“边运营，边养护”是公路路面与铁路轨道的显著特征。上期分享了路面养护组(PG)研究中联合处治(Combination Treatments)相关施工、性能和关键成果。本期将分享路面养护措施之冷再生(Cold Recycling)相关研究与发现。限于认知水平与理解能力，多有不妥之处，敬请各位道友批评指正！

　　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施工概况冷再生是沥青路面一系列修复方法，通过不加热和再利用现有或存储的材料（通常以再生沥青混合料RAP形式存在）。该工艺可在现场使用专门的设备列车进行（即现场冷再生，CIR），也可以在指定位置利用移动式设备完成（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）是另一项技术，在该技术中，沥青层的全部厚度以及部分预定的基层材料一同被再生。尽管全厚度再生不被认为是冷再生技术，但在本研究中将其纳入冷再生处理技术组。冷再生试验路段的位置见表1。试验路段的设计和施工均使用了沥青再生剂（泡沫沥青或乳化沥青）以形成ABR混合料，并遵循沥青再生与回收协会（ARRA）的指导原则。处治情况详情见表2表4。表1 不同位置的冷再生试验段NA：此地点不可用表2 LR-159冷再生处治

　　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冷再生处治

　　Table 3 US-280 Cold Recycling Treatment

　　70th街区道路冷再生处治

　　Cold regeneration treatment of 70th block road

　　各路段的路面结构有所不同，如图1和图2所示。对于LR-159路段，所有沥青材料被移除，替换为4英寸（约10cm）厚的泡沫冷再生混合料，并铺设了3/4英寸（约1.9cm）的新罩面。在US-280路段，现有结构各异，如图3所示。在所有情况下，冷再生层的厚度均为4英寸，而保留的沥青混凝土层的厚度则在3.412.5英寸（约8.631.7cm）之间。此外，需要注意的是，CIR路段没有基层。鉴于US-280的交通量增加，作为表面层的罩面厚度增1英寸（约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.

　　温区的路面横断面在70th街区路段，原有路面结构为4英寸（约10cm）厚的沥青混凝土层，铺设在6英寸（约15.2cm）厚的粒料基层之上，而基层下方为黏土路基。CIR和CCPR层的厚度为3英寸（约7.6cm），保留了原有路面1英寸（约2.5cm）。FDR路段的施工厚度为7英寸（约17.8cm），替换掉了所有原有的沥青材料，同时保留了3英寸的粒料基层。此外，还在两个路段采用了更传统的处理方式即铣刨和填补修复方法；其中一段深度为2英寸（约5cm），另一段为3英寸。所有路段的表面均铺设了1英寸厚的ABR罩面，其中7个路段的薄层直接铺设在现有的、严重破损的路面上，这些路段被指定为“控制段”，代表了各机构为了保持路面短期内可使用而常采取的应急措施。图2展示了70街路段的测试段布局示意图。由于时间和后勤限制，本项目主要集中在东行车道上，但也在西行车道上铺设了一些修复方案。

　　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.

　　图2 70th街道路面横断面图3 70th街道试验段布局(磨耗层为1寸ABR罩面)在施工过程中，使用了维特根KM220移动拌和设备在附近场地（温区的NCAT环道和寒区的MnROAD）生产CCPR混合料。混合料随后被运送施工现场，并使用常规摊铺设备进行铺设。CIR路段的再生施工则采用了维特根3800CR再生机，该设备可以一次性完成整车道的再生，并使用沥青剂进行稳定处理（见图4）。对于FDR路段，维特根WR 250i再生设备被调配70街区路段，但由于机械故障和时间限制，该设备未能使用。因此，现有路面通过CIR设备进行铣刨和加工。材料在摊铺前被置于料堆中，再用平地机摊铺，并采用羊足碾和钢轮振动压路机进行压实。NCAT移动实验室也在现场通过对不同再生混合料进行取样测试进行质量控制，测试内容包括总含水率、添加的沥青含量和集料级配。压实样品经过养护后，根据所用再生剂的不同，进行劈裂抗拉强度或稳定性测试。

　　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.

　　图4 70th街区道路CIR设备列车

　　Figure 4 CIR equipment train on the 70th block road

　　图5 FDR部分回收材料3性能和主要发现

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

　　冷再生路段提供了一种耐久的修复替代方案。即使采用较薄的沥青面层，这些测试路段依然能够承受大交通量，并保持“良好”到“一般”的性能。总体而言，再生混合料相比于对照路段表现出更明显的车辙和平整度变化，但在第二阶段结束时仍处于“良好”到“一般”状态。裂缝状况也维持在“良好”到“一般”范围内，温区路段的裂缝主要集中在轨迹内，而寒区路段则主要表现为横向裂缝。图6显示了US-280测试路段的总体状况。泡沫CCPR路段的裂缝为显著，由于细料的抽吸作用，这些裂缝更加明显。此外，该路段在施工前的沥青层薄，因此部分被CCPR混合料替换，导致冷再生层与沥青混凝土层接近1:1的比例。相较于其他测试路段，这一结构导致了较低的复合模量。

　　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年后的整体状况? ?

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

　　在这种情况下，FDR路段的裂缝比例。从2020年开始，各城市将封缝作为常规维护的一部分来进行。在70街区段观察到的一种现象是主横向裂缝周围出现次生裂缝（图8）。这可能与冻胀作用及主裂缝两侧路面的竖向移动有关。这种类型的劣化在FDR路段和控制路段中更加严重。

　　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街区冷再生路段服役4年的整体状况图8?70th街区试验段的横向裂缝尽管现有路面的状况较差，不适合用于罩面铺装处治，但控制路段仍从该处治应用中获益，使路面服务水平得到了提升。特别是国际平整度指数（IRI）值，从处理前的274到429英寸每英里（in/mi）（约4.3到6.8m/km）范围显著降低90 in/mi（约1.4m.km）以下，并且在研究期间未进入“差”状况。然而，裂缝性能预期较差，到第二阶段末，所有路段的裂缝比例均超过20%。图9展示了控制路段状况的一个示例。这些结果表明了项目选择关重要。罩面对状况较好的路面具有良好效果；尽管它可以暂时改善状况较差的道路，其使用寿命和预期效益会大打折扣。传统的铣刨和填补处治表现，但现场结果表明，冷再生技术也可以成为可持续的沥青路面修复替代方案。其附加的环境效益和潜在的生命周期成本优势可能会成为推广该方案的重要因素。

　　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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