裂缝是沥青路面的顽症，以开裂为主的路面损伤具有显著的多因素耦合和多尺度特征。在道路材料类型丰富、路面结构组合多样，以及多变的交通荷载和复杂的环境影响下，沥青路面的开裂损伤机制难以掌握，病因的不确定性造成了裂缝处治存在“头痛医头，脚痛医脚”的现象，裂缝防治成为道路工程界的国际性难题，建立高质量、高效率、强保障的路面开裂病害防治技术体系迫在眉睫。

从“亡羊补牢”到“未雨绸缪”的理念转变

长期以来，沥青路面损伤演化机理不明晰，病害处治技术普遍存在施工效率低、材料耐久性差等问题，沥青路面病害防治亟需理论突破和技术发展。在解决沥青路面裂缝防治的重大技术难题上，还存在着裂缝防控难和裂缝处治难的挑战，几乎所有的沥青路面均发生不同程度的裂缝病害，大多数公路通车一年后即出现裂缝，并且处治材料失效率高、次生病害多、施工效率低等问题时有发生。

针对这些国际性技术难题，同济大学、北京航空航天大学、交通运输部公路科学研究院、中交第一公路勘察设计研究院有限公司、北京中天路业科技有限公司、北京路新沥青混凝土有限公司、太原理工大学、上海浦东路桥（集团）有限公司和上海浦东建筑设计研究院共同组成的研究团队依托20多项国家自然科学基金、国家重点研发计划、交通运输部科技项目等课题资助，历经10余年的系统研究，沿着“精确解析-主动防控-高效处治”的技术路线，突破了路面损伤起裂演化机理、路面裂缝主动愈合方法、路面病害高效处治技术等系列瓶颈 问题，创建了具有自主知识产权、经大规模工程应用验证的路面开裂病害防治技术体系。 

该项目的研发思路是从“亡羊补牢”的被动式养护到“未雨绸缪”的主动式防控与高效处治，解决“沥青材料损伤演化机理精确解析”这一科学问题，面向裂缝防治这一道路工程界的国际性难题，研发裂缝主动防控和高效处治技术。 

项目组以理论为指引，应用为导向，就多因素耦合作用下沥青混合料界面断裂失效机理、界面弱化影响下的沥青混合料性能劣化演变规律、沥青混合料裂纹萌生到扩展的多尺度联动机制、沥青材料裂纹自愈合行为理论与评价、沥青路面微胶囊自愈技术、铁氧体微波自愈技术、裂缝处治材料性能表征及技术应用、冷补料和地聚合物灌浆材料研发与应用、高弹抗裂超薄罩面材料研发与应用等方面开展了深入的研究，解决了面向裂缝防治“高效耐久”的工程需求和技术难题。

创新全生命周期路面损伤诊治技术

项目组利用跨学科交叉互补研究的方式，结合中医学理论中“审证求因，审因论治”的核心思想，形成了包括“明病理—沥青路面界面开裂的多尺度演化机理”“治未病—沥青路面损伤主动愈合方法”“治已病—沥青路面裂缝高效处治技术的系列创新成果”，对道路工程界裂缝防治这一国际性难题的破解起到了巨大的推动作用，项目创新成果总体达到国际领先水平。 

明病理 沥青路面界面开裂的多尺度演化机理 

沥青胶浆和集料之间的界面是沥青混合料中的薄弱环节，界面抵抗开裂的能力直接影响沥青混合料的强度及耐久性。在微观尺度，项目采用分子动力学，从能量角度和分子运动角度明确了多因素影响下的沥青分子在集料表面的吸附和扩散机制；揭示了沥青膜厚度、集料表面粗糙度、水、老化等对界面断裂模式(黏附性破坏/黏聚性破坏)的耦合作用机理。从细观尺度上，项目提出了沥青混合料界面微区性能采集的标准实验方法，构建了考虑界面的等效集料模型，克服了界面区尺寸过小而难以进行数值模拟的瓶颈，阐释了界面对性能劣化（蠕变性 能、弹性模量、裂纹扩展）的影响。在宏观尺度，项目提出了考虑自愈效应的开裂区黏弹塑本构模型，采用数字图像相关技术和单轴蠕变等试验，获取了不同温度、加载频率下开裂区本构参数，通过两阶段耦合模型，建立材料性能与路面结构性能之间的定量关系。 

