Study On The Key Technology Of Warm Mix Asphalt For Pavement Construction

Warm mix of asphalt is a new technology of green road construction. Compared with the traditional hot mix asphalt (HMA), the mixing and compaction temperatures are relatively low, energy consumption and emissions is relatively small and has good road performance for warm mix asphalt (WMA). And it is a new way of energy saving environmentally friendly materials, has very broad application prospects. However, as the time is short in the applications of construction, there are some problems about its application such as no design specifications, lack of theoretical basis for a reasonable mixing and compaction temperatures determined, wether can be constructed in the low-temperature environment. Relying on the transportation construction projects in Gansu Province—Research on pavement construction technology for the warm mix, fire retardant modified asphalt, a series of key technical issues in the design and construction was researched based on the extensive collection and analysis of warm mix asphalt at home and abroad.The agent at 5℃and softening point before and after aging was analyzed and comparised for the SBS modified asphalt and SBS modified asphalt adding 5% Evotherm-DAT. The SHRP PG (performance grade) test was done about two asphalt. At same time, brookfield viscosity was examined for the SBS modified asphalt adding 5% Evotherm-DAT.The relationship of voids and density with molding temperature was discussed using Marshall compaction method and rotary compaction molding specimens. Based on this, the molding method suitable for warm mix asphalt is determined. The densification energy index (CEI) and traffic densification index(TDI) in the construction process are introduced to refect inherent information of asphalt mixture. And the compaction molding temperature was obtained.Based on fractal geometry theory, the fractal characteristics of aggregate distribution composed with fractal dimension and self-similarity in dense-gradation asphalt mixture was researched based on the fractal model of aggregate distribution and fuzzy fractal dimension defined. And the relationship between the fractal dimension(D) and pavement performance was researched by testing volume parameter of mixtures, dynamic stability and bending strain energy at 0℃. The technical indicators in the process of design for the mixture and control indicators of asphalt pavement performance were proposed by the experiment of WMA road performance at the optimum asphalt content.The temperature field analysis model was established in different parts of transport vehicles during transport for asphalt mixture. And the reliability of the mathematical model built was verified by the temperature measurement in the construction site. Space- time Distribution Characteristics of Temperature Field During Asphalt Pavement Paving was researched by the collection of temperature measurement in the construction site.The primary and secondary each factor were compared about cooling rate of warm mix asphalt by the method of gray correlation analysis.Based on the principle of non-state heat conduction in the thermal process of asphalt pavement, thermal diffusivity of asphalt mixture formula was derived. The required parameters thermal conductivity coefficient was obtained by the thermal conductivity tests. Based on this, the effect of different temperature and void on the thermal conductivity coefficient was analyzed. According to finite element method of the temperature field, the temperature field model in the process of warm mix asphalt compaction was built. And the influence factors on cooling rate of warm asphalt mix in the the process of compaction of asphalt pavement was analyzed.Based on the effect of time available for asphalt mixture compaction, a kind of fuzzy analysis is provided by synthesizing all factors.The accuracy of cool features for asphalt mixture predicted was verified by the software of Pavecool through measuring the temperature at the surface and internal asphalt mixture at various times in different environments. Combined with the environmental and climatic characteristics in the Tianshui and Dingxi of Gansu province, the minimum ambient temperature conditions was determined for different thickness and environments of the asphalt mix construction.Relying on pavement construction from Tianshui to Dingxi, the construction engineering technology was studied and energy saving and emission reduction of warm mixed asphalt was quantitatively analyzed. The results showed that asphalt pavement compaction can get better by the warm mix asphalt. Comparing with the HMA, harmful gas emissions of WMA in mixing process can be greatly decreased, and WMA can reduce energy consumption 20% comparing with the corresponding HMA.