外文翻譯--發(fā)泡的瀝青混合設(shè)計(jì)程序

1、<p><b>　　外文翻譯</b></p><p>　　專 業(yè) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 </p><p>　　學(xué) 生 姓 名 </p><p>　　班 級 </p><p>　　學(xué) 號(hào)

2、 </p><p>　　指 導(dǎo) 教 師 </p><p><b>　　.</b></p><p>　　發(fā)泡的瀝青混合-混合設(shè)計(jì)程序</p><p>　　K M Muthen</p><p><b>　　譯者 劉洪</b></p>&

3、lt;p>　　摘 要: 提取發(fā)泡的瀝青代表瀝青產(chǎn)業(yè)的驅(qū)動(dòng)往省能源， 環(huán)境友好和有效的解答為路大廈。 發(fā)泡的瀝青提到路大廈聚集體和發(fā)泡的瀝清一個(gè)瀝青混合物， 由一個(gè)冷的混合過程生產(chǎn)。 雖然瀝清過程被開發(fā)了超過40年前并且由研究員贊美世界， 它被相信缺乏規(guī)范化的設(shè)計(jì)程序?qū)夹g(shù)的有限的實(shí)施在南非貢獻(xiàn)了， 當(dāng)實(shí)習(xí)者傾向更加熟悉和更加有大量文件證明的產(chǎn)品。 最近有重大興趣在產(chǎn)品上， 特別是在建筑原地方法， 并且需要對于一個(gè)標(biāo)準(zhǔn)混合設(shè)計(jì)程序現(xiàn)

4、在變得根本。 也許被證明是障礙到標(biāo)準(zhǔn)化發(fā)泡的瀝青技術(shù)的一個(gè)元素是各種各樣的私有的瀝清起泡沫的技術(shù)誕生</p><p>　　關(guān)鍵詞:泡沫瀝清， 發(fā)泡的瀝青， 膨脹的瀝青， 膨脹的瀝清</p><p><b>　　1介紹</b></p><p><b>　　1.1引言</b></p><p>　　一種基

5、本成分在南非路面產(chǎn)業(yè)的成功是被承受的研究， 新和供選擇的路大廈方法的發(fā)展和實(shí)施， 由經(jīng)濟(jì)和路面材料缺乏原因刺激。 它是通常承認(rèn)的土壤加固法技術(shù)為升級品質(zhì)差材料是適當(dāng)?shù)?，以便這些材料能使用到他們的潛能在路面結(jié)構(gòu)。 瀝清土壤加固法技術(shù)是導(dǎo)致被提煉的混合設(shè)計(jì)程序?yàn)楫a(chǎn)品例如ETBs最近研究主動(dòng)性的焦點(diǎn)等瀝清材料。 瀝清土壤加固法的一個(gè)共同的方面是少量的并網(wǎng)黏合劑， 在一個(gè)冷的混合的做法， 哪浩大地增加剪(內(nèi)聚)力量， 疲勞被對待的材料的抵抗和防

6、潮性。 雖然冷混合瀝青產(chǎn)品用于南非在研究主動(dòng)性之前， 他們的用途和好處在產(chǎn)業(yè)之內(nèi)現(xiàn)在獲得增加的支持。</p><p>　　對發(fā)泡的瀝青的用途， 一個(gè)供選擇的冷的混合做法， 在路路面的建筑在南非也有有限的應(yīng)用。 然而， 規(guī)范化的混合設(shè)計(jì)程序不是可利用的。 雖然發(fā)泡的瀝清過程被開發(fā)了超過40年前并且由研究員贊美世界， 它被相信缺乏規(guī)范化的設(shè)計(jì)程序?qū)@技術(shù)的有限的實(shí)施在南非貢獻(xiàn)了， 傾向更加熟悉和更加有大量文件證明的產(chǎn)