治未病 沥青路面损伤主动愈合方法 

沥青具有一定损伤自愈合能力，但自愈效率较低，如能通过技术措施强化沥青混合料的自愈合行为，将显著延长沥青路面的服役寿命。项目构建了考虑裂面处沥青分子浸润及沥青分子扩散的两阶段裂纹自愈合模型，提出活化能指数评价沥青材料自愈合能力，为自愈合沥青混合料组成设计确立理论基础；开发了适用于沥青路面的微胶囊自愈合材料，使沥青路面萌生微裂纹初期即可自动响应并主动修复，添加微胶囊后的沥青混合料疲劳寿命提升2.2倍。项目研发了铁氧体微波自愈技术，自主研发了微波辅助设备，通过微波加热的方法实现多次、全域裂纹愈合，疲劳寿命提升2.3倍；提出“断裂过程区裂纹发育程度”的评价指标，以制定微波自愈养护优化方案。 

治已病 沥青路面裂缝高效处治技术 

面向路面病害高效耐久处治的工程需求，聚焦路面裂缝及其衍生病害，从技术标准、材料研 发和施工工艺三方面克服了传统技术普遍存在的技术瓶颈。项目研究建立了沥青路面裂缝坑槽材料标准体系，广泛调研了裂缝处治失效破坏模式，提出了材料性能表征方法，开发了相关试验仪器；研发了沥青路面裂缝及其衍生病害的高效处治材料，实现了裂缝、网裂、唧浆等路面裂缝类病害发展各阶段的全覆盖；提出了沥青路面病害高效处治成套技术，攻克了传统沥青路面裂缝处治存在的技术难题。

应用前景广阔 社会经济效益兼顾

推广应用

项目技术成果在北京市延庆冬奥会馆项目等全国近30个省份沥青路面中得到推广，累计应用超过1500万延米，并在北美洲和大洋洲等国开展了试验路修补，在“一带一路”沿线国家进行试验性推广与应用。项目各应用材料的性能优异，施工工艺成熟，对沥青路面开裂的防控具有绝对优势，具有广阔的推广应用前景。

项目形成了产学研用一体化协同攻关、创新驱动的格局，有效提升了研发效率，极大地推动了技术转化并提高了现实生产力，通过交通运输部典型示范工程应用及标准图编制，为项目研究成功以后的推广应用提供了充分的理论基础、技术支撑和实践经验。

项目主要完成人在《国际工程科学（International Journal o f Engineering Science）》（期刊的影响因子IF：9.219）、《水泥与混凝土研究（Cement and Concrete Research）》（期刊的影响因子IF：8.328）、《 清 洁 生 产 杂 志 （Journal of CleanerProduction）》（期刊的影响因子IF：7.246）、《工程(Engineering)》（期刊的影响因子IF：8.328）、《胶体和界面科学杂志（Advances in Colloid and Interface Science）》（期刊的影响因子IF:9.922）、《中国公路学报》《科学通报》等国际权威学术期刊、中文卓越期刊发表相关论文75余篇，3次获“科学指南（ScienceDirect）”颁发的最热门文章奖，4篇论文连续多次入选ESI高被引论文（前1%），1篇ESI热点论文（前1‰），通过介绍项目研究成果，提升了研究成果的国际影响力。同时，项目通过出版沥青混合料自愈领域的专著、发明专利等途径，进一步推广项目研究成果。

