“邊運營，邊養護”是公路路面與鐵路軌道的顯著特征。上期分享了路面養護組(PG)研究中聯合處治(Combination Treatments)相關施工、性能和關鍵成果。本期將分享路面養護措施之冷再生(Cold Recycling)相關研究與發現。限于認知水平與理解能力，多有不妥之處，敬請各位道友批評指正！

　　The prominent feature of highway pavement and railway track is "simultaneous operation and maintenance". The previous issue shared the construction, performance, and key achievements related to Combination Treatment in the research of the Pavement Maintenance Group (PG). This issue will share research and findings related to cold recycling in road maintenance measures. Due to limited cognitive level and comprehension ability, there are many inappropriate aspects. We kindly ask for criticism and correction from fellow practitioners!

　　2施工概況冷再生是瀝青路面一系列修復方法，通過不加熱和再利用現有或存儲的材料（通常以再生瀝青混合料RAP形式存在）。該工藝可在現場使用專門的設備列車進行（即現場冷再生，CIR），也可以在指定位置利用移動式設備完成（即集中冷再生，CCPR）。

　　Cold recycling is a series of repair methods for asphalt pavement, which involves not heating and reusing existing or stored materials (usually in the form of recycled asphalt mixture RAP). This process can be carried out on-site using specialized equipment trains (i.e. on-site cold regeneration, CIR), or at designated locations using mobile equipment (i.e. centralized cold regeneration, CCPR).

　　全厚式再生（FDR）是另一項技術，在該技術中，瀝青層的全部厚度以及部分預定的基層材料一同被再生。盡管全厚度再生不被認為是冷再生技術，但在本研究中將其納入冷再生處理技術組。冷再生試驗路段的位置見表1。試驗路段的設計和施工均使用了瀝青再生劑（泡沫瀝青或乳化瀝青）以形成ABR混合料，并遵循瀝青再生與回收協會（ARRA）的指導原則。處治情況詳情見表2表4。表1 不同位置的冷再生試驗段NA：此地點不可用表2 LR-159冷再生處治

　　Full thickness regeneration (FDR) is another technology in which the entire thickness of the asphalt layer and a portion of the predetermined base material are regenerated together. Although full thickness regeneration is not considered a cold regeneration technology, it is included in the cold regeneration treatment group in this study. The location of the cold regeneration test section is shown in Table 1. Asphalt recycling agent (foam asphalt or emulsified asphalt) is used in the design and construction of the test section to form ABR mixture, and the guidelines of the Asphalt Recycling and Recovery Association (ARRA) are followed. The details of the treatment are shown in Tables 2 to 4. Table 1 Cold regeneration test sections NA at different locations: This location is not applicable Table 2 LR-159 Cold regeneration treatment

　　表3 US-280冷再生處治

　　Table 3 US-280 Cold Recycling Treatment

　　70th街區道路冷再生處治

　　Cold regeneration treatment of 70th block road

　　各路段的路面結構有所不同，如圖1和圖2所示。對于LR-159路段，所有瀝青材料被移除，替換為4英寸（約10cm）厚的泡沫冷再生混合料，并鋪設了3/4英寸（約1.9cm）的新罩面。在US-280路段，現有結構各異，如圖3所示。在所有情況下，冷再生層的厚度均為4英寸，而保留的瀝青混凝土層的厚度則在3.412.5英寸（約8.631.7cm）之間。此外，需要注意的是，CIR路段沒有基層。鑒于US-280的交通量增加，作為表面層的罩面厚度增1英寸（約2.5cm），并采用了ABR混合料。

　　The pavement structure of each road section is different, as shown in Figure 1 and Figure 2. For LR-159 section, all asphalt materials were removed and replaced with 4-inch (about 10cm) thick foam cold recycled mixture, and a new overlay of 3/4-inch (about 1.9cm) was laid. On the US-280 road section, the existing structures vary, as shown in Figure 3. In all cases, the thickness of the cold recycled layer is 4 inches, while the thickness of the retained asphalt concrete layer ranges from 3.4 to 12.5 inches (approximately 8.6 to 31.7 cm). Additionally, it should be noted that the CIR section does not have a base layer. Due to the increased traffic volume of US-280, the thickness of the cover as a surface layer has been increased to 1 inch (approximately 2.5cm), and ABR mixture has been used.