7、品的實(shí)習(xí)者。</p><p><b>　　1.2目標(biāo)和范圍</b></p><p>　　這個(gè)項(xiàng)目宗旨將開發(fā)和核實(shí)混合設(shè)計(jì)程序?yàn)榘l(fā)泡的瀝青。 本文在發(fā)泡的瀝青包含出版研究研究結(jié)果文學(xué)回顧。 信息從早先研究和當(dāng)前實(shí)踐用于開發(fā)指南為發(fā)泡的瀝青混合設(shè)計(jì)用于南非。</p><p>　　1.3發(fā)泡的瀝青的定義</p><p>　　“

8、泡沫瀝青”， 如用于本文， 提到路面建筑聚集體和發(fā)泡的瀝清混合物。 發(fā)泡的瀝清， 或膨脹的瀝清， 由水被注射入熱的瀝清的一個(gè)過程生產(chǎn)， 造成自發(fā)起泡沫。 瀝清的有形資產(chǎn)臨時(shí)地被修改，當(dāng)被注射的水， 在聯(lián)絡(luò)與熱的瀝清， 把變成在數(shù)以萬計(jì)被困住微小的瀝清泡影的蒸氣。 然而泡沫在較少比一分鐘和瀝清恢復(fù)它原始的物產(chǎn)消散。 為了生產(chǎn)起了泡沫瀝青， 瀝清必須被合并到聚集體里，當(dāng)仍然在它發(fā)泡的狀態(tài)時(shí)。</p><p>　　2發(fā)

9、泡的瀝青的概要和好處</p><p><b>　　2.1引言</b></p><p>　　1956年發(fā)泡的瀝清潛力為使用作為土壤黏合劑首先發(fā)揮了由博士。 Ladis H. Csanyi， 在工程學(xué)實(shí)驗(yàn)駐地在衣阿華州立大學(xué)。 從那以后， 發(fā)泡的瀝青技術(shù)在許多國家成功地使用了， 以原始的瀝清起泡沫的對應(yīng)的演變過程作為經(jīng)驗(yàn)在它的用途被獲取了。 原始的過程包括注射蒸汽入熱的瀝

10、清。 蒸汽起泡沫的系統(tǒng)為瀝青植物是非常方便的，蒸汽是欣然可利用的，但它證明不切實(shí)際的為在原處起泡沫的操作， 由于對特別設(shè)備的需要例如蒸汽鍋爐。 1968年， MOBIL油澳洲， 哪些獲取了專利權(quán)為Csanyi的發(fā)明， 通過加冷水修改了原始的過程而不是蒸汽入熱的瀝清。 瀝清起泡沫的過程因而變得更多實(shí)用和經(jīng)濟(jì)為一般用途。</p><p>　　起泡沫增加瀝清的表面和可觀地減少它的黏度， 使它非常合適為混合與冷和潮濕聚集

11、體。 發(fā)泡的瀝清可以使用與各種各樣的材料， 范圍從常規(guī)優(yōu)質(zhì)被分級的材料和被回收的路面材料到少量的材料例如有的那些一個(gè)高可塑性索引。 發(fā)泡的瀝青可以被制造在原處或在一棵中央植物中。 黏合劑內(nèi)容根據(jù)混合設(shè)計(jì)， 并且被確定作為為混合(由重量)要求的百分比有最宜的物產(chǎn)。</p><p>　　2.2發(fā)泡的瀝青混合的好處</p><p>　　發(fā)泡的瀝青的以下好處是有大量文件證明的：</p>

12、<p>　　? 發(fā)泡的黏合劑增加切變強(qiáng)度并且減少顆粒狀材料的濕氣感受性。 發(fā)泡的瀝青方法的力量特征那些被鞏固的材料， 但發(fā)泡的瀝青是靈活和疲勞抗性。</p><p>　　? 泡沫治療比其他冷的混合過程可以使用與大范圍集合類型。</p><p>　　? 減少的黏合劑和運(yùn)輸費(fèi)用， 起泡沫瀝青比冷混合的其他類型要求較少黏合劑和水。</p><p>　　? 挽

