針對乳化瀝青與泡沫瀝青冷再生技術發展過程中的關鍵問題，介紹了冷再生技術的發展現狀，分析了乳化瀝青與泡沫瀝青混合料的材料組分性能，總結了冷再生瀝青混合料配合比設計方法和路面結構設計方法，論述了相關路用性能演化規律以及施工工藝和施工設備，提出了冷再生技術的未來發展趨勢。研究結果表明：冷再生瀝青混合料的材料組成成分間相互作用機制及強度破壞機理復雜，回收瀝青混合料來源和摻量以及瀝青老化程度、瀝青以及外加劑種類及含量均會顯著影響冷再生瀝青混合料的材料性能；不同的冷再生瀝青混合料設計方法在級配選擇、瀝青等級、成形方法、養護方式以及性能評價指標等方面差別較大，大多采用試驗測試法指導配合比設計；冷再生瀝青路面設計方法經歷了從經驗法到力學－經驗法的轉變，通常將冷再生材料視為無黏結顆粒材料或者瀝青黏結材料進行結構設計，目前仍缺乏符合冷再生瀝青混合料材料特性的力學失效設計準則；在工程應用方面，應充分考慮冷再生結構層位及力學響應，明確抗車轍、抗水損害、抗疲勞和低溫抗開裂的性能需求，以指導冷再生瀝青混合料的材料組成設計；未來應從施工工藝和材料組成兩方面加強冷再生瀝青混合料性能優化研究，建立以力學指標為基礎的養生時間評估體系，完善適用于氣候條件的冷再生結構層施工規范，加強現場試驗的數據檢測和收集工作，實現對冷再生瀝青路面結構設計方程的有效標定。

　　In view of the key problems in the development of cold recycling technology of emulsified asphalt and foam asphalt, this paper introduces the development status of cold recycling technology, analyzes the material composition performance of emulsified asphalt and foam asphalt mixture, summarizes the mix proportion design method and pavement structure design method of cold recycling asphalt mixture, discusses the evolution law of relevant road performance, construction technology and construction equipment, and puts forward the future development trend of cold recycling technology. The research results indicate that the interaction mechanism and strength failure mechanism between the material components of cold recycled asphalt mixture are complex. The source and dosage of recycled asphalt mixture, as well as the degree of asphalt aging, the type and content of asphalt and additives, will significantly affect the material properties of cold recycled asphalt mixture; Different design methods for cold recycled asphalt mixtures vary greatly in terms of gradation selection, asphalt grade, forming method, curing method, and performance evaluation indicators. Most of them use experimental testing methods to guide mix design; The design method of cold recycled asphalt pavement has undergone a transformation from empirical method to mechanical empirical method. Cold recycled materials are usually regarded as non bonded granular materials or asphalt bonding materials for structural design. Currently, there is still a lack of mechanical failure design criteria that meet the characteristics of cold recycled asphalt mixture materials; In terms of engineering applications, the cold recycling structure layer and mechanical response should be fully considered, and the performance requirements for anti rutting, anti water damage, anti fatigue, and low-temperature anti cracking should be clarified to guide the material composition design of cold recycling asphalt mixtures; In the future, research on optimizing the performance of cold recycled asphalt mixtures should be strengthened from two aspects: construction technology and material composition. A health time evaluation system based on mechanical indicators should be established, and construction specifications for cold recycled structural layers suitable for Chinese climate conditions should be improved. Data detection and collection work for on-site testing should be strengthened to achieve effective calibration of the design equation for cold recycled asphalt pavement structures.

　　針對乳化瀝青與泡沫瀝青冷再生技術發展過程中的關鍵問題，介紹了冷再生技術的發展現狀，分析了乳化瀝青與泡沫瀝青混合料的材料組分性能，總結了冷再生瀝青混合料配合比設計方法和路面結構設計方法，論述了相關路用性能演化規律以及施工工藝和施工設備，提出了冷再生技術的未來發展趨勢。研究結果表明：冷再生瀝青混合料的材料組成成分間相互作用機制及強度破壞機理復雜，回收瀝青混合料來源和摻量以及瀝青老化程度、瀝青以及外加劑種類及含量均會顯著影響冷再生瀝青混合料的材料性能；不同的冷再生瀝青混合料設計方法在級配選擇、瀝青等級、成形方法、養護方式以及性能評價指標等方面差別較大，大多采用試驗測試法指導配合比設計；冷再生瀝青路面設計方法經歷了從經驗法到力學－經驗法的轉變，通常將冷再生材料視為無黏結顆粒材料或者瀝青黏結材料進行結構設計，目前仍缺乏符合冷再生瀝青混合料材料特性的力學失效設計準則；在工程應用方面，應充分考慮冷再生結構層位及力學響應，明確抗車轍、抗水損害、抗疲勞和低溫抗開裂的性能需求，以指導冷再生瀝青混合料的材料組成設計；未來應從施工工藝和材料組成兩方面加強冷再生瀝青混合料性能優化研究，建立以力學指標為基礎的養生時間評估體系，完善適用于氣候條件的冷再生結構層施工規范，加強現場試驗的數據檢測和收集工作，實現對冷再生瀝青路面結構設計方程的有效標定。

　　In view of the key problems in the development of cold recycling technology of emulsified asphalt and foam asphalt, this paper introduces the development status of cold recycling technology, analyzes the material composition performance of emulsified asphalt and foam asphalt mixture, summarizes the mix proportion design method and pavement structure design method of cold recycling asphalt mixture, discusses the evolution law of relevant road performance, construction technology and construction equipment, and puts forward the future development trend of cold recycling technology. The research results indicate that the interaction mechanism and strength failure mechanism between the material components of cold recycled asphalt mixture are complex. The source and dosage of recycled asphalt mixture, as well as the degree of asphalt aging, the type and content of asphalt and additives, will significantly affect the material properties of cold recycled asphalt mixture; Different design methods for cold recycled asphalt mixtures vary greatly in terms of gradation selection, asphalt grade, forming method, curing method, and performance evaluation indicators. Most of them use experimental testing methods to guide mix design; The design method of cold recycled asphalt pavement has undergone a transformation from empirical method to mechanical empirical method. Cold recycled materials are usually regarded as non bonded granular materials or asphalt bonding materials for structural design. Currently, there is still a lack of mechanical failure design criteria that meet the characteristics of cold recycled asphalt mixture materials; In terms of engineering applications, the cold recycling structure layer and mechanical response should be fully considered, and the performance requirements for anti rutting, anti water damage, anti fatigue, and low-temperature anti cracking should be clarified to guide the material composition design of cold recycling asphalt mixtures; In the future, research on optimizing the performance of cold recycled asphalt mixtures should be strengthened from two aspects: construction technology and material composition. A health time evaluation system based on mechanical indicators should be established, and construction specifications for cold recycled structural layers suitable for Chinese climate conditions should be improved. Data detection and collection work for on-site testing should be strengthened to achieve effective calibration of the design equation for cold recycled asphalt pavement structures.

　　引言

　　Introduction

　　進入２１世紀以來，國內道路建設規模和建設速度持續增 長。近年來隨著公路設計服務年限的臨近，各地道路陸續出現一系列病害，由此導致道路養護里程和養護規模急速增長，在此過程中不可避免地產生大量的瀝青銑刨料，其中包括回收瀝青混合料（ＲｅｃｙｃｌｅｄＡｓｐｈａｌｔＰａｖｅｍｅｎｔ，ＲＡＰ）以及回收水泥穩定基層料［１－２］。露天堆放、填埋等傳統處理方法會造成環境污染以及資源浪費。此外，隨著天然集料和瀝青材料的供應緊缺和上漲，對道路建設成本以及施工進度產生了一定的負面影響，因此，再生技術得到了廣泛的關注和應用［３－４］。再生技術主要包括熱再生技術和冷再生技術。相比于熱再生，冷再生技術通常采用乳化瀝青或泡沫瀝青作為瀝青膠結料，在常溫下進行拌和和壓實，可降低瀝青膠結料的初始老化［５］，且能量消耗僅為生產同等瀝 青 混 合 料 的 ２０％～４０％［６－７］，具 有節 能、可持續性強和經濟效益高等優勢。根據施工工藝、銑刨深度以及拌和場地的不同，冷再生技術細分為就地 冷 再 生（ＣｏｌｄＩｎ－Ｐ１ａｃｅＲｅｃｙｃｌｉｎｇ，ＣＩＲ）、廠拌冷再生（ＣｏｌｄＣｅｎｔｒａｌＰｌａｎｔＲｅｃｙｃｌｉｎｇ，ＣＣＰＲ）和全深式冷再生（ＦｕｌｌＤｅｐｔｈＲｅｃｙｃｌｉｎｇ，ＦＤＲ）。冷再生技術經過幾十年的發展已被世界各國廣泛應用，在美國、加拿大、法國、德國、澳大利亞等已較為成熟。目前冷再生技術主要應用于輕交通等級的路面修復，弗吉尼亞州交通部的研究表明冷再生技術對于重交通道路的修復也具有明顯的適用性和顯著的成本效益［８］。

　　Since the beginning of the 21st century, the scale and speed of domestic road construction have continued to grow. In recent years, as the service life of highway design approaches, a series of road diseases have emerged in various regions, leading to a rapid increase in road maintenance mileage and scale. In this process, a large amount of asphalt milling materials are inevitably generated, including recycled asphalt pavement (RAP) and recycled cement stabilized base materials [1-2]. Traditional methods such as open-air stacking and landfilling can cause environmental pollution and waste of non renewable resources. In addition, with the shortage and price increase of natural aggregates and asphalt materials, it has had a certain negative impact on road construction costs and construction progress. Therefore, recycling technology has received widespread attention and application [3-4]. Regeneration technology mainly includes hot regeneration technology and cold regeneration technology. Compared with hot recycling, cold recycling technology usually uses emulsified asphalt or foam asphalt as asphalt binder. Mixing and compaction at normal temperature can reduce the initial aging of asphalt binder [5], and the energy consumption is only 20%~40% of the production of the same asphalt mixture [6-7]. It has the advantages of energy conservation, environmental protection, strong sustainability and high economic benefits. According to different construction techniques, milling depths, and mixing sites, cold recycling technology is divided into on-site cold recycling (CIR), factory mixed cold recycling (CCPR), and full depth recycling (FDR). Cold regeneration technology has been widely applied in countries around the world after decades of development, and has become relatively mature in countries such as the United States, Canada, France, Germany, and Australia. At present, cold recycling technology is mainly applied to the repair of light traffic grade road surfaces. Research by the Virginia Department of Transportation has shown that cold recycling technology also has significant applicability and cost-effectiveness for the repair of heavy traffic roads [8].

　　目前，眾多學者主要從冷再生瀝青混合料的材料組成性能分析、混合料配合比設計方法和路面結構設計方法、混合料路用性能分析以及施工技術和施工裝備等方面對冷再生技術開展研究。冷再生瀝青混合料材料組成及其相互作用機制復雜，眾多學者主 要 研 究 ＲＡＰ 料、乳 化瀝 青／泡 沫 瀝 青 膠 結 料，水泥／石灰添加劑等因素對冷再生瀝青混合料性能的影響。研究結果表明，ＲＡＰ料變異性大，ＲＡＰ料來源、瀝青老化程度及 ＲＡＰ料摻量都會影響冷再生瀝青混合料性能，此外，泡沫瀝青和乳化瀝青作為膠結料的混合料強度形成機理以及水泥和石灰對混合料力學性能提升效果也存在差異［９］，冷再生瀝青混合料的材料組分相互作用機制和強度破壞機理有待進一步明確，因此，在世界范圍內尚未形成統一的冷再生瀝青混合料配合比設計方法和路面結構設計方法。國外通常采用的配合比設計方法有 ＡＡＳＨＴＯ 修正馬歇爾法、Ｈｖｅｅｍ 設計法、俄勒岡州設計法、ＡＩ設計法等［１０］。發布了《公路瀝青路面再生技術規范》（ＪＴＧ／Ｔ５５２１—２０１９），并 在２０１９年 進行 了 修 訂，規定了采用雙面擊實５０＋２５次的馬歇爾法。此外，路面結構設計方法存在冷再生路面破壞失效準則不統一、模型預估值與路面檢測值不匹配等問題。以上原因制約了冷再生技術的廣泛應用。本文總結了冷再生技術類別及發展現狀、乳化瀝青和泡沫瀝青混合料材料組成性能分析、配合比設計及路面結構設計方法、路用性能分析以及冷再生技術工藝和施工設備等研究現狀，并對相關技術方法進行了對比分析，提出了冷再生技術的關鍵研究問題和未來發展趨勢，旨在進一步促進冷再生技術在實際工程中的應用。

　　At present, many scholars mainly conduct research on cold recycling technology from the aspects of material composition and performance analysis of cold recycled asphalt mixture, mixture mix design method and pavement structure design method, mixture road performance analysis, as well as construction technology and equipment. The composition of cold recycled asphalt mixture and its interaction mechanism are complex. Many scholars mainly study the influence of RAP material, emulsified asphalt/foam asphalt binder, cement/lime additives and other factors on the performance of cold recycled asphalt mixture. The research results show that RAP material has great variability. The source of RAP material, asphalt aging degree and the amount of RAP material will affect the performance of cold recycled asphalt mixture. In addition, the strength formation mechanism of mixture with foam asphalt and emulsified asphalt as binder and the improvement effect of cement and lime on the mechanical performance of mixture are also different [9]. The interaction mechanism of material components and strength destruction mechanism of cold recycled asphalt mixture need to be further clarified. Therefore, there is no unified mix design method of cold recycled asphalt mixture and pavement structure design method in the world. The commonly used mix design methods abroad include AASHTO modified Marshall method, Hveem design method, Oregon design method, AI design method, etc. [10]. China has released the "Technical Specification for Highway Asphalt Pavement Recycling" (JTG/T5521-2019) and revised it in 2019, stipulating the use of Marshall method with double-sided compaction of 50+25 times. In addition, there are some problems in the pavement structure design method, such as the failure criteria of cold recycled pavement are not unified, and the predicted values of the model do not match the measured values of the pavement. The above reasons restrict the widespread application of cold regeneration technology. This paper summarizes the category and development status of cold recycling technology, composition and performance analysis of emulsified asphalt and foam asphalt mixture materials, mix design and pavement structure design methods, road performance analysis, cold recycling technology process and construction equipment, and other research status.

　　１冷再生技術發展現狀

　　1. Development Status of Cold Recycling Technology

　　1.1 北美

　　1.1 North America

　　美國早在１９１５年開展冷再生技術研究，但在１９７４年 前 開 展 的 相 關 試 驗 研 究 較 少，在 ２０ 世 紀７０年代后逐步得到推 廣 應 用［１１］。截 止１９８５年 底，賓夕法尼亞交通部完成了包括就地冷再生、廠拌冷再生和全深式冷再生在內的大約９０個冷再生項目，旨在推動冷再生在基層應用建立標準規范，并為相關工程項目提供施工技術指導。自１９８４年以來，美國交通部開展了１２０余項就地冷再生項目，并持續對該技術的施工工藝和材料性能進行評估。到２０世紀８０年代末，美國瀝青再生料用量已占到全部瀝青混合料的一半。堪薩斯州交通部自１９８６年采用冷再生技術修復路面，并在１９９０～１９９２年期間修建了４條試驗 路。截 １９９６年，愛 荷華 州 已 完 成９７個就地冷再生項目［１２］。美國２５個州的瀝青再生料使用 規 模 已 達 到 近 ２ 億 噸。Ｍｏｒｉａｎ 等［１３］介 紹 了美國賓夕法尼亞州４４條實施冷再生技術的路段使用情況，調查結果顯示冷再生路面抗反射裂縫性能較傳統熱拌混合料直接加鋪的方式提高了１～２倍，且成本低于其２／３。

　　The United States first conducted research on cold regeneration technology in 1915, but there were relatively few related experimental studies conducted before 1974, and it gradually gained promotion and application after the 1970s [11]. By the end of 1985, the Pennsylvania Department of Transportation had completed approximately 90 cold recycling projects, including on-site cold recycling, factory mixed cold recycling, and full depth cold recycling, aimed at promoting the establishment of standard specifications for cold recycling applications at the grassroots level and providing construction technical guidance for related engineering projects. Since 1984, the US Department of Transportation has carried out over 120 on-site cold recycling projects and continuously evaluated the construction process and material properties of this technology. By the late 1980s, the use of recycled asphalt in the United States had accounted for half of all asphalt mixtures. The Kansas Department of Transportation has been using cold recycling technology to repair road surfaces since 1986 and built four test roads between 1990 and 1992. As of 1996, Iowa had completed 97 on-site cold recycling projects. The use of asphalt recycled materials in 25 states in the United States has reached nearly 200 million tons. Morian et al. [13] introduced the usage of cold recycling technology in 44 road sections in Pennsylvania, USA. The survey results showed that the anti reflective crack performance of cold recycled pavement was 1-2 times higher than that of traditional hot mix direct paving, and the cost was less than 2/3 of it.

　　美國瀝青路面協會年度調查顯示，２０１８年９９％以上的 ＲＡＰ料被回收利用［１４］。目 前，美 國 聯 邦 公 路 局 頒 布 了 ＦｅｄｅｒａｌＬａｎｄｓＨｉｇｈｗａｙＳｐｅｃｉｆｉｃａｔｉｏｎｓ，并對ＣＩＲ和ＦＤＲ兩種再生工藝進行了規范，此外全美目前有４１個州少頒布了一種冷再生技術規范；加拿大１０個省或地區中有３個省或地區制定了有關冷再生的技術規范。北美地區 的 冷 再 生 技 術 規 范 的 制 定 情 況 如 圖 １ 所示［１５］，共涉及８３個冷再生技術規范，其中大約５４％（４５個規范）規 范 了 ＣＩＲ，１７％（１４ 個 規范）規 范 了ＣＣＰＲ，２９％（２４個規范）規范了 ＦＤＲ。ＲＡＰ料除了應用于瀝青混合料，還作為碎石材料應用于道路建設。工程實踐已證明 ＲＡＰ料可應用于無黏結 基 層 材 料 和 底 基 層 材 料，但 ＲＡＰ 料 級配是 限 制 其 應 用 的 主 要 因 素。美 國 ４９ 個 州 已 將ＲＡＰ料應用于瀝青混合料中，包括佛吉尼亞州在內的１３個州應用于基層，其中４個州應用于底基層，２個州應用于穩定基層材料和路肩集料［１６］。總體來說，將 ＲＡＰ 料 應用于級配碎石基層和底基層具有良好的路用性能。

　　The annual survey of the National Asphalt Pavement Association in the United States shows that more than 99% of RAP materials were recycled in 2018 [14]. At present, the Federal Highway Administration of the United States has issued the Federal Lands Highway Specifications and standardized the CIR and FDR recycling processes. In addition, there are currently 41 states in the United States that have issued at least one cold recycling technology specification; Three out of ten provinces or territories in Canada have established technical specifications for cold regeneration. The development of cold regeneration technology specifications in North America is shown in Figure 1 [15], involving a total of 83 cold regeneration technology specifications, of which approximately 54% (45 specifications) regulate CIR, 17% (14 specifications) regulate CCPR, and 29% (24 specifications) regulate FDR. RAP material is not only used in asphalt mixtures, but also as crushed stone material in road construction. Engineering practice has proven that RAP material can be applied to non bonded base materials and sub base materials, but the gradation of RAP material is the main factor limiting its application. Forty nine states in the United States have applied RAP material to asphalt mixtures, including 13 states including Virginia for base use, with 4 states for subbase and 2 states for stabilizing base materials and shoulder aggregates [16]. Overall, applying RAP material to graded crushed stone base and subbase has good road performance.

