropriate for asphalt modified with rubber,

49 Polymer Modified Asphalt ——Commonly Used modified asphalts
2.3.1 Type of thermoplastic elastomer (热塑性橡胶类)—— SBS(苯乙烯丁二烯嵌段聚合物); Type of rubber(橡胶类)—— SBR(丁苯橡胶); Type of thermoplastic resin(热塑性树脂类)—— PE(聚乙烯),EVA(乙烯-乙酸乙烯共聚物); Type of thermosetting resin(热固性树脂类)——EP(环氧树脂).

50 Polymer Modified Asphalt ——SBS modified asphalt
2.3.1 SBS modified asphalt is most widely used on road pavement at present. Because this type modified asphalt can be benefit both to high and low temperature performances. SBS is a polymer made of butadiene (丁二烯) and styrene (苯乙烯) in embedded way. It is this special structure that makes SBS particular features. SBS原料

51 Polymer Modified Asphalt ——SBS modified asphalt
2.3.1 单体丁二烯与苯乙烯以嵌段方式进行聚合,也就是说每一个SBS高聚物的中间部分是由丁二烯单体相连的B段,而两端则是由苯乙烯单体相连的S段,所以称之为SBS; SBS既可以是线形结构,也可以若干个丁二烯链段在中间连接形成星型结构; 苯乙烯链段(S段)聚集在一起,形成物理交联区域,成为“硬段”(塑性段)。丁二烯链段(B段)聚集在一起形成“软段”(橡胶段) ,呈高弹态; 由于SBS高聚物两种不同链段的同时存在,使得SBS具有两个玻璃化温度,分别是80℃和-80 ℃,分别是属于聚苯乙烯段和丁二烯段.

52 Polymer Modified Asphalt ——SBS modified asphalt
2.3.1 SBS作为改性剂通过高温混合、溶解、溶胀等过程与沥青形成改性沥青。在通常使用状态下,由于温度低于苯乙烯的玻璃化温度,使沥青能够保持较高的抗变形能力,所以这种改性沥青赋予沥青混合料较好的高温稳定性; 而当处于冬季较低温度时,由于环境温度肯定会高于丁二烯的玻璃化温度,所以SBS赋予沥青较好的低温柔韧变形能力,从而使沥青混合料又具备了较好的低温性能,这就是SBS改性沥青具有兼顾高低温性能要求的原因所在.

53 Polymer Modified Asphalt ——SBS modified asphalt
2.3.1 Compatibility is a key factor that affects modification effect. Benefits to compatibility include: ——The ratio of S/B, 30:70 is better than 40/60; ——Molecular weight is great, it has fine modification result, but the processes becomes difficult; ——SBS with star style has better modification result than the line style, but also is difficult to process of preparation; ——The more aromatics in asphalt, the more benefit to compatibility.

54 Polymer Modified Asphalt
——Technical Requirements for Modified Asphalt 2.3.1 According to the type of Polymer, the modified asphalts are classified to three categories: Ⅰ(SBS), Ⅱ (SBR), Ⅲ(EVA and PE); Each type of category is classified to A、B、C and D (except II) grade based on softening point. From A to D, penetration becomes smaller, viscosity becomes increase, which means performance on high temperature is improved while performance on low temperature becomes poor. Besides ordinary evaluation indexes, some special indexes such as segregation, elastic recovery, toughness and tenacity are offered to evaluate the performances of modified asphalt.

55 Polymer Modified Asphalt
——Technical requirements for modified asphalt 2.3.1 Indexes. SBS (I)(热塑性弹性体类) SBR (II)(橡胶类) EVA、PE (III)(树脂类) I-A I-B I-C I-D II-A II-B II-C III-A III-B III-C III-D Penetration oC, , 5s (0.1mm) >100 80-100 60-80 30-60 >80 40-60 30-40 Penetration Index  ≥ -1.2 -0.8 -0.4 -1.0 -0.6 5 oC,5cm/min (cm) ≥ 50 40 30 20 60 Softening point TR&B (℃) ≥ 45 55 48 52 56 3 Flash point (℃) ≥ 230 Solubility (%) ≥ 99 Recovery of elasticity 25℃(%) ≥ 65 75 Toughness and tenacity (N·m) ≥ 5 Toughness (N·m) ≥ 2.5 Storage stability Segregation, difference of softening point after 48h ( ℃) ≤ 无改性剂明显析出、凝聚 TFOT(或RTFOT)后残留物 Quality loss % 1.0 Penetration ratio after 25℃(%) ≤ 58 (cm) ≥ 25 15 10 55

56 Emulsified asphalt 2.3.2

57 Emulsified asphalt ——Introduction
2.3.2 Asphalt heated in liquid state is scattered in mixture of water and emulsified agent by mechanical action to form emulsified asphalt. Advantages of emulsified asphalt: ——It can be used under normal temperature so as to save energy and reduce pollution; ——It can prolong seasonal construction, which is rarely affected by low temperature and rain day. ——It has good adhesiveness and workability to aggregates, so as to save asphalt and ensure construction quality.

58 Emulsified asphalt ——Composition
2.3.2 Asphalt: higher grade asphalt is suitable to emulsify. Water: low hardness water is preferred. Emulsified agent: it is also known as surface activity agent which plays very important role. Stabilizing agent: it improves stability of emulsified asphalt.

59 Emulsified asphalt ——Emulsified Agent
2.3.2 Emulsified agent is one of the surface activity agents. This substance has special molecular structure which consists two parts: one is polarity on the end of molecular and one is no polarity on the another end of molecular; Emulsified agent can be classified into: Types of emulsified agents Nonionic surfactant (非离子型) Ionic surfactant (离子型) Cation surfactant (阳离子型) Anionic surfactant (阴离子型) Zwitterionic surfactant (两性离子型)

60 ——Mechanism of Emulsification
Emulsified asphalt ——Mechanism of Emulsification 2.3.2 Because any one molecular of emulsified agent has two different structure, this molecular can be absorbed on the surface of asphalt directionally, which nonionic part is towards to asphalt while ionic part is towards to water. In this way, surface energy between asphalt and water is reduced remarkably. Asphalt can be scattered steady in the water to form emulsified asphalt.

61 ——Mechanism of demulsification
Emulsified asphalt ——Mechanism of demulsification 2.3.2 In order to bring into play asphalt cohesiveness, asphalt is surely released from emulsified solution, which is known as demulsification. The causes to demulsify include: —charge adsorption; —water evaporation; —acid-base neutralization.

62 Emulsified asphalt Retained mass after sieving;
——Evaluation Indexes for Emulsified Asphalt 2.3.2 Retained mass after sieving; Residue after evaporation and properties; Viscosity; Adhesiveness; Stability in storage, and stability in storage at low temperature; Feature on ionic electric charge; Speed of demulsification.

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