　　溫區的路面橫斷面在70th街區路段，原有路面結構為4英寸（約10cm）厚的瀝青混凝土層，鋪設在6英寸（約15.2cm）厚的粒料基層之上，而基層下方為黏土路基。CIR和CCPR層的厚度為3英寸（約7.6cm），保留了原有路面1英寸（約2.5cm）。FDR路段的施工厚度為7英寸（約17.8cm），替換掉了所有原有的瀝青材料，同時保留了3英寸的粒料基層。此外，還在兩個路段采用了更傳統的處理方式即銑刨和填補修復方法；其中一段深度為2英寸（約5cm），另一段為3英寸。所有路段的表面均鋪設了1英寸厚的ABR罩面，其中7個路段的薄層直接鋪設在現有的、嚴重破損的路面上，這些路段被指定為“控制段”，代表了各機構為了保持路面短期內可使用而常采取的應急措施。圖2展示了70街路段的測試段布局示意圖。由于時間和后勤限制，本項目主要集中在東行車道上，但也在西行車道上鋪設了一些修復方案。

　　The cross-section of the road surface in the temperate zone is located on the 70th block section, with the original road structure consisting of a 4-inch (about 10cm) thick asphalt concrete layer laid on top of a 6-inch (about 15.2cm) thick granular base layer, and a clay subgrade below the base layer. The thickness of the CIR and CCPR layers is 3 inches (approximately 7.6cm), retaining the original road surface by 1 inch (approximately 2.5cm). The construction thickness of the FDR section is 7 inches (approximately 17.8cm), replacing all existing asphalt materials while retaining a 3-inch granular base layer. In addition, more traditional processing methods such as milling and filling repair were adopted in two road sections; One section has a depth of 2 inches (about 5cm), and the other section is 3 inches. All road sections are covered with a 1-inch thick ABR overlay, with 7 sections having thin layers directly laid on existing, severely damaged road surfaces. These sections are designated as "control sections", representing emergency measures often taken by various agencies to maintain the road surface usable in the short term. Figure 2 shows a schematic diagram of the layout of the test section on the 70th Street section. Due to time and logistical constraints, this project mainly focuses on the eastbound lane, but some repair plans have also been laid on the westbound lane.

　　圖2 70th街道路面橫斷面圖3 70th街道試驗段布局(磨耗層為1寸ABR罩面)在施工過程中，使用了維特根KM220移動拌和設備在附近場地（溫區的NCAT環道和寒區的MnROAD）生產CCPR混合料?；旌狭想S后被運送施工現場，并使用常規攤鋪設備進行鋪設。CIR路段的再生施工則采用了維特根3800CR再生機，該設備可以一次性完成整車道的再生，并使用瀝青劑進行穩定處理（見圖4）。對于FDR路段，維特根WR 250i再生設備被調配70街區路段，但由于機械故障和時間限制，該設備未能使用。因此，現有路面通過CIR設備進行銑刨和加工。材料在攤鋪前被置于料堆中，再用平地機攤鋪，并采用羊足碾和鋼輪振動壓路機進行壓實。NCAT移動實驗室也在現場通過對不同再生混合料進行取樣測試進行質量控制，測試內容包括總含水率、添加的瀝青含量和集料級配。壓實樣品經過養護后，根據所用再生劑的不同，進行劈裂抗拉強度或穩定性測試。

　　Figure 2 Cross section of the 70th Street Pavement Figure 3 Layout of the 70th Street Test Section (with a 1-inch ABR overlay for the wearing layer) During the construction process, the Wittgen KM220 mobile mixing equipment was used to produce CCPR mixture at nearby sites (NCAT ring road in warm regions and MnROAD in cold regions). The mixture is then transported to the construction site and laid using conventional paving equipment. The regeneration construction of the CIR section adopts the Wittgen 3800CR regeneration machine, which can complete the regeneration of the entire lane at once and use asphalt agent for stabilization treatment (see Figure 4). For the FDR section, the Wirtgen WR 250i regeneration equipment was deployed to the 70 block section, but due to mechanical failure and time constraints, the equipment was not used. Therefore, the existing road surface is milled and processed through CIR equipment. The material is placed in a pile before paving, then spread with a grader and compacted with a sheep foot roller and a steel wheel vibratory roller. NCAT Mobile Laboratory also conducts quality control on site by sampling and testing different recycled mixtures, including total moisture content, added asphalt content, and aggregate gradation. After curing, the compacted sample is subjected to splitting tensile strength or stability testing according to the different rejuvenators used.