　　１.2 歐洲

　　1.2 Europe

　　２０世紀７０年代中期，德國、荷蘭以及芬蘭等陸 續 開 展 了 路 面 再 生 料 的 研 究。歐 盟 頒 布 的ＷａｓｔｅＦｒａｍｅｗｏｒｋＤｉｒｅｃｔｉｖｅ（２００８／９８／ＥＣ）中 明確了瀝青再生技術的重要性，到２０２０年非危害性建筑垃圾（包括 瀝 青 垃 圾）的 回 收 率 應 達 到７０％。德 國目前 已 實 現 了 將１００％ＲＡＰ 料 回收 再 利 用。芬 蘭將路面再生材料主要應用于輕交通等級路面的面層和基層，近年來逐漸應用于高等級公路［１７］。法國將冷再生技術推廣于高速公路和主要交通道路的修復工程。比利時于１９８９年引進了冷再生技術，并在１９８９～２００１ 年 修 復 了 ３０ 萬 平 方 米 的 再 生 路面［１８］。在冷再生瀝青混合料的規范標準方面，英國總結了 ＲＡＰ料在道路修復和泡沫瀝青結構層中的應用情況，《公路工程規范》的第９４７和９４８條中規范了就地冷再生和廠拌冷再生的設計流程，對配合比設計方法以及冷再生瀝青路面的預期剛度模量提供指導［１９］。1.3

　　In the mid-1970s, countries such as Germany, the Netherlands, and Finland successively conducted research on road recycled materials. The Waste Framework Directive (2008/98/EC) issued by the European Union emphasizes the importance of asphalt recycling technology, and by 2020, the recycling rate of non hazardous construction waste (including asphalt waste) should reach 70%. Germany has currently achieved the recycling and reuse of 100% RAP materials. Finland mainly applies recycled pavement materials to the surface and base layers of light traffic grade pavements, and has gradually applied them to high-grade highways in recent years [17]. France will focus on promoting cold recycling technology in the repair projects of highways and major transportation roads. Belgium introduced cold recycling technology in 1989 and repaired 300000 square meters of recycled road surfaces from 1989 to 2001. In terms of specifications and standards for cold recycled asphalt mixture, the UK summarized the application of RAP material in road repair and foam asphalt structural layer. Articles 947 and 948 of the Highway Engineering Specifications standardize the design process of in situ cold recycling and plant mix cold recycling, providing guidance for mix design methods and the expected stiffness and modulus of cold recycled asphalt pavement [19]. 1.3 China

　　截２０２１年末， 公 路 總 里 程５２８萬 ，隨著公路里程的增加，公路養護投入不斷加大。交通部《公路網規劃（２０１３～２０３０年）》指出，９７％的國道、省道及縣鄉道將進行升級改造，公路養護設備和服務市場規模達２０００億人民幣。建設較早的高等級公路多為半剛性基層瀝青路面，由于瀝青面層較薄，道路易發生結構性損傷，在道路養護過程中通常將瀝青面層銑刨破碎后對半剛性基層進行處治。從１９９８年開始對冷再生瀝青混合料進行大規模的研究和應用工作，經過多年的研究和推廣已在高等級公路或干線公路得到一定程度的應用。２００７年之前，冷再生瀝青混合料主要應用于高速公路的基層和底基層，近幾年逐步推廣應用下面層。２０１０年后，對泡沫瀝青的研究越來越多，截２０１７年泡沫瀝青已分別在江蘇、浙江、湖北、廣 東、江西以及天津等地得到一定規模的應用［２０］。２０１７年和２０１８年包茂高速陜蒙段和青銀高速靖王段的路面大修工程，將乳化瀝青廠拌冷再生作為下面層進行大面積推廣應用，共利用了路面銑刨料約３０萬噸，經濟效益與環境效益顯著［２１］。《“十四五”公路養護管理發展綱要》提出了大力推動廢舊路面材料、工業廢棄物等再生利用，提升資源利用效率。目前高速公路瀝青路面材料循環利用率為９５％，普通國省道瀝青路面材料循環利用率為８０％。１.4 冷再生技術對比分析

　　As of the end of 2021, the total length of highways in China was 5.28 million kilometers, and with the increase of highway mileage, investment in highway maintenance continues to increase. The National Highway Network Plan (2013-2030) issued by the Ministry of Transport states that 97% of China's national highways, provincial highways, and county and township roads will be upgraded and renovated, and the market size of highway maintenance equipment and services will reach 200 billion yuan. China's early construction of high-grade highways mostly used semi-rigid base asphalt pavement. Due to the thin asphalt surface layer, the road is prone to structural damage. In the process of road maintenance, the asphalt surface layer is usually milled and crushed before treating the semi-rigid base layer. China has been conducting large-scale research and application of cold recycled asphalt mixture since 1998, and after years of research and promotion, it has been applied to a certain extent on high-grade highways or main roads in China. Before 2007, cold recycled asphalt mixture was mainly used for the base and subbase of highways, and in recent years, it has gradually been promoted and applied to the lower layers. Since 2010, more and more research has been done on foam asphalt in China. As of 2017, foam asphalt has been applied in Jiangsu, Zhejiang, Hubei, Guangdong, Jiangxi, Tianjin and other places on a certain scale [20]. In 2017 and 2018, the road surface overhaul projects of the Shaanxi Inner Mongolia section of the Baomao Expressway and the Jingwang section of the Qingyin Expressway promoted the large-scale application of emulsified asphalt plant mixed cold recycling as the lower layer, using a total of about 300000 tons of road milling materials, with significant economic and environmental benefits [21]. The "14th Five Year Plan for the Development of Highway Maintenance Management" proposes to vigorously promote the recycling of waste road materials, industrial waste, and other materials to improve resource utilization efficiency. At present, the recycling rate of asphalt pavement materials on Chinese highways is 95%, and the recycling rate of asphalt pavement materials on ordinary national and provincial roads is 80%. 1.4 Comparative analysis of cold regeneration technology

　　表１總結分析了３種冷再生技術適用的病害處治形式，參 照 《公路瀝青路面預防養護技術規范》（ＪＴＧ／Ｔ５１４２－０１—２０２１）對病害形式分類為路表病害、變形 類 病 害 和 裂 縫 類 病 害 ３ 種 形 式［２２］。表 １中：√為適用；Δ為可用；×為不；上標ａ表示如果病害只發生在道路表層，可直接設置加鋪層，或者進行就地冷再生處理；上標ｂ表示盡管該再生方式可處治該類型病害，但經濟性較差，不采用；上標ｃ表示需對下承層進行加固處理；上標ｄ表示如果路基承載能力不足，可采取水泥、石灰等化學改良方法進行加固處理。

　　Table 1 summarizes and analyzes three types of disease treatment forms applicable to cold recycling technology. Referring to the "Technical Specification for Preventive Maintenance of Asphalt Pavement on Highways" (JTG/T5142-01-2021), the disease forms are classified into three types: surface diseases, deformation diseases, and crack diseases [22]. In Table 1: √ is applicable; Δ is available; X is not recommended; The superscript 'a' indicates that if the disease only occurs on the surface of the road, an additional layer can be directly added or on-site cold recycling treatment can be carried out; The superscript b indicates that although this regeneration method can treat this type of disease, its economy is poor and it is not recommended to use it; The superscript c indicates the need for reinforcement treatment of the underlying layer; The superscript d indicates that if the bearing capacity of the roadbed is insufficient, chemical improvement methods such as cement and lime can be used for reinforcement treatment.

　　２冷再生瀝青混合料材料組成性能分析

　　Analysis of Composition and Performance of Cold Recycled Asphalt Mixture Materials

　　冷再生瀝青混合料的材料組成復雜，包含 ＲＡＰ料、新集料、乳化瀝青／泡沫瀝青、水泥等組分，各組成成分的力學性能及相對含量的變化會影響混合料的力學性能，因此，有必要對冷再生瀝青混合料的組成成分進 行 性 能 及 力 學 評 估。本 文 選 取 ＲＡＰ 料、乳化瀝青／泡沫瀝青膠結料以及水泥／水泥外添劑進行組分性能分析。2.1 ＲＡＰ料

　　The material composition of cold recycled asphalt mixture is complex, including RAP material, new aggregate, emulsified asphalt/foam asphalt, cement and other components. The change of mechanical properties and relative content of each component will affect the mechanical properties of the mixture. Therefore, it is necessary to conduct performance and mechanical evaluation on the components of cold recycled asphalt mixture. In this paper, RAP material, emulsified asphalt/foam asphalt binder and cement/cement additive are selected for component performance analysis. 2.1 RAP material

　　ＲＡＰ料中的粗集料顆粒假定具有較好的強度和抗變形能力，由細集料和老化瀝青膠漿組成的老化砂漿具有一定的脆性和塑性，這取決于瀝青的老化和氧化程度以及溫度等因素。同時，三軸蠕變試驗的相關結果也驗證了 ＲＡＰ料具有一定的黏性和溫度依賴性，老化瀝青能夠影響冷再生瀝青混合料力學性能，因此，在冷再生瀝青混合料配合比設計中應充分考慮 ＲＡＰ料性能，分析老化瀝青性能，以確定瀝青摻量。ＪＴＧ／Ｔ５５２１—２０１９中規定了瀝青路面回收料的取樣與試驗分析方法，在回收料使用前對 ＲＡＰ料 的含 水 率、級 配、砂 當 量、瀝 青 含 量及性能、抽提后的舊集料級配及集料性質進行測試。眾多學者主要從 ＲＡＰ料來源、瀝青老化程度、ＲＡＰ摻量等方面研究 ＲＡＰ料對冷再生瀝青混合料的性能影響。不同 來 源 的 ＲＡＰ 料 主要 在 級 配 組 成、老 化 瀝青砂漿性能方面存在差異。瀝青路面在長期荷載作用下會發生集料顆粒破損，以及受銑刨、破碎和存儲等流程的影 響，導 致 ＲＡＰ 料 具有 更 多 的 細 集 料 成分［２３－２４］。此外，由于 老 化 瀝 青 的 黏 結 作 用，ＲＡＰ 料存在大量虛假顆粒團，在混合料壓實過程中虛假顆粒團會發生破裂，從而改變混合料的設計級配，其中細顆粒中的 虛 假 顆 粒 團 成 分 高 于 粗 顆 粒［２５］，因 此，在應用前應對其顆粒團聚特性進行評估。

　　The coarse aggregate particles in RAP material are assumed to have good strength and deformation resistance, while the aged mortar composed of fine aggregate and aged asphalt binder has certain brittleness and plasticity, which depend on factors such as the aging and oxidation degree of asphalt and temperature. At the same time, the relevant results of the triaxial creep test also verified that RAP material has certain viscosity and temperature dependence, and aged asphalt can affect the mechanical properties of cold recycled asphalt mixture. Therefore, in the design of the mix proportion of cold recycled asphalt mixture, the performance of RAP material should be fully considered, and the performance of aged asphalt should be analyzed to determine the optimal asphalt dosage. JTG/T5521-2019 specifies the sampling and testing analysis methods for recycled asphalt pavement materials. Prior to the use of recycled materials, the moisture content, gradation, sand equivalent, asphalt content and properties of RAP materials, as well as the gradation and properties of extracted old aggregates, are tested. Many scholars have mainly studied the influence of RAP materials on the performance of cold recycled asphalt mixtures from the aspects of RAP material source, asphalt aging degree, RAP dosage, etc. RAP materials from different sources mainly have differences in grading composition and performance of aged asphalt mortar. Asphalt pavement will experience aggregate particle damage under long-term load, as well as the influence of milling, crushing, and storage processes, resulting in RAP materials having more fine aggregate components [23-24]. In addition, due to the bonding effect of aged asphalt, RAP material contains a large number of false particle clusters. During the compaction process of the mixture, the false particle clusters will break, thereby changing the design gradation of the mixture. The composition of false particle clusters in fine particles is higher than that in coarse particles [25]. Therefore, its particle aggregation characteristics should be evaluated before application.

　　此外，不同來源的 ＲＡＰ料表面裹附的老化瀝青砂漿差異較大，包括瀝青種類、瀝青含量及礦粉性能等因素，并且瀝青是一 種 溫 度 敏 感 性 材 料，不 同 ＲＡＰ 料 在同一溫 度 下 的 性 能 各 異。ＲＩＬＥＭ 技 術 委 員 會 在２３７－ＳＩＢＴＧ６技術方法中提出采用破碎試驗評價不同級配 區 間 ＲＡＰ 料 在 擊 實 荷 載 下 的 顆 粒 細 化 特征，基于通過１．６ｍｍ 篩孔尺寸通過率對不同來源的 ＲＡＰ 料 進 行 初 步 分 檔；其 次 開 展 不 同 溫 度 下ＲＡＰ料破碎試驗，基于不同溫度與５ ℃的１．６ｍｍ篩孔通過率 的 比 值 表 征 ＲＡＰ 料 的溫 度 敏 感 性，以反映老化瀝青在冷再生瀝青混合料中黏聚程度，并對 ＲＡＰ料進行二 次 分 檔，進 而 對 不 同 來 源 的 ＲＡＰ料進行有效的質量控制［２５－２７］。不同使用年限的 ＲＡＰ料對冷再生瀝青混合料性能的影響主要在于瀝青老化程度的差異，使用年限越長，瀝青老化程度越高。研究表明：瀝青老化能夠提高新舊瀝青的黏結程度［２８－２９］，并隨著老化程度的增加而降 低［３０］。瀝 青老 化 導 致 混 合 料 空 隙 率 增大，間接劈裂強度、斷裂能和水穩定性下降，高溫穩定性增加［３１－３２］。以 上可 知，由 于 ＲＡＰ 料 中老 化 瀝青的存在，導 致 ＲＡＰ 料 在荷 載 作 用 下 更 易 發 生 變形或斷裂；隨著 ＲＡＰ料摻量的增大，再生瀝青路面的整體路用性能呈下降趨勢［３３－３４］。

　　In addition, the aged asphalt mortar coated on the surface of RAP materials from different sources varies greatly, including factors such as asphalt type, asphalt content, and mineral powder properties. Moreover, asphalt is a temperature sensitive material, and the performance of different RAP materials varies at the same temperature. The RILEM Technical Committee proposed in the 237-1IBTG6 technical method to evaluate the particle refinement characteristics of RAP materials with different grading ranges under compaction loads using crushing tests, and to preliminarily classify RAP materials from different sources based on the pass rate through a 1.6mm sieve size; Secondly, RAP material crushing tests were conducted at different temperatures, and the temperature sensitivity of RAP material was characterized based on the ratio of 1.6mm sieve pass rate at different temperatures to 5 ℃, in order to reflect the degree of agglomeration of aged asphalt in cold recycled asphalt mixture. RAP material was further divided into two grades to effectively control the quality of RAP material from different sources [25-27]. The influence of RAP materials with different service lives on the performance of cold recycled asphalt mixtures mainly lies in the difference in the degree of asphalt aging. The longer the service life, the higher the degree of asphalt aging. Research has shown that asphalt aging can improve the adhesion between new and old asphalt [28-29], and decrease with increasing aging [30]. Asphalt aging leads to an increase in the void fraction of the mixture, a decrease in indirect splitting strength, fracture energy, and water stability, and an increase in high-temperature stability [31-32]. As can be seen from the above, the presence of aged asphalt in RAP material makes it more prone to deformation or fracture under load; With the increase of RAP content, the overall road performance of recycled asphalt pavement shows a downward trend [33-34].

　　針對老化瀝 青，楊建萍［３５］研究了 ＲＡＰ 料中瀝青分布、瀝青 含 量 分布規律并提出了瀝青變異性控制模型，建立了評價老化瀝青對新瀝青選取影響的波動范圍評價方法。眾多學者對冷再生瀝青混合料中 ＲＡＰ料摻量進行研究。隨 著 ＲＡＰ 料 摻量 增 大，冷 再 生 瀝 青 混合料內部孔隙率增大，降低了抗開裂性能、水穩定性和高溫穩定性［３１］。目前，越來越多的學者研究大摻量 ＲＡＰ料 的 冷 再 生 瀝 青 混 合 料 力 學 性 能 的 適 用性［３６］。Ｄｏｎｇ等［３７－３８］研 究 表 明 １００％ ＲＡＰ 料 摻 量的試件相比密級配基層材料試件具有更高的剛度、回彈 模 量，但 抗 剪 強 度 較 低，抗 變 形 能 力 較 差。將ＲＡＰ料作為無黏 結 基 層 材 料 時，隨 著 ＲＡＰ 料 摻量的增 加，加 州 承 載 比 （ＣａｌｉｆｏｒｎｉａＢｅａｒｉｎｇ Ｒａｔｉｏｎ，ＣＢＲ）降低，在外力作用下呈現一定的蠕變特性，這主要是由于在荷載作用下老化瀝青砂漿發生接觸滑移。根據澳大利亞等的實踐經驗，建議在工程應用中摻入一定比例的新料以達到強度和變形的規范要求，ＲＡＰ 料 摻量 建 議 不 超 過５０％［３９］。在 實際工程中應基于冷再生瀝青結構層位對其相應的力學指標進行測試，建立冷再生瀝青混合料性能指標與ＲＡＰ料摻量的定量關系，并根據道路等級對應的混合料性能要 求 嚴 格 控 制 ＲＡＰ 料 摻量，以 滿 足 結 構設計規范要求的材料性能［４０－４４］。

　　Regarding aged asphalt, Yang Jianping [35] studied the distribution and content of asphalt in RAP materials, proposed an asphalt variability control model, and established a fluctuation range evaluation method to assess the impact of aged asphalt on the selection of new asphalt. Numerous scholars have conducted research on the dosage of RAP in cold recycled asphalt mixtures. With the increase of RAP content, the internal porosity of cold recycled asphalt mixture increases, which reduces the cracking resistance, water stability, and high temperature stability [31]. At present, more and more scholars are studying the applicability of mechanical properties of cold recycled asphalt mixtures with high RAP content [36]. Dong et al. [37-38] found that specimens with 100% RAP content have higher stiffness and rebound modulus compared to specimens with dense graded base materials, but lower shear strength and poorer deformation resistance. When RAP material is used as a non bonded base material, as the RAP content increases, the California Bearing Ratio (CBR) decreases and exhibits certain creep characteristics under external forces, mainly due to contact slip of aged asphalt mortar under load. Based on the practical experience of countries such as Australia, it is recommended to add a certain proportion of new materials in engineering applications to meet the specifications for strength and deformation. The recommended RAP material content should not exceed 50% [39]. In practical engineering, the corresponding mechanical indicators of cold recycled asphalt should be tested based on its structural layer, and a quantitative relationship between the performance indicators of cold recycled asphalt mixture and the RAP content should be established. The RAP content should be strictly controlled according to the performance requirements of the road grade corresponding to the mixture, in order to meet the material properties required by the structural design specifications [40-44].

