道路工程外文文獻翻譯---瀝青混合料的應用、理論和原則

1、<p><b>　　外文文獻翻譯</b></p><p><b>　　原文：</b></p><p>　　Asphalt Mixtures-Applications, Theory and Principles</p><p>　　1 . Applications</p><p>　　As

2、phalt materials find wide usage in the construction industry. The use of asphalt as a cementing agent in pavements is the most common of its applications, however, and the one that will be considered here.</p><

3、;p>　　Asphalt products are used to produce flexible pavements for highways and airports. The term “flexible” is used to distinguish these pavements from those made with Portland cement, which are classified as rigid pa

4、vements, that is, having beam strength. This distinction is important because it provides they key to the design approach which must be used for successful flexible pavement structures.</p><p>　　The flexible

5、 pavement classification may be further broken down into high and low types, the type usually depending on whether a solid or liquid asphalt product is used. The low types of pavement are made with the cutback, or emulsi

6、on, liquid products and are very widely used throughout this country. Descriptive terminology has been developed in various sections of the country to the extent that one pavement type may have several names. However, th

7、e general process followed in construction is si</p><p>　　The high type of asphalt pavements is made with asphalt cements of some selected penetration grade. </p><p>　　Fig. ?1 A modern asphalt

8、concrete highway. Shoulder striping is used as a safely feature.</p><p>　　Fig. ?2 Asphalt concrete at the San Francisco International Airport.</p><p>　　They are used when high wheel loads and h

9、igh volumes of traffic occur and are, therefore, often designed for a particular installation. </p><p>　　2 . Theory of asphalt concrete mix design</p><p>　　High types of flexible pavement are co

10、nstructed by combining an asphalt cement, often in the penetration grade of 85 to 100, with aggregates that are usually divided into three groups, based on size. The three groups are coarse aggregates, fine aggregates, a

11、nd mineral filler. These will be discussed in detail in later chapter.</p><p>　　Each of the constituent parts mentioned has a particular function in the asphalt mixture, and mix proportioning or design is th

12、e process of ensuring that no function is neglected. Before these individual functions are examined, however, the criteria for pavement success and failure should be considered so that design objectives can be establishe

13、d.</p><p>　　A successful flexible pavement must have several particular properties. First, it must be stable, that is to resistant to permanent displacement under load. Deformation of an asphalt pavement can

14、 occur in three ways, two unsatisfactory and one desirable. Plastic deformation of a pavement failure and which is to be avoided if possible. Compressive deformation of the pavement results in a dimensional change in the

15、 pavement, and with this change come a loss of resiliency and usually a degree of rou</p><p>　　The pavement should be durable and should offer protection to the subgrade. Asphalt cement is not impervious to

16、the effects of weathering, and so the design must minimize weather susceptibility. A durable pavement that does not crack or ravel will probably also protect the roadbed. It must be remembered that flexible pavements tra

17、nsmit loads to the subgrade without significant bridging action, and so a dry firm base is absolutely essential.</p><p>　　Rapidly moving vehicles depend on the tire-pavement friction factor for control and s

18、afety. The texture of the pavement surfaces must be such that an adequate skid resistance is developed or unsafe conditions result. The design procedure should be used to select the asphalt material and aggregates combin

19、ation which provides a skid resistant roadway.</p><p>　　Design procedures which yield paving mixtures embodying all these properties are not available. Sound pavements are constructed where materials and met

20、hods are selected by using time-tested tests and specifications and engineering judgments along with a so-called design method.</p><p>　　The final requirement for any pavement is one of economy. Economy, aga

21、in, cannot be measured directly, since true economy only begins with construction cost and is not fully determinable until the full useful life of the pavement has been recorded. If, however, the requirements for a stabl

22、e, durable, and safe pavement are met with a reasonable safety factor, then the best interests of economy have probably been served as well.</p><p>　　With these requirements in mind, the functions of the con

23、stituent parts can be examined with consideration give to how each part contributes to now-established objectives or requirements. The functions of the aggregates is to carry the load imposed on the pavement, and this is

24、 accomplished by frictional resistance and interlocking between the individual pieces of aggregates. The carrying capacity of the asphalt pavement is, then, related to the surface texture (particularly that of the fine a

25、ggr</p><p>　　The asphalt cement in the flexible pavement is used to bind the aggregate particles together and to waterproof the pavements. Obtaining the proper asphalt content is extremely important and bear

26、s a significant influence on all the items marking a successful pavement. A chief objective of all the design methods which have been developed is to arrive at the best asphalt content for a particular combination of agg