　　圖4 70th街區道路CIR設備列車

　　Figure 4 CIR equipment train on the 70th block road

　　圖5 FDR部分回收材料3性能和主要發現

　　Figure 5 Performance and main findings of FDR partially recycled material 3

　　冷再生路段提供了一種耐久的修復替代方案。即使采用較薄的瀝青面層，這些測試路段依然能夠承受大交通量，并保持“良好”到“一般”的性能?？傮w而言，再生混合料相比于對照路段表現出更明顯的車轍和平整度變化，但在第二階段結束時仍處于“良好”到“一般”狀態。裂縫狀況也維持在“良好”到“一般”范圍內，溫區路段的裂縫主要集中在軌跡內，而寒區路段則主要表現為橫向裂縫。圖6顯示了US-280測試路段的總體狀況。泡沫CCPR路段的裂縫為顯著，由于細料的抽吸作用，這些裂縫更加明顯。此外，該路段在施工前的瀝青層薄，因此部分被CCPR混合料替換，導致冷再生層與瀝青混凝土層接近1:1的比例。相較于其他測試路段，這一結構導致了較低的復合模量。

　　The cold recycling section provides a durable alternative repair solution. Even with a thinner asphalt surface layer, these test sections can still withstand high traffic volumes and maintain "good" to "average" performance. Overall, the recycled mixture showed more significant changes in rutting and flatness compared to the control section, but remained in a "good" to "average" state at the end of the second stage. The crack condition is also maintained within the range of "good" to "average", with cracks mainly concentrated within the trajectory in warm regions and transverse cracks in cold regions. Figure 6 shows the overall condition of the US-280 test section. The cracks in the foam CCPR section are the most obvious, and these cracks are more obvious due to the suction of fine materials. In addition, the asphalt layer on this section was the thinnest before construction, so some parts were replaced with CCPR mixture, resulting in a ratio of nearly 1:1 between the cold recycled layer and the asphalt concrete layer. Compared to other test sections, this structure resulted in a lower composite modulus.

　　US-280冷再生段7年后的整體狀況? ?

　　What is the overall condition of the US-280 cold regeneration section after 7 years?  ?

　　在這種情況下，FDR路段的裂縫比例。從2020年開始，各城市將封縫作為常規維護的一部分來進行。在70街區段觀察到的一種現象是主橫向裂縫周圍出現次生裂縫（圖8）。這可能與凍脹作用及主裂縫兩側路面的豎向移動有關。這種類型的劣化在FDR路段和控制路段中更加嚴重。

　　In this case, the FDR section has the highest proportion of cracks. Starting from 2020, cities will include sealing seams as part of routine maintenance. One phenomenon observed in the 70 block section is the appearance of secondary cracks around the main transverse crack (Figure 8). This may be related to frost heave and vertical movement of the road surface on both sides of the main crack. This type of degradation is more severe in FDR and control sections.

　　70th街區冷再生路段服役4年的整體狀況圖8?70th街區試驗段的橫向裂縫盡管現有路面的狀況較差，不適合用于罩面鋪裝處治，但控制路段仍從該處治應用中獲益，使路面服務水平得到了提升。特別是國際平整度指數（IRI）值，從處理前的274到429英寸每英里（in/mi）（約4.3到6.8m/km）范圍顯著降低90 in/mi（約1.4m.km）以下，并且在研究期間未進入“差”狀況。然而，裂縫性能預期較差，到第二階段末，所有路段的裂縫比例均超過20%。圖9展示了控制路段狀況的一個示例。這些結果表明了項目選擇關重要。罩面對狀況較好的路面具有良好效果；盡管它可以暫時改善狀況較差的道路，其使用壽命和預期效益會大打折扣。傳統的銑刨和填補處治表現，但現場結果表明，冷再生技術也可以成為可持續的瀝青路面修復替代方案。其附加的環境效益和潛在的生命周期成本優勢可能會成為推廣該方案的重要因素。

　　The overall condition of the cold recycling section of the 70th block after 4 years of service is shown in Figure 8? Although the transverse cracks in the 70th block test section are in poor condition and not suitable for overlay pavement treatment, the control section still benefits from the application of this treatment, which has improved the service level of the road surface. In particular, the International Roughness Index (IRI) values significantly decreased from the pre-treatment range of 274 to 429 inches per mile (in/mi) (approximately 4.3 to 6.8 m/km) to below 90 in/mi (approximately 1.4 m/km), and did not enter a "poor" state during the study period. However, the expected crack performance was poor, and by the end of the second phase, the crack proportion in all road sections exceeded 20%. Figure 9 shows an example of controlling road conditions. These results indicate that project selection is crucial. Covering roads with good conditions has a good effect; Although it can temporarily improve poor condition roads, its service life and expected benefits will be greatly reduced. Traditional milling and filling treatments perform the best, but on-site results indicate that cold recycling technology can also be a sustainable alternative to asphalt pavement repair. The additional environmental benefits and potential lifecycle cost advantages may become important factors in promoting this solution.

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