　　2.2 瀝青膠結料

　　2.2 Asphalt binder

　　乳化瀝青和泡沫瀝青是冷再生瀝青混合料常用的膠結料類型，除了為冷再生瀝青混合料提供黏結強度外，還有助于再生和軟化老化瀝青。泡沫瀝青和乳化瀝青中含有一定量的水分，在常溫下具有一定的流動性從而實現常溫拌和。冷再生瀝青混合料由于水分的存在，導致初始強度低，但隨著養護時間增長和水分揮發，混合料強度逐漸增大。2.2.1泡沫瀝青泡沫瀝青是冷再生瀝青混合料常用的膠結料，自２０世紀７０年代后被廣泛用作冷再生材料的再生劑和黏結劑。泡沫瀝青是在高溫條件下在發泡裝置中加入高溫瀝青和一定比例的水，將水與高溫瀝青混合后形成蒸汽，促使瀝青迅速膨脹生成泡沫狀，如圖２所示［４５］。發 泡效 果 的 主 要 技 術 指 標 為 膨 脹 期和半衰期，通常認為膨脹率高、半衰期長的泡沫瀝青質量較好。為充分評價泡沫瀝青的發泡質量，國內外提出了多種評價方法，包括發泡指數以及從能量角度確定發泡條件和發泡特性，研究表明發泡劑種類、溫 度、氣壓和外加水對發泡性能具有顯著影響［４１－４２］。升高溫度能夠降低瀝青黏度，提高發泡膨脹率［４３］，發泡溫度為１５０ ℃～１７０ ℃［４４］；同 時，隨著用水量的 增 加，膨 脹 率 逐 漸 增 大，半 衰 期 逐 漸 降低［４４］。此外，李強等［４］對比了３種發泡劑對瀝青發泡特性的影響，結果表明十六烷基三甲基溴化銨發泡劑表現出更優的發泡特性，且成型的再生混合料力學強度。１９５６年泡沫瀝青在愛荷華州的基層修復中作為穩定 劑 被 使 用。１９６８年美孚石油改善了 泡沫瀝青的生產工藝，促進了泡沫瀝青的發展。２０世紀７０年代，泡沫瀝青技術被廣泛應用于許多。２０世紀８０年代初，美國對泡沫瀝青再生技術進行了系統的研究，并實施了一批現場試驗段。

　　Emulsified asphalt and foam asphalt are common types of binders for cold recycled asphalt mixture. In addition to providing bond strength for cold recycled asphalt mixture, they also help to regenerate and soften aging asphalt. Foam asphalt and emulsified asphalt contain a certain amount of water and have a certain fluidity at room temperature to achieve mixing at room temperature. Due to the presence of moisture, the initial strength of cold recycled asphalt mixture is low, but as the curing time increases and moisture evaporates, the strength of the mixture gradually increases. 2.2.1 foam asphalt foam asphalt is a common binder for cold recycled asphalt mixture, and has been widely used as a regenerant and binder for cold recycled materials since the 1970s. Foam asphalt is to add high temperature asphalt and a certain proportion of water into the foaming device under high temperature conditions, mix water with high temperature asphalt to form steam, and promote the asphalt to expand rapidly to form foam, as shown in Figure 2 [45]. The main technical indicators of foaming effect are expansion period and half life. Generally, foam asphalt with high expansion rate and long half life is considered to be of good quality. In order to fully evaluate the foaming quality of foam asphalt, experts at home and abroad have proposed a variety of evaluation methods, including foaming index and determination of optimal foaming conditions and foaming characteristics from the perspective of energy. Research shows that the type of foaming agent, temperature, air pressure and added water have a significant impact on the foaming performance [41-42]. Raising the temperature can reduce the viscosity of asphalt and increase the foaming expansion rate [43]. The optimal foaming temperature is between 150 ℃ and 170 ℃ [44]; Meanwhile, as the water usage increases, the expansion rate gradually increases and the half-life gradually decreases [44]. In addition, Li Qiang et al. [4] compared the effects of three foaming agents on the foaming characteristics of asphalt, and the results showed that hexadecyltrimethylammonium bromide foaming agent exhibited better foaming characteristics, and the formed recycled mixture had the best mechanical strength. In 1956, foam asphalt was first used as a stabilizer in the base course repair in Iowa. In 1968, Mobil Petroleum improved the production process of foam asphalt and promoted the development of foam asphalt. In the 1970s, foam asphalt technology was widely used in many countries. In the early 1980s, the United States carried out a systematic study on the recycling technology of foam asphalt, and implemented a number of on-site test sections.

　　在２０世紀末，國外泡沫瀝青冷再生技術已相對成熟。２０１６年弗吉尼亞州 交 通 部 開 展 了 １００％ＲＡＰ 摻 量的 泡 沫瀝青混合料替代傳統瀝青基層的試驗段，后期調查結果顯示路面未出現明顯的開裂或車轍病害［４６］。２０１３年馬里蘭 州 公 路 管 理 局 制 定 了 泡 沫 瀝 青 穩 定基層材料的技術指南，包括配合比設計、材料選擇、現場施工以及質量控制等環節［４７］。從２０世紀９０年代開始對泡沫瀝青冷再生技術進行研究和應用。以國內典型工程———北京市盧丘路大修工程為例［４８］，現場工程應用情況表明泡沫瀝青再生混合料具有較高的模量、較小的溫度收縮應力和良好的抗疲勞性能，可用于基層以減少路面反射裂縫；半剛性基層上加鋪冷再生結構層形成的復合結構性能穩定，強度較高；泡沫瀝青混合料適用于交通量較小的高速公路。隨著泡沫瀝青含量增多，冷再生瀝青混合料的水穩定性和劈裂強度均呈現先增高后降低的趨勢，且養生方式的差異會影響混合料終的力學性能［２０］。2.2.2 乳化瀝青乳化瀝青是將高溫熔融后流動狀態的瀝青加入含有乳化劑的皂液中，通過機械高速剪切作用，使瀝青變成微小顆粒并分散在含有穩定劑－乳 化劑 的 水溶液中，形成一種較穩定的水包油結構。評判乳化瀝青的指標包括破乳速度、篩上殘留物（１．１８ｍｍ）、黏度以及蒸發殘留物等。

　　At the end of the 20th century, the cold recycling technology of foam asphalt abroad was relatively mature. In 2016, the Virginia Department of Transportation carried out a test section in which 100% RAP foam asphalt mixture was used to replace the traditional asphalt base, and the later investigation results showed that there was no obvious cracking or rutting disease on the pavement [46]. In 2013, Maryland Highway Administration formulated a technical guide for foam asphalt stabilized base course materials, focusing on mix design, material selection, on-site construction and quality control [47]. China began to research and apply the cold recycling technology of foam asphalt in the 1990s. Taking Beijing Luqiu Road Overhaul Project, a typical domestic project, as an example [48], the field engineering application shows that foam asphalt recycled mixture has high modulus, low temperature shrinkage stress and good fatigue resistance, which can be used for base course to reduce pavement reflection cracks; The composite structure formed by adding a cold recycled structural layer on a semi-rigid base has stable performance and high strength; Foam asphalt mixture is suitable for expressway with small traffic volume. With the increase of foam asphalt content, the water stability and splitting strength of cold recycled asphalt mixture show a trend of first increasing and then decreasing, and the difference in curing methods will affect the final mechanical properties of the mixture [20]. 2.2.2 Emulsified Asphalt Emulsified asphalt is the process of adding high-temperature melted and flowing asphalt to a soap solution containing emulsifiers. Through mechanical high-speed shearing, the asphalt is transformed into small particles and dispersed in an aqueous solution containing stabilizers and emulsifiers, forming a relatively stable water in oil structure. The indicators for evaluating emulsified asphalt include demulsification speed, residue on the sieve (1.18mm), viscosity, and evaporation residue.

　　在適當的制備工藝和存儲條件下，乳化瀝青可存儲幾個月。在乳化瀝青冷再生瀝青混合料強度形成機理方面，乳化瀝青液滴表面帶有電荷，當瀝青乳液與集料顆粒表面電荷電性相反時，由于異性電荷相吸，使膠結料與集料的界面黏結強度增大，不同類型瀝青乳液與集料的相容性如表２［７］所示。當瀝青乳液與集料 混合接觸時，瀝青傾向于與水分發生分離并黏附在集料顆粒表面，該過程稱為破乳。圖３示意了乳化瀝青混合料的２種破壞模式：在養護初期，由于瀝青乳液－水泥砂漿相與集料界面存在水膜，是混合料發生斷裂的強度薄弱界面，黏附破壞為主要破壞模式；隨著養護時間增加，在水泥水化反應、乳化瀝青破乳的持續進行以及水分揮發作用下，瀝青聚集成膜并均勻裹附在集料表面，界面黏附強度超過了瀝青砂漿的黏聚強度，砂漿相的黏聚破壞成為主要破壞模式。對于廠拌冷再生技術，破乳時間需大于冷再生瀝青混合料拌和、運輸以及攤鋪碾壓時間，避免乳化瀝青提前破乳并造成混合料的和易性下降。此外，乳化瀝青混合料中通常加入一定比例的水泥，水泥與水分發生水化反應，加速了破乳過程；水化產物與破乳后的瀝青形成加筋結構，進一步提高了冷再生瀝青混合料的強度［４９］。

　　Under appropriate preparation processes and storage conditions, emulsified asphalt can be stored for several months. In terms of strength formation mechanism of emulsified asphalt cold recycled asphalt mixture, the surface of emulsified asphalt droplets is charged. When the surface charge of asphalt lotion is opposite to that of aggregate particles, the interfacial bonding strength of binder and aggregate will increase due to the absorption of anisotropic charges. The compatibility of different types of asphalt lotion with aggregates is shown in Table 2 [7]. When asphalt lotion is mixed with aggregate, asphalt tends to separate from water and adhere to the surface of aggregate particles. This process is called demulsification. Figure 3 shows two failure modes of emulsified asphalt mixture: at the initial stage of maintenance, there is a water film between the asphalt lotion cement mortar phase and the aggregate interface, which is the weak strength interface where the mixture breaks, and adhesion failure is the main failure mode; As the curing time increases, under the continuous hydration reaction of cement, emulsion breaking of emulsified asphalt, and water evaporation, asphalt aggregates into a film and uniformly adheres to the surface of the aggregate. The interfacial adhesion strength exceeds the cohesive strength of asphalt mortar, and the cohesive failure of mortar phase becomes the main failure mode. For the factory mixed cold recycling technology, the demulsification time should be greater than the mixing, transportation, and paving rolling time of the cold recycled asphalt mixture to avoid premature demulsification of emulsified asphalt and reduce the workability of the mixture. In addition, a certain proportion of cement is usually added to emulsified asphalt mixture, which undergoes hydration reaction with water to accelerate the demulsification process; The hydration products form a reinforced structure with the emulsified asphalt, further improving the strength of the cold recycled asphalt mixture [49].

　　李云良等［５０］研究了不同 水泥－乳化瀝青比例下復合膠漿的老化試驗及頻率掃描試驗，結果表明不同相對含量的水泥－瀝青乳液的老化性能具有明顯差異，在混合料設計中應進行考慮。此外，借鑒熱拌瀝青路面工程中使用改性瀝青的工程經驗，可以采用改性乳化瀝青以獲得更加優良的路用性能，提高冷再生瀝青結構層的應用層位。鄭俊秋［５１］制備了３種普通乳化瀝青以及改性乳化瀝青，結果表明改性乳化瀝青能夠顯著改善高溫和低溫性能。2.2.3性能對比分析對于乳 化 瀝 青 混 合 料，乳 化 瀝 青 吸 附 聚 集 成膜并均勻 裹 附 在 集 料 表 面，水 泥 水 化 加 速 了 乳 化瀝青破乳，同時生成針狀和簇狀的水化產物與瀝青相互 交 織，形 成 空 間 網 絡 結 構。泡 沫 瀝 青 在 集料表面呈非連續 分 布，具 有 局 部 黏 結 的 點 焊 特 征，除了受基質瀝青性能和水分影響外，仍 受 瀝 青 與填（細）料的裹附均 勻 程 度 以 及 膠（砂）漿 的 點 狀 分布狀態影 響［５２－５３］。

　　Li Yunliang et al. [50] studied the aging test and frequency scanning test of composite mortar under different cement asphalt emulsion ratios. The results show that the aging performance of cement asphalt lotion with different relative contents has obvious differences, which should be considered in the mixture design. In addition, drawing on the engineering experience of using modified asphalt in hot mix asphalt pavement projects, modified emulsified asphalt can be used to achieve better road performance and improve the application level of cold recycled asphalt structural layers. Zheng Junqiu [51] prepared three types of ordinary emulsified asphalt and modified emulsified asphalt, and the results showed that modified emulsified asphalt could significantly improve high and low temperature performance. 2.2.3 Performance Comparison Analysis: For emulsified asphalt mixtures, emulsified asphalt adsorbs and aggregates into a film, which uniformly adheres to the surface of the aggregate. Cement hydration accelerates the demulsification of emulsified asphalt, while generating needle shaped and cluster shaped hydration products that interweave with asphalt, forming a spatial network structure. The foam asphalt is distributed discontinuously on the aggregate surface and has the characteristics of spot welding of local bonding. In addition to the influence of the performance and moisture of the base asphalt, it is also affected by the uniformity of the coating of asphalt and filler (fine) materials and the spot distribution of mortar (sand) [52-53].

　　２種瀝青的黏結特性導致 冷 再生瀝青混合料的受力特征具有差異，進 而 影 響 混合料性能。相同瀝青摻量的泡沫瀝青混合料的孔隙率、抗水損害、抗低溫開裂性優于乳化瀝青混合料［５４］。隨著瀝青摻量的增加，乳化瀝青混合料的剛度模量呈下降趨勢，泡沫瀝青混合料呈增大趨勢，這主要是由于２種再生劑對于冷再生瀝青混合料強度形成機理存在差異性。乳化瀝青中含有大量的水，以流體形式包裹細 集 料 和 粗 集 料。隨 著 乳 化 瀝 青 含 量 的 增加，瀝青以潤滑劑的形式降低了集料間的摩阻力，導致剛度模量降低。相反，泡沫瀝青與礦粉和細集料形成瀝青砂漿，再與粗集料黏結形成強度，瀝青與粗集料呈點接觸狀態。增加瀝青含量可增加泡沫瀝青混合料 內 部 的 黏 結 界 面，從 而 提 高 剛 度 模 量。基于２種瀝青在混合料內部的分布特點，乳化瀝青混合料具有顯著的溫度和頻率依賴特性［５３，５５］。

　　The bonding characteristics of two types of asphalt lead to differences in the stress characteristics of cold recycled asphalt mixtures, which in turn affect the performance of the mixture. The porosity, water damage resistance and low-temperature cracking resistance of foam asphalt mixture with the same asphalt content are better than those of emulsified asphalt mixture [54]. With the increase of asphalt content, the stiffness modulus of emulsified asphalt mixture decreases, while that of foam asphalt mixture increases. This is mainly due to the difference in the strength formation mechanism of the two kinds of regenerants for cold recycled asphalt mixture. Emulsified asphalt contains a large amount of water, which wraps fine and coarse aggregates in a fluid form. With the increase of emulsified asphalt content, asphalt reduces the frictional resistance between aggregates in the form of lubricant, resulting in a decrease in stiffness modulus. On the contrary, foam asphalt first forms asphalt mortar with mineral powder and fine aggregate, and then forms strength with coarse aggregate. Asphalt and coarse aggregate are in point contact. Increasing the asphalt content can increase the bonding interface inside foam asphalt mixture, thus improving the stiffness modulus. Based on the distribution characteristics of two types of asphalt inside the mixture, emulsified asphalt mixture has significant temperature and frequency dependence characteristics [53, 55].

　　2.3 化學添加劑

　　2.3 Chemical additives

　　水泥等穩定劑加入冷再生材料，不僅可以作為填料改善級配，還可以提高冷再生的早期強度和長期性能，且外添劑含量和性能也會對冷再生瀝青混合料的力學性能產生較大影響［５６］。2.3.1水泥眾多學者研究了水泥及水泥水化產物對冷再生混合料強度特性的影響，冷再生瀝青混合料中通常加入１．０％～２．５％的水泥以提高混合料的早期強度、高溫穩定性［５７－５８］，并可作為添加劑以增強砂漿與集料的黏結性，提高抗水損害性能［５９－６０］。其次，水泥可提高冷再生瀝青混合料的無側限抗壓強度、間接抗拉強度、回 彈 模 量 和 抗 車 轍 性 能 等 力 學 性 能［５８］，但水泥摻量與冷再生瀝青混合料力學性能的提高幅度并非呈線 性 正 相 關。以 水 泥－乳 化瀝 青 混 合 料 為例，當水泥摻量超過２％，冷再生瀝青混合料的間接拉伸強度 增 強 效 果 較 小［６１］。Ｘｉａｏ等［５８］研 究表 明，當乳化 瀝 青 摻 量 為８％，水 泥 摻 量 由０增 加 到４％時，其間接抗 拉 強 度 先 增 大 后 減 小，水 泥 摻 量 約 為３％時，抗壓強度和回彈性模量。雖然水泥能夠多方面地提升冷再生瀝青混合料性能，但是不利于抗疲勞性能和低溫開裂，尤其對于冷再生混合料應用于基層或者下面層，對抗疲勞性能具有一定的要求。

　　Adding stabilizers such as cement to cold recycled materials can not only improve the gradation as fillers, but also enhance the early strength and long-term performance of cold recycled asphalt mixtures. Moreover, the content and performance of external additives can also have a significant impact on the mechanical properties of cold recycled asphalt mixtures [56]. 2.3.1 Many scholars have studied the influence of cement and cement hydration products on the strength characteristics of cold recycled asphalt mixtures. Usually, 1.0% to 2.5% cement is added to cold recycled asphalt mixtures to improve the early strength and high-temperature stability of the mixture [57-58], and can be used as an additive to enhance the bonding between mortar and aggregate, and improve the resistance to water damage [59-60]. Secondly, cement can improve the mechanical properties such as unconfined compressive strength, indirect tensile strength, rebound modulus, and rutting resistance of cold recycled asphalt mixtures [58], but the increase in cement content is not linearly positively correlated with the improvement in mechanical properties of cold recycled asphalt mixtures. Taking cement emulsified asphalt mixture as an example, when the cement content exceeds 2%, the indirect tensile strength enhancement effect of cold recycled asphalt mixture is relatively small [61]. Xiao et al. [58] found that when the emulsified asphalt content is 8% and the cement content increases from 0% to 4%, its indirect tensile strength first increases and then decreases. When the cement content is about 3%, the compressive strength and elastic modulus are the highest. Although cement can improve the performance of cold recycled asphalt mixture in various aspects, it is not conducive to fatigue resistance and low-temperature cracking, especially for the application of cold recycled mixture in the base or lower layer, which has certain requirements for fatigue resistance.