社会效益

项目研发的主动防控和高效处治材料与技术，有利于降低道路的维修养护频次，减少由于养护维修造成的拥堵和滞留，保障高速公路、城市道路的安全、高效运营。项目部分成果纳入6部交通行业标准和两部地方标准，被广泛用于道路工程的建设、维修与养护。

此外，裂缝处治材料在美国加州、加拿大多伦多等地，以及泰国、越南、埃及等“一带一路”沿线7个国家进行了试验性推广应用，高性能冷补料出口巴布新几内亚和关岛等国家和地区，推动了我国裂缝处治材料的技术进步和高端产品的国产化，强力支撑了我国“一带一路”等国家战略的推进，实现了科研成果走出国门，为实现交通强国提供了强有力的理论基础和技术支撑。 

经济效益 

研发的微胶囊自修复技术可使沥青混合料疲劳寿命提升两倍，铁氧体微波自愈技术使沥青路面疲劳寿命延长至233%。研发的裂缝处治材料累计应用超过1500万延米，施工效率提高两倍至4倍，冷补料和灌浆料年应用量超过2000吨。高弹抗裂超薄罩 面在青海、贵州、河北等地成功应用。成果在包括北京市延庆冬奥会馆、上海市沪南公路等我国近30个省区市得到成功应用，并在海外各个国家和地区进行了试验性推广应用，直接经济效益达到2.1亿 元，间接经济效益15.2亿元。经济社会效益显著，推广应用前景广阔。

Preventive Diagnosis and Treatment of Cracks in Asphalt Pavement

Text by Pang Yafeng of Tongji University

Asphalt pavement has always been plagued by cracks. Damage to pavement, mainly cracking, shows significant multi-factor coupling and multi-scale characteristics. As a result of the rich types of road materials, diverse pavement structures, and variable traffic loads and complex environment, it is difficult to pin down the cracking damage mechanism of asphalt pavement. As root causes remain elusive, cracks are eliminated using stopgap measures. Crack prevention and control has become a headache for the global road engineering community. It is imperative to establish a high-quality, efficient and guaranteed technical system for pavement crack prevention and control.

Shift from passive treatment to preventive treatment 

For a long time, the mechanism of evolution of damage to asphalt pavement has remained unclear, and the disease disposal technology has generally had defects such as construction inefficiency and poor material durability. Theoretical breakthroughs and technological development are badly needed for the prevention and control of asphalt pavement diseases. There remain challenges to preventing and controlling asphalt pavement cracks. Almost all asphalt pavement suffer crack diseases to varying degrees, and most of highways develop cracks one year after being opened to traffic. Moreover, problems such as high failure rate of treatment materials, secondary damage, and construction inefficiency occur from time to time. 

In response to these global technical challenges, the research team composed of members from Tongji University, Beihang University, Research Institute of Highway of the Ministry of Transport, CCCC First Highway Consultants Co., Ltd., Beijing Zhongtian Luye Technology Co., Ltd., Beijing Luxin Asphalt Concrete Co., Ltd., Taiyuan University of Technology, Shanghai Pudong Road and Bridge (Group) Co., Ltd. and Shanghai Pudong Architectural Design & Research Institute conducted over 10 years of systematic research according to the technical route of “accurate analysis-active prevention and control-efficient treatment” under over 20 projects funded by the National Natural Science Foundation of China, the National Key R&D Program, Science and Technology Projects of the Ministry of Transport, etc., and has made breakthroughs in the mechanism of evolution of pavement damage cracking, active healing of pavement cracks, the efficient treatment of pavement diseases and other areas, and established a pavement cracking prevention and control technology system with independent intellectual property rights that has been verified by large-scale engineering application. 

This project adopts the R&D idea of shifting from passive maintenance to active prevention and control as well as efficient treatment. Active crack prevention and control as well as efficient treatment technology has been developed to solve the problem of “accurate analysis of the mechanism of evolution of damage to asphalt materials” and the global challenge of cracking prevention and treatment in the road engineering field. 