27、regates.</p><p>　　3 . Mix design principles</p><p>　　Certain fundamental principles underlie the design procedures that have been developed. Before these procedures can be properly studied or ap

28、plied, some consideration of these principles is necessary. </p><p>　　Asphalt pavements are composed of aggregates, asphalt cement, and voids. Considering the aggregate alone, all the space between particles

29、 is void space. The volume of aggregate voids depends on grading and can vary widely. When the asphalt cement is added, a portion of these aggregate voids is filled and a final air-void volume is retained. The retention

30、of this air-void volume is very important to the characteristics of the mixture. The term air-void volume is used, since these voids are weight</p><p>　　An asphalt pavement carries the applied load by partic

31、le friction and interlock. If the particles are pushed apart for any reason , then the pavement stability is destroyed. This factor indicates that certainly no more asphalt should be added than the aggregate voids can re

32、adily hold. However ,asphalt cement is susceptible to volume change and the pavement is subject to further compaction under use. If the pavement has no air voids when placed, or if it loses them under traffic, then the e

33、xpandi</p><p>　　Fig. ?3 Cross section of an asphalt concrete pavement showing the aggregate framework bound together by asphalt cement.</p><p>　　The need for a minimum air-void volume (usually

34、2 or 3 per cent ) has been established. In addition, a maximum air-void volume of 5 to 7 per cent should not be exceed. An excess of air voids promotes raveling of the pavement and also permits water to enter and speed u

35、p the deteriorating processes. Also, in the presence of excess air the asphalt cement hardens and ages with an accompanying loss of durability and resiliency.</p><p>　　The air-void volume of the mix is deter

36、mined by the degree of compaction as well as by the asphalt content. For a given asphalt content, a lightly compacted mix will have a large voids volume and a lower density and a greater strength will result. In the labo

37、ratory, the compaction is controlled by using a specified hammer and regulating the number of blows and the energy per blow. In the field, the compaction and the air voids are more difficult to control and tests must be

38、made no specimens tak</p><p>　　Asphalt content has been discussed in connection with various facets of the ix design problem. It is a very important factor in the mix design and has a bearing an all the char

39、acteristics ld a successful pavement: stability, skid resistance, durability, and economy. As has been mentioned, the various design procedures are intended to provide a means for selecting the asphalt content . These te

40、sts will be considered in detail in a future chapter ,but the relationship between asphalt content and t</p><p>　　Fig.4 Variations in stability, unit weight, and air-void content with asphalt cement content.

41、</p><p>　　If the gradation and type of aggregate, the degree of compaction, and the type of asphalt cement are controlled, then the strength varies in a predictable manner. The strength will increase up to s

42、ome optimum asphalt content and then decrease with further additions. The pattern of strength variation will be different when the other mix factors are changed, and so only a typical pattern can be predicted prior to ac

43、tual testing.</p><p>　　Unit weight varies in the same manner as strength when all other variable are controlled. It will reach some peak value at an asphalt content near that determined from the strength cur

44、ve and then fall off with further additions.</p><p>　　As already mentioned, the air-void volume will vary with asphalt content. However, the manner of variation is different in that increased asphalt content

45、 will decrease air-void volume to some minimum value which is approached asymptotically. With still greater additions of asphalt material the particles of aggregate are only pushed apart and no change occurs in air-void

46、volume.</p><p>　　In summary, certain principles involving aggregate gradation, air-void volume, asphalt content, and compaction mist be understood before proceeding to actual mix design. The proper design ba

47、sed on these principles will result in sound pavements. If these principles are overlooked, the pavement may fail by one or more of the recognized modes of failure: shoving, rutting, corrugating, becoming slick when the

48、max is too ‘rich’; raveling, cracking, having low durability when the mix is too ‘lean’. </p><p>　　It should be again emphasized that the strength of flexible is, more accurately, a stability and does not i

49、ndicate any ability to bridge weak points in the subgrade by beam strength. No asphalt mixture can be successful unless it rests on top of a properly designed and constructed base structure. This fact, that the surface i

50、s no better than the base, must be continually in the minds of those concerned with any aspect of flexible pavement work.</p><p><b>　　譯文：</b></p><p>　　瀝青混合料的應用、理論和原則</p><p

51、><b>　　1、應用</b></p><p>　　瀝青材料如今在建筑行業(yè)廣泛使用。瀝青最常見的應用是作為的瀝青路面的粘結劑使用。然而，這一點必須在這里予以介紹。</p><p>　　瀝青產品常用于生產公路和機場柔性路面。所謂“柔性”是用來區(qū)分與硅酸鹽水泥制成的路面，它被列為剛性路面，也就是這些路面具有剛性強度。這個區(qū)別很重要，因為它提出了成功進行柔性路面結構設