13、救及時(shí)， 因?yàn)榘l(fā)泡的瀝青立刻變緊密并且可能幾乎運(yùn)載交通，在擊實(shí)完成之后。</p><p>　　? 能量守恒， 因?yàn)樾枰訜醿H瀝清，當(dāng)聚集體被混合，當(dāng)寒冷和潮濕時(shí)時(shí)(對干燥的沒有需要)。</p><p>　　? 起因于揮發(fā)性的蒸發(fā)的環(huán)境副作用從混合從治療被避免不導(dǎo)致?lián)]發(fā)性發(fā)行</p><p>　　? 發(fā)泡的瀝青可以儲(chǔ)備沒有黏合劑決賽或水蛭吸血的風(fēng)險(xiǎn)。 因?yàn)榘l(fā)泡的瀝青保

14、持可使用在非常延長的期間， 通常時(shí)間限制為達(dá)到擊實(shí)， 塑造和完成層數(shù)被避免。</p><p>　　? 發(fā)泡的瀝青層數(shù)在有害天氣情況可以被修建， 例如在冷氣候或小雨， 沒有影響實(shí)用性或完成的層數(shù)的質(zhì)量。</p><p><b>　　3設(shè)計(jì)考慮</b></p><p><b>　　3.1引言</b></p>&l

15、t;p>　　在發(fā)泡的瀝青進(jìn)行的實(shí)驗(yàn)室試驗(yàn)應(yīng)該評估對變形的抵抗， 并且在內(nèi)聚和力量上的變化以濕氣和溫度。 因?yàn)榘l(fā)泡的瀝青混合力量對濕氣情況是極端敏感的， 在測試方法應(yīng)該考慮到這些。 由于發(fā)泡的瀝青混合可能承擔(dān)范圍從顆粒狀材料的特征到那些高質(zhì)量瀝青材料， 選擇的測試方法應(yīng)該能處理大范圍物質(zhì)類型。 關(guān)聯(lián)領(lǐng)域表現(xiàn)以實(shí)驗(yàn)室試驗(yàn)結(jié)果為了開發(fā)適當(dāng)?shù)闹笜?biāo)值(標(biāo)準(zhǔn))是適當(dāng)?shù)臑閷?shí)驗(yàn)室被測量的物產(chǎn)。</p><p><b&

16、gt;　　3.2瀝清物產(chǎn)</b></p><p>　　發(fā)泡的瀝清， 也指膨脹的瀝清， 是從液體臨時(shí)地被轉(zhuǎn)換了成泡沫狀態(tài)被水的一種熱的瀝青黏合劑(典型地2%)的小百分比加法。 發(fā)泡的瀝清被描繪根據(jù)擴(kuò)展比率和半衰期。 一旦泡沫消散了，泡沫的擴(kuò)展比率被定義作為比率在泡沫狀態(tài)達(dá)到的最大體積和黏合劑之間的最后的容量。 半衰期是時(shí)間， 在幾秒鐘內(nèi)， 在片刻之間泡沫達(dá)到它消散到最大體積的一半的最大體積和時(shí)間。<

17、;/p><p>　　3.2.1起泡沫的潛力</p><p>　　在發(fā)泡的瀝青生產(chǎn)期間，混合的階段瀝清的起泡沫的特征扮演一個(gè)重要角色。 它可以期望最大化的擴(kuò)展比率和半衰期在混合之內(nèi)將促進(jìn)黏合劑分散作用。佛朗哥和Wood (1983)發(fā)現(xiàn)任何瀝清， 不問等級或起源， 能起泡沫以噴管類型的一個(gè)適當(dāng)?shù)慕M合， 水， 空氣和瀝清射入壓力。 然而， abel (1978)發(fā)現(xiàn)了：</p>&l