Guided by theory and geared to application, the project team conducted in-depth research on the interfacial fracture failure mechanism of asphalt mixture under multi-factor coupling, evolution law of performance deterioration of asphalt mixture under the influence of interfacial weakening, the multi-scale linkage mechanism of asphalt mixture crack emergence to propagation, the theory and evaluation of self-healing behavior of asphalt material crack, microcapsule self-healing technology for asphalt pavements, ferrite microwave self-healing technology, characterization of crack treatment material performance and technical application, R&D and application of cold paving materials and geopolymer grouting material, R&D of high-elastic and crack-resistant ultra-thin overlay, etc., and met the engineering needs for “efficient and durable” prevention and control of cracks.

Innovative diagnosis and treatment technology for pavement damage throughout life cycle

The project team made innovative achievements using interdisciplinary complementary research, in conjunction with the traditional Chinese medicine theory’s core idea of “determining etiologic factors based on differentiation and giving treatment according to cause”, including “multi-scale evolution mechanism of interfacial cracking of asphalt pavement”, “method of active healing of asphalt pavement damage” and “efficient treatment of asphalt pavement cracks”, which contribute significantly to solving the global problem of crack prevention and control in the road engineering industry. The innovative results of the project are world-leading. 

Multi-scale evolution mechanism of interfacial cracking of asphalt pavement

The interface between asphalt mortar and aggregate is a weak link in asphalt mixture, and its capacity to resist cracking directly affects the robustness and durability of asphalt mixtures. At the microcosmic level, it used molecular dynamics to ascertain the adsorption and diffusion mechanism of asphalt molecules on the surface of aggregates under the influence of multiple factors from the perspective of energy and molecular motion, and revealed the coupling mechanism of asphalt membrane thickness, roughness of aggregate surface, water, aging, etc. for the interfacial fracture mode (adhesive failure /cohesive failure). At the meso-scale, the project team developed a standard experimental method for studying micro-domain performance of asphalt mixture interface, and created an equivalent aggregate model with consideration to the interface, which remove the problem that the interface size is too small to be numerically simulated, and explain the impact of the interface on performance deterioration (creep property, elasticity modulus, and crack propagation). At the macro scale, the project created a viscoelastic-plastic constitutive model for the cracking zone with consideration of the self-healing effect, and obtained the constitutive parameters of the cracking zone at different temperatures and loading frequencies using digital image correlation (DIC) technology and experiments on uniaxial creep, etc. The quantitative relationship between material properties and pavement structural properties was established through the two-stage coupling model. 

Method of active healing of damaged asphalt pavement 

Asphalt has self-healing ability, but its self-healing is inefficient. If the self-healing property of asphalt mixture can be reinforced using technical means, the service life of asphalt pavement will be significantly prolonged. In this project, the project team constructed a two-stage crack self-healing model considering asphalt molecular infiltration and diffusion at the crack surface, and used the activation energy index to evaluate the self-healing capacity of asphalt materials, which provided a theoretical basis for the composition design of self-healing asphalt mixtures. It developed a microcapsule self-healing material suitable for asphalt pavements, which can automatically respond and repair emerging microcracks in asphalt pavements. The fatigue life of asphalt mixture added with microcapsules is increased by 2.2 times. The project team developed ferrite microwave self-healing technology and microwave auxiliary equipment, which realize multiple global crack healing through microwave heating, thus extending fatigue life by 2.3 times. It adopted the evaluation index for “crack development degree in fracture process zone” in order to draw up an optimal plan for microwave self-healing. 

