Field Performance And Experimental Research On Additive Type Warm Mix Asphalt And Recycled Warm Mix Asphalt

By the end of 2013, the total mileage of highway had been up to 4,356,200 kilometers due to the rapid development of highway construction and highway maintenance in China, among which the total maintenance mileage was 4,251,400 kilometers, the national grade highway mileage was 3,755,600 kilometers, the second-class highway and above was 524,400 kilometers and the freeway mileage was up to 104,400 kilometers. Therefore, it is of significance to rapidly promote the research, application and popularization of environmental-friendly warm mix asphalt(WMA) and warm mix asphalt with reclaimed asphalt pavemet(RAP-WMA) with the advantage of energy conservation and emission reduction. Currently, the researches of laboratory experiment and theoretical analysis on WMA are still in preliminary stages at home. Although a few test roads have been constructed, there are few cases that hot mix asphalt(HMA) is widely replaced by WMA and RAP-WMA during design and construction of asphalt pavement due to the restrictions of various conditions and reasons. Additionally, the agreements with the influence of different warm mix additives on asphalt performance, their compatibility and mechanism with asphalt, the determination of design method and production temperature of WMA, the pavement performance of WMA and RAP-WMA as well as the material parameters utilized to calculate pavement structure design aren’t achieved. Consequently, it is necessary to perform further investigation to accomplish this goal. In this paper, combined with relative projects such as the key project of Hunan Provincial Science & Technology Department Science and Technology Plans ―Asphalt pavement warm mix recycled technology study(2011SK2022)‖ and so on, a variety of in-depth studies on laboratory test and theoretical analysis are carried out to further improve its design theory and engineering application technology.Firstly, through systematically investigation and analysis of warm mix technology at home and abroad, the representative warm mix additives were selected. The in-depth and systematic studies on the influence of additives on traditional performance of asphalt binder, high temperature, low temperature and asphalt PG grades were performed. Then, the relationship between the penetration of asphalt binder with warm mix additive and high temperature grade of PG grade was preliminarily researched and analyzed in order to analyze the mechanism of interaction between warm mix additive and asphalt and the performance differences of asphalt with various warm mix additives. Meanwhile, the methods of d ifferential scanning calorimetry analysis, thermogravimetic analysis and atomic force microscopy analysis were applied to research the thermal properties and microstructure of warm mix asphalt with adding different types of warm mix additives. Based on these, the foundation for the study of the mechanism of reaction of warm mix additives and asphalt are established.Secondly, through deeply research on the main road performances of WMA mixture and traditional HMA mixture and their construction technologies, the similarities and differences of these two technologies were presented, based on which the corresponding mix design methods were researched. The results indicate that the technical indicators of mix design of WMA mixture and the technical requirements of mineral aggregate gradation and raw materials of WMA mixture can be consistent with those of HMA. However, the performance of asphalt mixture is considerably influenced by temperature because of the viscoelastic characteristics of asphalt. Therefore, in order to achieve or be not lower than hot mix asphalt mixture performance, it is the key to determine the production temperature of WMA. Consequently, the systematical comparison tests on determining the mixing and compaction temperatures were performed utilizing the viscosity-temperature relationship of asphalt and the equal-viscosity and equal-volume principle combined with voids-temperature relationship of mixture. The conclusions are achieved that the latter method is more realistic.Then, the systematic experimental studies on performance of WMA mixture and material parameters for the calculation of pavement structure design were carried out using the equal-viscosity and equal-volume principle. According to the laboratory testing results, WMA mixture test sections with different combined structures were designed and constructed. Additionally, the calculation and analysis of economic and social benefits were conducted on WMA test road.Finally, based on the research results and conclusions of WMA and combined with the advantages of recycled technology and warm mix technology, the aged asphalt mixture of pavement was recycled with warm mix technology. The systematic laboratory studies were performed on asphalt binder of RAP-WMA, mix design of RAP-WMA, determination of production temperature, performances of RAP-WMA and material parameters for pavement structure design. The results indicate that the equal-viscosity and equal-volume principle is also suitable for RAP-WMA mixture and its universal applicability is verified. The influence of various aged asphalt mixture contents on the performance of RAP-WMA mixture is different, but of which the technology indictors all meet the requirements of the current relevant technical specifications.