18、t;p>　　?包含硅樹脂的瀝清可能減少了起泡沫的能力;</p><p>　　?瀝清以更低的黏度比瀝清欣然起了泡沫并且有更高的泡沫比率和半衰期以更高的黏度， 但對高黏性瀝清的用途導(dǎo)致優(yōu)越聚集涂層;</p><p>　　? 反剝離的代理增強(qiáng)了瀝清的起泡沫的能力， 并且</p><p>　　? 可接受起泡沫只達(dá)到了在溫度在149°C之上。</p>

19、;<p>　　3.2.2發(fā)泡的瀝清內(nèi)容(BC)</p><p>　　在起泡沫瀝青混合最宜的瀝清內(nèi)容不可能清楚地經(jīng)常被確定，它能在情況下熱混合瀝青。 的黏合劑內(nèi)容的范圍可以使用(BC)在混合的穩(wěn)定限制由損失在范圍的上端和由水感受性在末端。 看起來一個(gè)重大參量是黏合劑內(nèi)容比與罰款內(nèi)容， i.e. 黏合劑罰款灰漿的黏度在混合穩(wěn)定扮演一個(gè)重大角色(參見第3.3部分)。 表3.1也許用于作為指南選擇根據(jù)混合的

20、罰款內(nèi)容的適當(dāng)?shù)酿ず蟿﹥?nèi)容。 akeroyd和Hicks (1988)也提出了對比例黏合劑罰款關(guān)系的用途選擇黏合劑內(nèi)容， 范圍從3,5%黏合劑黏合劑內(nèi)容為5%罰款內(nèi)容對5%黏合劑內(nèi)容為20%罰款內(nèi)容。 然而這種方法可能不是可適用的為材料的所有類型， 由于罰款的變化的黏合劑吸收特征， 反過來， 取決于來源(父母)材料。</p><p><b>　　3.3聚集物產(chǎn)</b></p>

21、<p>　　研究表示，大范圍聚集體也許使用與起泡沫瀝清， 范圍從被擊碎的石頭到沙子和對礦石跟蹤， 如表3.2所顯示。 土壤的某些類型也許要求石灰治療和分級的調(diào)整使他們令人滿意地執(zhí)行。 圖3.1顯示MOBIL泡沫安定分級的圖(Akeroyd， 1988)。 材料符合圖的區(qū)域A被發(fā)現(xiàn)適當(dāng)?shù)臑榕菽委煘槌林乇唤灰椎穆贰?材料符合區(qū)域B為輕微被交易的路是適當(dāng)?shù)模?但能對區(qū)域A材料被調(diào)整被粗糙的分?jǐn)?shù)的加法。 除非罰款增加，材料在區(qū)域C在

22、罰款上是短少并且為泡沫安定不是適當(dāng)?shù)摹?lt;/p><p><b>　　3.4濕氣情況</b></p><p>　　濕氣含量在混合和擊實(shí)期間由許多研究員認(rèn)為最重要的混合設(shè)計(jì)準(zhǔn)則為發(fā)泡的瀝青混合。 在聚集體要求濕氣變?nèi)岷秃凸收细骄郏?援助在瀝清分散作用在混合期間和為領(lǐng)域擊實(shí)。 ruckel等(1982)建議濕氣密度關(guān)系在試驗(yàn)混合的公式化被考慮。 不足的水在黏合劑的不充分的

23、分散作用減少混合和結(jié)果的實(shí)用性， 當(dāng)許多水加長治愈時(shí)間時(shí)， 減少變緊密的混合的力量和密度，并且可以減少聚集體的涂層。 最宜的濕氣含量(OMC)變化， 根據(jù)被優(yōu)選的混合物產(chǎn)(力量， 密度， 吸水性， 脹大)。 然而， 因?yàn)闈駳鉃榛旌虾蛽魧?shí)是重要的， 這些操作，當(dāng)優(yōu)選濕氣含量時(shí)，應(yīng)該考慮。</p><p><b>　　3.5治療適應(yīng)</b></p><p>　　研究表示，