52、計的方法的關鍵。</p><p>　　柔性路面的分類可進一步細分為高、低的類別，分類通常取決于是否有使用固體或液體瀝青產品。低類型路面結構類型通過減少瀝青用量或使用乳化劑、液體瀝青，是非常廣泛的應用在全國范圍內。在全國的范圍內各地區(qū)已開發(fā)各自的描述性術語，一個路面類型可能有好幾個名字。但是，一般對大多數(shù)低型路面其施工方法確是相似，可描述為瀝青產品通常單獨或其混合結構應用于行車道，形成路面。</p>

53、<p>　　高級瀝青路面用經過選擇的具有好的滲透性的瀝青混凝土制成。</p><p>　　圖1 現(xiàn)代瀝青混凝土公路 路肩設置路標線具有安全地特點</p><p>　　圖2 舊金山國際機場瀝青混凝土跑道</p><p>　　它們被用于重荷載和大交通量道路，因此，人們會進行特殊的結構設計。</p><p>　　2、瀝青混凝土設計原理&l

54、t;/p><p>　　高等級柔性路面是用瀝青混凝土建造而成，通常根據(jù)集料的85%-100%通過率將其分為三種類型。這三種分別為粗集料、細集料和礦粉。這些將在后面的章節(jié)中進行詳細討論。</p><p>　　瀝青混合料的每一個組成部分都有特定的功能，混合料配合比設計是確保沒有功能被忽略的過程。然而，在這些個別功能檢查之前，對于路面的成功和失敗的標準應該考慮，這樣路面的設計目標才能確定。</p

55、><p>　　一個成功的柔性路面必須有幾個特定的屬性。首先，它必須是穩(wěn)定的，即抵抗負荷下的永久位移。瀝青路面變形的可能發(fā)生在三種方式，二個是不理想的形變，一個是可以接受的。塑性變形對路面來說是要盡量避免的失敗。路面的壓縮變形導致的路面鋪裝的尺寸變化，這種變化將引起路面彈性和粗糙度的損失。這種變形沒有剛剛描述的那種那么嚴重，但它也同樣導致路面破壞。理想類型的變形是一種彈性變形，這實際上有利于柔性路面，并對于其長壽命是十

56、分必要的。</p><p>　　路面應該耐用并能夠保護路基。瀝青混凝土是受環(huán)境的影響的，因此設計必須降低對氣候敏感性。一個耐用的路面要不開裂或擁包才能保護路基。我們必須記住，柔性路面將荷載直接傳至路基，所以堅實的基礎是絕對必要的。</p><p>　　快速移動的車輛依靠的輪胎路面摩擦力實現(xiàn)控制和保證安全。路面表面紋理必須保證足夠的防滑性否則將產生不安全的后果。設計過程通過瀝青材料的選擇和集

57、料的組合設計提供了防滑路面。</p><p>　　設計程序放棄鋪面結合料所有這些表面特性都無法使用。合理的路面建造所需的材料和方法是經過使用時間考驗和規(guī)范和工程判斷和在一起所稱的設計方法選定。</p><p>　　對于任何路面最后一個要求是經濟性。經濟性不能一開始就確定，準確的經濟是從開始建設直到路面整個壽命期的成本。然而，如果對于路面穩(wěn)定，耐久，安全性的要求都達到一個合理的安全系數(shù)，那么

58、對經濟的最佳利益或許已經實現(xiàn)。</p><p>　　考慮到路面的這些要求，可通過檢查各組成部分的功能如何有助于現(xiàn)在已經確定的目標或要求。瀝青混凝土功能是承擔路面上施加的負荷，這是由混合料各材料之間相互咬合和摩擦阻力實現(xiàn)。也就是瀝青路面的承載能力與路面的表面紋理（尤其是細集料）和密度或者混合料的“密實度”相關，表面結構隨集料的不同而不同，雖然理想的表面具有粗糙紋理，但在有些情況下卻不能實現(xiàn)。密級配混合物通過使用自然

59、或人為的連續(xù)級配集料得到。這意味著細骨料的存在填補了粗骨料的空隙。這除了影響混合料的密度和強度特性之外，也影響施工性能。當粗骨料使用過量時，混合料將變得堅硬而且難以施工；當?shù)V物填料使用過多時，混合料將變得較軟，影響使用性能。</p><p>　　柔性路面中的瀝青膠結材料用于將集料粘結在一起并充當防水材料。選取適當?shù)臑r青含量是非常重要的，它對于成功的路面在項目的整個評分過程中具有重要的影響。設計的首要目標是對于特定