　　為保證冷再生瀝青混合料的低溫抗開裂性能，水泥摻量應低于２％［６２－６４］。對于冷再生混合料的抗疲勞性能，以乳化瀝青瀝青混合料為例，研究表明其疲勞性能取決于初始應變水平，當微應變低于３００με時，水泥有利于提高疲勞壽 命，應 變水平高于３００με時 則相 反［６５－６６］。冷再生瀝青混合料應用于基 層 時，其應變水平通常低于 ２００με，因此，在冷再生瀝青路面設計方法中應充分對其進行研究，提出符合冷再生瀝青混合料材料特性的疲勞失效設計準則。美國瀝青學會建議將水泥用量限制在１％，將水泥摻量確定為１．５％，以降低水泥對疲勞性能的弱化影響，但在其他相關研究中也提出可采用３％的水泥摻量［６５，６７］。以上總結了水泥對于冷再生瀝青混合料性能的影響，并以乳化瀝青或者泡沫瀝青混合料的試驗結果進行了分析論述。水泥對于乳化瀝青混合料和泡沫瀝青混合料力學性能的影響規律較為一致，由于乳化瀝青和泡沫瀝青混合料的強度形成機理存在差異，以及其他材料組分性能及相對含量的差異會影響水泥摻量。2.3.2石灰石灰通常作為一種活性添加劑，通常以熟石灰和石灰漿的形式加入冷再生瀝青混合料以改善其力學性能［６８－６９］，熟石灰是常見的一種添加劑，添加量通常為集料質量的１％～３％［７０］。熟石灰相比于普通的石灰石礦粉填料具有更高的孔隙率，石灰石礦粉壓實后孔隙率通常為３０％～３４％，而熟石灰孔隙率通常為６０％～７０％。其次，熟石灰作為一種填料對瀝青的增果高于普通填料［６７］。

　　To ensure the low-temperature anti cracking performance of cold recycled asphalt mixture, the cement content should be less than 2% [62-64]. For the fatigue resistance of cold recycled mixtures, taking emulsified asphalt mixtures as an example, research has shown that their fatigue performance depends on the initial strain level. When the micro strain is below 300 μ ε, cement is beneficial for improving fatigue life, while when the strain level is above 300 μ ε, the opposite is true [65-66]. When cold recycled asphalt mixture is applied to the base layer, its strain level is usually below 200 μ ε. Therefore, in the design method of cold recycled asphalt pavement, it should be fully studied and fatigue failure design criteria that meet the material characteristics of cold recycled asphalt mixture should be proposed. The American Asphalt Institute recommends limiting the cement content to 1%, while China sets the cement content at 1.5% to reduce the weakening effect of cement on fatigue performance. However, other related studies have also suggested using a cement content of 3% [65,67]. The above summarizes the influence of cement on the performance of cold recycled asphalt mixture, and analyzes and discusses the test results of emulsified asphalt or foam asphalt mixture. The influence of cement on the mechanical properties of emulsified asphalt mixture and foam asphalt mixture is relatively consistent. Due to the difference in the strength formation mechanism of emulsified asphalt and foam asphalt mixture, and the difference in the performance and relative content of other material components, the optimal cement content will be affected. 2.3.2 Lime is usually used as an active additive, usually added to cold recycled asphalt mixtures in the form of hydrated lime and lime slurry to improve their mechanical properties [68-69]. Hydrated lime is the most common additive, usually added in an amount of 1% to 3% of the aggregate mass [70]. Compared to ordinary limestone powder fillers, hydrated lime has a higher porosity. The porosity of compacted limestone powder is usually 30% to 34%, while the porosity of hydrated lime is usually 60% to 70%. Secondly, as a filler, hydrated lime has a higher reinforcing effect on asphalt than ordinary fillers [67].

　　研究表明，以填料與瀝青的質量比為指標，將針入 度（單 位１０－１ ｍｍ）為２００的瀝青軟化點提高２０ ℃，熟石灰與瀝青的比值為０．７～１．０，而礦粉填料的質量比為１．５～２．５。熟石灰在美國得到關注和研究，被 用 于熱拌瀝青混合料中以提高其抗水損害和凍融破壞，同時還能夠提 高 混 合 料 的 模 量 及 抗 車 轍、抗 疲勞性能，增強混合料的耐久性［７１］。這 主要 是 由 于熟石灰能夠改善集料與瀝青的黏附狀態，游 離 的鈣離子沉 積 在 集 料 表 面，促 進 與 瀝 青 中 的 酸 性 物質發生物化反應，增 強 集 料 與 瀝 青 的 黏 結 強 度，進而提高抗水損害性能［６８］，這一現象對酸性集料尤為明顯。其次，相關室內試驗和現場調研結果表明，石灰能夠降低冷再生瀝青混合料孔隙率，從而提高混合料抗拉強度、抗變形能力和剛度，但石灰漿增果更優［７２－７４］。以上總結了石灰的物理特性以及與瀝青膠結料的化學反應特性，揭示了石灰對冷再生混合料性能的影響機理，該方面的總結同樣適用于乳化瀝青和泡沫瀝青等多種瀝青膠結料的冷再生瀝青混合料。

　　Research has shown that using the mass ratio of filler to asphalt as an indicator, the softening point of asphalt with a penetration degree (unit 10-1mm) of 200 can be increased by 20 ℃. The ratio of hydrated lime to asphalt is 0.7-1.0, while the mass ratio of mineral powder filler is 1.5-2.5. Hydrated lime first received attention and research in the United States, and was used in hot mix asphalt mixtures to improve their resistance to water damage and freeze-thaw failure, as well as to increase the modulus, rutting resistance, and fatigue resistance of the mixture, enhancing its durability [71]. This is mainly due to the fact that hydrated lime can improve the adhesion state between aggregates and asphalt. Free calcium ions deposit on the surface of aggregates, promote biological reactions with acidic substances in asphalt, enhance the bonding strength between aggregates and asphalt, and thus improve the water damage resistance performance [68]. This phenomenon is particularly evident for acidic aggregates. Secondly, relevant indoor tests and on-site investigations have shown that lime can reduce the porosity of cold recycled asphalt mixtures, thereby improving the tensile strength, resistance to permanent deformation, and stiffness of the mixture. However, lime slurry has a better reinforcement effect [72-74]. The above summarizes the physical characteristics of lime and the chemical reaction characteristics with asphalt binder, and reveals the influence mechanism of lime on the performance of cold recycled asphalt mixture. The summary in this aspect is also applicable to cold recycled asphalt mixture of various asphalt binders such as emulsified asphalt and foam asphalt.

　　2.3.3性能對比分析水泥的主要成分為硅酸二鈣和硅酸三鈣，與水發生水化反應生成水化硅酸鈣和氫氧化鈣，其中水化硅酸鈣是形成強度的主要物質。熟石灰的主要成分為氫氧化鈣，其比表面積約為水泥的１０倍，可為乳化瀝青或泡沫瀝青提供較好的分散相，但遇水不發生水化反應。２種活性填料對冷再生瀝青混合料的強度性能具有顯著差異，主要表現為：

　　2.3.3 Performance Comparison Analysis The main components of cement are dicalcium silicate and tricalcium silicate, which react with water to form hydrated calcium silicate and calcium hydroxide. Hydrated calcium silicate is the main substance that forms strength. The main component of hydrated lime is calcium hydroxide, whose specific surface area is about 10 times that of cement. It can provide a better dispersion phase for emulsified asphalt or foam asphalt, but it will not react with water. There is a significant difference in the strength performance of cold recycled asphalt mixture between two types of active fillers, mainly manifested as:

　　（１）加入水泥可顯著提高冷再生瀝青混合料的模量，但熟石灰的強度提升效果不顯著［７５－７６］，當需要提高早期及長期強度時建議添加水泥；（２）加入水泥的冷再生瀝青混合料不具有應力依賴性，混合料呈現膠結材料的特征，加入熟石灰的混合料具有較為明顯的應力依賴性，即模量隨圍壓改變而變化，更多呈現無黏結顆粒材料特性［５３］；（３）水 泥作為添加劑的冷再生瀝青混合料在高應變水平下的抗疲勞性能較差［７３］，在工程設計時應充分考慮冷再生結構層的應力及應變水平，以防止疲勞開裂；（４）在潮濕多雨環境里建議采用水泥穩定劑并適當提高用量，以提高抗水損害能力。由此可見，在冷再生瀝青混合料材料設計過程中應充分考慮當地氣候條件、冷再生材料所應用的結構層位及其對應的性能需求，以選擇合適的添加劑。如果要求提高冷再生瀝青混合料的早期強度且具有較好的抗水損害和抗變形能力，建議采用水泥作為外加劑［６８］。2.4冷再生材料組分相互作用機制

　　(1) Adding cement can significantly improve the modulus of cold recycled asphalt mixture, but the strength improvement effect of hydrated lime is not significant [75-76]. It is recommended to add cement when early and long-term strength needs to be improved; (2) The cold recycled asphalt mixture with added cement does not have stress dependence, and the mixture exhibits the characteristics of a bonding material. The mixture with added hydrated lime has a more obvious stress dependence, that is, the modulus changes with the change of confining pressure, and more exhibits the characteristics of a non bonding particle material [53]; (3) The anti fatigue performance of cold recycled asphalt mixture with cement as an additive is poor at high strain levels [73]. In engineering design, the stress and strain levels of the cold recycled structural layer should be fully considered to prevent fatigue cracking; (4) In humid and rainy environments, it is recommended to use cement stabilizers and increase their dosage appropriately to enhance their resistance to water damage. From this, it can be seen that in the design process of cold recycled asphalt mixture materials, local climate conditions, the structural layers and corresponding performance requirements of the cold recycled materials should be fully considered to select appropriate additives. If it is required to improve the early strength of cold recycled asphalt mixture and have good resistance to water damage and permanent deformation, it is recommended to use cement as an admixture [68]. 2.4 Interaction mechanism of components in cold recycled materials

　　瀝青與水泥相互作用形成復合膠漿，決定了冷再生瀝青混合料的流變特性和力學屬性。由圖４［６１，７７］所示的冷再生瀝青復合膠漿微觀形貌可以看出：水泥水化生成的水化產物包括針刺狀鈣礬石，板狀氫氧化鈣晶體以及纖維狀水化硅酸鈣 凝 膠，瀝青與水化產物相互交織并附著在水化產物表面，針狀的鈣礬石晶體刺破瀝青膜。此外，瀝青能夠包裹一部分水泥顆粒，阻礙其進一步發生水化反應。研究表明水泥與瀝青的相對含量的變化會影響冷再生瀝青混合料的力學特性，當瀝青與水泥質量比大于１且水泥用量低于１％時可視為瀝青穩定類材料，當質量比大于１且水泥用量大于１％時可視為水泥穩定類材料［５６］。瀝青－水泥復合膠漿與舊料和新料可形成不同的界面形態，水泥水化產物能夠增強砂漿相與集料間的黏附性，界面性能的強弱決定了混合料破壞模式。其次，瀝青與水泥的加入時機能夠改變界面形式和界面強度進而影響冷再生瀝青混合料性能。在傳統的施工工藝中，通常將水泥和乳化瀝青／泡沫瀝青依次加入并與集料進行拌和，會使集料表面包裹一層水泥水化產物，界面過渡區內呈現較多的微裂紋，不利于冷再生瀝青混合料的抗裂性能和抗水損害。溫彥凱等［２８，７８］研究表明，將水泥、乳化瀝青／泡沫瀝青和礦粉先充分拌和，形成各相分散均勻的復合膠漿再與集料進行拌和，通過掃描電子顯微鏡測試觀測到復合膠漿在集料表面可形成較好的浸潤和黏附效果，從而提高冷再生瀝青混合料的力學性能。由于 ＲＡＰ料表層存在老化瀝青，瀝青具有疏水性特性，阻礙了 ＲＡＰ料 內部微孔隙對水的吸收，因此，ＲＡＰ料 對外加水的吸收程度低于新集料。

　　The interaction between asphalt and cement forms a composite slurry, which determines the rheological and mechanical properties of cold recycled asphalt mixtures. It can be seen from the microscopic morphology of cold recycled asphalt composite mortar shown in Figure 4 [61, 77] that the hydration products generated by cement hydration include needle like ettringite, plate like calcium hydroxide crystal and fibrous calcium silicate hydrate gel. The asphalt and hydration products are intertwined and attached to the surface of the hydration products, and needle like ettringite crystal punctures the asphalt film. In addition, asphalt can encapsulate some cement particles, hindering their further hydration reaction. Research has shown that changes in the relative content of cement and asphalt can affect the mechanical properties of cold recycled asphalt mixtures. When the mass ratio of asphalt to cement is greater than 1 and the cement content is less than 1%, it can be considered as asphalt stabilized material. When the mass ratio is greater than 1 and the cement content is greater than 1%, it can be considered as cement stabilized material [56]. Asphalt cement composite mortar can form different interface shapes with old and new materials. Cement hydration products can enhance the adhesion between mortar and aggregate, and the strength of interface performance determines the failure mode of the mixture. Secondly, the timing of adding asphalt and cement can change the interface form and strength, thereby affecting the performance of cold recycled asphalt mixtures. In the traditional construction process, cement and emulsified asphalt/foam asphalt are usually added in turn and mixed with the aggregate, which will make the aggregate surface wrapped with a layer of cement hydration products, and there are many microcracks in the interface transition zone, which is not conducive to the crack resistance and water damage resistance of cold recycled asphalt mixture. Wen Yankai et al. [28, 78] research shows that cement, emulsified asphalt/foam asphalt and mineral powder are fully mixed to form a composite mortar with evenly dispersed phases and then mixed with the aggregate. Through scanning electron microscope testing, it is observed that the composite mortar can form a better wetting and adhesion effect on the surface of the aggregate, thus improving the mechanical properties of cold recycled asphalt mixture. Due to the presence of aged asphalt on the surface of RAP material, which has hydrophobic properties, it hinders the absorption of water by the internal micropores of RAP material. Therefore, the absorption of water by RAP material is lower than that of new aggregate.

　　Ｍａ等［６１］研究表明 ＲＡＰ料抽提后的比表面積約為抽提前的３倍，因此，瀝青含量和含水量會隨著ＲＡＰ料摻量的增加而降低［７９］，如圖５［８０］所示，圖中瀝青含量與 ＲＡＰ料含量均為質量百分含量。在恒定水灰比下具有更多的自由水與水泥膠凝材料發生反應，從而提高水化反應程度。其次，ＲＡＰ料內部集料顆粒與老化瀝青的界面黏結強度較差，以上原因都會降低冷再生瀝青混合料抗開裂性能［６１，８０］。由以上分析可知，冷再生瀝青混合料材料組分及其相互作用機制復雜，界面形式多變，ＲＡＰ料摻量及性能、添加劑以及瀝青膠結料類型和含量等都會影響冷再生瀝青混合料的力學性能。在工程應用前，應對各材料組分進行測試與表征，基于性能需求對冷再生瀝青混合料進行組分設計和試驗驗證。3 冷再生瀝青混合料配合比及路面設計方法

　　Ma et al. [61] found that the specific surface area of RAP material after extraction is about three times that of pre extraction. Therefore, the optimal asphalt content and moisture content will decrease with the increase of RAP material content [79], as shown in Figure 5 [80], where the asphalt content and RAP material content are both mass percentage contents. At a constant water cement ratio, there is more free water to react with cement cementitious materials, thereby increasing the degree of hydration reaction. Secondly, the interface bonding strength between RAP aggregate particles and aged asphalt is poor, which can reduce the cracking resistance of cold recycled asphalt mixtures [61, 80]. From the above analysis, it can be seen that the components and interaction mechanisms of cold recycled asphalt mixture materials are complex, and the interface forms are varied. The dosage and performance of RAP material, additives, and the type and content of asphalt binder can all affect the mechanical properties of cold recycled asphalt mixture. Before engineering application, each material component should be tested and characterized, and the composition design and experimental verification of cold recycled asphalt mixture should be based on performance requirements. Mix proportion and pavement design method of cold recycled asphalt mixture

　　由于冷再生瀝青混合料中存在 ＲＡＰ料和水泥基穩定劑等組成成分，傳統的瀝青混合料設計方法難以適用于冷再生瀝青混合料。目前，關于冷再生材料的路面設計方法以及混合料設計方法得到眾多學者的研究，各國提出了不同的冷再生瀝青混合料設計方法和路面結構設計方法，但尚未形成統一的設計方法［８１］。3.1 冷再生瀝青混合料設計方法

　　Due to the presence of RAP and cement-based stabilizers in cold recycled asphalt mixtures, traditional asphalt mixture design methods are difficult to apply to cold recycled asphalt mixtures. At present, many scholars have studied the pavement design methods and mixture design methods of cold recycled materials. Different countries have proposed different design methods for cold recycled asphalt mixtures and pavement structures, but a unified design method has not yet been formed [81]. 3.1 Design Method for Cold Recycled Asphalt Mixture

　　3.1.1國外代表性配合比設計方法美國部分州和研究機構根據熱拌瀝青混合料設計方法，形成了不同的冷再生瀝青混合料設計方法。主要分為經驗公式法和試驗測試法２種，其中基于經驗公式法的設計理論包括美國瀝青協會的 ＡＩ設計法［８２］和俄勒岡州設計法，基于試驗測試法的設計理論包括 ＡＡＳＨＴＯ 修 正馬 歇 爾 法（Ｍａｒｓｈａｌｌ法）、Ｈｖｅｅｍ 設計法、賓夕法尼亞州設計法、Ｓｕｐｅｒｐａｖｅ設計法，各種設計方法的匯總如表３所 示［２１，８３－８４］。經驗公式法相比于試驗測試法設計步驟較簡略，測試過程較簡單，主 要 是 基 于 ＲＡＰ 料 中老 化 瀝 青 的 性能指標預估乳化瀝青含量，但是試驗結果的可靠性較低。試驗測試法是基于力學性能測試確定瀝青含量和含水量，主要分為２個方面：其一是密度法，即根據冷再生瀝青混合料試件的相對密度確定瀝青含量；其二是強度法，即根據冷再生混合料的回彈模量、劈裂強度、馬歇爾穩定度和水穩定性等指標確定瀝青含量。

　　3.1.1 Representative foreign mix design methods: Some states and research institutions in the United States have developed different design methods for cold recycled asphalt mixtures based on the design methods for hot mix asphalt mixtures. There are mainly two types of design methods: empirical formula method and experimental testing method. The design theory based on empirical formula method includes the AI design method of the American Asphalt Institute [82] and the Oregon design method. The design theory based on experimental testing method includes AASHTO modified Marshall method (Marshall method), Hveem design method, Pennsylvania design method, Superpave design method. The summary of various design methods is shown in Table 3 [21, 83-84]. The empirical formula method has simpler design steps and testing process compared to the experimental testing method. It mainly estimates the optimal emulsified asphalt content based on the performance indicators of aged asphalt in RAP material, but the reliability of the test results is lower. The experimental testing method is based on mechanical performance testing to determine the optimal asphalt content and moisture content, mainly divided into two aspects: one is the density method, which determines the optimal asphalt content based on the maximum relative density of cold recycled asphalt mixture specimens; The second method is the strength method, which determines the optimal asphalt content based on indicators such as the rebound modulus, splitting strength, Marshall stability, and water stability of cold recycled mixtures.