24、發(fā)泡的瀝青混合不在擊實(shí)以后開發(fā)他們充分的力量，直到混合的濕氣的大百分比丟失。 這個(gè)過程被命名治療。 治療是過程，藉以發(fā)泡的瀝青逐漸獲取對濕氣含量的減少隨著時(shí)間的過去陪同的力量。 ruckel等(1982)認(rèn)為，濕氣含量在治療的期間有一個(gè)重大效果在混合的強(qiáng)度極限。</p><p>　　然而， 李(1980)提供建議的實(shí)驗(yàn)證據(jù)一個(gè)前提對于在發(fā)泡的瀝青上的力量獲取混合的干耗。 哪些案件， 實(shí)驗(yàn)室混合設(shè)計(jì)程序?qū)⑿枰７轮?/p>

25、療過程的領(lǐng)域?yàn)榱岁P(guān)聯(lián)實(shí)驗(yàn)室制作的混合物產(chǎn)與那些領(lǐng)域混合。 因?yàn)橹委煱l(fā)泡的瀝青在領(lǐng)域混合發(fā)生在幾個(gè)月， 再生產(chǎn)治療條件在實(shí)驗(yàn)室里的實(shí)際領(lǐng)域是不切實(shí)際的。 需要治療做法的一個(gè)加速的實(shí)驗(yàn)室， 在哪些力量獲取特征可以關(guān)聯(lián)以領(lǐng)域行為， 特別是與早期， 被獲得的中間和強(qiáng)度極限。</p><p>　　這個(gè)描述特性是特別重要的，當(dāng)結(jié)構(gòu)容量分析， 基于實(shí)驗(yàn)室被測量的力量價(jià)值， 需要。 大多早先調(diào)查采取了治療做法的實(shí)驗(yàn)室由Bower

26、ing (1970) 提議， 例如，治療在溫度的3天烤箱60°C。 這個(gè)做法導(dǎo)致穩(wěn)定在大約0%到4%的濕氣含量， 哪些代表最干燥的狀態(tài)可達(dá)成在領(lǐng)域。 如此被治療的樣品的力量特征是在職狀態(tài)的代表近似地一年在建筑。 關(guān)心被表達(dá)了對也許發(fā)生在一個(gè)固化溫度60°C.的黏合劑變老。 并且， 因?yàn)檫@個(gè)溫度上述那軟化點(diǎn)共同的路品級瀝清， 在瀝清分散作用上的變化在混合之內(nèi)在治療期間是可能的。 在實(shí)驗(yàn)室檢驗(yàn)階段這項(xiàng)研究期間，這些問題將

27、被論及。 劉易斯建議的一個(gè)可選擇方法(1998)將烘干發(fā)泡的瀝青對恒定的大量， 在低溫(40° C)。</p><p><b>　　4 結(jié)論</b></p><p>　　起了泡沫冷的混合在大眾化獲取由于他們的好表現(xiàn)的瀝青， 建筑和兼容性舒適與大范圍集合類型。 和與所有瀝青混合， 有一個(gè)適當(dāng)?shù)幕旌显O(shè)計(jì)程序?yàn)榘l(fā)泡的瀝青混合為了優(yōu)選可利用的材料用法和優(yōu)選混合物產(chǎn)是

28、根本的。 幸運(yùn)地， 為發(fā)泡的瀝青混合， 混合設(shè)計(jì)可以完成由相對地簡單測試規(guī)程和通過遵守某些制約關(guān)于用于的材料。 在這項(xiàng)研究中， 早先經(jīng)驗(yàn)與發(fā)泡的瀝青材料在世界的其他地區(qū)被鞏固了入混合設(shè)計(jì)指南用于南非。 混合設(shè)計(jì)指南跟隨一個(gè)逐步程序， 從通過原材料的描述特性到最后測試變緊密的樣品。 保重保證被采取的規(guī)程是與標(biāo)準(zhǔn)測試方法和當(dāng)前被接受的實(shí)踐兼容。 除瀝清起泡沫的植物之外， 混合設(shè)計(jì)可以達(dá)到用標(biāo)準(zhǔn)設(shè)備可利用在瀝青實(shí)驗(yàn)室。</p>

