Experience and challenges of long-term performance research on asphalt pavement

Abstract

The long-term performance of China's asphalt roads has exhibited significant improvements in the past decades. The material-performance testing methods are being gradually established, the structural thickness-design method has been constructed, and construction technologies and quality-control methods have been developed. Additionally, hundreds of field-test sections were monitored, and accelerated-loading tests were conducted to identify the significant determinants that could potentially affect field performance, including the surface friction, permanent deformation, transverse crack, and fatigue crack. Field-distress-detection method and equipment have been developed to quickly obtain the performance information and provide critical feedbacks to road designers. The mechanisms that correspond to the most observed distresses in China were explored, and predictive models with varied performance in field roads were accordingly developed and validated. Road maintenance strategies were established, and materials that fit the varied field distresses were developed to improve maintenance quality. Despite the aforementioned efforts, asphalt pavements in different regions in China exhibit dramatically varying service lives, and we can see that the service life of roads is commonly lower than the design life. The main reasons are that the long-term performance studies mostly concentrated on small-scale test sections that could not fully represent the full-scale field-pavement sections, and the field test of roads were too concentrated in specific areas to include the effects of key parameters such as the variation in climatic conditions, traffic loads, water table, and local material properties. Furthermore, most research lacked national-level coordination and planning with short time duration, and obtaining the research reports online was difficult. In addition, the long-term performance-prediction models relied more on laboratory tests and lacked diversity and continuity. They were limited to single environmental factor, mismatched traffic loads and actual conditions, limited simulation of long-term-failure forms, and insufficient field validation. Thus, using these models as a guide to effectively design pavements with reasonable durability is difficult. In general, the long-term performance research of asphalt pavement in China has good preliminary foundations, and most policy makers and researchers possess the enthusiasm and confidence to design and construct better roads. However, many challenges remain be solved in terms of performance prediction with higher prediction accuracy, research orientation, research duration, all-round continuous observation, data quality control and standardization, and establishment of open database. We recommend carrying out nationwide deep-level, large-scale, and long-term pavement-performance observation as well as prediction research. The main subjects of these studies include but are not limited to the following: (1) Scaling to supplement and improve nationwide long-term performance field projects based on existing research and layout; (2) building a national unified, continuous, and long-term performance-observation network; (3) establishing a road life-cycle standardized database that includes design information, raw-material resource, construction procedure, service condition, and maintenance strategy and effectiveness; and (4) constructing performance prediction models that consider both mechanical calculated response (i.e., stress and strain) and statistical analysis, factors that cover climatic condition (i.e., environmental factors from different areas), traffic loads, structural thickness, and materials.