　　不同的冷再生瀝青混合料設計方法在級配選擇、瀝青等級、成形方法、養護方式以及性能評價指標等方面差別較大，但基本都是基于試驗測試法指導混合料配合比設計。在總結國內外冷再生瀝青混合料配合比設計方法的基礎上，表４對比分析了通常采用的 Ｍａｒｓｈａｌｌ、Ｓｕｐｅｒｐａｖｅ和 Ｈｖｅｅｍ 法的優缺點［８４］。常見冷再生瀝青混合料的壓實方法有沖擊法（馬歇爾壓實、普氏壓實）、揉壓法（旋轉壓實、線性碾壓）以及振動法，不同的壓實方法能夠對瀝青含量和含水量產生差異，從而影響混合料的體積參數和力學性能［８５－８６］。目前，國內外學者主要開展不同壓實方法對冷再生瀝青混合料性能影響的研究。Ｍｅｎｅｓｅｓ等［８６］研究表明旋轉壓實試件的孔隙含量變異系數小，馬歇爾壓實試件的孔隙率變異性，普氏壓實法會導致內部集料破碎，優先采用旋轉壓實方法；Ｊｉａｎｇ等［８７］對比分析了 Ｍａｒｓｈａｌｌ壓實和振動壓實，研究表明振動壓實成型試件的含水量和 瀝 青 含 量 比 Ｍａｒｓｈａｌｌ試 件分 別 降 低 了１１％和９％，具有更 好 的 水 穩 定 性，抗 開 裂、抗 車 轍和抗疲勞性能。與重型壓實相比，旋轉壓實成型的冷再生瀝青混合料試件的含水量降低了１８％，密度提高了３．５％［８５］。

　　Different design methods for cold recycled asphalt mixtures vary greatly in terms of gradation selection, asphalt grade, forming method, curing method, and performance evaluation indicators, but they are mostly based on experimental testing methods to guide the mix design of the mixture. On the basis of summarizing the mix design methods of cold recycled asphalt mixtures at home and abroad, Table 4 compares and analyzes the advantages and disadvantages of the commonly used Marshall, Superpave, and Hveem methods [84]. The common compaction methods for cold recycled asphalt mixtures include impact compaction (Marshall compaction, Proctor compaction), kneading compaction (rotary compaction, linear rolling), and vibration compaction. Different compaction methods can result in differences in the optimal asphalt content and moisture content, thereby affecting the volume parameters and mechanical properties of the mixture [85-86]. At present, domestic and foreign scholars mainly conduct research on the influence of different compaction methods on the performance of cold recycled asphalt mixtures. The study by Meneses et al. [86] showed that the coefficient of variation of pore content in rotary compaction specimens was the smallest, while the coefficient of variation of pore content in Marshall compaction specimens was the largest. The Proctor compaction method would cause internal aggregate fragmentation, and the rotary compaction method was recommended as the preferred method; Jiang et al. [87] compared and analyzed Marshall compaction and vibration compaction. The study showed that the optimal moisture content and asphalt content of vibration compaction formed specimens were reduced by 11% and 9% respectively compared to Marshall specimens, exhibiting better water stability, cracking resistance, rutting resistance, and fatigue resistance. Compared with heavy compaction, the optimal moisture content of cold recycled asphalt mixture specimens formed by rotary compaction decreased by 18% and the density increased by 3.5% [85].

　　目前，眾多學者 主 要 通 過 比較體積參數和力學性能對不同壓實方法進行定量化評價，然而配合比設計旨在冷再生瀝青混合料工程應用前對其進行測試，以預測瀝青路面性能，因此，的試件成型方式應符合現場壓實后混合料的相應指標。Ｌｉｕ等［８８］將現場巖樣與室內成型方法進行對 比，提出符合冷再生基層現場壓實條件的成型方法，即大Ｍａｒｓｈａｌｌ試件的初次壓實為１５０次，二次壓實為７５次，旋轉壓 實 次 數 為３０＋１５；Ｏｒｏｓａ等［８９］比較了靜 態 壓 實、旋轉壓實和馬歇爾壓實法成型試件 的 體 積 指 標，并與現場壓實目標值進行了對比分 析，驗證了旋轉壓實法能夠較好反映現場壓實水 平；Ｍａｒｔíｎｅｚ－Ｅｃｈｅｖａｒｒíａ等［９０］提 出了 一 種室內壓實 方 法，以與現場壓實后的冷再生瀝青結構層密度 保 持 一 致，并對比分析了現場芯樣與成型試樣的 動 態 模 量，驗證了所提出壓實方法的適用性。由以 上 分 析 可 得， 佳 成 型 方 法 應 與 現 場壓實后的混合料體 積 參 數 和 力 學 性 能 具 有 較 好 的一致性，以更好地反映冷再生材料在實際服役狀態下的性能優劣。冷再生瀝青混合料的室內養生過程主要是為了模擬現場冷再生瀝青結構層的固化條件，以確定上鋪瀝青結構層和開放交通的時間。養生條件決定了冷再生瀝青試件在養護過程中的強度增長，其主要包括養 生 時 間、溫 度 和 濕 度。

　　At present, many scholars mainly quantitatively evaluate different compaction methods by comparing volume parameters and mechanical properties. However, mix design aims to test cold recycled asphalt mixtures before their engineering application to predict asphalt pavement performance. Therefore, the optimal specimen forming method should comply with the corresponding indicators of the compacted mixture on site. Liu et al. [88] compared on-site rock samples with indoor forming methods and proposed a forming method that meets the on-site compaction conditions for cold recycled base layers, namely, the initial compaction of the large Marshall specimen is 150 times, the secondary compaction is 75 times, and the rotational compaction is 30+15 times; Orosa et al. [89] compared the volume indices of static compaction, rotary compaction, and Marshall compaction method formed specimens, and compared and analyzed them with the on-site compaction target values, verifying that the rotary compaction method can better reflect the on-site compaction level; Mart í nez Echevarr í a et al. [90] proposed an indoor compaction method to maintain consistency with the density of cold recycled asphalt structural layers after on-site compaction, and compared and analyzed the dynamic modulus of on-site core samples and formed samples to verify the applicability of the proposed compaction method. From the above analysis, it can be concluded that the optimal molding method should have good consistency with the volume parameters and mechanical properties of the compacted mixture on site, in order to better reflect the performance advantages and disadvantages of cold recycled materials in actual service conditions. The indoor curing process of cold recycled asphalt mixture is mainly to simulate the solidification conditions of the on-site cold recycled asphalt structural layer, in order to determine the time for laying the asphalt structural layer and opening traffic. The curing conditions determine the strength growth of cold recycled asphalt specimens during the curing process, mainly including curing time, temperature, and humidity.

　　Ｌｅｅ等［９１］開 展 了 如圖６所示的無密封養護、半密封養護和全密封養護３種室內養護方法，對應的強度增長規律如下。（１）無密封養護：２５ ℃、４０ ℃和６０ ℃烘箱內分別固化２ｄ，含水率降０，間 接 抗 拉 強 度 持 續 增 長２８ｄ。室溫養護１０ｈ，間 接抗 拉 強 度 沒 有 增 加，間 接抗拉強 度 與 含 水 率 之 間 無 相 關 性；從 １０ｈ 增 加到５０ｈ，間接抗拉強度有所增加。（２）半密封養護：室內養護１２ｈ后，間接抗拉強度沒有增加，從１２ｈ增加到１４ｄ，間接抗拉強度有所增加；在相同含 水 率 下，部 分 固 化１４ｄ試 件的 間接抗拉強度高于７ｄ的試件。（３）全密封養護：隨著養生時間增加，間接抗拉強度增大；４０ ℃烘箱中養護１４ｄ，當試樣初始含水率低于１．５％時，試樣間接抗拉強度提高；初始含水率高于１．５％時，間接抗拉強度沒有增加。

　　Lee et al. [91] conducted three indoor maintenance methods as shown in Figure 6: unsealed maintenance, semi sealed maintenance, and fully sealed maintenance. The corresponding strength growth patterns are as follows. (1) Unseal curing: Cured in ovens at 25 ℃, 40 ℃, and 60 ℃ for 2 days, with a moisture content reduced to 0, and indirect tensile strength continuously increased for 28 days. After 10 hours of room temperature curing, there was no increase in indirect tensile strength, and there was no correlation between indirect tensile strength and moisture content; The indirect tensile strength increased from 10h to 50h. (2) Semi sealed maintenance: After 12 hours of indoor maintenance, the indirect tensile strength did not increase. However, when it increased from 12 hours to 14 days, the indirect tensile strength increased slightly; At the same moisture content, the indirect tensile strength of partially cured 14d specimens is higher than that of 7d specimens. (3) Fully sealed maintenance: As the maintenance time increases, the indirect tensile strength increases; After curing in a 40 ℃ oven for 14 days, the indirect tensile strength of the sample increases when the initial moisture content of the sample is below 1.5%; When the initial moisture content is higher than 1.5%, the indirect tensile strength does not increase.

　　3.1.2國內配合比設計方法參考了國內外相關設計方法和工程應用情況，明確了采用馬歇爾設計方法指導冷再生瀝青混合料配合比設計。但是，已有的冷再生項目工程中對采用馬歇爾壓實成型還是旋轉壓實成型并沒有形成統一標準。相對于馬歇爾成型方式，旋轉壓實能夠 更 好 地 模 擬 冷 再 生 路 面 的 現 場 碾 壓 過 程。Ｗｅｉ等［９２］研究了旋轉壓實成型方法在乳化瀝青混合料中的應用，并根據劈裂強度對相關技術參數進行優化。ＪＴＧ／Ｔ５５２１—２０１９中冷再生配合比設計方法采用雙面擊 實５０＋２５次 的馬 歇 爾 法，養 生 條 件 為６０℃烘箱中少４０ｈ，采用１５℃劈裂強度或馬歇爾穩定度指標以確定乳化瀝青用量。馬歇爾設計方法是目前世界上應用為廣泛的一種瀝青混合料設計方法。它的優點是對混合料的體積指標都有著明確的要求，且設備便宜、操作簡單。3.2冷再生瀝青路面結構設計方法

　　3.1.2 Domestic Mix Proportion Design Method China has referred to relevant design methods and engineering applications at home and abroad, and clarified the use of Marshall design method to guide the mix proportion design of cold recycled asphalt mixtures. However, there is no unified standard for using Marshall compaction or rotary compaction in existing cold recycling projects in China. Compared to the Marshall molding method, rotary compaction can better simulate the on-site rolling process of cold recycled pavement. Wei et al. [92] studied the application of rotary compaction molding method in emulsified asphalt mixtures and optimized relevant technical parameters based on splitting strength. The JTG/T5521-2019 intercooled regeneration mix design method adopts the Marshall method of double-sided compaction 50+25 times, and the curing conditions are at least 40 hours in a 60 ℃ oven. The 15 ℃ splitting strength or Marshall stability index is used to determine the optimal emulsified asphalt dosage. The Marshall design method is currently the most widely used asphalt mixture design method in the world. Its advantage is that it has clear requirements for the volume index of the mixture, and the equipment is cheap and easy to operate. 3.2 Design Method for Cold Recycled Asphalt Pavement Structure

　　在冷再生技術規范指導方面，１９８１年美國交通運輸研究委員會出版了《路面廢料再生指南》，隨后瀝青協會在１９８３年出版了《瀝青路面冷拌再生技術手冊》。日本道路協會在１９８４年頒布了《路面廢舊材料再生利用技術指南》，并在２００４年出版了《路面回收指南》。南非在２００９年頒布了《瀝青穩定類再生設計和施工技術指南》，詳細介紹了冷再生瀝青混合料配合比設計、結構設計以及施工方法等。冷再生路面結構設計方法作為冷再生技術推廣應用的重要組成部分，在國內外大致可分為２類：一類是以工程經驗和室內試驗為依據的經驗設計法，典型的經驗設計法有 ＣＢＲ法和 ＡＡＳＨＴＯ 法；另一類是以力學分析為基 礎，考 慮 交 通、環境以及材料特性的力學－經驗法，包括 ＭＥＰＤＧ 和 ＡＡＳＨＴＯ２０１５。路面設計方法的發展也經歷了從經驗法到力學－經 驗法的轉變，目前冷再生瀝青路面的結構設計方法大多以瀝青路面結構設計方法為基礎。以下介紹幾種典型的冷再生瀝青路面結構設計方法。

　　In terms of guidance on cold recycling technology specifications, the Transportation Research Board of the United States published the "Guidelines for Road Waste Recycling" in 1981, followed by the Asphalt Institute publishing the "Handbook for Cold Mix Recycling Technology of Asphalt Pavement" in 1983. The Japan Road Association issued the "Technical Guidelines for the Recycling of Road Waste Materials" in 1984 and published the "Road Recycling Guidelines" in 2004. In 2009, South Africa issued the "Guidelines for Design and Construction Technology of Asphalt Stabilized Recycled Asphalt", which detailed the mix design, structural design, and construction methods of cold recycled asphalt mixtures. The design method of cold recycling pavement structure, as an important component of the promotion and application of cold recycling technology, can be roughly divided into two categories at home and abroad: one is the empirical design method based on engineering experience and indoor testing, and typical empirical design methods include CBR method and AASHTO method; Another type is based on mechanical analysis, considering traffic, environment, and material properties using mechanical empirical methods, including MEPDG and AASHTO2015. The development of pavement design methods has also undergone a transition from empirical methods to mechanics empirical methods. Currently, most structural design methods for cold recycled asphalt pavements are based on asphalt pavement structural design methods. The following introduces several typical design methods for cold recycled asphalt pavement structures.

　　3.2.1經驗法（１）ＡＡＳＨＴＯ 結構層系數設計法：針對冷再生瀝青路面結構設計并未提出針對性的設計方法，加鋪層厚度設計仍依托于結構數，加鋪層厚度計算包括冷再生層和加鋪層。結構數ａ的計算公式為乳化瀝青混 合 料 的 推 薦 結 構 層 系 數 為０．２８～０．３５［９３－９４］，泡 沫 瀝 青 混 合 料 的 推 薦 結 構 層 系 數 為０．３６～０．３９［９５］，相關研究中全深式冷再生瀝青混合料的值為０．２５～０．４１［９６］，瀝青混合料的結構層系數約為０．５。其 中結 構 層 系 數 可 以 通 過 有 效 結 構 數 進 行 表征，有 效 結 構 數 Ｓ 是基于落錘式彎沉儀 （ＦａｌｌｉｎｇＷｅｉｇｈｔＤｅｆｌｅｃｔｏｍｅｔｅｒ，ＦＷＤ）測試反演路基上方所有結構層的有效模量進行定量化計算，表示為（２）美國加利福尼亞州采用碎石當量法定義了各結構層材料在承受相同荷載作用下的碎石當量厚度。特定結構層的碎石當量厚度Ｇ 為（３）南非設計法：基于 ＡＡＳＨＴＯ 結構數的設計原理，南非提出了路面數設計法，將瀝青面層、水泥混凝土等膠結材料、瀝青穩定材料、無黏結材料和路基土的材料屬性進行材料性能等級劃分，并基于路面結構層從上下剛度依次遞減的原則，提出了層間模量比。具體設計步驟如下。步驟１：計算路基等效長期剛度，考慮氣候因素的濕度調整因子和厚度系數。步驟２：基于層間模量比依次計算路基上方各結構層模量，即該結構層的支撐層模量乘以模量比，取計算模量和允許模量的較小值。步驟３：對于瀝青混合料和瀝青穩定類材料（包含泡沫瀝青混合料和乳化瀝青混合料），需乘以厚度調整系數。

　　3.2.1 Empirical Method (1) AASHTO Structural Layer Coefficient Design Method: No targeted design method has been proposed for the structural design of cold recycled asphalt pavement. The design of overlay thickness still relies on the number of structures, and the calculation of overlay thickness includes both cold recycled layer and overlay layer. The calculation formula of structure number a is that the recommended structure layer coefficient of emulsified asphalt mixture is 0.28~0.35 [93-94], the recommended structure layer coefficient of foam asphalt mixture is 0.36~0.39 [95], the recommended value of full depth cold recycling asphalt mixture in relevant studies is 0.25~0.41 [96], and the structure layer coefficient of asphalt mixture is about 0.5. The structural layer coefficient can be characterized by the effective structure number, which S is quantitatively calculated based on the effective modulus of all structural layers above the roadbed inverted by the Falling Weight Deflectometer (FWD) test. It is expressed as (2) California, USA uses the gravel equivalent method to define the equivalent thickness of each structural layer material under the same load. The equivalent thickness G of crushed stone for a specific structural layer is (3) South African design method: Based on the design principle of AASHTO structural number, South Africa proposed the pavement number design method, which divides the material properties of asphalt surface layer, cement concrete and other bonding materials, asphalt stabilizing materials, non bonding materials and subgrade soil into material performance grades. Based on the principle of decreasing stiffness from top to bottom of the pavement structural layer, the interlayer modulus ratio is proposed. The specific design steps are as follows. Step 1: Calculate the equivalent long-term stiffness of the roadbed, taking into account the humidity adjustment factor and thickness coefficient of climate factors. Step 2: Calculate the modulus of each structural layer above the roadbed based on the interlayer modulus ratio, that is, multiply the modulus of the supporting layer of the structural layer by the modulus ratio, and take the smaller of the calculated modulus and the maximum allowable modulus. Step 3: For asphalt mixture and asphalt stabilized materials (including foam asphalt mixture and emulsified asphalt mixture), the thickness adjustment coefficient shall be multiplied.

　　步驟４：對于基層材料，模量需乘以基層可靠度因子。步驟５：計算所有結構層貢獻值總和，即路面數。步驟６：根據道路等級和路面數，確定標準軸載作用下的路面承載能力。

　　Step 4: For the base material, the modulus needs to be multiplied by the base reliability factor. Step 5: Calculate the total contribution value of all structural layers, i.e. the number of road surfaces. Step 6: Determine the minimum bearing capacity of the road surface under standard axle load based on the road grade and number of road surfaces.