29、<p>　　中央哲學(xué)在混合設(shè)計(jì)是優(yōu)選混合力量特征在最壞的操作環(huán)境，例如，在被浸泡的情況下。 間接抗拉強(qiáng)度測試提供如此評估變緊密的發(fā)泡的瀝青樣品一個(gè)方便方式。 樣品使用標(biāo)準(zhǔn)馬歇爾擊實(shí)用具在一個(gè)被浸泡的情況變緊密然后被測試。 通過舉辦測試在黏合劑內(nèi)容的范圍， 最宜的黏合劑內(nèi)容可以被選擇。 其他測試， 例如韌性模數(shù)， 動(dòng)態(tài)蠕動(dòng)和混合， 也被舉辦為了核實(shí)選擇的最宜的混合和保證混合的充分表現(xiàn)。 許多新的技術(shù)被開發(fā)達(dá)到起泡沫瀝清。 然而，

30、 因?yàn)榛旌显O(shè)計(jì)在優(yōu)選混合物產(chǎn)此中提出了集中， 它相等地很好與所有泡沫瀝青混合一起使用， 不問用具的種類曾經(jīng)生產(chǎn)發(fā)泡的瀝清</p><p>　　Foamed Asphalt Mixes - Mix Design Procedure</p><p>　　K M Muthen</p><p>　　Abstract Foamed asphalt epitomizes th

31、e asphalt industry’s drive towards energy efficient, environmentally friendly and cost-effective solutions for road-building. Foamed asphalt refers to a bituminous mixture of road-building aggregates and foamed bitumen,

32、produced by a cold mix process. Although thefoamed bitumen process was developed more than 40 years ago and lauded by researchers the world over, it is believed that the lack of standardized design procedures has contrib

33、uted to the limited im</p><p>　　Key words foamed bitumen, foamed asphalt, expanded asphalt, expanded bitumen</p><p>　　1 INTRODUCTION</p><p>　　1.1 General</p><p>　　An es

34、sential ingredient in the success of the South African pavement industry is the sustained research, development and implementation of new and alternative road-building methods, motivated by reasons of economy and the sca

35、rcity of pavement materials. It is generally accepted that soil stabilization techniques are suitable for upgrading poor quality materials so that these materials may be used to their full potential in the pavement struc

36、ture. Bitumen soil stabilization technology has been th</p><p>　　benefits are now gaining increased acceptance within the industry.</p><p>　　The use of foamed asphalt, an alternative cold mix pr

37、ocedure, has also had limited application in the construction of road pavements in South Africa. However, no standardized mix design procedure is available. Although the foamed bitumen process was developed more than 40

38、years ago and lauded by researchers the world over, it is believed that the lack of standardized design procedures has contributed to the limited implementation of this technology in South Africa, practitioners favouring

39、 more f</p><p>　　1.2 Aim and Scope</p><p>　　The objective of this project is to develop and verify a mix design procedure for foamed asphalt. This document contains a literature review of publis

40、hed research findings on foamed asphalt. Information from previous research and current practice was used to develop guidelines for foamed asphalt mix design for use in South Africa.</p><p>　　1.3 Definition

41、of Foamed Asphalt</p><p>　　The term ‘foamed asphalt’, as used in this document, refers to a mixture of pavement construction aggregates and foamed bitumen. The foamed bitumen, or expanded bitumen, is produce

42、d by a process in which water is injected into the hot bitumen, resulting in spontaneous foaming. The physical properties of the bitumen are temporarily altered when the injected water, on contact with the hot bitumen, i

43、s turned into vapour which is trapped in thousands of tiny bitumen bubbles. However the foam dissipa</p><p>　　2 OVERVIEW AND ADVANTAGES OF FOAMED ASPHALT</p><p>　　2.1 General</p><p>

