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1、土木工程材料第五章土木工程材料第五章1 15.1 Types of asphaltBitumen is a solid，semisolid，or viscous cementitious material，natural or manufactured，and composed principally of various mixtures of complex hydrocarbons (烃烃, 碳氢化合物碳氢化合物).Features of bitumenlCompletely soluble in carbon disulfide (CS2)lNonvolatilelSoften whe
2、n heated5.1.2 AsphaltsAsphalts are cementitious materials in which the predominant constituent materials are bitumens.Natural deposits or petroleum asphaltThe consistency of asphalts varies widely from solid to semisolid at normal temperatureThe natural deposits of asphalts are of two types：Natural
3、rock asphaltslDeposits of sandstone or limestone filled with asphaltsNative asphalts or lake asphaltslLake Trinidad特立尼达岛特立尼达岛，West Indies (a 110-acre lake containing about 40 percent bitumen mixed with water, fine siliceous silt, clay, and organic matter);lBermudez，Venezuela (lake asphalt containing
4、 about 65 percent bitumen)Trinidad Lake Asphalt特立尼达岛特立尼达岛 Petroleum asphaltPetroleum asphalts are classified into four types：lAsphalt cementslCutback asphaltslEmulsified asphaltslAir-blown asphaltsUsages of petroleum asphalts Petroleum asphalts are used in lconstruction of flexible pavementslroof co
5、nstruction (asphalt shingles, rolled roofing, and built-up roofing),lfor insulation (electrical insulation and building paper)lwaterproofing (sprays, paints, and bituminous fabrics) lcanal lining lseal subgrades against the migration of waterlJoint seals*5.2 Petroleum asphaltPetroleum asphalts are c
6、lassified into four types：lAsphalt cementslCutback asphaltslEmulsified asphaltslAir-blown asphalts5.2.1 Asphalt CementAsphalt cement is very sticky and highly viscous, especially prepared with the quality and consistency required in the manufacture of asphalt pavements (hot-mix pavements).It is obta
7、ined after separation of lubricating oils from crude petroleum. Properties of asphalt cement It possesses excellent binding properties and adheres very well to aggregate particles.lwhen used in pavement construction it is necessary to heat both the asphalt cement and the aggregates prior to mixingsu
8、perior waterproof qualitieslPavement built using paving asphalt is waterproof and resistant to many types of chemical attack.*5.2 Petroleum asphaltPetroleum asphalts are classified into four types：lAsphalt cementslCutback asphaltslEmulsified asphaltslAir-blown asphalts5.2.2 Cutback Asphalts Two type
9、s of asphalt are available in liquid form:lcutback asphalt lemulsified asphaltCutback asphalt- is asphalt cement that is liquefied by blending with petroleum solvents (called diluents). Cutback asphalt are divided into three typesSlow-curingMedium-curingRapid-curing Slow-curing cutback asphaltSlow-c
10、uring cutback asphalt is asphalt cement blended with oils of low volatility，such as diesel oil 柴油柴油. Its viscosity value is low and it hardens very slowly.It is used for cold laid pavement bases. Medium-curing cutback asphaltMedium-curing cutback asphalt is obtained by blending asphalt cement with k
11、erosene- 煤油煤油 type diluents of medium volatility. It hardens faster than the slow-curing and slower than the rapid-curing type.Used for cold-laid pavement bases (plant mixed and mixed in place) and surface treatmentsRapid-curing cutback asphaltRapid-curing cutback asphalt is asphalt cement blended w
12、ith naphtha or gasoline- 汽油汽油 type diluents of high volatility. The diluents in rapid-curing asphalt evaporate quickly.Used primarily in mixed-in-place pavement mixes and surface treatments.*5.2 Petroleum asphaltPetroleum asphalts are classified into four types：lAsphalt cementslCutback asphaltslEmul
13、sified asphaltslAir-blown asphalts5.2.3 Emulsified AsphaltEmulsified asphalt is composed of asphalt cement and water that contains a small amount of an emulsifying agentlSoapslwater-soluble chemicalslfine clay乳化沥青乳化沥青 乳化沥青是将通常高温使用的道路沥青，经过机械搅乳化沥青是将通常高温使用的道路沥青，经过机械搅拌和化学稳定的方法（乳化），扩散到水中而液化成拌和化学稳定的方法（乳化）
14、，扩散到水中而液化成常温下粘度很低、流动性很好的一种道路建筑材料。常温下粘度很低、流动性很好的一种道路建筑材料。可以常温使用，且可以和冷的和潮湿的石料一起使用。可以常温使用，且可以和冷的和潮湿的石料一起使用。当乳化沥青当乳化沥青破乳破乳凝固时凝固时- 还原为连续的沥青并且水分还原为连续的沥青并且水分完全排除掉，道路材料的最终强度才能形成。、完全排除掉，道路材料的最终强度才能形成。、在众多的道路建设应用中，乳化沥青提供了一种比热在众多的道路建设应用中，乳化沥青提供了一种比热沥青更为安全、节能和环保的系统，因为这种工艺避沥青更为安全、节能和环保的系统，因为这种工艺避免了高温操作、加热和有害排放。免
15、了高温操作、加热和有害排放。乳化沥青主要用于道路的升级与养护，如石屑封层，乳化沥青主要用于道路的升级与养护，如石屑封层，还有多种独特的、其它沥青材料不可替代的应用，如还有多种独特的、其它沥青材料不可替代的应用，如冷拌料、稀浆封层。乳化沥青亦可用于新建道路施工，冷拌料、稀浆封层。乳化沥青亦可用于新建道路施工，如粘层油、透层油等。如粘层油、透层油等。*advantages of emulsified asphaltemulsified asphalt can be applied during damp weather and with aggregates that are cold or ho
16、tthe quantity of materials applied is controlled automatically lbecause any excess (water) will drain into the subgradesaving energylThe use of emulsified asphalt also eliminates the use of fuel required to heat and dry the aggregates in the asphalt cement mixtureslreduces energy requirements throug
17、h reduction or elimination of petroleum distillates used in cutback asphalts. *disadvantage of emulsified asphaltpollutionlbecause the asphalt is suspended in water, it is susceptible to being washed off a road surface by rainwater if not sufficiently cured. The unbroken emulsions may be carried int
18、o streams, causing ground contamination.*5.2 Petroleum asphaltPetroleum asphalts are classified into four types：lAsphalt cementslCutback asphaltslEmulsified asphaltslAir-blown asphalts5.2.4 Blown AsphaltBlown asphalt is obtained by blowing air through the semisolid residue obtained during the later
19、stages of the distillation processProperties lrelatively firm in consistency lDuctilelweather resistant and can withstand temperature changes very wellUsages of Blown asphaltsBlown asphalts use in the manufacturelroofing materialslwaterproof paintsl joint fillers (for concrete pavements)lundersealing old，rigid pavementsl mineral rubber35 结束语结束语