Efficient treatment of asphalt pavement cracks

In view of the engineering needs for efficient and durable treatment of pavement diseases, the project team focused on pavement cracks and their derivative diseases, and removed technical bottlenecks common in traditional technologies in terms of technical standards, material R&D and construction technology. The project team studied and established a standard system of materials for asphalt pavement cracks and pits, extensively investigated the failure and destruction mode of crack treatment, adopted material performance characterization methods, and developed relevant test apparatus; developed materials for efficient treatment of asphalt pavement cracks and their derivative diseases, covering all stages of the development of pavement crack diseases such as cracks, net-shaped cracks and seepage of surface water into the base layer; developed a suite of technologies for efficient treatment of asphalt pavement diseases, and resolved the technical problems existing in the traditional treatment of asphalt pavement cracks. 

Broad application prospects, with consideration of social and economic benefits  Application

The technical achievements of this project have been applied to asphalt pavements in projects in nearly 30 provinces across the country, including the project of Yanqing Winter Olympic stadium in Beijing, with a length of over 15 million linear meters. These were also used for experimental road repair in North America and Oceania, and promoted in countries relevant to the Belt and Road Initiative. Thanks to application materials with excellent performance and mature construction technology, the project has absolute advantages in the prevention and control of asphalt pavement cracking, and has broad prospects for promotion. 

In this project, enterprises, universities, research institutes and users worked together to make technical breakthroughs and innovations. It has improved R&D efficiency, promoted technology commercialization and boosted productivity. It provides sufficient theoretical basis, technical support and practical experience for subsequent promotion and application of project results through typical demonstration projects under the Ministry of Transport and the compilation of standard drawings.

The main person involved in the project published more than 75 relevant papers in international authoritative academic journals and Chinese excellent journals such as International Journal of Engineering Science (IF: 9.219), Cement and Concrete Research (IF: 8.328), Journal of Cleaner Production (IF: 7.246), Engineering (IF: 8.328), Advances in Colloid and Interface Science (IF: 9.922), China Journal of Highway and Transport and Chinese Science Bulletin. He won the Most Popular Article Award issued by ScienceDirect three times. Four papers were selected as ESI Highly Cited Papers (top 1%) for many consecutive times, and one was rated as ESI Hot Paper (top 1‰). The international influence of research results has been enhanced through the introduction to the research results. At the same time, the research results of the project have been further promoted through the publication of monographs on self-healing asphalt mixture, invention patents, etc. 

Social benefits

The active prevention and control as well as efficient treatment materials and technologies developed under this project help reduce the frequency of road maintenance, ease congestion and retention caused by road repair, and ensure the safe and efficient operation of expressways and urban roads. The project results are widely used in the construction, repair and maintenance of road projects, with some incorporated into six pieces of transportation industry standards and two pieces of local standards. 

Moreover, cracking treatment materials have been experimentally applied in California, Toronto, etc. as well as 7 countries relevant to the Belt and Road Initiative such as Thailand, Vietnam, and Egypt. High-performance cold paving materials are exported to Papua New Guinea, Guam and other countries and regions. The project results have promoted the technological progress for cracking treatment materials as well as the localization of high-end products in China, supported the implementation of the “Belt and Road Initiative” and other national strategies, enabled the overseas use of scientific research achievements, and provided a strong theoretical basis and technical support for building China’s strength in transportation.

Economic benefits

The microcapsule self-healing technology developed can extend the fatigue life of asphalt mixture by two times, and the ferrite microwave self-healing technology extends the fatigue life of asphalt pavements by 233%. Cracking treatment materials have been applied to the repair of roads with a length of over 15 million linear meters, and the construction efficiency has been enhanced by two to four times. Over 2,000 tons of cold paving materials and grouting materials are used annually. High elasticity crack-resistant ultra-thin overlay has been applied in Qinghai, Guizhou, Hebei and other regions. The results have been applied to projects in nearly 30 provinces, autonomous regions and municipalities in China, including the Yanqing Winter Olympic stadium and Hunan Highway in Shanghai, and have been experimentally applied in many overseas countries and regions, generating direct economic benefits of 210 million yuan and indirect economic benefits of 1.52 billion yuan. The project results promise remarkable economic and social benefits, and broad prospects for application.