44、;　　The potential of foamed bitumen for use as a soil binder was first realised in 1956 by Dr. Ladis H. Csanyi, at the Engineering Experiment Station in Iowa State University. Since then, foamed asphalt technology has bee

45、n used successfully in many countries, with corresponding evolution of the original bitumen foaming process as experience was gained in its use. The original process consisted of injecting steam into hot bitumen. The ste

46、am foaming system was very convenient for asphalt plants where </p><p>　　Foaming increases the surface area of the bitumen and considerably reduces its viscosity, making it well suited for mixing with cold a

47、nd moist aggregates. Foamed bitumen can be used with a variety of materials, ranging from conventional high-quality graded materials and recycled pavement materials to marginal materials such as those having a high plast

48、icity index. Foamed asphalt can be manufactured in situ or in a central plant. Binder contents are based on the mix design, and are determined as </p><p>　　2.2 Advantages of Foamed Asphalt Mixes</p>&

49、lt;p>　　The following advantages of foamed asphalt are well documented:</p><p>　　? The foamed binder increases the shear strength and reduces the moisture susceptibility of granular materials. The strength

50、 characteristics of foamed asphalt approach those of cemented materials, but foamed asphalt is flexible and fatigue resistant.</p><p>　　? Foam treatment can be used with a wider range of aggregate types than

51、 other cold mix processes.</p><p>　　? Reduced binder and transportation costs, as foamed asphalt requires less binder and water than other types of cold mixing.</p><p>　　? Saving in time, becaus

52、e foamed asphalt can be compacted immediately and can carry traffic almost immediately after compaction is completed.</p><p>　　? Energy conservation, because only the bitumen needs to be heated while the agg

53、regates are mixed in while cold and damp (no need for drying).</p><p>　　? Environmental side-effects resulting from the evaporation of volatiles from the mix are avoided since curing does not result in the r

54、elease of volatile</p><p>　　? Foamed asphalt can be stockpiled with no risk of binder runoff or leeching. Since foamed asphalt remains workable for very extended periods, the usual time constraints for achie

55、ving compaction, shaping and finishing of the layer are avoided.</p><p>　　? Foamed asphalt layers can be constructed in adverse weather conditions, such as in cold weather or light rain, without affecting th

56、e workability or the quality of the finished layer.</p><p>　　3 DESIGN CONSIDERATIONS</p><p>　　3.1 General</p><p>　　Laboratory tests conducted on foamed asphalt should evaluate resis

57、tance to deformation, as well as variations in cohesion and strength with moisture and temperature. As the strength of foamed asphalt mixes is extremely sensitive to moisture conditions, these should be taken into accoun

58、t in the test methods. Because foamed asphalt mixes can take on characteristics ranging from granular materials to those of high quality asphalt materials, the test method selected should be able to handle a wide r</p

59、><p>　　3.2 Bitumen Properties</p><p>　　Foamed bitumen, also referred to as expanded bitumen, is a hot bituminous binder which has been temporarily converted from a liquid to a foam state by the add

60、ition of a small percentage of water (typically 2 per cent). The foamed bitumen is characterized in terms of expansion ratio and half-life. The expansion ratio of the foam is defined as the ratio between the maximum volu

61、me achieved in the foam state and the final volume of the binder once the foam has dissipated. The half-life is the time, </p><p>　　3.2.1 Foaming Potential</p><p>　　The foaming characteristics o

62、f bitumen play an important role during the mixing stage of foamed asphalt production. It can be expected that maximized expansion ratios and half-lives will promote binder dispersion within the mix. Castedo Franco and W

63、ood (1983) found that any bitumen, irrespective of grade or origin, could be foamed with an appropriate combination of nozzle type, water, air and bitumen injection pressure. However, Abel (1978) found that:</p>&

64、lt;p>　　?bitumen which contained silicones could have reduced foaming abilities;</p><p>　　?bitumens with lower viscosities foamed more readily and had higher foam ratios and half-lives than bitumens with h