60、的集料組合確定瀝青的最佳用量。</p><p>　　3 、混合料配合比設計原則</p><p>　　某些基本原則被制定為設計程序的基礎程序。在這些步驟之前，進行某些原則的的研究或應用是很有必要的。</p><p>　　瀝青路面由集料、瀝青膠結料和空隙組成。對于單獨的集料顆粒而言，它的周圍都是空隙空間，寂寥的空隙率和集料分級有關系并會在很大的范圍內變化。當瀝青用量增加

61、時，一部分集料的空隙將被填充，最后的空氣空隙將得到保留。這部分保留的空氣空隙對于混合料的特性是非常重要的。因為這些空隙沒有質量，因而常以體積計算，并通常作為混合料的壓實總體積百分數(shù)表示。</p><p>　　瀝青路面通過集料顆粒的摩擦和自鎖能力承載外加荷載。如果顆粒由于某種原因被擠出，那么路面的穩(wěn)定性將遭到破壞，這是由于混合料中沒有添加足夠的瀝青來有效地約束集料間的空隙的因素。然而，瀝青混凝土對空隙體積的變化時十

62、分敏感的，路面將根據(jù)使用情況進一步被壓實。如果路面修筑時沒有預留空隙，或者在交通荷載下空隙被擠壓，然后多余的瀝青將有條件溢出，這被稱作泛油。泛油的瀝青路面既減小路面厚度，也降低表面摩擦能力，使道路變得危險。</p><p>　　圖3瀝青混凝土路面橫截面顯示了瀝青膠結材料將集料骨架約束在一起</p><p>　　已經規(guī)定了一個最小的空隙率（通常是2%到3%），除此之外最大的空隙率（5%到7%

63、）也不能被超過。過大的空隙率將加快路面的剝落速度，并會讓水進入混合料內部加速路面的損壞速度。此外，過量的空氣的存在將導致瀝青混凝土硬化，并伴隨路面的耐久性和彈性，降低路面使用年限。</p><p>　　混合料的空隙率由路面的壓實度和瀝青用量決定。對于給定的瀝青用量，輕輕壓實結構將有較大的空隙體積和較低的密度和更大的強度。在實驗室，壓實控制通過使用指定的擊實錘和確定的打擊數(shù)和每擊能量。在現(xiàn)場，壓實度和空隙率更加難以

64、控制和測試，沒有試驗的混合料必須從壓實后的的路面檢查已經確定的壓實程度。交通對路面的進一步壓縮限度必須進行設計，對一個特殊混合料的實際資料需要對路面在較長時間內實行系統(tǒng)的檢查。然而，密度在百分之幾的變化是很常見的。</p><p>　　我們已經討論了瀝青用量與設計的多方面有關，它是混合料設計中的一個重要因素，決定著著路面的所有特征：穩(wěn)定性，防滑性，耐久性和經濟性。正如已經提到的，各種設計方法都是選擇瀝青含量的一種

65、手段，這些細節(jié)將在未來的章節(jié)的考慮，但瀝青含量和一些性能特性（如穩(wěn)定性、單位重量和空隙率）之間的關系將在這里討論。</p><p>　　圖4.穩(wěn)定性、密度、空隙率和瀝青用量之間的關系圖</p><p>　　如果集料的級配，壓實度，瀝青種類得到控制，那么強度的變化方式是可以預測的。強度將隨瀝青用量接近最佳用量增長，隨著瀝青用量的進一步增加，強度將逐漸降低。混合料的強度曲線將隨著其他組分的改變

66、而有所不同，因此在試驗之前只能預測一種標準的曲線。</p><p>　　當所有其他因素都保持不變時，強度和密度的變化有一定聯(lián)系。強度隨瀝青用量的增加達到一個峰值，并隨瀝青用量的繼續(xù)增加逐漸降低。</p><p>　　正如已經提到的，空氣空隙體積會隨瀝青含量變化。然而，變化的方式不同的是，增加瀝青含量將減少空氣孔洞體積并使之逐漸接近最低值，隨著瀝青用量的持續(xù)增加，集料顆粒將彼此脫離而空氣空隙

67、體積將保持不變。</p><p>　　總之，某些原則比如集料級配，空隙率，瀝青用量，壓實度等理解之后，再進行實際的配合比設計。正確設計以這些原則為基礎，將會有合理的路面。如果這些原則被忽視，這個道路可能會失敗，并伴隨多種病害：推移、車轍、波浪，當路面過厚時會變得光滑，剝落、開裂，耐久性降低當混合料總量過少時。</p><p>　　應該再次強調的是，更準確地說柔性強度穩(wěn)定的，并不表示路基強度