　　3.2.2力學－經驗法力學－經驗法是基于結構力學和材料模型來分析施加荷載時路面結構內部響應的應力、應變和撓度，通過傳遞函數將應力、應變或撓度與結構性能（荷載重復到破壞的次數）建立關聯，傳遞函數是一種經驗關系，來自研究和／或路面性能數據。路面分析模型一般采用彈性層狀體系理論，輸入參數包括結構層厚和各結構層材料對應的彈性模量和泊松比。力學－經驗法能夠對已有的路面結構層進行有效建模和分析，對冷再生瀝青路面設計具有顯著優勢。目前，尚未形成針對冷再生瀝青路面的設計方法，力學－經驗法將冷再生瀝青混合料視為一種無黏結基層材料，需確定回彈模量并作為力學輸入值［８］。然而，冷再生瀝青混合料具有一定的黏彈性力學特性，是一種介于無黏結顆粒材料與瀝青混合料的路面材料。以全深式冷再生為例，研究表明將冷再生結構層視為瀝青黏結層或是無黏結材料層對路面性能具有顯著影響［９６］。對冷再生瀝青路面結構設計方法的研究較少，主要基于《公路瀝青路面設計規范》（ＪＴＧ　Ｄ５０—２０１７）進行結構設計。目前，越來越多的學者將冷再生瀝青混合料作為一種瀝青黏結材料進行路面結構設計。當冷再生瀝青材料作為基層和下面層時，在荷載作用下冷再生結構層底部受拉，需要對其疲勞壽命進行驗算；其次，冷再生瀝青材料在荷載作用下會發生車轍變形，也需要對其變形進行驗算。目前，冷再生瀝青結構層的車轍預估模型和疲勞設計方程大多采用基于熱拌瀝青混合料的路面設計準則，但是冷再生瀝青材料與傳統熱拌瀝青混合料的性能具有一定差異，傳統瀝青路面結構設計準則對冷再生瀝青結構層的適用性仍需進一步研究［９７］。Ｇｕ等［８］將冷再生瀝青結構層作為基層，并考慮了其黏彈性力學特性，建立了符合冷再生瀝青路面的車轍預估模型和疲勞損傷模型。以如圖７［８］所示的車轍預估模型為例，車轍預測深度約為現場檢測值的２倍（Ｅ、Ｆ分別為乳化瀝青、泡沫瀝青，Ｐ、Ｍ分別為預測值、現場檢測值），該現象主要是由于力學－經驗法的模型校正系數存在偏差，以及室內試驗養護方法未能真實反映冷再生瀝青混合料的養護過程。傳統的疲勞設計方程是基于彈性假設的線性損傷累計，假定在疲勞損傷過程中瀝青混合料模量為定值，在控制應力模式下材料內部產生固定的應變水 平，未考慮冷再生瀝青混合料的非線性損傷演化。針對冷再生瀝青混合料疲勞準則的研究，Ｋｕｎａ等［９８］提出了如圖８所示的基于混合料剛度演化的疲勞壽命分階段累加設計方法，將 剛 度演化過程 劃 分 成 多 個 區 間，假 定 每 個 區 間 的 剛 度為該區間的均值，依 次 計 算 各 區 間 內 的 疲 勞 壽 命，并進行累加。

　　3.2.2 Mechanics Empirical Method Mechanics empirical method is based on structural mechanics and material models to analyze the stress, strain, and deflection of the internal response of pavement structures when loads are applied. It establishes a correlation between stress, strain, or deflection and structural performance (the number of times the load is repeated to failure) through a transfer function, which is an empirical relationship derived from research and/or pavement performance data. The pavement analysis model generally adopts the theory of elastic layered system, and the input parameters include the thickness of the structural layer and the corresponding elastic modulus and Poisson's ratio of each structural layer material. The mechanics experience method can effectively model and analyze existing pavement structural layers, which has significant advantages in the design of cold recycled asphalt pavement. At present, there is no design method for cold recycled asphalt pavement. The mechanical empirical method considers cold recycled asphalt mixture as a non bonded base material, and the rebound modulus needs to be determined as the mechanical input value [8]. However, cold recycled asphalt mixture has certain viscoelastic mechanical properties and is a pavement material that falls between non bonded granular materials and asphalt mixtures. Taking full depth cold recycling as an example, research has shown that treating the cold recycling structural layer as either an asphalt bonding layer or a non bonding material layer has a significant impact on pavement performance [96]. There is relatively little research on the design method of cold recycled asphalt pavement structure in China, mainly based on the "Design Specification for Highway Asphalt Pavement" (JTGD50-2017) for structural design. At present, more and more scholars are using cold recycled asphalt mixture as an asphalt bonding material for pavement structure design. When cold recycled asphalt material is used as the base and lower layer, the bottom of the cold recycled structural layer is subjected to tension under load, and its fatigue life needs to be verified; Secondly, cold recycled asphalt materials will undergo rutting deformation under load, and its permanent deformation also needs to be verified. At present, most of the rutting prediction models and fatigue design equations for cold recycled asphalt structural layers adopt pavement design criteria based on hot mix asphalt mixtures. However, the performance of cold recycled asphalt materials differs from that of traditional hot mix asphalt mixtures, and the applicability of traditional asphalt pavement structural design criteria to cold recycled asphalt structural layers still needs further research [97]. Gu et al. [8] used the cold recycled asphalt structural layer as the base layer and considered its viscoelastic mechanical properties, establishing a rutting prediction model and fatigue damage model that are suitable for cold recycled asphalt pavement. Taking the rut prediction model as shown in Figure 7 [8] as an example, the rut prediction depth is about twice the field detection value (E and F are emulsified asphalt and foam asphalt respectively, P and M are the prediction value and field detection value respectively). This phenomenon is mainly due to the deviation of the model correction coefficient of the mechanical empirical method, and the failure of the indoor test maintenance method to truly reflect the maintenance process of cold recycled asphalt mixture. The traditional fatigue design equation is based on the linear damage accumulation assumption of elasticity, assuming that the modulus of asphalt mixture is constant during the fatigue damage process, and a fixed strain level is generated inside the material under controlled stress mode, without considering the nonlinear damage evolution of cold recycled asphalt mixture. Kuna et al. [98] proposed a phased cumulative design method for fatigue life of cold recycled asphalt mixtures based on the evolution of mixture stiffness, as shown in Figure 8. The stiffness evolution process is divided into multiple intervals, and assuming that the stiffness of each interval is the mean of that interval, the fatigue life within each interval is calculated sequentially and accumulated.

　　3.2.3冷再生瀝青路面設計存在的問題結構數、碎 石 當 量 法 及 路 面 數 設 計 法 是 經 驗性的設計方法。結 構 數 和 碎 石 當 量 法 基 于 一 定 的標準值粗略地將冷 再 生 瀝 青 混 合 料 強 度 性 能 進 行等效系數 的 折 減，并未考慮路面結構整體的受力特性和結 構 層 合 理 設 置；路 面 數 設 計 法 考 慮 了 路面結構的 整 體 受 力 特 性，基 于 大 量 路 面 結 構 性 能檢測數據對各結構層模量進行了有效規范。以 上經驗法均未考慮冷 再 生 材 料 在 長 期 服 役 過 程 中 的剛度性能演化。研究表 明，冷 再 生 瀝 青 混 合 料 的 抗 疲 勞 性 能低于熱拌 瀝 青 混 合 料，且在道路結構中多應用于基層，在 交 通 荷 載 作 用 下 易 發 生 疲 勞 裂 縫。對 于力學經驗 法，目前針對冷再生瀝青路面的疲勞方程研究較 少，普遍按照熱拌瀝青混合料的設計方法進行 疲 勞 設 計，未 能 充 分 考 慮 其 抗 疲 勞 性 能。主要原因 在 于：１）由于冷再生瀝青混合料材料組成復雜，其強度組成機理與傳統的熱拌瀝青混合料差異較大，在服 役 前 期 隨 著 時 間 增 長，強 度 仍 出現一定程 度 的 提 高，以上因素導致冷再生瀝青混合料在全壽命周期 內 的 強 度 演 化 和 失 效 機 理 目 前尚未充分 明 確，如果按照傳統熱拌瀝青混合料的疲勞設計準則進行路面設計，會 導 致 計 算 得 到 的冷再生基 層 厚 度 過 大；２）缺少充足的冷再生瀝青路面現場 疲 勞 失 效 數 據，無 法 對 室 內 疲 勞 方 程 進行有效標定。冷再生瀝青路面設計研究應著重考慮冷再生材料自身材料屬性和結構層受力特性，深入研究不同材料組分影響下冷再生瀝青混合料的強度特性和破壞機理，建立符合冷再生瀝青混合料特性的力學失效設計準則，并系統開展大量的冷再生瀝青路面現場檢測，基于現場檢測數據對其路面設計準則進行校正，以建立真正符合冷再生瀝青路面的結構設計方法。

　　3.2.3 Problems in the design of cold recycled asphalt pavement: The structural number, gravel equivalent method, and pavement number design method are empirical design methods. The structural number and gravel equivalent method roughly reduce the strength performance of cold recycled asphalt mixture by equivalent coefficients based on certain standard values, without considering the overall stress characteristics of the pavement structure and the reasonable setting of structural layers; The pavement design method considers the overall stress characteristics of the pavement structure and effectively regulates the modulus of each structural layer based on a large amount of pavement structure performance testing data. The above empirical methods did not consider the stiffness performance evolution of cold recycled materials during long-term service. Research has shown that the fatigue resistance of cold recycled asphalt mixture is lower than that of hot mix asphalt mixture, and it is mostly used in the base layer of road structures, which is prone to fatigue cracks under traffic loads. For the empirical method of mechanics, there is currently little research on the fatigue equation of cold recycled asphalt pavement. The fatigue design is generally based on the design method of hot mix asphalt mixture, and its anti fatigue performance has not been fully considered. The main reason is that: 1) Due to the complex composition of cold recycled asphalt mixture materials, their strength composition mechanism is significantly different from that of traditional hot mix asphalt mixture. In the early stage of service, as time increases, the strength still shows a certain degree of improvement. The above factors have led to the strength evolution and failure mechanism of cold recycled asphalt mixture throughout its life cycle, which is currently not fully understood. If the pavement design is carried out according to the fatigue design criteria of traditional hot mix asphalt mixture, it will result in the calculated thickness of the cold recycled base layer being too large; 2) Lack of sufficient on-site fatigue failure data for cold recycled asphalt pavement makes it impossible to effectively calibrate indoor fatigue equations. The research on the design of cold recycled asphalt pavement should focus on the material properties and structural layer stress characteristics of cold recycled materials, deeply study the strength characteristics and failure mechanism of cold recycled asphalt mixtures under the influence of different material components, establish mechanical failure design criteria that conform to the characteristics of cold recycled asphalt mixtures, and systematically carry out a large number of on-site inspections of cold recycled asphalt pavement. Based on the on-site inspection data, the pavement design criteria should be corrected to establish a structural design method that truly conforms to cold recycled asphalt pavement.

　　4 冷再生瀝青混合料路用性能研究

　　Research on the Road Performance of 4 Cold Recycled Asphalt Mixtures

　　為了對冷再生材料的力學特性和應用效果進行定量化的評價，國內外學者進行了大量冷再生瀝青混合料路用性能試驗研究。4.1車轍性能

　　In order to quantitatively evaluate the mechanical properties and application effects of cold recycled materials, scholars at home and abroad have conducted a large number of experimental studies on the road performance of cold recycled asphalt mixtures. 4.1 Rutting performance

　　車轍是高溫條件下在載荷反復作用下引起的變形累積，剛度較大的瀝青混合料具有更強的抗車轍性能。冷再生材料主要應用于基層、底基層以及下面層，提高冷再生材料的強度可以為瀝青面層提供足夠的支撐力，從而減小路面縱向裂縫。目前，研究冷再生瀝青混合料車轍性能的主要試驗方法包括動態模量試驗、馬歇爾穩定度、重復加載試驗、三軸動態蠕變 試 驗、漢 堡 車 轍 儀 等［９９－１０１］。同 時，乳化瀝青／泡沫瀝青及其瀝青膠漿作為冷再生材料的膠結料，其抗變形能力也對冷再生瀝青混合料的性能影響較大。Ｖｉｇｎａｌｉ等［１０２］采用了溫度掃描試驗和多重應力蠕變恢復試驗表征冷再生膠漿材料的抗變形能 力；汪 德 才 等［１０３］采用車轍因子指標評價乳化瀝青殘留物的高溫抗變形能力；Ｒｅｚａｅｉ等［１０４］對比分析 了 ９ 種冷再生材料的車轍性能，試 驗 結果表明較高馬歇爾 模 數 的 冷 再 生 材 料 具 有 更 好 的抗車轍性能，與漢 堡 車 轍 試 驗 結 果 一 致，骨 料 粒 徑分布對車 轍 性 能 影 響 較 大，密 級 配 混 合 料 抗 車 轍性能優于開級 配；Ｇｕ等［８］對比分析了廠拌冷再生和就地冷再生瀝青混合料的抗車轍性能，級 配 較粗的 廠 拌 冷 再 生 混 合 料 的 抗 車 轍 性 能 更 佳。

　　Rutting is a permanent deformation accumulation caused by repeated loading under high temperature conditions, and asphalt mixtures with higher stiffness have stronger resistance to rutting. Cold recycled materials are mainly used in the base layer, sub base layer, and lower surface layer. Improving the strength of cold recycled materials can provide sufficient support for the asphalt surface layer, thereby reducing longitudinal cracks in the road surface. At present, the main experimental methods for studying the rutting performance of cold recycled asphalt mixtures include dynamic modulus test, Marshall stability test, repeated loading test, triaxial dynamic creep test, Hamburg rutting instrument, etc. [99-101]. At the same time, emulsified asphalt/foam asphalt and its asphalt mortar, as the binder of cold recycled materials, have a greater impact on the performance of cold recycled asphalt mixture in terms of its permanent deformation resistance. Vignali et al. [102] used temperature scanning tests and multiple stress creep recovery tests to characterize the resistance to permanent deformation of cold recycled adhesive materials; Wang Decai et al. [103] evaluated the high-temperature deformation resistance of emulsified asphalt residues using the rutting factor index; Rezaei et al. [104] compared and analyzed the rutting performance of 9 cold recycled materials. The experimental results showed that cold recycled materials with higher Marshall modulus had better rutting resistance, consistent with the Hamburg rutting test results. The particle size distribution of aggregates had a greater impact on rutting performance, and the rutting resistance of dense graded mixtures was better than that of open graded mixtures; Gu et al. [8] compared and analyzed the anti rutting performance of factory mixed cold recycled and on-site cold recycled asphalt mixtures, and found that the coarse-grained factory mixed cold recycled mixture had better anti rutting performance.

　　此外，廠拌冷再生可 以 對 ＲＡＰ料的變異性進行有效控制，相關研究結果表明廠拌泡沫瀝青混合料的抗車轍性能高于熱拌瀝青混合料，乳 化 瀝 青 混 合料稍差于熱拌混 合 料。其他研究表明泡沫瀝青混合料的模量高于乳化瀝青混合料，間 接 反 映 出 泡沫瀝青混合料具有更好的 抗 車 轍 性 能［５５］。這 主要是由于瀝青在混合料中分布方式的差異，泡 沫 瀝青混合料以點焊方式與集料進行黏合，而 乳 化 瀝青主要是以瀝青膜的形式包裹在集料表面，在 外力荷載作用下乳化 瀝 青 混 合 料 更 易 發 生 集 料 間 的滑移，從而造成 較 大 的 車 轍。高 超［１０５］開 展了 常 溫條件下 ＭＭＬＳ３加速加載試驗，并對試件 進 行Ｘ射線無損掃 描，表明車轍變形主要是由于泡沫砂漿試件壓密變形和集料在空間方向上的位移調整；Ｂａｂａｇｏｌｉ等［１０６］采用馬歇爾穩定度、動 態 蠕 變 及 車輪試驗評價水泥及石灰 對 ＳＢＳ改 性乳 化 瀝 青 混 合料的影響，加入水 泥 和 石 灰 能 夠 降 低 空 隙 率，提 高了馬歇爾穩定度和抗 變 形 能 力；其 次，ＲＡＰ料降低了冷再 生 瀝 青 混 合 料 的 熱－黏彈性力學特性，相比于傳統熱拌瀝 青 混 合 料 具 有 更 好 的 抗 永 久 變形 能 力［１０７］，但其抗車轍性能隨著 ＲＡＰ料 的 增 加而降低［１０８］。4.2抗水損害性能

　　In addition, plant mix cold recycling can effectively control the variability of RAP mixture. Relevant research results show that the anti rutting performance of plant mix foam asphalt mixture is higher than that of hot mix asphalt mixture, and the emulsified asphalt mixture is slightly worse than that of hot mix asphalt mixture. Other studies show that the modulus of foam asphalt mixture is higher than that of emulsified asphalt mixture, which indirectly reflects that foam asphalt mixture has better rutting resistance [55]. This is mainly due to the difference in the distribution of asphalt in the mixture. foam asphalt mixture is bonded to the aggregate by spot welding, while emulsified asphalt is mainly wrapped on the surface of the aggregate in the form of asphalt film. Under the external force load, emulsified asphalt mixture is more likely to slip between aggregates, resulting in large rutting. Gaochao [105] carried out the accelerated loading test of MMLS3 at room temperature, and carried out X-ray non-destructive scanning on the specimens. It showed that the rutting deformation was mainly due to the compaction deformation of foam mortar specimens and the displacement adjustment of aggregates in the spatial direction; Babagoli et al. [106] evaluated the effects of cement and lime on SBS modified emulsified asphalt mixture using Marshall stability, dynamic creep, and wheel tests. The addition of cement and lime can reduce porosity, improve Marshall stability, and enhance resistance to permanent deformation; Secondly, RAP material reduces the thermal viscoelastic mechanical properties of cold recycled asphalt mixture, and has better resistance to permanent deformation compared to traditional hot mix asphalt mixture [107]. However, its anti rutting performance decreases with the increase of RAP material [108]. 4.2 Water damage resistance performance