65、igher viscosities, but the use of high viscosity bitumens resulted in superior aggregate coating;</p><p>　　? anti-stripping agents intensified the foaming ability of bitumens, and</p><p>　　? acc

66、eptable foaming was only achieved at temperatures above 149° C.</p><p>　　3.2.2Foamed Bitumen Content (BC)</p><p>　　In foamed-asphalt mixes the optimum bitumen content often cannot be clearl

67、y determined as it can in the case of hot-mix asphalt. The range of binder contents (BC) that can be used is limited by the loss in stability of the mix at the upper end of the range and by water susceptibility at the lo

68、wer end. It appears that one significant parameter is the ratio of binder content to fines content, i.e. the viscosity of the binder-fines mortar plays a significant role in mix stability (see section 3.3).</p>&l

69、t;p>　　3.3 Aggregate Properties</p><p>　　Research has shown that a wide range of aggregates may be used with foamed-bitumen, ranging from crushed stone to silty sands and even to ore tailings, as shown in

70、 Table 3.2. Certain types of soil may require lime treatment and grading adjustments to enable them to perform satisfactorily. Figure 3.1 shows the Mobil foam stabilization grading chart (Akeroyd and Hicks, 1988). Materi

71、als conforming to Zone A of the chart have been found to be suitable for foam treatment for heavily trafficked roads.</p><p>　　3.4 Moisture Conditions</p><p>　　The moisture content during mixin

72、g and compaction is considered by many researchers to be the most important mix design criteria for foamed asphalt mixes. Moisture is required to soften and breakdown agglomerations in the aggregates, to aid in bitumen d

73、ispersion during mixing and for field compaction. Ruckel et al (1982) recommend that the moisture-density relationship be considered in the formulation of trial mixes. Insufficient water reduces the workability of the mi

74、x and results in inadequate</p><p>　　3.5 Curing Conditions</p><p>　　Studies have shown that foamed asphalt mixes do not develop their full strength after compaction until a large percentage of t

75、he mixing moisture is lost. This process is termed curing. Curing is the process whereby the foamed asphalt gradually gains strength over time accompanied by a reduction in the moisture content. Ruckel et al (1982) concl

76、uded that the moisture content during the curing period had a major effect on the ultimate strength of the mix.</p><p>　　However, Lee (1980) provided experimental evidence which suggested that moisture loss

77、wasnot a prerequisite for strength gain in foamed asphalt mixes. Whichever the case, a laboratory mix design procedure would need to simulate the field curing process in order to correlate the properties of laboratory- p

78、repared mixes with those of field mixes. Since the curing of foamed asphalt mixes in the field occurs over several months, it is impractical to reproduce actual field curing conditions in the la</p><p>　　Thi

79、s characterization is especially important when structural capacity analysis, based on laboratory-measured strength values, is required. Most of the previous investigations have adopted the laboratory curing procedure pr

80、oposed by Bowering (1970), i.e. 3 days oven curing at a temperature of 60° C. This procedure results in the moisture content stabilizing at about 0 to 4 per cent, which represents the driest state achievable in the

81、field. The strength characteristics of samples cured in this m</p><p>　　4 CONCLUSION</p><p>　　Foamed asphalt cold mixes are gaining in popularity owing to their good performance, ease of constr

82、uction and compatibility with a wide range of aggregate types. As with all bituminous mixes, it is essential to have a proper mix design procedure for foamed asphalt mixes in order to optimize the usage of available mate

83、rials and to optimize mix properties. Fortunately, for foamed asphalt mixes, the mix design can be accomplished by relatively simple test procedures and by adhering to certain restr</p><p>　　The central phil

84、osophy in the mix design is to optimize the mix strength characteristics at the worst-case operating environment, i.e.under soaked conditions. The indirect tensile strength test offers a convenient way of evaluating comp

85、acted foamed asphalt samples in this manner. Samples are compacted using standard Marshall compaction apparatus and then tested in a soaked condition. By conducting tests over a range of binder contents, the optimum bind