　　冷再生材料中加入乳化瀝青或泡沫瀝青，其中水分隨著養護齡期的增加而逐漸揮發，該過程會導致冷再生材料內部留下水分揮發后的微空隙，該部分空隙會在路面服役期內發生水分匯集，從而對冷再生材料產 生 水 損 害，造 成 各 項 力 學 性 能 的 衰 減。ＪＴＧ／Ｔ５５２１—２０１９采用凍融劈裂強度比、干 濕劈裂強度比作為控制冷再生材料水損害的控制指標，同時其他眾多學者也采用馬歇爾穩定度、間接拉伸強度、回彈模量、無側限抗壓強度等指標評價冷再生瀝青混 合 料 的 水 穩 性［１０９－１１２］。此 外，表面 能 試 驗 用于評價膠結料與集料的裹附程度及裹附質量，也被用于評價冷再生瀝青混合料的水穩定性［１１３］。冷再生瀝青混合料發生水損害后，材料內部出現微裂縫，導致空隙增大以及劈裂強度、模量及抗疲勞性能等降低［１１１］。在凍融循環過程中產生的膨脹應力、內應力以及溫度應力破壞水泥水化產物的立體網狀結構，微空隙數目減少，而大體積空隙數目顯著增多［１１４］，降低了集料與瀝青間的黏結性，造成混合料的抗剪性能衰減［１１１］。相關研究結果表明 ＲＡＰ料摻量是影響冷再生瀝青混合料水穩定性的主要因素，水穩定性 隨 著 ＲＡＰ 料 的摻 量 呈 先 增 大 后 減 小的趨勢［１１０］。考慮到集 料 類 型 的 影 響，ＲＡＰ料 與瀝青黏附效 果 差，其水穩性遠低于常規的花崗巖和石灰巖 集 料 類 型［１１３］。熟 石 灰 或 硅 酸 鹽 水 泥 不 僅可以作為冷再生材料的礦物摻合料，其 含 有 氫 氧化鈣和其 他 堿 性 成 分，遇水發生水化作用并與瀝青形成復 合 膠 漿，兩者交互作用增強了瀝青與集料的黏結 力，從而提高了冷再生瀝青混合料的水穩 定 性［３０，１１２，１１５］，但 是水 泥 摻 量 超 過１．５％后 抗水損害性能 的 增 強 效 果 變 小［１１０］；此 外，添 加 聚 合 物外加劑能夠提高冷再生瀝青混合料的水穩性［１１３］。4.3抗疲勞開裂性能

　　Emulsified asphalt or foam asphalt is added to the cold recycled materials, and the moisture in the cold recycled materials gradually evaporates with the increase of the curing age. This process will lead to micro voids left inside the cold recycled materials after the moisture volatilization. This part of voids will collect moisture during the service life of the pavement, thus causing water damage to the cold recycled materials, causing the attenuation of various mechanical properties. JTG/T5521-2019 uses freeze-thaw splitting strength ratio and dry wet splitting strength ratio as control indicators for water damage in cold recycled materials. At the same time, many other scholars have also used Marshall stability, indirect tensile strength, rebound modulus, unconfined compressive strength and other indicators to evaluate the water stability of cold recycled asphalt mixtures [109-112]. In addition, surface energy tests are used to evaluate the degree and quality of adhesion between binders and aggregates, as well as to evaluate the water stability of cold recycled asphalt mixtures [113]. After water damage occurs in cold recycled asphalt mixture, micro cracks appear inside the material, resulting in increased voids and decreased splitting strength, modulus, and fatigue resistance [111]. The expansion stress, internal stress, and temperature stress generated during the freeze-thaw cycle damage the three-dimensional network structure of cement hydration products, resulting in a decrease in the number of micro voids and a significant increase in the number of large volume voids [114]. This reduces the adhesion between aggregates and asphalt, leading to a decline in the shear performance of the mixture [111]. The relevant research results indicate that the dosage of RAP material is the main factor affecting the water stability of cold recycled asphalt mixture, and the water stability shows a trend of first increasing and then decreasing with the dosage of RAP material [110]. Considering the influence of aggregate types, RAP material has poor adhesion to asphalt and its water stability is much lower than conventional granite and limestone aggregate types [113]. Hydrated lime or Portland cement can not only be used as mineral admixtures for cold recycled materials, but also contain calcium hydroxide and other alkaline components. When it comes into contact with water, it undergoes hydration and forms a composite slurry with asphalt. The interaction between the two enhances the adhesion between asphalt and aggregate, thereby improving the water stability of cold recycled asphalt mixtures [30112115]. However, the enhancement effect of water damage resistance decreases when the cement content exceeds 1.5% [110]; In addition, adding polymer additives can improve the water stability of cold recycled asphalt mixtures [113]. 4.3 Fatigue cracking resistance performance

　　冷再生材料目前在國內工程應用中主要應用于基層和底基層，為了保證冷再生材料具有足夠承載能力，通常采用摻入１．０％～２．５％水泥以提高冷再生結構層的抗變形能力，但同時也導致其脆性增加，在一定程度上降低了其抗疲勞性能。目前，關于冷再生瀝青混合料疲勞性能的研究主要集中于疲勞試驗方法、破壞特征、壽命預估以及控制指標等方面。冷再生瀝青混合料的疲勞試驗通常采用間接拉伸疲勞試 驗、四 點 彎 曲 試 驗［１１６－１１７］、盤 狀緊 湊 拉 伸［１１８］和半圓彎曲試 驗［１１９］等 方法，采取應力控制模式或者應變控制模式［１２０］。常用的性能分析指標包括斷裂能［１１８］、抗拉強度、耗散能等指標。通過冷再生路面裂縫調查結果發現，室內試驗的斷裂能指標與冷再生 路 面 的 橫 向 裂 紋 數 量 具 有 較 好 的 相 關 性。

　　Cold recycled materials are currently mainly used in domestic engineering applications for base and sub base layers. In order to ensure that cold recycled materials have sufficient bearing capacity, 1.0% to 2.5% cement is usually added to improve the deformation resistance of the cold recycled structural layer. However, this also leads to an increase in its brittleness, which to some extent reduces its fatigue resistance. At present, research on the fatigue performance of cold recycled asphalt mixtures mainly focuses on fatigue testing methods, failure characteristics, life estimation, and control indicators. The fatigue test of cold recycled asphalt mixture usually adopts methods such as indirect tensile fatigue test, four point bending test [116-117], disc compact tensile test [118], and semi-circular bending test [119], and adopts stress control mode or strain control mode [120]. Common performance analysis indicators include fracture energy [118], tensile strength, dissipated energy, and other indicators. Through the investigation of cracks in cold recycled pavement, it was found that the fracture energy index of indoor tests has a good correlation with the number of transverse cracks in cold recycled pavement.

　　Ｔｅｓｈａｌｅ等［１２１］采用斷裂能為指標，研究了盤狀緊湊拉伸和半圓彎曲斷裂試驗方法對評價就地冷再生混合料抗裂性 能 的 適 用 性；孫 立 軍 等［１２２］采 用劈 裂 強度試驗和應力控制模式的劈裂疲勞試驗對比研究了在役冷再生瀝青混合料與新成型乳化瀝青混合料的疲勞損傷特 性；汪 德 才 等［１１９］采用間接拉伸疲勞試驗研究了不同的應力水平、材料組成及摻量對冷再生瀝青混合料疲勞性能的影響，結果表明乳化瀝青性能、ＲＡＰ摻量對疲勞壽命的影響為顯著，應力水平和水泥用量的影響小，其中，冷再生試件斷裂能隨著 ＲＡＰ料摻量 的 增 加 先 增 大 后 減 小，當 ＲＡＰ料摻量超過１０％時，冷再生試件的斷裂能相比常規熱拌混合料顯著降低［１２３］；嚴金海等［１２４］采用間接拉伸疲勞試驗對比分析了有無水泥摻量下乳化瀝青混合料的斷裂特性和疲勞壽命，結果表明其疲勞破壞形式為塑性破壞，在低應力和低應變水平下抗疲勞性能優于無水泥添加的乳化瀝青混合料，而在高應力和高應變水平下卻相反［１２５－１２６］。

　　Teshale et al. [121] used fracture energy as an indicator to study the applicability of disc compact tensile and semi-circular bending fracture test methods for evaluating the crack resistance of in-situ cold recycled mixtures; Sun Lijun et al. [122] compared the fatigue damage characteristics of in-service cold recycled asphalt mixture and newly formed emulsified asphalt mixture using splitting strength test and stress control mode splitting fatigue test; Wang Decai et al. [119] used indirect tensile fatigue tests to study the effects of different stress levels, material compositions, and dosages on the fatigue performance of cold recycled asphalt mixtures. The results showed that emulsified asphalt performance and RAP dosage had the most significant impact on fatigue life, while stress levels and cement dosage had the smallest impact. Among them, the fracture energy of cold recycled specimens increased first and then decreased with the increase of RAP dosage. When the RAP dosage exceeded 10%, the fracture energy of cold recycled specimens significantly decreased compared to conventional hot mix mixtures [123]; Yan Jinhai et al. [124] used indirect tensile fatigue tests to compare and analyze the fracture characteristics and fatigue life of emulsified asphalt mixtures with and without cement content. The results showed that its fatigue failure mode was plastic failure, and its fatigue resistance was better than that of emulsified asphalt mixtures without cement addition at low stress and low strain levels, but the opposite was true at high stress and high strain levels [125-126].

　　對于瀝青黏結劑種類，泡沫瀝青混合料在低應力水平下疲勞壽命較高，疲勞損傷表現為脆性斷裂；乳化瀝青混合料在高應力水平下疲勞壽命較高，疲勞損傷表現為塑性破壞［５５］。這主要是 由 于 泡 沫 瀝 青 混 合 料 在 相 同 瀝 青摻量下強度更高，具有類似于半剛性材料的力學特性；乳化瀝青能夠較均勻地裹附在集料表面，具有較為明顯的黏彈性力學特性，在高應力水平下抗疲勞性能更佳。4.4 低溫性能

　　For the type of asphalt binder, the fatigue life of foam asphalt mixture is higher at low stress level, and the fatigue damage is brittle fracture; Emulsified asphalt mixture has a higher fatigue life under high stress levels, and fatigue damage manifests as plastic failure [55]. This is mainly due to the higher strength of foam asphalt mixture under the same asphalt content, which has mechanical properties similar to semi-rigid materials; Emulsified asphalt can be uniformly coated on the surface of aggregates, with obvious viscoelastic mechanical properties and better fatigue resistance under high stress levels. 4.4 Low temperature performance

　　對于冷再生材料低溫性能的研究，通常采用間接拉伸蠕變試驗，研究低溫下材料的強度和蠕變柔量［１２３］；除此之外，低溫開裂和抗疲勞開裂數據可以作為 ＭＥＰＤＧ 的 輸入 參 數 來 預 測 路 面 病 害。老 化的 ＲＡＰ料能夠 提 高 冷 再 生 瀝 青 混 合 料 的 剛 度，同時會增強低溫脆性。Ｂｅｈｎｉａ等［１２３］采用聲發射技術表征了冷再 生 試 件 的 脆 化 溫 度，加 入 ＲＡＰ 料 試件的脆化溫度高于相同瀝青和新集料組成的熱拌瀝青混合料，這主 要 是 由 于 ＲＡＰ 料 中的 老 化 瀝 青 增 加了冷再生材 料 的 脆 性 特 性，但 不 同 ＲＡＰ 料 摻量 的冷再生瀝青混合料脆化溫度差異較小；Ｙａｎ等［１２７］研究表明加入１％～２％的 水泥 可 以 提 高 乳 化 瀝 青混合料的高溫穩定性和低溫抗裂性，但水泥摻量超過１．５％時，其 低溫 抗 開 裂 性 能 增 加 到 大 值 后 隨之降低；徐金枝等［６２］開展了不同泡沫瀝青和水泥含量的冷再生低溫抗裂試驗，結果表明冷再生材料的低溫柔韌性隨泡沫瀝青用量的增加而增大，但隨著水泥用量的增加而呈拋物線變化規律，因此，當水泥摻量超過一定水平時，冷再生瀝青混合料具有更高的低溫脆性。4.5小結

　　For the study of low-temperature performance of cold recycled materials, indirect tensile creep tests are usually used to investigate the strength and creep compliance of materials at low temperatures [123]; In addition, low-temperature cracking and fatigue cracking data can be used as input parameters for MEPDG to predict road surface diseases. Aging RAP material can improve the stiffness of cold recycled asphalt mixture and enhance low-temperature brittleness. Behnia et al. [123] used acoustic emission technology to characterize the brittleness temperature of cold recycled specimens. The brittleness temperature of specimens with RAP added was higher than that of hot mix asphalt mixtures composed of the same asphalt and new aggregate. This is mainly due to the increased brittleness of cold recycled materials caused by aged asphalt in RAP, but the difference in brittleness temperature of cold recycled asphalt mixtures with different RAP content is small; Yan et al. [127] found that adding 1% to 2% cement can improve the high-temperature stability and low-temperature crack resistance of emulsified asphalt mixtures. However, when the cement content exceeds 1.5%, its low-temperature crack resistance increases to its maximum value and then decreases; Xu Jinzhi et al. [62] carried out cold recycling low temperature crack resistance tests with different foam asphalt and cement content, and the results showed that the low temperature flexibility of cold recycling materials increased with the increase of foam asphalt content, but it showed a parabolic change law with the increase of cement content. Therefore, when the cement content exceeded a certain level, the cold recycling asphalt mixture had higher low-temperature brittleness. 4.5 Summary

　　由以上分析可知，冷再生瀝青混合料的材料組成及性能決定了其路用性能。密級配和粗級配的混合料骨架結構有助于提高冷再生瀝青混合料的抗車轍性能。相比 對 無 ＲＡＰ 料 的混 合 料 試 件，ＲＡＰ 料能夠提高冷再生瀝青混合料的抗車轍性能，并隨著ＲＡＰ料 摻量 的 增 加 呈 降 低 趨 勢，但 不 利 于 抗 水 損害、抗疲勞以及低溫開裂性能。添加水泥和石灰能夠增加冷再生瀝青混合料的剛度，提升抗車轍性能，且作為一種外加劑能夠改善集料與瀝青的黏附效果，增強抗水損害性能；低應力應變水平下添加水泥和石灰有利于提高抗疲勞性能，高應力應變水平下則相反；低溫開裂性能隨著水泥和石灰摻量的增加呈先增長、后降低的趨勢。由于乳化瀝青和泡沫瀝青在冷再生瀝青混合料中分布方式的差異，在其他條件相同下，泡沫瀝青混合料的模量高于乳化瀝青混合料，抗車轍性能更佳。此外，泡沫瀝青混合料在低應變水平下的抗疲勞性能更佳，而高應變水平下乳化瀝青混合料的抗疲勞性能更優。

　　From the above analysis, it can be concluded that the material composition and performance of cold recycled asphalt mixture determine its road performance. The skeleton structure of dense and coarse graded mixtures helps to improve the anti rutting performance of cold recycled asphalt mixtures. Compared to specimens without RAP material, RAP material can improve the anti rutting performance of cold recycled asphalt mixture, and shows a decreasing trend with the increase of RAP material content. However, it is not conducive to water damage resistance, fatigue resistance, and low-temperature cracking performance. Adding cement and lime can increase the stiffness of cold recycled asphalt mixture, enhance its resistance to rutting, and as an additive, improve the adhesion between aggregate and asphalt, enhancing its resistance to water damage; Adding cement and lime at low stress-strain levels is beneficial for improving fatigue resistance, while the opposite is true at high stress-strain levels; The low-temperature cracking performance shows a trend of first increasing and then decreasing with the increase of cement and lime content. Due to the difference in distribution of emulsified asphalt and foam asphalt in cold recycled asphalt mixture, the modulus of foam asphalt mixture is higher than that of emulsified asphalt mixture under the same other conditions, and the rutting resistance is better. In addition, the anti fatigue performance of foam asphalt mixture is better at low strain level, while the anti fatigue performance of emulsified asphalt mixture is better at high strain level.

　　由此可 見，冷 再 生 瀝 青 混 合 料 的 材 料 組 成 對其力學性能影響的差異較大，在 實 際 工 程 中 應 充分考慮冷再生材料所在的結構層位，分 析 其 力 學響應以及對應的力學失效模式，明 確 關 鍵 性 能 需求。當冷再生瀝青 混 合 料 應 用 于 面 層 并 作 為 主 要承載層時，應充分 考 慮 其 抗 車 轍 性 能，開 展 室 內 試驗明確 ＲＡＰ料摻量 與 車 轍 變 形 的 對 應 關 系，水 泥和石灰作為外加劑可提高混合料的剛度和強度。相反，當冷再生瀝 青 混 合 料 作 為 結 構 基 層 時，應 嚴格控制水 泥 和 石 灰 摻 量，以 防 止 服 役 期 內 過 早 出現疲勞裂縫。5 冷再生技術施工工藝及施工設備

　　From this, it can be seen that the material composition of cold recycled asphalt mixture has a significant impact on its mechanical properties. In practical engineering, the structural layer where the cold recycled material is located should be fully considered, and its mechanical response and corresponding mechanical failure modes should be analyzed to clarify key performance requirements. When cold recycled asphalt mixture is applied to the surface layer and used as the main bearing layer, its anti rutting performance should be fully considered. Indoor tests should be conducted to clarify the corresponding relationship between RAP content and rutting deformation. Cement and lime as additives can improve the stiffness and strength of the mixture. On the contrary, when cold recycled asphalt mixture is used as the structural base, the cement and lime content should be strictly controlled to prevent premature fatigue cracks during service life. 5 Cold Recycling Technology Construction Process and Equipment

　　5.1 冷再生技術施工工藝

　　5.1 Cold Recycling Technology Construction Process

　　冷再生瀝青路面施工工藝是實現預期路面性能的關 鍵 步 驟。以 就 地 冷 再 生 技 術 為 例，主 要 包括施工準備、銑刨拌和、攤鋪碾壓、養生等步驟。

　　The construction process of cold recycled asphalt pavement is a key step in achieving the expected pavement performance. Taking on-site cold recycling technology as an example, it mainly includes steps such as construction preparation, milling and mixing, paving and rolling, and curing.

　　（１）施工準備施工前為保證施工性，需提前封閉交通并設置提醒牌，對施工路段進行清掃。其次，若原路面存在病害，要對路面病害進行預處理。根據設計要求計算所需水泥用量并采用撒布機在路面進行鋪撒，如需添加一定級配要求的碎石，將碎石按照設計量均勻撒布在路面上。

　　(1) Before construction preparation, in order to ensure construction safety, it is necessary to close traffic and set up reminder signs in advance, and clean the construction section. Secondly, if there are defects on the original road surface, pre-treatment of the road surface defects is necessary. According to the design requirements, calculate the required amount of cement and use a spreader to spread it on the road surface. If it is necessary to add crushed stones with certain grading requirements, evenly spread the crushed stones on the road surface according to the design amount.

　　（２）銑刨拌和利用冷再生機推動灑水車和再生劑膠結料罐車前進，使 ＲＡＰ 料、新 料、再生 劑 和 水 均 勻 拌 和。應綜合考慮路面損害狀況、銑刨深度、再生層厚度等因素，合理確定再生機組前進速度，一 般 控 制 在 ３～６ｍ·ｍｉｎ－１。每段銑刨長度控制在８０～１００ｍ，在再生機起步開始作業和結束作業處，安排人員及時整平，防止影響接縫處的平整度和密實性。縱向接縫搭接寬度不宜小于１００ｍｍ。

　　(2) Milling and mixing utilize cold regeneration energy to drive the sprinkler truck and the recycling agent binder tank truck forward, ensuring even mixing of RAP material, new material, recycling agent, and water. The forward speed of the regeneration unit should be reasonably determined by considering factors such as road damage, milling depth, and thickness of the regeneration layer, and generally controlled at 3-6m · min-1. The length of each milling section should be controlled between 80-100m. At the starting and ending points of the regeneration machine, personnel should be arranged to level it in a timely manner to prevent affecting the flatness and compactness of the joints. The longitudinal seam overlap width should not be less than 100mm.

　　（３）攤鋪碾壓攤鋪機應均勻、連續，速度宜控制在２～４ｍ·ｍｉｎ－１范圍內，攤鋪寬度應與再生銑刨寬度保持一致。攤鋪能力應與再生能力基本匹配，應在水泥初凝時間內完成材料攤鋪壓實。松鋪系數應根據試驗段的結果確定。攤 鋪 完 成 后 采 用 鋼 輪 振 動 壓 路 機 進 行 初壓，速度宜為１．５～３．０ｋｍ·ｈ－１，碾壓２～３遍；隨后采用鋼輪振動壓路機進行復壓，碾壓４～６遍，速度宜為２～４ｋｍ·ｈ－１；采用膠輪壓路機終壓４～６遍，速度 宜 為２～４ｋｍ·ｈ－１。就 地冷 再 生 技術的完整施工工藝見圖９。

　　(3) The paving and rolling paving machine should be uniform and continuous, and the speed should be controlled within the range of 2-4m · min-1. The paving width should be consistent with the width of the regenerated milling machine. The paving capacity should be basically matched with the regeneration capacity, and the material paving and compaction should be completed within the initial setting time of cement. The coefficient of looseness should be determined based on the results of the test section. After the paving is completed, a steel wheel vibratory roller should be used for initial compaction at a speed of 1.5-3.0 km · h-1, with 2-3 passes of rolling; Subsequently, a steel wheel vibratory roller is used for re compaction, rolling 4-6 times at a speed of 2-4 km · h-1; Finally, a rubber roller should be used for 4-6 passes of final compaction, with a speed of 2-4 km · h-1. The complete construction process of on-site cold recycling technology is shown in Figure 9.

　　（４）養生冷再生層宜在封閉交通的條件下進行養生，養生時間不宜小于７ｄ，不應少于４８ｈ。當滿足下述２個條件時可提前結束養生：再生層使用φ１５０ｍｍ 鉆頭的鉆芯機可取出完整的芯樣；再生層含水率低于２％。與就地冷再生技術相比，廠拌冷再生技術是將銑刨的 ＲＡＰ料運輸拌合站，并按照配合比進行冷再生瀝青混合料拌和，然后運輸施工現場進行攤鋪碾壓。車輛數要滿足機組出料和攤鋪速度相互協調，機組和施工現場不宜過遠，車頂裸露的混合料需進行覆蓋以減少水分蒸發損失。混合料采用攤鋪機攤鋪，熨平板無需加熱，振頻和振幅以高頻低幅為宜，初始密實度達到８５％以上，速度控制在２～４ｍ·ｍｉｎ－１。碾壓速度應均勻，初壓速度宜為１．５～３．０ｋｍ·ｍ－１，復壓和終壓速 度 宜 為２～４ｋｍ·ｍ－１。同 時，需配備一臺小型振動壓路機，以保證邊角處的壓實度。對于冷再生結構層養生條件，不同的現場條件（溫度、濕度、風速、降雨等）、冷再生瀝青混合料組分（ＲＡＰ 料 性 能、膠 結 料 以 及 活 性 填 料 類 型 和 含 量等）、結構層特性（冷再生結構層厚度、密度、初始含水率）都會對冷再生結構層的強度增長產生影響。

　　(4) The cold regeneration layer for health preservation should be carried out under closed traffic conditions, and the health preservation time should not be less than 7 days and not less than 48 hours. When the following two conditions are met, the health preservation can be ended in advance: the regeneration layer can use a core drilling machine with a diameter of 150mm drill bit to extract complete core samples; The moisture content of the regeneration layer is less than 2%. Compared with on-site cold recycling technology, factory mixed cold recycling technology transports the milled RAP material to the mixing station, mixes the cold recycled asphalt mixture according to the mix proportion, and then transports it to the construction site for paving and rolling. The number of vehicles should be coordinated with the discharge and paving speed of the unit, and the unit and construction site should not be too far apart. The exposed mixture on the roof should be covered to reduce water evaporation loss. The mixture is spread using a paver, and the ironing board does not require heating. The vibration frequency and amplitude should be high and low, with an initial density of over 85% and a speed controlled between 2-4m · min-1. The compaction speed should be uniform, with an initial compaction speed of 1.5-3.0km · m-1 and a secondary and final compaction speed of 2-4km · m-1. At the same time, a small vibratory roller is required to ensure compaction at the corners. For the curing conditions of cold recycled structural layers, different on-site conditions (temperature, humidity, wind speed, rainfall, etc.), cold recycled asphalt mixture components (RAP material performance, binder and active filler type and content, etc.), and structural layer characteristics (cold recycled structural layer thickness, density, initial moisture content) will all have an impact on the strength growth of cold recycled structural layers.

　　此外，研究表明當含水率趨于穩定后，冷再生結構層的強度性能仍會持續增長。目前，冷再生技術規范主要基于控制養護時間和含水率的施工經驗確定開放交通以及加鋪上層結構，未充分考慮與路面承載性能直接相關的剛度 和 強 度 的 要 求，將含水率作為養生條件具有一定的局限性，因此，建議將 ＦＷＤ／輕型落錘彎沉儀（ＬｉｇｈｔＷｅｉｇｈｔＤｅｆｌｅｃｔｏｍｅｔｅｒ，ＬＷＤ）作為評價冷再生結構層承載性能的評判方法，即以力學性能的變化來評估養生程度并確定養生時間，而不是依賴于含水率的測量。其次，應完善符合氣候條件的冷再生結構層施工環境條件規范。以美國各州規范為例［１２８］，科羅拉多州和堪薩斯州交通部門規定大氣溫度應高于１３℃，印第安納州規定路表溫度應高于１３ ℃且夜間溫度應高于２ ℃，紐約州規定當空氣或地表溫度低于７ ℃或作業開始后２４ｈ內低于４ ℃時不允許進行施工。5.2 冷再生技術施工設備

　　In addition, studies have shown that when the moisture content stabilizes, the strength performance of the cold regenerated structural layer will continue to increase. At present, the specifications for cold recycling technology are mainly based on the construction experience of controlling maintenance time and moisture content to determine open traffic and adding upper structures, without fully considering the requirements for stiffness and strength directly related to the pavement bearing performance. Using moisture content as a maintenance condition has certain limitations. Therefore, it is recommended to use FWD/Light Weight Deflectometer (LWD) as the evaluation method for evaluating the bearing performance of cold recycling structural layers, that is, to evaluate the degree of maintenance and determine the maintenance time based on changes in mechanical properties, rather than relying on the measurement of moisture content. Secondly, it is necessary to improve the environmental conditions for the construction of cold recycling structural layers that meet the climate conditions in China. Taking the regulations of various states in the United States as an example [128], the transportation departments of Colorado and Kansas stipulate that the atmospheric temperature should be higher than 13 ℃, Indiana stipulates that the road surface temperature should be higher than 13 ℃ and the nighttime temperature should be higher than 2 ℃, and New York state stipulates that construction is not allowed when the air or surface temperature is below 7 ℃ or below 4 ℃ within 24 hours after the start of the operation. 5.2 Cold Recycling Technology Construction Equipment

　　國外關于就地冷再生設備的生產公司主要有美國卡特皮勒公司、德國寶馬公司、法國奔能公司以及德國維特根公司，其中維特根公司是世界上、的再生設備廠家。近年來，國內工程機械廠家也逐漸重視冷再生機的研發和生產。山東公路機械廠研發出 具 有 國 際 先 進 水 平 的 ＬＺＳ２４００就 地冷再生機，西安筑路機械公司研發了就地冷再生拌合機 ＣＲ２５００，徐工研發了新款再生設備－ＸＬＺ２３０Ⅱ路面冷再生機。與國外再生機相比，國產冷再生機在品種類型和總體性能方面都存在一定的差距。通過多年的研發和改進，目前冷再生機能夠實現銑拌轉子在和小轉速之間無極調速，增大了冷再生銑刨深度。目前，市場上主要以維特根的 ＷＲ２５００Ｓ和ＷＲ２０００為主［４５］。維特根wr250再生機全深式冷再生技術是就地冷再生技術的一種，主要在再生層厚方面與常規的就地冷再生技術存在差 異，銑 刨 深 度 取 決 于 銑 刨 機 的 類 型 和 功 率。Ｐａｖｅｍｅｎｔ公司開發的銑刨機回收系統深度可達５４８．６４ｃｍ，維特根公司研發的 Ｗ３８０Ｃｒｉ再生機能夠修復３５０ｍｍ 深度的病害，都 能 夠 較 好 地 滿 足全深式冷再生的要求。關于就地冷再生設備研究方面，主要集中在轉子刀具的布置特點與土壤切削理論，開展冷再生機銑削轉子刀具在工作過程中動力學方面的研究。維特根w380cr再生機施工中的w380cr再生機組廠拌冷再生技術是將 ＲＡＰ料運輸拌合站進行拌和，可使用間歇式、滾筒式或連續式拌和設備。連續式拌和設備是應用廣的一種，以德國維特根公司生產的連續式拌和再生設備 ＫＭＡ２００為知名。國內具有代表性的設備有中交西筑的 ＣＲＳ３００廠拌冷再生攪拌設備，采用二次攪拌技術，實現了乳化瀝青混合料性能更加穩定；高遠圣工的 ＧＹＣＢＬ２００型 廠拌冷再生設備具有攪拌力度大、效率高、混合均勻等特點；鐵拓 ＴＣＭ２５０型廠拌冷再生設備解決了小摻量添加劑攪拌不均勻問題。目前，關于廠拌冷再生設備研究方面，主要集中在設備結構與拌和時間、拌和均勻性間關系的研究。維特根KMA廠拌設備中交西筑的 ＣＲＳ３００設備６冷再生技術未來發展展望

　　The main foreign companies producing on-site cold recycling equipment include Caterpillar from the United States, BMW from Germany, Benen from France, and Wittgen from Germany. Among them, Wittgen is the world's largest and most advanced manufacturer of recycling equipment. In recent years, domestic construction machinery manufacturers have gradually attached importance to the research and production of cold recycling machines. Shandong Highway Machinery Factory has developed the internationally advanced LZS2400 on-site cold recycling machine, Xi'an Road Construction Machinery Company has developed the on-site cold recycling mixing machine CR2500, and XCMG has developed a new recycling equipment - XLZ230II pavement cold recycling machine. Compared with foreign regeneration machines, there is a certain gap in the variety and overall performance of domestic cold regeneration machines. Through years of research and development and improvement, the current cold regeneration technology can achieve infinite speed regulation of milling and mixing rotors between maximum and minimum speeds, increasing the maximum milling depth of cold regeneration. At present, the market is mainly dominated by Wirtgen's WR2500S and WR2000 [45]. The full depth cold regeneration technology of the Wirtgen WR250 regeneration machine is a type of in-situ cold regeneration technology, which mainly differs from conventional in-situ cold regeneration technology in terms of regeneration layer thickness. The milling depth depends on the type and power of the milling machine. The maximum depth of the milling machine recycling system developed by Pavement can reach 548.64cm, and the W380Cri regeneration machine developed by Wittgen can repair defects at a depth of 350mm, both of which can meet the requirements of full depth cold regeneration. Regarding the research on on-site cold recycling equipment, the main focus is on the layout characteristics of rotor cutting tools and soil cutting theory, and the study of the dynamics of cold recycling machine milling rotor cutting tools during the working process. The w380cr regeneration unit cold mixing regeneration technology in the construction of the Wittgen w380cr regeneration machine is to transport RAP materials to the mixing station for mixing, which can use intermittent, drum or continuous mixing equipment. Continuous mixing equipment is the most widely used type, with the KMA200 continuous mixing and recycling equipment produced by the German company Wittgen being the most well-known. Representative equipment in China includes the CRS300 plant mixing cold recycling mixing equipment from CCCC West Construction, which uses secondary mixing technology to achieve more stable performance of emulsified asphalt mixture; The GYCB200 factory mixing cold recycling equipment from Gaoyuan Shenggong has the characteristics of high mixing force, high efficiency, and uniform mixing; The Tietuo TCM250 plant mixing cold recycling equipment solves the problem of uneven mixing of small dosage additives. At present, research on cold recycling equipment for factory mixing mainly focuses on the relationship between equipment structure, mixing time, and mixing uniformity. Future Development Prospects of CRS300 Equipment 6 Cold Recycling Technology in Jiaoxi Construction of Wirtgen KMA Plant Mixing Equipment

　　冷再生技術經過幾十年的技術研究和工程應用，在材料性能、設計方法和工程經驗方面均取得一系列重要進展，但仍有一些關鍵技術需繼續開展研究。

　　After decades of technical research and engineering application, cold recycling technology has made significant progress in material properties, design methods, and engineering experience. However, there are still some key technologies that need to be further studied.

　　（１）冷再生結構層施工完成后需要較長的養護周期，在后續研究中可考慮從材料和工藝兩方面提升冷再生瀝青混合料的早期性能。一方面可以添加減水劑、低聚物等外加劑，通過改進材料以提高冷再生瀝青混合料的早期強度和長期性能。其次，可以開展生產拌和順序和現場壓實工藝的優化研究，優化拌和工藝可以改善 混 合 料 內 部 砂 漿 形 態 及 砂 漿－集料的界面黏附強度，優化現場壓實工藝可以提高冷再生層密實度并降低內部空隙，以提高冷再生瀝青混合料的強度特性和長期性能。

　　(1) After the construction of the cold recycled structural layer is completed, a longer curing period is required. In subsequent research, it is possible to consider improving the early performance of the cold recycled asphalt mixture from both material and process aspects. On the one hand, additives such as water reducing agents and oligomers can be added to improve the early strength and long-term performance of cold recycled asphalt mixtures by improving the materials. Secondly, research can be conducted on optimizing the production mixing sequence and on-site compaction process. Optimizing the mixing process can improve the internal mortar morphology of the mixture and the interfacial adhesion strength between mortar and aggregate. Optimizing the on-site compaction process can improve the compactness of the cold recycled layer and reduce internal voids, thereby enhancing the strength characteristics and long-term performance of the cold recycled asphalt mixture.

　　（２）繼續開展冷再生瀝青路面結構設計方法的研究：開展冷再生結構層位的溫度分布、頻率響應以及力學分析方面的研究，獲取符合冷再生結構層位受力特性的力學響應，是開展冷再生瀝青路面結構力學分析的關鍵；開展冷再生瀝青路面疲勞壽命預估方程的研究，加強現場試驗路的數據檢測和收集工作，對疲勞方程進行現場標定，以指導冷再生路面結構設計。

　　(2) Continuing the research on the design method of cold recycled asphalt pavement structure: conducting research on the temperature distribution, frequency response, and mechanical analysis of cold recycled structure layers, obtaining mechanical responses that conform to the stress characteristics of cold recycled structure layers, is the key to conducting mechanical analysis of cold recycled asphalt pavement structure; Conduct research on the fatigue life prediction equation for cold recycled asphalt pavement, strengthen data detection and collection on on-site test roads, calibrate the fatigue equation on site to guide the structural design of cold recycled pavement.

　　7結語

　　7 Conclusion

　　（１）冷再生瀝青混合料材料組分相互作用機制復雜，ＲＡＰ料 來源、瀝 青 老 化 程 度、ＲＡＰ 摻 量會 影響瀝 青 含 量、ＲＡＰ 料－瀝 青界 面 強 度 以 及 混 合料整體力學性能，因此，在工程應用前應對 ＲＡＰ料進行的測試和表征。

　　(1) The interaction mechanism between the components of cold recycled asphalt mixture materials is complex. The source of RAP material, the degree of asphalt aging, and the RAP dosage will affect the optimal asphalt content, RAP asphalt interface strength, and overall mechanical properties of the mixture. Therefore, comprehensive testing and characterization of RAP material should be carried out before engineering application.

　　（２）乳化瀝青和泡沫瀝青作為膠結料在冷再生瀝青混合料強度形成機理方面存在差異，水泥、石灰外加劑種類及相對含量對混合料的性能提升效果也具有顯著差異。在工程應用中應根據性能需求對冷再生瀝青混合料進行合理設計和試驗驗證。

　　(2) Emulsified asphalt and foam asphalt, as binders, have differences in the strength formation mechanism of cold recycled asphalt mixture, and the types and relative contents of cement and lime admixtures also have significant differences in improving the performance of the mixture. Reasonable design and experimental verification of cold recycled asphalt mixture should be carried out according to performance requirements in engineering applications.

　　（３）目前尚未形成統一的冷再生瀝青混合料配合比設計方法和路面結構設計方法，國內外大多采用 Ｍａｒｓｈａｌｌ、Ｓｕｐｅｒｐａｖｅ和 Ｈｖｅｅｍ 配合比設計方法和 力 學－經 驗 法 路 面 結 構 設 計 方 法，中 國 采 用Ｍａｒｓｈａｌｌ配合比設 計 方 法 和 力 學－經 驗法 的 路 面 設計方法，在進行冷再生瀝青路面設計時應對其車轍變形和疲勞壽命進行驗算。

　　(3) At present, there is no unified method for designing the mix proportion and pavement structure of cold recycled asphalt mixture. Most domestic and foreign countries adopt Marshall, Superpave, and Hveem mix proportion design methods and mechanical empirical pavement structure design methods. China adopts Marshall mix proportion design method and mechanical empirical pavement design method. When designing cold recycled asphalt pavement, its rutting deformation and fatigue life should be verified.

　　（４）材料組分性能和相對含量的變化會對冷再生瀝青混合料的抗車轍、抗水損害、抗疲勞開裂及低溫性能產生影響，充分考慮冷再生材料所在的結構層位，分析其力學響應以及對應的力學失效模式，明確關鍵性能需求。當冷再生瀝青混合料應用于面層并作為主要承載層時，應充分考慮其抗車轍性能；當作為結構基層時，應嚴格控制水泥和石灰摻量，以防止服役期內過早出現疲勞裂縫。

　　(4) The changes in the properties and relative content of material components will have an impact on the anti rutting, anti water damage, anti fatigue cracking, and low-temperature performance of cold recycled asphalt mixtures. It is necessary to fully consider the structural layer where the cold recycled material is located, analyze its mechanical response and corresponding mechanical failure modes, and clarify the key performance requirements. When cold recycled asphalt mixture is applied to the surface layer and used as the main bearing layer, its anti rutting performance should be fully considered; When used as a structural base, the dosage of cement and lime should be strictly controlled to prevent premature fatigue cracks during service life.

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